Tire for large off-road motorcycles

Abstract

The invention relates to a large endurance type motorcycle tire mainly used for off-road use. The tire of the present invention improves off-road and road drivability on both dry and wet road surfaces due to the specific "crown and base" arrangement of the tread band and the specific mechanical properties of the composites making up the tread band.

Description

Technical Field

[0001] The present invention relates to a tire for motorcycles, in particular to a tire for large endurance type motorcycles. Background Art

[0002] Large enduro or / off-road motorcycles, also called large adventure or dual-purpose motorcycles, are motorcycles with large engine capacity, high power and high mass, designed to be ridden both on tarmac roads and off-road. These motorcycles typically have a cylinder displacement greater than or equal to 1000cm 3 , power greater than or equal to 100hp, maximum torque greater than or equal to 100Nm, and mass greater than or equal to 180kg.

[0003] Examples of large enduro motorcycles are the BMW GS1250R, Ducati Multistrada V4, KTM1290Super Adventure R and Honda CRF1100L Africa Twin.

[0004] The use of motorcycles in this category is very wide, ranging from pure road use (comparable to sport touring and tending towards super sport) to off-road use that is more severe than the humble road, such as riding on unpaved racing courses (so-called tape roads) or on routes that include river beds, soft terrain, mud, sand and rough surfaces of various types and difficulties.

[0005] To cater for all these types of uses, there are different tire products on the market, each focusing on a clearly defined application, such as sports driving on the road, touring driving on the road, touring combined with driving on unpaved racing tracks, road driving combined with light off-roading, or severe off-roading combined with road driving.

[0006] Typically, tires for large enduro-type motorcycles, intended primarily for a combination of severe off-road use and road riding, are marked M+S and, for example, are approved for a maximum speed of 160 km / h (ETRTO speed index: Q). These tires typically have a maximum radial section width of between 90 mm and 170 mm (e.g., between 90 mm and 120 mm for the front tire and between 130 mm and 170 mm for the rear tire) and are mounted on rims having a mounting diameter typically between about 17 inches and about 21 inches (e.g., between 19 inches and 21 inches for the front tire and between 17 inches and 18 inches for the rear tire).

[0007] Tires primarily intended for road use maximize performance in terms of high-speed stability, grip on wet and dry roads, handling, mileage, traction and braking on wet surfaces, comfort on asphalt roads and wear regularity. In particular, these tires, which are typically used in all weather conditions throughout the year, must allow high reliability and performance on roads with reduced grip (e.g. wet roads).

[0008] Tires intended primarily for off-road, even severe off-road conditions, maximize the performance in terms of grip, traction, controllability and directionality on uneven, slippery and / or less consistent terrain (e.g. sand, mud, gravel) in order to effectively transmit even high driving and braking torques to the ground. These tires must also allow the above-mentioned performance on wet roads.

[0009] Typically, tires are inflated at much lower pressures for off-road use than for road use to increase the deflection of the tread in contact with the ground, thereby increasing the motorcycle's footprint, traction and grip.

[0010] In road use, the pressure must then be properly restored to the reference values ​​usually indicated by the motorcycle manufacturer.

[0011] The handling of a motor vehicle as perceived by the driver depends on an ideal balance of inflation pressures which balances in the most favourable way all the variations in physical parameters caused by the pressure on the tyre itself.

[0012] In fact, the reduction in pressure causes a decrease in the static stiffness (its components: lateral, vertical and longitudinal), so that the tire itself deforms more in all directions during operation, and also in the dynamic stiffness (drift and camber stiffness and self-righting torque), so that the tire's ability to generate dynamic forces in response to the various stresses that can be very intense on the road due to speed and large camber angles is reduced.

[0013] Tires inflated at a pressure lower than the reference pressure deform more and inevitably operate at higher thermal conditions, which can lead to premature aging of the tire, because once a certain level of thermal stress exposure is exceeded, all components age and lose their physical and mechanical characteristics. In addition, due to the higher compliance of the profile, the tire is more difficult to steer and changes direction more slowly.

[0014] Therefore, it is recommended to adjust the tire pressure when switching from on-road driving to off-road driving or vice versa, even by changing the tire pressure quite drastically (e.g., up to about 1.5 bar) to extend tire life and maximize performance.

[0015] Typically, large enduro-type motorcycle tires comprise a tread band having a tread pattern defined by a plurality of blocks separated by circumferential and transverse grooves, the blocks being arranged both in a central annular portion of the tread band and in opposite annular shoulder portions of the tread band. Such tires typically have a solid / void ratio of between about 0.40 and about 0.65.

[0016] To optimize performance, in motorcycle tires the tread band is usually made into a double-layer structure.

[0017] This double-layer structure includes a rolling layer or portion (called a crown) and a bottom layer (called a base) located radially inward of the rolling layer, thereby constituting a so-called "crown and base" structure.

[0018] Typically in motorcycle tires, the cap layer and the base layer extend axially annularly, wherein the cap overlaps the base over the entire width of the tread band, the radially outermost cap forming the entire rolling surface, while the base is radially innermost and never reaches the rolling surface, as shown for example in EP 3 530 487 A1.

[0019] Thus, it is possible to use an elastomeric material capable of providing the crown with wear and crack resistance, while the elastomeric material of the base may be particularly useful for adequately supporting the crown and / or having low hysteresis characteristics cooperating with reduced rolling resistance. The base may be arranged between the belt structure and the rolling layer.

[0020] In some alternative embodiments, however, which relate to motorcycle tires specifically for road use (supersport sector), such as those shown in WO2019082012A1 and WO2021090152A1, the rolling surface of the tread band may comprise a central annular portion consisting of a bottom layer present on the surface with one or more annular sectors consisting of different compounds on both sides. In such applications, the riding style of motorcycles is completely different from that of large endurance types, which are characterized by even very high camber angles, which make the shoulder portion of the tread constantly in contact with the road surface.

[0021] JP2007125988A discloses a crown & base tire for motorcycles, wherein a crown layer (32) extends axially over the entire width of a center annular portion (W2), and a base layer (34) extends axially over the entire width of the center annular portion and on each annular portion of a shoulder (W1).

[0022] The document does not report the presence of blocks with a specific solid / void ratio in the tread, nor the extension of the annular portion. Without further specifying the test conditions, the values ​​of the elastic modulus E1 and E2 of the composite of both the cap layer (32) and the base layer (34) measured at 60°C are 11 kgf / mm 2 ≤E1≤16kgf / mm 2 and 7kgf / mm 2 ≤E2≤13kgf / mm 2 (Paragraph 0019).

[0023] JP6053550B2 discloses a crown & base tire for two-wheeled vehicles, which includes a base layer (38), an intermediate layer (40) and a cover layer (42) laminated in a radial direction. The document does not mention the elastic modulus value of the composite constituting these layers. Summary of the invention

[0024] The applicant has found itself that, when considering the market segments of motorcycles, the segment of "large enduro" motorcycles, as previously mentioned, has very broad usage.

[0025] The Applicant has observed that, in order to optimally cover its entire range of uses, a large enduro type motorcycle should be equipped with tyres suitable for allowing high performance both on road (mainly high speed stability, wet and dry grip, handling) and off road (mainly traction, controllability and directionality) and which also have the ability to travel several kilometres.

[0026] However, the Applicant has found that there is a growing tendency to exaggerate on-road performance on the one hand and off-road performance on the other, the two performance characteristics being at least partially mutually contradictory. In fact, tyres that allow high on-road performance often have limited performance in harsh off-road conditions, and vice versa.

[0027] The Applicant has also noticed that a tire combining on-road and off-road use with a good compromise cannot achieve satisfactory extreme performance in both fields (on-road and off-road). In this regard, it should be noted that recently, according to customer requirements, the market has turned to more specialized solutions, thus envisaging several market segments for large enduro type motorcycle tires, each of these segments focusing on a specific popular use of motorcycles.

[0028] Heretofore, the present applicant has proposed large endurance type motorcycle tires mainly suitable for road use and large endurance type motorcycle tires mainly suitable for off-road use.

[0029] The applicant has focused its attention on the market segment of tires designed for off-road use on large enduro-type motorcycles.

[0030] These tires are usually chosen by users who seek off-road performance and expect on-road use to be limited to commuting to and from off-road trails.

[0031] This tire is approved for road use, but is mainly used off-road, even on bad surfaces. In this specific application, unlike the main road use, the motorcycle is driven in a substantially vertical position or with a limited rolling angle (camber) of the order of 25° to 30°, and the shoulder part of the tire tread band hardly touches the ground.

[0032] The Applicant has considered creating a tyre capable of maintaining excellent off-road performance and whose on-road behaviour is adapted to allow the user to undertake longer and more articulated road trips in safe and comfortable conditions than simply travelling back and forth on an off-road route, thereby improving its behaviour on dry roads and, in particular, improving its behaviour on wet roads where grip becomes a particularly critical aspect.

[0033] The Applicant has found that, in order to improve the aforementioned road behaviour while maintaining off-road performance, it is advisable to provide a tread band formed by at least one cap and a base, wherein, contrary to the typical configuration discussed above, the surfaces of the base layer, the base and the radially outer portions of the tread band are in the lateral annular portions (shoulder portions) of the tread band, while the radially outer central annular portion is formed by the cap layer. This arrangement of layers, coupled with the choice of a suitable elastomeric compound with suitable properties for the composition of the cap and base layers, means above all that during off-road use, the tread band of the tire flexes more at the shoulder portions and offers a larger footprint, thus offering better traction, controllability and comfort even at full tire pressure.

[0034] This greater flexibility of the shoulder portion and the resulting greater footprint of the tread band give it an advantage in off-road performance regardless of the pressure used, in fact allowing excellent off-road driving performance even at pressures comparable to or slightly below road pressures.

[0035] In addition, this tire has unexpectedly better road performance in terms of stability, handling and comfort, both on dry and wet road surfaces.

[0036] The result is completely innovative and goes against the common perception in this specific segment of large enduro-type tires that are primarily intended for off-road use.

[0037] The Applicant has discovered that by adopting the present cap and base configurations and selecting compounds having properties adapted to the precise performance requirements in the specific position of the tread band in which they are located, it is possible to maintain or even improve the off-road performance while improving the on-road performance, even at full inflation pressure or with minimal deflation.

[0038] In fact, the Applicant has intuitively known that in large endurance type tyres, mainly intended for off-road use, the tread band is generally subjected to different stress and thermal conditions during operation:

[0039] - Maximum value of the central annular portion for operation in constant contact with both on-road and off-road surfaces;

[0040] - intermediate values ​​for the shoulder portion, which does not touch the ground in the case of a segment dominated by straight-line riding, but is subjected to continuous bending, especially off-road, and

[0041] - Minimum values ​​for internal subfloors which never touch the road surface and are not subjected to such pronounced and repeated flexures.

[0042] The Applicant has therefore realised that, with the innovative crown and base configuration of the present invention, it is possible to satisfy the very high performance requirements of the central annular portion with a specific first crown compound having certain optimal properties (higher wear resistance, better adhesion), and to satisfy the different requirements of the shoulder portion (flexibility) and the inner bottom layer (thermal stability) with a second base compound having properties different from those of the first crown compound, which forms the bottom layer and rises appropriately to the surface only in the shoulder portion.

[0043] The present invention therefore relates to a tyre (1) for on-road / off-road motorcycles (large endurance type), said tyre comprising a tread band (8) of total radial thickness S, said tread band comprising a plurality of blocks and grooves defining in the tread band (8) a void / solid ratio comprised between 0.40 and 0.65, said tread band (8) comprising a central annular portion (A) and a pair of annular shoulder portions (B), the central annular portion being arranged symmetrically across an equatorial plane (XX), said pair of annular shoulder portions being arranged symmetrically on opposite sides of said central annular portion (A) and adjacent to the central annular portion, wherein:

[0044] - the central annular portion (A) extends axially over a width comprised between 70% and 90% of the width of the tread band and comprises a rolling layer (8a) of radial thickness S1 situated in the outermost radial position and a base layer (8b) of radial thickness S2 arranged adjacent to the rolling layer in the innermost radial position, the tread band (8) having a total radial thickness S=S1+S2,

[0045] The rolling layer (8a) extends axially across the entire width of the central annular portion (A), while the bottom layer (8b) extends axially across the entire width of the central annular portion (A) and across the entire width of each annular shoulder portion (B),

[0046] - each annular shoulder portion (B) extends axially with a width comprised between 5% and 15% of the width of the tread band and is made of said underlying layer (8b) for the entire total radial thickness S of the tread band,

[0047] Wherein, the rolling layer (8a) comprises a first elastomeric compound characterized by an E' modulus (measured at 70°C and 10 Hz according to the method described in the experimental part) between 5.00 MPa and 6.50 MPa, and the bottom layer (8b) comprises a second elastomeric compound characterized by an E' modulus (measured at 70°C and 10 Hz) between 3.50 MPa and 4.60 MPa, and wherein the percentage ratio between the E' modulus of the second elastomeric compound and the E' modulus of the first elastomeric compound is between 70% and 90%.

[0048] definition

[0049] "Tyre for motorcycles" refers to a vulcanized tire having a high curvature ratio (generally greater than 0.20) and capable of reaching high camber angles during cornering.

[0050] The term “curvature ratio” is used to indicate the ratio between the distance between the radially highest point of the tread band and the maximum radial cross-sectional width of the tire (this distance also called “curvature”) in a tire section and the same maximum radial cross-sectional width of the tire.

[0051] The "camber angle" is the angle between the equatorial plane of the tire mounted on the motorcycle wheel and a plane perpendicular to the road surface.

[0052] “Maximum radial section width” or “maximum chord length” means the maximum width of the tire profile, ie the dimension of the segment terminated by the two axially outermost points of the tread band profile.

[0053] The "equatorial plane" of a tire is the plane perpendicular to the tire's axis of rotation and dividing the tire into two symmetrically equal parts.

[0054] “Tread pattern” means the representation of all points of the tread band (including the grooves) on a plane perpendicular to the equatorial plane of the tire and tangential to the greatest diameter of the tire. The tread pattern is defined by a plurality of blocks separated by grooves and possibly including notches.

[0055] "Block" means a portion of the tread band delimited by grooves. If a block is positioned on the axially outermost portion of the tread band, it is delimited in axial direction by the axially outermost portion of the tread band and in an axially innermost position by at least one groove.

[0056] “Groove” means a groove formed in the tread band for delimiting a portion of a block.

[0057] Measurements of angles, and / or linear quantities (distance, width, length, amplitude, axial and / or circumferential segments, etc.) and / or surfaces are understood to be with reference to the tread pattern as defined above.

[0058] "Width" refers to the dimension measured in a direction normal to the equatorial plane.

[0059] "Girth" refers to a dimension measured along a direction lying on or parallel to the equatorial plane.

[0060] The expression "maximum extension" relating to a block denotes the distance between two axially or circumferentially outermost points of the block measured respectively in a direction perpendicular to the equatorial plane or in a direction parallel to or lying on the equatorial plane.

[0061] The terms "radial" and "axial" and the expressions "radially inner / outer" and "axially inner / outer" are used to refer to the direction parallel to the equatorial plane of the tire and the direction perpendicular to the equatorial plane of the tire, respectively, that is, to the direction perpendicular to the axis of rotation of the tire and the direction parallel to the axis of rotation of the tire, respectively.

[0062] The terms “circumferential” and “circumferentially” are used with reference to directions of the circumferential development of the tire (ie the rolling direction of the tire) which correspond to directions lying in a plane coinciding with or parallel to the equatorial plane of the tire.

[0063] "Circumferential extension" of a tyre, a tread band or a portion thereof is intended to mean the planar extension of the radially outermost surface of the tyre, the tread band or a portion thereof, on a plane tangential to the tyre.

[0064] The expressions “axially innermost” and “axially outermost” respectively refer to a position closer to the equatorial plane and a position farther from the equatorial plane with respect to a reference element.

[0065] By annular portion of the tread band is meant that portion of the tread band which extends in the circumferential direction of the entire tread band and which has a predetermined axial extension.

[0066] The distance of the annular tread portion from the equatorial plane is assessed axially with reference to a plane of the closest end of the annular tread portion parallel to the equatorial plane.

[0067] “Substantially axial direction” means a direction inclined at an angle between 70° and 90° relative to the equatorial plane of the tire.

[0068] “Substantially circumferential direction” means a direction oriented at an angle between 0° and 20° relative to the equatorial plane of the tire.

[0069] A "circumferential groove" refers to a groove comprising at least one groove portion extending in a substantially circumferential direction.

[0070] A "transverse groove" is understood to mean a groove comprising at least one groove portion extending in the axial direction of the base.

[0071] The expression "substantially parallel" refers not only to a completely parallel state but also to a state where an angle deviating from the completely parallel state is not greater than 10°.

[0072] "Solid / void ratio" means the ratio of the total groove surface of a given annular portion of a tire's tread pattern (which may be the entire tread band or tread pattern) to the surface of a given tread pattern portion (which may be the entire tread band or tread pattern).

[0073] The "footprint area" of a tire is that portion of the tire that contacts the ground or road surface when the tire is mounted on a rim and a predetermined vertical load is applied to the tire.

[0074] The term "phr" (abbreviation for parts per hundred parts of rubber) denotes the parts by weight of a given elastomeric compound component per 100 parts by weight of elastomeric polymer, exclusive of any plasticizing, extending oil.

[0075] "Elastomeric material" means a material comprising a vulcanizable natural or synthetic polymer and a reinforcing filler, wherein such material after vulcanization readily undergoes deformation caused by a force at room temperature and is capable of rapidly and positively recovering to substantially original shape and size after the deforming force is removed (as defined in ASTM D1566-11 Standard Terminology Relating to Rubber).

[0076] The term "diene polymer" refers to a polymer or copolymer obtained by polymerization of one or more different monomers, at least one of which is a conjugated diene (conjugated diene).

[0077] The term "elastomeric compound" means a compound obtained by mixing and possibly heating at least one elastomeric polymer with at least one additive usually used in the preparation of tyre compounds.

[0078] The term "vulcanizable elastomeric compound" denotes an elastomeric mixture ready for vulcanization, which is obtainable by incorporating into the elastomeric compound all additives including vulcanizing additives.

[0079] The term "vulcanized elastomeric compound" refers to a material obtained by vulcanizing a vulcanizable elastomeric compound.

[0080] The term "vulcanization" denotes the crosslinking reaction in natural or synthetic rubber caused by generally sulfur-based crosslinking agents.

[0081] The term "vulcanizing agent" means a product capable of transforming natural or synthetic rubber into an elastic and resistant material due to the formation of a three-dimensional network of intermolecular and intramolecular bonds. Typical vulcanizing agents are sulfur-based compounds, such as elemental sulfur, polymeric sulfur, sulfur-donating agents, such as bis[(trialkoxysilyl)propyl]polysulfide, thiuram, dimorpholine dithioate and caprolactam disulfide.

[0082] The term "vulcanization accelerator" denotes compounds capable of shortening the duration of the vulcanization process and / or lowering the operating temperature, for example TBBS, sulfenamides, thiazoles, dithiophosphates, dithiocarbamic acids, guanidines and sulfur donors such as thiuram.

[0083] The term "vulcanization activator" denotes a product that is able to further accelerate the vulcanization, thereby allowing the vulcanization to take place in a shorter time and possibly at a lower temperature. An example of an activator is the stearic acid-zinc oxide system.

[0084] The term "vulcanization retarder" refers to a product capable of delaying the onset of the vulcanization reaction and / or inhibiting undesirable side reactions, such as N-(cyclohexylthio)phthalimide (CTP).

[0085] The term "vulcanization package" refers to a vulcanizing agent and one or more vulcanization additives selected from the group consisting of vulcanization activators, vulcanization accelerators and vulcanization retarders.

[0086] The term "reinforcing filler" refers to reinforcing materials commonly used in this field to improve the mechanical properties of tire rubber, preferably selected from carbon black, traditional silica (such as silica from sand precipitated with strong acids), preferably amorphous diatomaceous earth, calcium carbonate, titanium dioxide, talc, aluminum oxide, aluminosilicates, kaolin, silicate fibers and mixtures thereof.

[0087] The term "white filler" refers to conventional reinforcing materials used in this field, selected from conventional silicas and silicates, such as sepiolite, palygorskite (also known as attapulgite), montmorillonite, halloysite and the like, which may be modified by acid treatment and / or derivatized. Typically, white fillers have surface hydroxyl groups.

[0088] The expression “reinforcement cord” or simply “cord” is used to denote a thread-like element composed of one or more elongated elements (hereinafter also called “yarns”), optionally coated with or embedded in a matrix of elastomeric material.

[0089] Detailed description of the invention

[0090] In the remainder of this specification and in the subsequent claims, even if not explicitly stated, any numerical value is to be understood as being preceded by the term "about" in order to also denote any numerical value that slightly deviates from the stated value, for example in view of typical dimensional tolerances in the referenced art.

[0091] Additionally, when referring to a range of any values ​​between a minimum value and a maximum value, the above minimum and maximum values ​​should be understood to be included in the above range unless otherwise expressly specified.

[0092] Additionally, all ranges include any combination of the recited maximum and minimum values ​​and include any intermediate ranges, even if not specifically recited.

[0093] The tyre according to the invention is characterised in that it has one or more of the following features, alone or in combination.

[0094] The tyre according to the invention comprises a tread band (8) of total radial thickness S.

[0095] The total radial thickness S of the tread band (8), the radial thickness S1 of the rolling layer (8a) and the radial thickness S2 of the base layer (8b) refer to the thickness after the tire is molded and vulcanized.

[0096] Preferably, the total radial thickness S of the tread band is between 10 mm and 20 mm, more preferably between 12 mm and 16 mm, for example 14.5 mm, to allow adequate tread life and tire integrity. In addition, the thickness of the tread band must be sufficient to ensure that after vulcanization the grooves are not too close to the carcass ply and / or the belt structure.

[0097] The total radial thickness S of the tread band may not be constant, in particular it may vary from the central annular portion to the shoulder portions.

[0098] In one embodiment, the total radial thickness S is greater in the central annular portion (A) than in the annular shoulder portions (B). Preferably, the total radial thickness S of the central annular portion (A) is between 110% and 120% of the total radial thickness S of the annular shoulder portions B.

[0099] Preferably, the radial thickness S1 of the rolling layer (8a) in the central annular portion (A) is between 9 mm and 17 mm, more preferably between 11 mm and 15 mm.

[0100] The radial thickness S2 of the bottom layer (8b) in the central annular portion (A) is generally not uniform because it is subjected to sliding and deformation imposed by the molds used to define the blocks and grooves during the vulcanization process, in particular during the molding step.

[0101] Preferably, the radial thickness S2 of the bottom layer (8b) of the central annular portion (A) is between 0.8 mm and 4 mm, more preferably between 1.0 mm and 3 mm, even more preferably between 1.0 mm and 2.0 mm, in order to provide sufficient support.

[0102] In the annular shoulder portion (B), the radial thickness S2 of the base layer (8b) instead corresponds to the total radial thickness S of the tread band.

[0103] In the tyre of the invention, the sum of the width of the axial extension of the two shoulder portions (B) and the width of the axial extension of the central annular portion (A) corresponds to the width of the axial extension of the tread band (8).

[0104] Preferably, the central annular portion (A) extends axially over a width comprised between 75% and 85% of the width of the tread band.

[0105] Preferably, each annular shoulder portion (B) extends axially over a width comprised between 7.5% and 12.5% ​​of the width of the tread band.

[0106] Preferably, the axial extension of the two annular shoulder portions (B) have the same width.

[0107] In the tyre of the invention, said rolling layer (8a) is preferably formed entirely of said first elastomeric compound and / or said bottom layer (8b) is preferably formed entirely of said second elastomeric compound.

[0108] In the tire of the present invention, the dynamic elastic compression modulus E' (measured at 70°C and 10 Hz according to the method described in the experimental part) of the first elastomeric compound of the rolling layer of the central annular portion (A) is greater than the E' modulus (70°C, 10 Hz) of the second elastomeric compound of the annular shoulder portion (B).

[0109] Preferably, the first elastomeric compound and the second elastomeric compound are selected so that the finished (vulcanized) tire has a vulcanized elastomeric material at the annular shoulder portion (B), the dynamic elasticity E' modulus of the vulcanized elastomeric material (measured at 70°C and 10 Hz) being between 75% and 90%, more preferably between 80% and 85%, of the dynamic elasticity E' modulus of the vulcanized elastomeric material at the rolling surface of the central annular portion (A) (measured at 70°C and 10 Hz).

[0110] Preferably, said first elastomeric compound is characterized by an E' modulus (measured at 70°C, 10 Hz) of not more than 6.50 MPa, more preferably not more than 6.00 MPa.

[0111] Preferably, said first elastomeric compound is characterized by an E' modulus (measured at 70°C, 10 Hz) comprised between 5.00 MPa and 6.00 MPa, more preferably between 5.00 MPa and 5.50 MPa.

[0112] Preferably, said first elastomeric compound is characterized by an E' modulus (measured at 70°C, 10 Hz) greater than 5.00 MPa, more preferably greater than 5.50 MPa.

[0113] Preferably, said second elastomeric compound is characterized by an E' modulus (measured at 70°C, 10 Hz) of not more than 4.60 MPa, more preferably not more than 4.50 MPa, even more preferably not more than 4.40 MPa.

[0114] Preferably, said second elastomeric compound is characterized by an E' modulus (measured at 70°C, 10 Hz) greater than 4.00 MPa, more preferably greater than 4.20 MPa.

[0115] Preferably, said second elastomeric compound is characterized by an E' modulus (measured at 70°C, 10 Hz) comprised between 4.00 MPa and 4.50 MPa, more preferably between 4.20 MPa and 4.40 MPa.

[0116] In one embodiment, the first elastomeric compound is characterized by an E' modulus (measured at 70°C, 10 Hz) greater than 5.00 MPa, more preferably greater than 5.50 MPa, and the second elastomeric compound is characterized by an E' modulus (measured at 70°C, 10 Hz) not greater than 4.60 MPa, more preferably not greater than 4.50 MPa, even more preferably not greater than 4.40 MPa

[0117] Preferably, the difference between the E' modulus of the first elastomeric compound and the E' modulus of the second elastomeric compound (measured at 70°C, 10 Hz) is between 0.3 and 2.3 MPa, more preferably between 0.4 and 1.5 MPa, even more preferably between 0.6 and 1.1 MPa.

[0118] In the tire of the present invention, the first elastomeric compound of the rolling layer of the central annular portion (A) and the second elastomeric compound of the bottom layer of the tread band (8) are selected so that the finished (vulcanized) tire has at the rolling surface of the central annular portion (A) such a vulcanized elastomeric material whose tan delta (dielectric loss tangent) (measured at 70°C and 10 Hz) is greater than the tan delta (measured at 70°C and 10 Hz) of the vulcanized elastomeric material of the annular shoulder portion (B).

[0119] Preferably, the first elastomeric compound and the second elastomeric compound are chosen so that the finished (vulcanized) tyre has at the annular shoulder portion (B) a vulcanized elastomeric material having a tan delta (measured at 70°C and 10 Hz) which is between 45% and 65%, more preferably between 50% and 60%, of the tan delta (measured at 70°C and 10 Hz) of the vulcanized elastomeric material at the rolling surface of the central annular portion (A).

[0120] Preferably, said first elastomeric compound is characterized by a tan delta (measured at 70°C, 10 Hz) greater than 0.220, more preferably greater than 0.230.

[0121] Preferably, said first elastomeric compound is characterized by a tan delta (measured at 70°C, 10 Hz) between 0.220 and 0.280, more preferably between 0.230 and 0.270.

[0122] Preferably, said second elastomeric compound is characterized by a tan delta (measured at 70°C, 10 Hz) of not greater than 0.180, more preferably not greater than 0.170.

[0123] Preferably, said second elastomeric compound is characterized by a tan delta (measured at 70°C, 10 Hz) comprised between 0.120 and 0.180, more preferably between 0.135 and 0.150.

[0124] Preferably, said first elastomeric compound is characterized by an IRHD hardness of less than 78, more preferably less than 75 and / or greater than 66, more preferably greater than 68, measured at 23°C.

[0125] Preferably, said first elastomeric compound is characterized by an IRHD hardness measured at 23°C comprised between 66 and 76, more preferably between 68 and 74.

[0126] Preferably, said second elastomeric compound is characterized by an IRHD hardness of less than 73, more preferably less than 71 and / or greater than 63, more preferably greater than 65, measured at 23°C.

[0127] Preferably, said second elastomeric compound is characterized by an IRHD hardness measured at 23°C comprised between 63 and 73, more preferably between 65 and 71 .

[0128] In the present tyre, the load CA3 at 300% elongation of said first elastomeric compound, measured at 23° C. according to the UNI 6065:2001 standard, is preferably lower than the load CA3 of the second elastomeric compound.

[0129] Preferably, the first elastomeric compound is characterized by a load CA1 at 100% elongation of between 1.7 MPa and 2.3 MPa, more preferably between 1.9 MPa and 2.1 MPa, and / or a load CA3 at 300% elongation of between 7.7 MPa and 10.5 MPa, more preferably between 8.6 MPa and 9.5 MPa, measured at 23°C according to UNI 6065:2001 standard.

[0130] Preferably, the second elastomeric compound is characterized by a load CA1 at 100% elongation of between 1.7 MPa and 2.3 MPa, more preferably between 1.9 MPa and 2.1 MPa, and / or a load CA3 at 300% elongation of between 8.6 MPa and 11.7 MPa, more preferably between 9.7 MPa and 10.7 MPa, measured at 23°C according to UNI 6065:2001 standard.

[0131] In a preferred embodiment of the tire of the present invention, the first elastomeric compound of the rolling layer of the central annular portion (A) of the tread band (8) has a load value CA3 measured at 23°C between 7.7MPa and 10.5MPa, a dynamic elastic modulus E' measured at 70°C and 10Hz between 5.00MPa and 6.00MPa, a tan delta measured at 70°C and 10Hz between 0.220 and 0.280, a dynamic elastic modulus E' measured at 23°C and 10Hz between 6.60MPa and 10.00MPa and a tan delta measured at 23°C and 10Hz between 0.320 and 0.431.

[0132] More preferably, the first elastomeric compound has a load value CA3 measured at 23°C between 8.6 MPa and 9.5 MPa, a dynamic elastic E' modulus measured at 70°C and 10 Hz between 5.00 MPa and 5.50 MPa, a tan delta measured at 70°C and 10 Hz between 0.230 and 0.270, a dynamic elastic E' modulus measured at 23°C and 10 Hz between 7.00 MPa and 8.60 MPa, and a tandelta measured at 23°C and 10 Hz between 0.337 and 0.412.

[0133] In a preferred embodiment of the present invention, the second elastomeric compound of the bottom layer has a load value CA3 measured at 23°C between 8.6 MPa and 11.7 MPa, a tandelta measured at 70°C and 10 Hz between 0.120 and 0.180, and a dynamic elastic E' modulus measured at 70°C and 10 Hz between 4.00 MPa and 4.50 MPa, a dynamic elastic E' modulus measured at 23°C and 10 Hz between 4.80 MPa and 6.50 MPa, and a tan delta measured at 23°C and 10 Hz between 0.262 and 0.354.

[0134] More preferably, the second elastomeric compound has a load value CA3 measured at 23°C between 9.7 MPa and 10.7 MPa, a tan delta measured at 70°C and 10 Hz between 0.135 and 0.150, and a dynamic elastic E' modulus measured at 70°C and 10 Hz between 4.20 MPa and 4.40 MPa, a dynamic elastic E' modulus measured at 23°C and 10 Hz between 5.10 MPa and 6.30 MPa, and a tandelta measured at 23°C and 10 Hz between 0.277 and 0.339.

[0135] In the preferred embodiment, the first elastomeric compound has a hardness IRHD between 69 and 73 at 23° C., while the second elastomeric compound has a hardness IRHD between 65 and 69.

[0136] Generally, to prepare the compounds of the tyre according to the invention, use may be made of the ingredients listed below and other ingredients commonly used in the tyre industry sector.

[0137] In particular, for the preparation of the base layer (8b) composite and the rolling layer (8a) composite, an elastomeric composition can be used comprising at least one elastomeric diene polymer, which is chosen, for example, from the elastomeric diene polymers conventionally used in sulfur-crosslinkable elastomeric compositions (vulcanization), peroxides or other systems known to those skilled in the art and particularly suitable for the production of tires, or from elastomeric polymers or copolymers having unsaturated chains, whose glass transition temperature (Tg) is generally below 20°C, preferably in the range of 0°C to -110°C.

[0138] The base layer (8b) compound and the rolling layer (8a) compound comprise 100 phr of at least one diene elastomeric polymer, preferably comprising at least one styrene-butadiene rubber selected from: solution polymerized styrene-butadiene rubber (S-SBR), emulsion polymerized styrene-butadiene rubber (E-SBR), or mixtures thereof. The content of styrene-butadiene rubber may range, for example, from 20 to 90 phr.

[0139] Commercial examples of SBR polymers that can be used in the present invention are Tufdene E581 and E680 polymers from Ashai-Kasei (Japan), SPRINTAN SLR4602, SLR3402 and SLR4630 from Trinseo (Germany), HPR620 from JSR Corporation (Japan), BUNA SL-4518, BUNA SE 1502 and BUNA CB 22 from Arlanxeo (Germany), Europrene 5543T, Europrene 1739 and Intol 1789 from ENI (Italy), HP 755 from Japan Synthetic Rubber Co. (Japan), and NIPOL NS 522 from Zeon Co. (Japan).

[0140] The bottom layer (8b) compound and the rolling layer (8a) compound may include at least one butadiene polymer (BR), preferably low cis-functionalized BR, in an amount of, for example, 10 to 50 phr.

[0141] The bottom layer (8b) composite and the rolling layer (8a) composite may comprise one or more liquid polymers selected from olefin-based liquid polymers and copolymers, preferably based on butadiene (BR), isoprene (IR), isoprene / butadiene rubber (IBR), styrene / butadiene rubber (SBR), optionally functionalized with hydroxyl and epoxy groups, or selected from depolymerized liquid natural polymers (NR), in an amount of, for example, 1 to 40 phr.

[0142] The base layer (8b) compound and the rolling layer (8a) compound may include at least one resin.

[0143] At least one resin may be a polyterpene resin selected from homopolymers or copolymers of α-pinene, β-pinene, limonene and vinyl aromatic monomers (styrene) and / or aromatic monomers (phenol).

[0144] Examples of commercially available terpene-based natural resins are: Piccolyte F90 and Piccolyte F105 Resin 2495 manufactured by PINOVA; and Dercolyte A 115 and Dercolyte M 115 manufactured by DRT.

[0145] At least one of the resins may be a hydrocarbon resin, for example selected from the group consisting of resins derived from coumarone-indene, styrene-indene, styrene-alkylstyrene, and aliphatic resins.

[0146] A specific example of a commercially available hydrocarbon resin is NOVARESC resin (indene-coumarone synthetic resin) produced by RUTGERS CHEMICAL GmbH.

[0147] Examples of commercially available styrene-indene resins are UNILENE A 100 produced by Braskem and Novares TT 90 produced by Ruetgers.

[0148] The at least one resin may be present in an amount of, for example, 0 to 50 phr.

[0149] The base layer (8b) compound and the rolling layer (8a) compound according to the invention may comprise at least one plasticizing oil.

[0150] The term "plasticizing oil" refers to a process oil derived from petroleum or mineral oil or vegetable oil or synthetic oil or a combination thereof.

[0151] The plasticizing oil may be a process oil derived from petroleum selected from paraffins (saturated hydrocarbons), cycloparaffins, aromatic polycyclic hydrocarbons, and mixtures thereof.

[0152] Examples of suitable process oils derived from petroleum are aromatic oils, paraffinic oils, naphthenic oils, such as those known in the industry as MES (mild extraction solvate), DAE (distillate aromatic extract), TDAE (treated distillate aromatic extract), TRAE (treated residual aromatic extract), RAE (residual aromatic extract).

[0153] The plasticizing oil may be a natural oil or a synthetic oil obtained by esterification of glycerol with fatty acids, including triglycerides, diglycerides, monoglycerides or mixtures thereof.

[0154] Examples of suitable vegetable oils are sunflower oil, soybean oil, linseed oil, rapeseed oil, castor oil and cottonseed oil.

[0155] The plasticizing oil may be a synthetic oil selected from alkyl or aryl esters of phthalic acid or phosphoric acid.

[0156] An example of an oil used in the composite is tri(2-ethylhexyl) phosphate (TOF) from Lanxess.

[0157] Preferably, the natural (eg vegetable) oil or synthetic oil has a glass transition temperature (Tg) below -70°C (according to ISO 28343:2010 standard).

[0158] Examples of suitable commercially available plasticizing oils are those derived from petroleum: NYTEX 4700 sold by Nynas, EXTENSOIL 1471 sold by Repsol, VIVATEC 500 sold by H&R; and vegetable oils: RADIA 6132 sold by Oleon, Agripure AP 18 and Agripure AP 75 sold by Cargill.

[0159] The total amount of oil (including added oil and oil that may already be present as diluent for the elastomeric polymer) may be, for example, from 10 phr to 70 phr.

[0160] The base layer ( 8 b ) compound and the rolling layer ( 8 a ) compound may comprise at least one reinforcing filler in an amount ranging, for example, from 10 phr to 150 phr.

[0161] The reinforcing filler may be selected from carbon black, white filler, silicate fiber or mixtures thereof.

[0162] In one embodiment, the reinforcing filler is a white filler selected from metal hydroxides, oxides and hydrated oxides, salts and hydrated salts, silicate fibers or mixtures thereof. Preferably, the white filler is silicon dioxide.

[0163] Commercial examples of suitable conventional silicas are Zeosil 1165MP from Solvay and Ultrasil 7000GR from Evonik.

[0164] In one embodiment, the reinforcing filler is carbon black.

[0165] Preferably, the carbon black is selected from carbon black having a surface area of ​​not less than 20 m 2 / g, preferably greater than 50m 2 / g of carbon black (determined by STSA-Statistical Thickness Surface Area according to ISO 18852:2005).

[0166] The carbon black may be, for example, N234, N326, N330, N375 or N550, N660 sold by Birla Group (India) or CRX 1391 sold by Cabot Company.

[0167] Reinforcing fillers may include mixtures, such as a mixture of carbon black and silica.

[0168] The base layer (8b) compound and the rolling layer (8a) compound may comprise at least one vulcanizing agent in an amount ranging, for example, from 0.5 phr to 7 phr.

[0169] The at least one vulcanizing agent is preferably selected from sulfur or alternatively sulfur-containing molecules (sulfur donors) such as bis(trialkoxysilyl)propyl]polysulfides and mixtures thereof.

[0170] Preferably, the vulcanizing agent is sulfur, preferably selected from soluble sulfur (crystalline sulfur), insoluble sulfur (polymeric sulfur), (iii) oil-dispersible sulfur and mixtures thereof.

[0171] Commercial examples of vulcanizing agents suitable for use in the elastomeric composition of the present invention are Rhenocure(R) IS90P from RheinChemie or sulphur Redball Superfine from International Sulfur Inc.

[0172] In the elastomer compound of the present invention, the vulcanizing agent may be used together with auxiliary agents known to those skilled in the art (such as a vulcanization activator, a vulcanization accelerator and / or a vulcanization retardant).

[0173] The base layer (8b) compound and the rolling layer (8a) compound may include at least one vulcanization activator.

[0174] Suitable vulcanization activators for the present elastomeric composites are zinc compounds, in particular ZnO, ZnCO3, zinc salts of saturated or unsaturated fatty acids containing 8 to 18 carbon atoms, which are preferably formed in situ in the elastomeric composite by reaction of ZnO and fatty acids or mixtures thereof. For example, zinc stearate (preferably formed in situ from ZnO and fatty acids) or magnesium stearate (formed from MgO) or mixtures thereof may be used.

[0175] The content of vulcanization activator present in the elastomeric compound of the invention may be, for example, from 0.2 phr to 15 phr.

[0176] The preferred activator is derived from the reaction of zinc oxide and stearic acid.

[0177] Examples of activators are Aktiplast ST Rheinchemie and zinc bisneodecanoate VALIKAT Zn1910 Umicore.

[0178] The base layer (8b) compound and the rolling layer (8a) compound may include at least one vulcanization accelerator.

[0179] Commonly used primary and secondary vulcanization accelerators may, for example, be selected from dithiocarbamates, guanidines, thioureas, thiazoles, sulfonamides, sulfonylimides, thiurams, amines, xanthates or mixtures thereof.

[0180] Preferably, the accelerator is selected from mercaptobenzothiazole (MBT), N-cyclohexyl-2-benzothiazolesulfenamide (CBS), N-tert-butyl-2-benzothiazolesulfenamide (TBBS), dibenzothiazyl disulfide (MBTS) and mixtures thereof.

[0181] A commercial example of an accelerator suitable for use in the present elastomeric composite is N-cyclohexyl-2-benzothiazolesulfenamide sold by Lanxess. (CBS or CZ) and N-tert-butyl 2-benzothiazolesulfenamide NZ / EGC, Tetrabenzylthiuram disulfide ( TBzTD), dibenzothiazyl disulfide Rhenogran MBTS 80, N-tert-butyl-2-benzothiazolesulfenamide sold by Huatai Chemicals TBBS.

[0182] The vulcanization accelerator may be used in an amount of, for example, 0.05 to 10 phr.

[0183] The base layer (8b) compound and the rolling layer (8a) compound may include at least one vulcanization retardant.

[0184] The vulcanization retarder may be selected from urea, phthalic anhydride, N-nitrosodiphenylamine, N-cyclohexylthiophthalimide (CTP or PVI) and mixtures thereof.

[0185] A commercial example of a suitable retarder is N-cyclohexylthiophthalimide VULKALENT G from Lanxess.

[0186] The content of the vulcanization retarder may be, for example, 0.05 to 2 phr.

[0187] The base layer (8b) composite and the rolling layer (8a) composite may include at least one silane coupling agent in an amount of, for example, 0.5 phr to 10.0 phr.

[0188] Preferably, the coupling agent is selected from agents having at least one hydrolyzable silane group, which can be identified, for example, by the following structural formula (III):

[0189] (R')3Si-C n H 2n -X(III)

[0190] wherein the R' groups are identical or different and are selected from: alkyl, alkoxy or aryloxy or halogen atoms, provided that at least one of the R' groups is an alkoxy group or an aryloxy group; n is an integer from 1 to 6; and X is a group selected from: nitroso, mercapto, amino, epoxide, vinyl, imide, chlorine, -(S) m C n H 2n -Si-(R')3 and -S-COR', wherein m and n are integers from 1 to 6, and the R' group is as defined above.

[0191] Preferred silane coupling agents are bis(3-triethoxysilylpropyl)tetrasulfide and bis(3-triethoxysilylpropyl)disulfide. The coupling agents may be added directly or mixed with an inert filler such as carbon black to facilitate their incorporation into the elastomeric compound.

[0192] An example of a silane coupling agent is TESPT: bis(3-triethoxysilylpropyl)tetrasulfide Si69 sold by Evonik.

[0193] The base layer (8b) compound and the rolling layer (8a) compound may include additional ingredients commonly used in the art, such as antioxidants and / or antiozonants (anti-aging agents), waxes, adhesives, and the like.

[0194] The base layer (8b) compound and the rolling layer (8a) compound may comprise at least one wax, such as a petroleum wax or a paraffin wax mixture, in an amount ranging for example from 0.1 phr to 20 phr.

[0195] Commercial examples of suitable waxes are Repsol N - paraffin wax mixture and 654 microcrystalline wax.

[0196] The base layer (8b) composition and the rolling layer (8a) composition may include at least one antioxidant in a total amount ranging from 0.1 phr to 20 phr, for example.

[0197] The antioxidant is preferably selected from N-isopropyl-N'-phenyl-p-phenylenediamine (IPPD), N-(1,3-dimethyl-butyl)-n'-phenyl-p-phenylenediamine (6PPD), N,N'-bis-(1,4-dimethyl-pentyl)-p-phenylenediamine (77PD), N,N'-bis-(1-ethyl-3-methyl-pentyl)-p-phenylenediamine (DOPD), N,N'-bis-(1,4-dimethyl-pentyl)-p-phenylenediamine, N,N'-diphenyl-p-phenylenediamine (DPPD), N,N'-ditolyl-p-phenylenediamine (DTPD), N,N'-di-β-naphthyl-p-phenylenediamine (DNPD), N,N'-bis(1-methylheptyl)-p-phenylenediamine, N,N'-di-sec-butyl-p-phenylenediamine (44PD), N-phenyl-N-cyclohexyl-p-phenylenediamine, N-phenyl-N'-1-methylheptyl-p-phenylenediamine and the like and mixtures thereof.

[0198] A commercial example of a suitable antioxidant is 6PPD from Solutia / Eastman.

[0199] In a preferred embodiment, the first elastomer compound is obtained by vulcanizing an elastomer composition comprising:

[0200] 0 to 30 phr of at least one liquid polymer,

[0201] 0 to 20 phr of at least one resin,

[0202] 10 to 60 phr of at least one plasticizing oil,

[0203] wherein the sum of the liquid polymer, the resin (if present) and the plasticizing oil is 20 to 90 phr,

[0204] 100 phr of a mixture of solid diene elastomeric polymers, wherein the mixture of solid diene elastomeric polymers comprises:

[0205] 10 to 50 phr of at least one solid polybutadiene (BR) having a weight average molecular weight Mw between 300,000 g / mol and 600,000 g / mol and a cis double bond content of at least 95%,

[0206] 10 to 70 phr of at least one emulsion polymerized solid styrene butadiene copolymer (E-SBR) having a Tg of -60°C to -20°C, a Mooney viscosity of 30 MU to 70 MU at 160°C, and a styrene content of between 15% and 50%,

[0207] 10 to 80 phr of at least one solution polymerized solid styrene butadiene copolymer (S-SBR) chain functionalized with a multibranched coupling agent having:

[0208] a weight average molecular weight Mw greater than 500,000 g / mol; and / or

[0209] Styrene in an amount between 25% and 50% and vinyl in an amount between 10% and 50%; and / or

[0210] A Tg between -50°C and -20°C; and / or

[0211] Mooney viscosity between 60 MU and 100 MU at 160°C,

[0212] at least 40 phr of at least one reinforcing filler, and

[0213] At least 1.0 phr of at least one vulcanizing agent.

[0214] In a preferred embodiment, the second elastomeric compound is obtained by vulcanizing an elastomeric composition comprising:

[0215] 0 to 20 phr of at least one liquid polymer,

[0216] 5 to 40 phr of at least one resin,

[0217] 10 to 60 phr of at least one plasticizing oil,

[0218] The total amount of liquid polymer, resin (if present) and plasticizing oil is between 15 and 120 phr,

[0219] 100 phr of a mixture of solid diene elastomeric polymers, wherein the mixture of solid diene elastomeric polymers comprises:

[0220] 10 to 40 phr of at least one solid polybutadiene (BR), preferably having a weight average molecular weight Mw between 200,000 and 600,000 g / mol and a cis double bond content of at least 30%,

[0221] 60 to 90 phr of at least one continuously produced end-functionalized solution-polymerized solid styrene butadiene copolymer (S-SBR), preferably having a weight average molecular weight Mw greater than 500,000 g / mol, preferably greater than 800,000 g / mol, more preferably greater than 900,000 g / mol, an amount of styrene between 25% and 50%, an amount of vinyl between 10% and 70%, preferably between 10% and 50%, a Tg between -50°C and -10°C, and / or a Mooney viscosity at 100°C between 50 MU and 100 MU,

[0222] at least 50 phr of at least one reinforcing filler, and

[0223] At least 1.0 phr of at least one vulcanizing agent. BRIEF DESCRIPTION OF THE DRAWINGS

[0224] Figure 1 is a schematic diagram of a radial section of a rear tyre for motorcycles according to the present invention, wherein, for ease of illustration, the tread band is shown without grooves and blocks, wherein the arrangement of the crown (8a) and base (8b) is highlighted.

[0225] Figure 2 is a perspective view of a typical large endurance type knobby rear tire according to the present invention, in which the central annular portion (A) and the annular shoulder portions (B) can be seen in dotted lines. DETAILED DESCRIPTION

[0226] refer to Figure 1 and Figure 2 , reference numeral 1 denotes a motorcycle tire according to the present invention.

[0227] Tire 1 is a rear tire, but the following description is equally applicable to the front tire, except that specific reference is made to the rear tire.

[0228] Tire 1 is a motorcycle tire, which is defined as having a large engine capacity (e.g., equal to 1000 cm 3 ) and a large endurance type motorcycle with high power (e.g. equal to 100 hp), and the mass of the motorcycle in the riding position is equal to, for example, 200 kg or more.

[0229] The tire 1 typically has a maximum radial cross-sectional width of between 90 mm and 170 mm (e.g., between 90 mm and 120 mm in the case of a front tire and between 130 mm and 170 mm in the case of a rear tire) and is intended to be mounted on wheels having a seating diameter of between about 17 inches and about 21 inches (e.g., between 19 inches and 21 inches in the case of a front tire and between 17 inches and 18 inches in the case of a rear tire).

[0230] In tire 1, an equatorial plane "XX" ( Figure 1 ) and the rotation axis R( Figure 2 ). A circumferential direction arranged according to the direction of rotation of the tyre 1 and therefore parallel to the equatorial plane XX, and an axial direction r perpendicular to the equatorial plane "XX" and / or parallel to the axis of rotation R are also defined.

[0231] The tyre 1 comprises a carcass structure 2 formed by at least one carcass ply 3 consisting of a sheet of elastomeric material incorporating a plurality of reinforcing cords made of a fibrous textile material (not shown).

[0232] exist Figure 1 In the tire, the carcass structure 2 is of radial type, that is, the reinforcing cords of the at least one carcass layer 3 are substantially parallel to each other and arranged in radial direction, that is, at an angle between 70° and 110°, more preferably between 80° and 100°, relative to the circumferential direction.

[0233] In an embodiment not shown, the carcass structure comprises at least two radially superimposed carcass plies. In this case, the reinforcing cords are substantially parallel to each other in each carcass ply and are oriented in an inclined direction (e.g. at least 45°) relative to the equatorial plane of the tire in each carcass ply and according to the opposite direction of the cords relative to the radially adjacent carcass ply 3 (cross-ply carcass).

[0234] The carcass structure 2 is usually coated on its inner wall with a sealing layer 100 or so-called liner, which is mainly composed of a layer of airtight elastomeric material suitable for ensuring the airtightness of the tyre 1 itself after inflation.

[0235] The (or each) carcass ply 3 is shaped according to a substantially annular configuration and its axially opposite lateral edges 3a are turned up towards respective annular reinforcing structures 4 intended to retain the tyre 1 on a corresponding mounting rim (not shown). The annular reinforcing structures 4 are generally called bead cores.

[0236] A conical elastomeric filler 5 is applied to the peripheral edge of the bead core 4 , occupying the space defined between each carcass ply 3 and the corresponding turned-up lateral edge 3 a of the carcass ply 3 .

[0237] In another alternative embodiment that is not shown, each carcass ply has opposite lateral edges associated without flaps with a specific annular reinforcing structure provided with two annular metal inserts.

[0238] The region of the tyre 1 comprising the bead core 4 and the elastomeric filler 5 forms a so-called bead 9 intended to anchor the tyre 1 to a rim (not shown).

[0239] Preferably, at a radially outer position to the carcass (whether radial or cross-ply), a carcass reinforcement structure may advantageously be arranged.

[0240] The reinforcement structure comprises a crown ply arranged radially outermost of the radially external carcass plies, at least for the crown portion. The crown ply is made of reinforcing elements arranged parallel to each other and arranged so that the reinforcing elements have an opposite angle with respect to the equatorial plane than the reinforcing elements of the radially outermost carcass ply. Optionally, the carcass reinforcement structure comprises two plies arranged laterally to the crown ply and axially opposite with respect to the equatorial plane and not associated with the respective beads.

[0241] In one embodiment thereof, the carcass ply 3 (or each carcass ply 3) is composed of a plurality of strips of elastomeric material reinforced by the aforementioned cords.

[0242] A belt structure 6 is circumferentially applied to the carcass structure 2 at a radially outer position, said carcass structure comprising at least one belt layer 6a, typically formed of rubberized textile or metal cords.

[0243] Preferably, the belt structure 6 is of the zero degree type, i.e. the belt layer 6a is made of cords arranged substantially parallel and side by side to form a plurality of turns. Such turns are substantially oriented according to a circumferential direction (generally with an angle between 0° and 5°), this direction generally referred to as "zero degree" with reference to its lay relative to the circumferential direction of the tyre 1.

[0244] Preferably, the belt layer 6a, often called "zero degree", may comprise a single cord or axially side-by-side windings of a rubberized fabric belt comprising axially side-by-side cords.

[0245] The cords of the zero-degree belt 6a are generally metal cords made of high-carbon steel wires, ie steel wires having a carbon content of at least 0.6%-0.7%. Preferably, these metal cords have a high elongation (HE).

[0246] In order to improve the adhesion between the belt structure 6 and the carcass structure 2, an adhesive layer 7 made of elastomeric material may be interposed between the two structures.

[0247] In various embodiments, the belt structure 6 has two or more radially superposed belt layers, each layer consisting of an elastomeric material reinforced with cords arranged parallel to one another. The layers are arranged in such a way that the cords of a first belt layer are oriented obliquely with respect to the equatorial plane of the tire, while the cords of a radially adjacent belt layer also have an orientation oblique but crossed with respect to the cords of the first layer (so-called cross belts), and the same is true for any other belt layers. The cross belts are usually fabric cords.

[0248] Superimposed circumferentially on the belt structure 6 is a tread band (8) on which, after a moulding operation carried out simultaneously with the vulcanisation step of the tyre 1, circumferential and transverse grooves are generally obtained, arranged so as to define a plurality of blocks according to the geometry detailed in the remainder of this specification.

[0249] According to a preferred embodiment, the tread band (8) (as well as the other components of the tyre) are made of an elastomeric material as described above.

[0250] The tread band (8) comprises a central annular portion (A) and a pair of annular shoulder portions (B), wherein the central annular portion is symmetrically arranged across the equatorial plane (XX), and the pair of annular shoulder portions (B) are symmetrically arranged on opposite sides relative to the central annular portion (A) and adjacent to the central annular portion.

[0251] The central annular portion (A) extends over a width comprised between 70% and 90%, preferably between 75% and 85% of the tread band width.

[0252] The tread band (8) is of the crown and base type, having overall a total radial thickness S which can vary between the center and the shoulder, and comprising a rolling layer (8a) (crown) located in the radially outermost position and having a radial thickness S1, and a bottom layer (8b) (base) arranged in the radially innermost position and adjacent thereto and having a radial thickness S2. The total radial thickness S of the tread band (8) = S1 + S2.

[0253] The rolling layer (8a) extends axially across the entire width of the central annular portion (A), while the base layer (8b) extends axially across the entire width of the tread band or across the entire width of said central annular portion (A) and across the entire width of each annular shoulder portion (B).

[0254] Each annular shoulder portion (B) extends axially for a width between 5% and 15%, preferably between 7.5% and 12.5% ​​of the tread band width and is made of said underlayer (8b) for the entire total radial thickness S of the tread band.

[0255] Table 1 below provides some examples of possible measurements of crown and base extensions for certain types of tires according to the invention:

[0256] Table 1

[0257]

[0258] The tyre 1 may also comprise a pair of sidewalls 10 applied laterally to opposite sides of said carcass structure 2 .

[0259] refer to Figure 1 , the tyre 1 has a cross-sectional height "H" measured on the equatorial plane "XX" between the top of the tread band (8) and the fitting diameter identified by a reference line "r" passing through the bead 9 of the tyre 1.

[0260] The tyre 1 also has a maximum radial section width "C" defined by the distance between the laterally opposite ends "E" of the tread band 8 measured on the equatorial plane "XX" of the tyre 1, and a deflection "f" defined by the distance between the top of the tread band (8) and a line passing through said laterally opposite ends "E" measured on the equatorial plane "XX" of the tyre 1. The laterally opposite ends "E" of the tread band (8) may be formed with corners.

[0261] The tire 1 has a "camber ratio" (f / C) which is defined by the ratio between the deflection "f" and the aforementioned maximum radial section width "C".

[0262] The tire 1 has a "deflection height to total height" ratio (f / H) given by the ratio between the deflection "f" and the section height "H".

[0263] Figure 1 Reference numerals ("H", "XX", "r", "C", "f", "E") for the rear tires have been indicated, but they are also the same as the reference numerals for the front tires.

[0264] Preferably, the deflection "f" of the tyre 1 is between about 40 mm and about 60 mm.

[0265] The camber ratio "f / C" of the tire 1 is between about 0.25 and about 0.35, for example equal to about 0.26.

[0266] The ratio of the deflection height to the total height "f / H" of the tire 1 is between about 0.40 and about 0.60, for example equal to about 0.43.

[0267] In the case of a front tire, the deflection "f" is between about 35 mm and about 60 mm, and the camber ratio "f / C" is between about 0.30 and about 0.40, for example equal to 0.38.

[0268] Still in the case of a front tire, the ratio of the deflection height to the total height "f / H" is between about 0.40 and about 0.60, for example equal to about 0.53.

[0269] like Figure 2 As shown, the tyre 1 according to the invention is of the articulated type, ie it comprises a plurality of transverse and circumferential grooves which define a plurality of blocks spaced apart from one another.

[0270] The blocks and the grooves define a tread pattern having a hollow / solid ratio between 0.40 and 0.65, preferably between 0.50 and 0.60, for example a hollow / solid ratio equal to 0.51 in the case of a rear tire measuring 170 / 60 / R17 and a hollow / solid ratio equal to 0.56 in the case of a rear tire measuring 150 / 70 / R18.

[0271] Experimental Section

[0272] Evaluation Methodology

[0273] The static mechanical properties (CA1 load at 100% elongation, CA3 load at 300% elongation) were measured at 23°C on samples of elastomeric material vulcanized at 170°C for 10 minutes according to UNI 6065:2001 standard.

[0274] The dynamic mechanical properties E', E" and Tan delta were measured using an Instron model 1341 dynamic device in the tension-compression mode as described herein. The cross-linked material specimens (170°C, 10 minutes) were subjected to dynamic sinusoidal strain with an amplitude of ±3.5% relative to the length under preload and a frequency of 10 Hz or 100 Hz. The cross-linked material specimens were cylindrical in shape (length = 25 mm; diameter = 14 mm), compressively preloaded until the longitudinal strain reached 25% of the initial length and maintained at a predetermined temperature of 23°C or 70°C during the entire test. The dynamic mechanical properties are expressed as dynamic elastic modulus (E'), dynamic viscous modulus (E") and Tan delta (loss factor). The Tan delta value is calculated as the ratio between the viscous dynamic modulus (E") and the dynamic elastic modulus (E'). In accordance with ISO48:2007 standard, the IRHD hardness (23°C) was measured on the above-mentioned elastomeric material samples vulcanized at 170°C for 10 minutes.

[0275] Preparation of complexes

[0276] The base complexes MB1 (INV), MB2 (REF) and the crown complexes MC1 (INV) and MC2 (REF) were prepared starting from the compositions detailed in Table 2 below:

[0277] Table 2: Composition of the complex (phr)

[0278]

[0279]

[0280]

[0281] Wherein, *Extender oil (total polymer + oil phr*)

[0282] NR is natural rubber (Standard Thai Rubber STR20-Thaiteck Rubber);

[0283] TUFDENE E680 (S-SBR) is a solution polymerized styrene-butadiene polymer with 37.5 parts of TDAE oil per 100 parts of dry polymer (107.3 phr of Tufdene E680 contains 78 phr of dry polymer);

[0284] SBR 1739 is SB 1739-Schkopau, E-SBR made by cold emulsion polymerization using mixed rosin / fatty acid soaps. It is plasticized with 37.5 parts of TDAE oil relative to solid rubber (60.5 phr and 76 phr of SB 1739 contained 44 and 55.3 phr of dry polymer, respectively);

[0285] YB03 Asaprene is a low cis-functionalized polybutadiene polymer;

[0286] SBR 1723 is a styrene-butadiene polymer in emulsion obtained by cold polymerization using a mixture of rosin acid and fatty acid soap as emulsifier, with a Tg of about -50°C, with 37.5 parts of TDAE oil;

[0287] HPR620 is a styrene butadiene copolymer prepared in solution by a continuous process as described in SG 10201800553S(A) and functionalized in the chain by a polyorganosiloxane multibranched coupling agent, having a weight average molecular weight of about 1,000,000 g / mol, a styrene content of about 40%, a vinyl content of about 25%, a Tg of about -33°C, a Mooney viscosity of about 80 MU (Mooney viscosity ML(3+4) at 160°C), and 25 parts of TDAE oil relative to solid rubber (32.5 phr of HPR620 contains 26 phr of dry polymer);

[0288] BR is Neocis BR 60, a polybutadiene with a high cis content (minimum 97%) produced in solution using a neodymium organometallic catalyst;

[0289] N234 is a high surface area carbon black (STSA 112m 2 / g);

[0290] CRX 1391 is a high surface area carbon black (STSA 156m 2 / g);

[0291] PERKASIL 408 is KS 408 precipitated silica, which has a high surface area (BET 175m 2 / g);

[0292] ZEOSIL 1165MP is a microsphere silica with a high specific surface area BET 165m 2 / g;

[0293] ULTRASIL 7000 is a high surface area (BET 175m 2 / g) of precipitated silica;

[0294] RICON 100 is a low molecular weight (Mn 4500) liquid (25% styrene) butadiene styrene copolymer (PBS) with a Tg of -57°C;

[0295] TDAE is a distilled aromatic extract treated with an aromatic oil plasticizer. 500(plasticizer);

[0296] POLYVEST 130 is a stereospecific, low viscosity, unsaponifiable liquid polybutadiene with a high content of 1,4-cis double bonds (77% 1,4-cis double bonds, 22% 1,4-trans double bonds, 1% 1,2-vinyl double bonds), a Tg of -99°C, and a weight average molecular weight of 12,000 g / mol;

[0297] TOF is a plasticizer: tri(2-ethylhexyl) phosphate;

[0298] RESIN 2495 is a terpene resin;

[0299] RASINA CUMARON is a coumarone resin;

[0300] RHENOSIN TT 90 is a tackifying dispersed hydrocarbon resin;

[0301] NOVARES TT 30 is a hydrocarbon resin produced by polymerization of C9 / C10 unsaturated aromatic hydrocarbons;

[0302] α-Methylstyrene resin is a thermoplastic resin;

[0303] Zinc neodecanoate 50 is the zinc salt of neodecanoic acid;

[0304] RHENOGRAN ZNO is zinc oxide;

[0305] ACID GRAS SARE DE ZINC is the zinc salt of fatty acids;

[0306] The liquid silane was SI 69-bis[3-(triethoxysilyl)propyl]polysulfide;

[0307] The wax is BMO1, which is a mixture of N-alkanes and isoalkanes;

[0308] 6PPD is N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine, which is an antiozonant;

[0309] Sulfur is Lanxess IS 90-20, which is a mixture of insoluble sulfur / soluble sulfur in a ratio of 90:10 with 20% oil added;

[0310] TBBS is N-tert-butyl-2-benzothiazolesulfonamide;

[0311] MBTS 80 is dibenzothiazyl disulfide;

[0312] DURALINK TS is hexamethylene-1,6-bis(thiosulfate) disodium salt;

[0313] TBZTD is ( TBzTD) Tetrabenzylthiourea disulfide.

[0314] The elastomeric compound was prepared according to the following process.

[0315] The mixing of the components was carried out in two steps using an internal mixer (Banbury, Intermix or Brabender).

[0316] In the first step (1), all ingredients except the vulcanizing agent and the accelerator have been introduced. Mixing lasts for a maximum of 5 minutes, with a temperature of about 145°C. Subsequently, in a second step (2), again using an internal mixer, the vulcanizing agent and the accelerator are added and mixing is continued for about 4 minutes, while keeping the temperature below 100°C. The compound is then unloaded. After cooling, at least 12 hours from preparation, some samples of the compound are vulcanized in a press at 170°C for 10 minutes to obtain samples that can be used for mechanical properties.

[0317] Properties of the composite

[0318] The main static and dynamic properties and hardness of the above elastomer composite measured by the above method are shown in Table 3 below:

[0319] Table 3

[0320]

[0321]

[0322] Keywords: base complex MB (second complex), crown complex MC (first complex); INV: present invention; REF: reference

[0323] The compounds used to make the tyres according to the invention were MB1 and MC1, wherein MC1 constituted the radially external central annular portion (A) of the tread band and MB1 constituted the radially internal sublayer rising to the surface in the annular shoulder portions (B) (see comparative tests below).

[0324] As can be seen from Table 3, the compounds MB1 and MC1 suitable for making the tyre of the invention have quite different properties compared to the previous compounds of base layer MB2 and rolling layer MC2 used in conventional cap and base tread bands (see tyre REF1 below).

[0325] In particular, it can be observed that, under all conditions tested, the base composite MB1 and the crown composite MC1 have significantly lower IRHD hardness and E' modulus values ​​compared to the composites MB2 and MC2, respectively.

[0326] The Applicant has realized that, despite the simultaneous presence of different compounds in the tread band of the present tire, it behaves quite homogeneously in use, almost as if it were made of a single material with tread moduli and hysteresis in the various parts being comparable to each other under operating conditions.

[0327] This phenomenon is emphasized by the modulus and hysteresis measurements obtained under real conditions for the different compounds running in the specific portion of the tread band in which they are located, as evidenced by the E' and tan delta values ​​for the different regimes shown in this Table 3.

[0328] In this regard, the dynamic mechanical properties of the composites of the invention were evaluated at different levels of dynamic stress (stress of samples at frequencies of 10 Hz and 100 Hz) and at different temperatures (23°C and 70°C) in order to reproduce the conditions to which they are subjected in on-road and off-road driving.

[0329] In particular, considering highway driving, it is possible to identify the following thermal conditions and relative measurement conditions of the modulus that may occur during operation, as shown in Table 4 below:

[0330] Table 4: Highway driving

[0331]

[0332] *See below for the configuration of the tire according to the invention

[0333] As can be seen in Table 3, under these conditions (ie 100 Hz, 23° C. for the shoulders and 10 Hz, 23° C. for the core), the E′ modulus of the shoulder compound (MB1) and the core compound (MC1) are almost identical (7.77 and 7.79).

[0334] Instead, considering off-road driving, it is possible to identify the following thermal conditions that may occur during operation and the relative measurement conditions of the modules, as shown in Table 5 below:

[0335] Table 5: Off-road driving

[0336]

[0337] During off-road driving, the center ring section is at high temperatures, but the stresses are macroscopic (block bonding) rather than microscopic (sliding), so the measurement frequency is 10 Hz.

[0338] As can be seen from Table 3, under these conditions (ie 100 Hz, 70°C for the shoulders and 10 Hz, 70°C for the core), the shoulder compound (MB1) and the core compound (MC1) have very close E' moduli (4.90 and 5.20).

[0339] Comparison Test

[0340] The applicant has produced an example of a rear tire 1 measuring 170 / 60R17 according to one embodiment of the invention and in particular having Figure 1 The crown and base arrangement shown and having Figure 2Tread pattern shown.

[0341] The cap layer is made of MC1 compound, while the base layer is made of MB1 compound. This tire is hereinafter referred to as INV.

[0342] Two reference rear tires were also produced, called REF1 and REF2, which:

[0343] - in REF1, the cap and base layers are annular and extend axially along the entire width of the tread band and consist of MC2 and MB2 respectively;

[0344] - In REF2, the crown and base layers are arranged according to the invention and consist of MC2 and MB1 respectively.

[0345] Outdoor tests were carried out to compare the tire of the invention with tires REF1 and REF2.

[0346] The REF1 tyre is a large endurance type tyre produced by the applicant and is appreciated by customers for its excellent off-road performance and its performance on both dry and wet roads, which is considered more acceptable.

[0347] The REF2 tire is a prototype tire built for comparison purposes to evaluate the impact of the properties of the cap and base compounds on the performance of tires having the same tread structure (cap and base arranged according to the invention).

[0348] The relevant measurement results of the tread band and its components of the tire INV of the present invention and the comparative tires REF1 and REF2 are shown in Table 6 below:

[0349] Table 6

[0350]

[0351]

[0352] The test was conducted by mounting a tire (inflated with the same pressure) on the rear wheel of a BMW GS1250R motorcycle and mounting the same tire on the front wheel under essentially the same environmental conditions. The front tire size was 120 / 70R19 with a 3.00×19 rim, and the inflation pressure was 2.0 bar for off-road testing and 2.5 bar for road testing. The rear tire size was 170 / 60R17 with a 4.50x17 rim, and the inflation pressure was 2.0 bar for off-road testing and 2.9 bar for road testing.

[0353] The behaviour of the INV, REF1 and REF2 tyres in on-road (dry and wet) and off-road conditions was evaluated and the drivers' opinions were asked. In particular, the items listed in the following Tables 7, 8 and 9 were evaluated, in which the opinions expressed by the drivers are also shown. The on-road tests were carried out along a route with straight sections and curves, both including dry and wet roads. The off-road tests were carried out by covering a straight section of a predetermined length several times, which was prepared with mud and sand that simulates the conditions that may occur in the natural environment, keeping the ground as homogeneous as possible after each test. 2 sensors were installed on the straight to determine when the motorcycle enters and exits, which is equipped with appropriate instruments (GPS sensor, engine throttle opening sensor and speed sensors on both wheels).

[0354] Table 7 relates to dry road testing. Table 8 relates to wet road testing. Table 9 relates to off-road testing.

[0355] In Tables 7-9, "=" indicates that the rating is equivalent to the rating obtained by the REF1 tire, and "+" and "-" indicate improvement or deterioration compared to the REF1 tire.

[0356] Table 7: Dry road test

[0357]

[0358]

[0359] Table 8: Wet road test

[0360]

[0361] Table 9: Off-road test

[0362]

[0363] Tables 7 and 8 show that the INV tire unexpectedly provides improved performance overall on road surfaces compared to the REF1 tire, particularly in terms of comfort and handling in contact with dry road surfaces and wet road grip, while in other evaluation items, its behavior is consistent with that of the REF1 tire. On the other hand, the REF2 tire proves to be inferior because the crown composite MC2 does not have the characteristics of the crown composite MC1 of the present invention.

[0364] The Applicant has thus demonstrated that the tyre of the invention, using a specific compound combined with a specific arrangement, actually achieves a surprising improvement in performance both on dry and on wet road surfaces.

[0365] Table 9, on the contrary, highlights the unexpected improvement in off-road performance in all the test items. This improvement was unforeseeable and far exceeded the expectations of the Applicant, which had set the goal of maintaining the excellent off-road performance of the reference tire (REF1).

Claims

1. A tyre (1) for an on-road / off-road motorcycle (large endurance type), said tyre comprising a tread band (8) of total radial thickness S, said tread band comprising a plurality of blocks and grooves defining in the tread band (8) a void / solid ratio between 0.40 and 0.65, said tread band (8) comprising a central annular portion (A) and a pair of annular shoulder portions (B), said central annular portion being arranged symmetrically across an equatorial plane (XX), said pair of annular shoulder portions being arranged symmetrically on opposite sides relative to said central annular portion (A) and adjacent to said central annular portion, wherein: - said central annular portion (A) extends axially over a width comprised between 70% and 90% of the width of said tread band and comprises a rolling layer (8a) of radial thickness S1 situated in the outermost radial position and a base layer (8b) of radial thickness S2 arranged adjacent to said rolling layer in the innermost radial position, said tread band (8) having a total radial thickness S=S1+S2, said rolling layer (8a) extending axially across the entire width of said central annular portion (A), and said bottom layer (8b) extending axially across the entire width of said central annular portion (A) and across the entire width of each of said annular shoulder portions (B), - each said annular shoulder portion (B) extends axially over a width comprised between 5% and 15% of the width of said tread band and is constituted by said base layer (8b) over the entire total radial thickness S of said tread band, wherein the rolling layer (8a) comprises a first elastomeric compound characterized by an E' modulus between 5.00 MPa and 6.50 MPa, wherein the bottom layer (8b) comprises a second elastomeric compound characterized by an E' modulus between 3.50 MPa and 4.60 MPa, and wherein the E' modulus is measured at 70°C and 10 Hz according to the method described in the experimental section, and wherein the percentage ratio between the E' modulus of the second elastomeric compound and the E' modulus of the first elastomeric compound is between 70% and 90%.

2. The tire according to claim 1, wherein: Said total radial thickness S of said tread band (8) is between 10 and 20 mm, preferably between 12 and 16 mm.

3. The tire according to claim 1 or 2, wherein: The radial thickness S1 of the rolling layer (8a) in the central annular part (A) is between 9 mm and 17 mm, preferably between 11 mm and 15 mm, and the radial thickness S2 of the bottom layer (8b) in the central annular part (A) is between 0.8 mm and 4 mm, more preferably between 1.0 mm and 3 mm.

4. A tyre according to any one of the preceding claims, wherein: Said central annular portion (A) extends axially over a width comprised between 75% and 85% of the tread band width and said annular shoulder portions (B) each extend axially over a width comprised between 7.5% and 12.5% ​​of said tread band width.

5. A tyre according to any one of the preceding claims, wherein: The percentage of said E' modulus of said second elastomeric compound to said E' modulus of said first elastomeric compound is between 75% and 90%, preferably between 80% and 85%.

6. A tyre according to any one of the preceding claims, wherein: The difference between the E' modulus of the first elastomeric compound and the E' modulus of the second elastomeric compound is between 0.3 MPa and 2.3 MPa, preferably between 0.4 MPa and 1.5 MPa, more preferably between 0.6 MPa and 1.1 MPa.

7. A tyre according to any one of the preceding claims, wherein: The first elastomeric compound is characterized by an E' modulus between 5.00 MPa and 6.00 MPa, preferably between 5.00 MPa and 5.50 MPa, and the second elastomeric compound is characterized by an E' modulus between 4.00 MPa and 4.50 MPa, preferably between 4.20 MPa and 4.40 MPa.

8. A tyre according to any one of the preceding claims, wherein: The first elastomeric compound is characterized by a tan delta between 0.220 and 0.280, preferably between 0.230 and 0.270, and the second elastomeric compound is characterized by a tan delta between 0.120 and 0.180, preferably between 0.135 and 0.150, wherein the tandelta is measured at 70°C, 10 Hz.

9. A tyre according to any one of the preceding claims, wherein: The first elastomeric compound is characterized by an IRHD hardness between 66 and 76, preferably between 68 and 74, and the second elastomeric compound is characterized by an IRHD hardness between 63 and 73, preferably between 65 and 71, wherein the IRHD hardness is measured at 23°C.

10. The tire according to any one of the preceding claims, wherein: said first elastomeric compound being characterized by a load CA1 at 100% elongation of between 1.7 MPa and 2.3 MPa, preferably between 1.9 MPa and 2.1 MPa, and / or a load CA3 at 300% elongation of between 7.7 MPa and 10.5 MPa, preferably between 8.6 MPa and 9.5 MPa, and - Said second elastomeric compound is characterized by a load CA1 at 100% elongation of between 1.7 MPa and 2.3 MPa, preferably between 1.9 MPa and 2.1 MPa, and / or a load CA3 at 300% elongation of between 8.6 MPa and 11.7 MPa, preferably between 9.7 MPa and 10.7 MPa, wherein said load CA1 and load CA3 are measured at 23°C according to UNI 6065:2001 standard.

11. The tire according to any one of the preceding claims, wherein: The first elastomeric compound for the rolling layer (8a) is obtained by vulcanizing an elastomeric composition comprising: 0 to 30 phr of at least one liquid polymer, 0 to 20 phr of at least one resin, 10 to 60 phr of at least one plasticizing oil, wherein the sum of the liquid polymer, the resin and the plasticizing oil, if present, is from 20 to 90 phr, 100 phr of a mixture of solid diene elastomeric polymers, wherein the mixture of solid diene elastomeric polymers comprises: 10 to 50 phr of at least one solid polybutadiene (BR) having: a weight average molecular weight Mw between 300,000 g / mol and 600,000 g / mol, and A cis double bond content of at least 95%, 10 to 70 phr of at least one emulsion-polymerized solid styrene butadiene copolymer (E-SBR) having: -60℃ to -20℃ Tg, a Mooney viscosity between 30 MU and 70 MU at 160°C, and A styrene content between 15% and 50%, 10 to 80 phr of at least one solution polymerized solid styrene butadiene copolymer (S-SBR) chain functionalized with a multibranch coupling agent, the solution polymerized solid styrene butadiene copolymer having: a weight average molecular weight Mw greater than 500,000 g / mol, and / or Styrene in an amount between 25% and 50% and vinyl in an amount between 10% and 50%, and / or Tg between -50°C and -20°C, and / or Mooney viscosity between 60MU and 100MU at 160°C, at least 40 phr of at least one reinforcing filler, and At least 1.0 phr of at least one vulcanizing agent.

12. A tyre according to any one of the preceding claims, wherein: The second elastomeric compound for the base layer (8b) is obtained by vulcanizing an elastomeric composition comprising: 0 to 20 phr of at least one liquid polymer, 5 to 40 phr of at least one resin, 10 to 60 phr of at least one plasticizing oil, wherein the sum of the liquid polymer, the resin and the plasticizing oil, if present, is from 15 to 120 phr, 100 phr of a mixture of solid diene elastomeric polymers, wherein said mixture of solid diene elastomeric polymers comprises: 10 to 40 phr of at least one solid polybutadiene (BR), preferably having a weight average molecular weight Mw between 200,000 and 600,000 g / mol and a cis double bond content of at least 30%, 60 to 90 phr of at least one continuously prepared end-functionalized solution-polymerized solid styrene butadiene copolymer (S-SBR), preferably having a weight average molecular weight Mw greater than 500,000 g / mol, an amount of styrene between 25% and 50% and an amount of vinyl between 10% and 70%, a Tg between -50°C and -10°C and / or a Mooney viscosity at 100°C between 50 MU and 100 MU, at least 50 phr of at least one reinforcing filler, and At least 1.0 phr of at least one vulcanizing agent.

13. A tyre according to any one of the preceding claims, intended primarily for off-road use.

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