Big enduro motorcycle tires

Abstract

The present invention relates mainly to a big enduro type motorcycle tire for off-road use. By virtue of a specific "cap and base" configuration of the tread band and of the specific mechanical properties of the compounds constituting it, the tire according to the invention improves the performance both on dry and wet surfaces, both in off-road and road driving.

Description

[Technical Field]

[0001] The present invention relates to tires for motorcycles, and more particularly to tires for motorcycles of the big enduro type. [Background technology]

[0002] Big enduro or on / off-road motorcycles, also known as big adventuring or dual-purpose, are motorcycles with high engine displacement, power, and mass that are designed to be ridden both on paved roads and off-road. These motorcycles are generally designed for a maximum of 1000 cm 3 It has a cylinder volume of more than 100 hp, a maximum torque of more than 100 Nm, and a mass of more than 180 kg.

[0003] Examples of big enduro motorcycles are the BMW GS 1250R, Ducati Multistrada V4, KTM 1290 Super Adventure R, and Honda CRF1100L Africa Twin.

[0004] Motorcycles in this segment have a very wide range of uses, ranging from purely road use, corresponding to sport touring, which also tends towards supersports, to off-road use that is more demanding than simply levelled roads, such as driving on so-called taped, unpaved tracks or on routes including riverbeds, soft terrain, mud, sand and bumps of various types and difficulties.

[0005] To satisfy all these types of uses, there are a variety of tire products on the market, each focused on a clearly defined use, such as for example road sports driving, road tourist driving, combined off-road driving, on-road driving combined with easy off-road driving, or heavy off-road driving combined with on-road driving.

[0006] Typically, big enduro motorcycle tires, which are primarily intended for severe off-road use combined with road riding, are marked M+S and are approved to reach a maximum speed of, for example, 160 km / h (ETRTO Speed ​​Index: Q). These tires generally have a maximum radial section width of 90 to 170 mm (e.g., 90 to 120 mm for front tires and 130 to 170 mm for rear tires), and are mounted on wheel rims that typically have a seating diameter of about 17 inches (43.18 cm) to about 21 inches (53.34 cm) (e.g., 19 inches (48.26 cm) to 21 inches (53.34 cm) for front tires and 17 inches (43.18 cm) to 18 inches (45.72 cm) for rear tires).

[0007] Tires primarily for road use are designed to maximize performance in terms of high-speed stability, dry and wet grip, wet handling, fuel economy, traction, and braking, as well as comfort and wear regularity on asphalt surfaces. In particular, these tires are often used in all-weather conditions throughout the year and must enable high reliability and performance on surfaces with reduced grip, such as wet roads.

[0008] Instead, tires intended primarily for severe off-road use are engineered to maximize performance in terms of grip, traction, handling, and direction-keeping on uneven, slippery, and / or inconsistent terrain (e.g., sand, mud, gravel) so as to effectively transfer high driving and even braking torques to the ground. These tires must also enable the aforementioned performance on wet surfaces.

[0009] Typically, in off-road use, tires are generally used at inflation pressures significantly lower than those used in road use to increase tread deflection from contact with the ground and, consequently, the motorcycle's footprint area, traction, and road grip.

[0010] In road use, the pressure must then be suitably restored to a standard value typically indicated by the motorcycle manufacturer.

[0011] The handling of a motor vehicle as perceived by the driver depends on an ideal compromise of inflation pressure that balances in the most beneficial way all of the pressure-induced variations in the physical parameters of the tire itself.

[0012] In practice, a reduction in pressure is accompanied by both a reduction in static stiffness (of its components lateral, vertical and longitudinal), so that the tire itself deforms more in all directions during operation, and a reduction in dynamic stiffness (drift and camber stiffness as well as self-aligning moments), so that the tire is less able to respond to various stresses and generate dynamic forces that can become very strong on the road due to speed and higher camber angles.

[0013] A tire inflated to a pressure lower than the nominal pressure will deform more and inevitably operate in a higher thermal regime. This can lead to premature tire failure, as all components deteriorate and lose their physical and mechanical characteristics once exposed to thermal stress beyond a certain level. Furthermore, the greater compliance of the profile makes the tire harder to steer and slower to change direction.

[0014] Therefore, when moving from road to off-road driving, and vice versa, it is advisable to adapt the tire pressures, even modifying them significantly (e.g., up to about 1.5 bar), to extend tire life and maximize performance.

[0015] Typically, big enduro motorcycle tires have a tread band with a tread pattern defined by a plurality of blocks separated by circumferential and transverse grooves. Such blocks are located in both a central annular portion of the tread band and annular shoulder portions on either side of the tread band. Such tires generally have a solid / void ratio of about 0.40 to about 0.65.

[0016] To optimize performance, motorcycle tires typically have a two-ply tread band.

[0017] Such a two-layer structure comprises a rolling layer or portion (called the cap) and a lower layer (called the base) radially inward of the rolling layer, forming a so-called "cap and base" structure.

[0018] Typically in motorcycle tyres, the cap and base layers extend annularly and axially, with the cap overlapping the base over the entire width of the tread band, with the radially outermost cap forming the entire rolling surface and the radially innermost base not reaching the rolling surface, as shown for example in EP 3 530 487 A1.

[0019] Thus, it is possible to use an elastomeric material that can provide the cap with resistance to abrasion and crack formation, while the elastomeric material of the base may be particularly aimed at providing adequate support for the cap and / or being characterized by low hysteresis while cooperating in reducing the rolling resistance. The base may be disposed between the belt structure and the rolling layer.

[0020] However, in some alternative embodiments for motorcycle tyres expressly intended for road use (super sports sector), as shown for example in WO2019082012A1 and WO2021090152A1, the rolling surface of the tread band may comprise a central annular portion consisting of an exposed sublayer, which is bordered on both sides by one or more annular sectors of a different compound. In this application, motorcycle riding is completely different from the big enduro type, which is characterized by very high camber angles that keep the shoulders of the tread in continuous contact with the road surface.

[0021] JP 2007-125988 A discloses a cap and base tire for a motorcycle, in which a cap layer (32) extends axially over the entire width of a central annular portion (W2), and a base layer (34) extends axially over the entire width of the central annular portion (W2) and to each annular portion of a shoulder (W1).

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

[0023] Japanese Patent No. 6053550 discloses a cap and base tire for two-wheeled vehicles, which comprises a radially laminated base layer (38), an intermediate layer (40), and a cover layer (42). The document does not mention the elastic modulus values ​​of the compounds making up those layers. Summary of the Invention [Problem to be solved by the invention]

[0024] By examining the motorcycle segment, the applicant has found that "big enduro" type motorcycles, as already mentioned, have a very wide range of uses.

[0025] The Applicant has realised that, in order to optimally cover the entire range of use, big enduro motorcycles should be equipped with tyres suitable for enabling high performance both on road (mainly stability at high speeds, grip in dry and wet conditions, handling) and off-road (mainly traction, manoeuvrability and direction-keeping) in line with the ability to cover many kilometres.

[0026] However, the applicant has found that, due to the current and ever-growing trend of emphasizing road performance on the one hand and off-road performance on the other, the aforementioned performance characteristics are at least partially in contrast to one another: in effect, tires that enable high performance on roads usually have performance limitations in severe off-road conditions, and vice versa.

[0027] The Applicant has also noted that a tire combining on-road and off-road use with a good compromise solution does not allow a satisfactory best performance to be achieved in either of the two areas (road and off-road). In this regard, it is noted that nowadays the market has moved towards more specialized solutions according to customer requirements and has envisaged several segments of tires for big enduro type motorcycles, each of these segments being focused on a particular popular use of the motorcycle.

[0028] Consistently, the applicant has proposed a tire for a big enduro type motorcycle that is primarily suitable for use on roads, and a tire for a big enduro type motorcycle that is primarily suitable for use off-road.

[0029] Applicant has focused on the segment of tires designed for off-road use, which is prevalent for big enduro type motorcycles.

[0030] These tires are generally selected by users who require performance on off-road routes and who expect their road use to be limited to travel to and from the off-road route.

[0031] Although approved for road use, this type of tire is primarily intended for off-road, even severe, off-road use. In this particular application, unlike primarily road use, the motorcycle is driven in a substantially vertical position or with a roll angle (camber) limited to around 25°-30°, and the shoulders of the tire's tread band barely come into contact with the ground.

[0032] The Applicant has conceived the idea of ​​creating a tire that is able to maintain good off-road performance and that has suitable road behavior to allow the user to take longer and clearer road journeys in safety and comfort compared to simple trips to / from off-road routes, and that improves road behavior on dry and, above all, wet roads, where grip is a particularly critical quality.

[0033] The Applicant has found that, in order to improve the aforementioned on-road behavior while maintaining the off-road behavior, it is expedient to provide, contrary to the above-mentioned typical configuration, a tread band formed by at least one cap and base layer, the surface of the lower or base layer being in the radially outer portion of the tread band at the lateral annular portions (shoulder portions) of the tread band, while the radially outer central annular portion is formed by a cap layer.

[0034] This arrangement of layers, combined with the selection of suitable elastomeric compounds with suitable properties for the cap and base layer compositions, means that first, during off-road use, even at maximum inflation pressures, the tire tread band will flex more at the shoulders, resulting in a larger footprint area and therefore better traction, handling, and comfort.

[0035] This greater flexibility in the shoulder areas, and the resulting larger footprint area of ​​the tread band, provides an advantage in off-road performance regardless of the pressure used, and in fact allows for excellent off-road driving performance even when the pressure is equal to or only slightly less than road pressure.

[0036] Furthermore, the tire has unexpectedly better road performance in terms of stability, handling and comfort on both dry and wet roads.

[0037] This result is completely innovative and goes against conventional wisdom in the particular sector of big enduro type tires, primarily for off-road use.

[0038] The Applicant has found that by using this cap and base configuration, and by selecting to achieve a compound having properties suited to the usage performance required precisely at the particular location of the tread band where the compound is present, it is possible to maintain or even improve off-road performance, even at maximum inflation pressure or minimum deflation, while improving on-road performance.

[0039] The Applicant has intuited that in practice, in big enduro type tires intended primarily for off-road use, the tread band is typically subjected to different stress and heat regimes in operation. The different stress and heat regimes are: - Maximum for the central annulus, which is in constant contact with road and off-road surfaces; - It is intermediate to the shoulder area, which does not touch the ground in most straight riding in this sector, but is subject to continuous curvature, especially off-road. - Minimal for the inner sub-layers, which do not touch the road surface and are not subject to such pronounced and repeated curvatures.

[0040] Thus, the applicant has recognized that by using this innovative cap and base configuration, it is possible to both meet the extremely high performance requirements of the central annular portion with a specific first cap compound having certain optimal properties (higher wear resistance, better adhesion), and to comply with the different requirements of the shoulder portion (flexibility) and inner underlayer (temperature stability) with a second base compound having different properties relative to the first compound, with the second compound forming the underlayer and occurring appropriately on the surface only in the shoulder portion. [Means for solving the problem]

[0041] Accordingly, the present invention relates to a tire (1) for an in- / off-road motorcycle (big enduro), comprising a tread band (8) of total radial thickness S, including a plurality of blocks and grooves defining a void / solid ratio in the tread band (8) of 0.40 to 0.65, the tread band (8) comprising a central annular portion (A) symmetrically disposed across an equatorial plane (XX), and a pair of annular shoulder portions (B) adjacent to the central annular portion (A) and symmetrically disposed on both sides of the central annular portion (A); the central annular portion (A) extends axially over a width of 70% to 90% of the width of the tread band and comprises a rolling layer (8a) of radial thickness S1 at its outermost radial position and a lower layer (8b) of radial thickness S2 adjacent to the rolling layer (8a) and arranged at its innermost radial position, the tread band (8) having a total radial thickness S=S1+S2; the rolling layer (8a) extends axially over the entire width of the central annular portion (A), and the lower layer (8b) extends axially over the entire width of the central annular portion (A) and over the entire width of each annular shoulder portion (B); - each annular shoulder portion (B) extends axially over a width of between 5% and 15% of the width of the tread band and the entire total radial thickness S of the tread band is made up of said underlayer (8b), The rolling layer (8a) comprises a first elastomeric compound characterized by an elastic modulus E' (E' modulus) of 5.00 to 6.50 MPa (measured at 70°C and 10 Hz according to the method described in the experimental part), and the lower layer (8b) comprises a second elastomeric compound characterized by an elastic modulus E' (E' modulus) of 3.50 to 4.60 MPa (at 70°C and 10 Hz), the percentage ratio between the modulus E' of the second compound and the modulus E' of the first compound being 70% to 90%.

[0042] definition The term "motorcycle tire" means a vulcanized tire having a large curvature ratio (typically greater than 0.20) and capable of reaching large camber angles during cornering.

[0043] "Curvature ratio" means 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 is also identified as "deflection") and said maximum width of the tire in the cross-sectional area of ​​the tire.

[0044] "Camber angle" means the angle between the equatorial plane of a tire mounted on a motorcycle wheel and a plane perpendicular to the road surface.

[0045] "Maximum Radial Section Width" or "Maximum Chord" means the maximum width of the tire profile, i.e., the dimension of the line segment having as its endpoints the two axially outermost points of the tread band profile.

[0046] The "equatorial plane" of a tire means the plane perpendicular to the tire's axis of rotation and dividing the tire into two symmetrical equal parts.

[0047] "Tread pattern" means the tread band (including grooves) represented by all points in a plane perpendicular to the tire's equatorial plane and tangent to its maximum diameter. The tread pattern is defined by blocks separated by grooves and possibly containing recesses.

[0048] "Block" means a portion of a tread band bounded by a groove. When the block is positioned at the axially outermost portion of the tread band, the block is bounded axially by the axially outermost surface of the tread band, and at the axially innermost location, the block is bounded axially by at least one groove.

[0049] "Groove" means a groove formed in a tread band to separate portions of a block.

[0050] Angular and / or linear quantities (such as distance, width, length, amplitude, axial cross section, and / or circumferential cross section), and / or surface measurements should be understood as referring to the tread pattern as defined above.

[0051] "Width" means the dimension measured along a direction perpendicular to the equatorial plane.

[0052] "Circumferential length" means a dimension measured along a direction on or parallel to the equatorial plane.

[0053] The expression "maximum extension" with respect to a block refers to the distance between the two outermost axial or circumferential points of the block measured along a direction perpendicular to the equatorial plane or along a direction parallel to or on the equatorial plane, respectively.

[0054] The terms "radial" and "axial" and the expressions "radially inner / outer" and "axially inner / outer" are used to refer to directions parallel to and perpendicular to the tire's equatorial plane, respectively, i.e., directions perpendicular to and parallel to the tire's axis of rotation, respectively.

[0055] The terms "circumferential" and "circumferentially" are used to refer to the direction of circumferential development of the tire, i.e., the direction of rolling of the tire, which corresponds to an orientation on a plane coincident with or parallel to the equatorial plane of the tire.

[0056] "Circumferential development" of the tire or tread band or portion of a tread band means the plan development of the radially outermost surface of the tire or tread band or portion of a tread band in a plane tangential to the tire.

[0057] The expressions "axially innermost" and "axially outermost" refer to positions closer to and further from the equatorial plane, respectively, relative to a reference element.

[0058] By annular portion of the tread band is meant a tread band portion that extends circumferentially around the entire tread band and has a given axial extension.

[0059] The distance of the annular tread portion from the equatorial plane is estimated axially by referencing the nearest edge of the annular portion that is parallel to the equatorial plane.

[0060] "Substantially axial" means a direction inclined at an angle between 70° and 90° relative to the equatorial plane of the tire.

[0061] "Substantially circumferential" means a direction oriented at an angle between 0° and 20° relative to the equatorial plane of the tire.

[0062] "Circumferential groove" means a groove having at least one groove portion extending along a substantial circumferential direction.

[0063] "Transverse groove" means a groove having at least one groove portion extending along a substantial axial direction.

[0064] The expression "substantially parallel" refers not only to a state of perfect parallelism, but also to a state in which something deviates from perfect parallelism by an angle of 10° or less.

[0065] By "solid / void ratio" is meant the ratio between the total surface of the grooves of a given annular portion of the tire tread pattern (of the entire tread band or tread pattern, as the case may be) and the surface of a given tread pattern portion (of the entire tread band or tread pattern, as the case may be).

[0066] "Footprint area" of a tire means that portion of the tire that contacts the ground or road surface when the tire is mounted on a wheel rim and a predetermined vertical load is applied to the tire.

[0067] The term "phr" (an acronym for parts per hundreds of rubber) refers to the parts by weight of a given elastomeric compound component per 100 parts by weight of elastomeric polymer, taking into account the net amount of any plasticizing extender oil.

[0068] "Elastomeric material" means a material comprising a vulcanizable natural or synthetic polymer and a reinforcing filler, such that after vulcanization at room temperature (as defined in ASTM D1566-11 Standard Terminology Relating to Rubber) such material is susceptible to deformation by force and is capable of rapidly and actively recovering substantially its original shape and dimensions after removal of the deforming force.

[0069] The term "diene polymer" refers to a polymer or copolymer derived from the polymerization of one or more different monomers, at least one of which is a conjugated diene (conjugated diolefin).

[0070] The term "elastomeric compound" denotes a compound obtainable by mixing at least one elastomeric polymer with at least one of the additives customarily used in the preparation of tire compounds, and optionally heating.

[0071] The term "vulcanizable elastomeric compound" denotes an elastomeric compound in a state ready for vulcanization, obtainable by incorporating into the elastomeric compound all additives, including additives for vulcanization.

[0072] The term "vulcanized elastomeric compound" means a material obtainable by vulcanizing a vulcanizable elastomeric compound.

[0073] The term "vulcanization" refers to the crosslinking reaction of natural or synthetic rubber, typically induced by a sulfur-based crosslinking agent.

[0074] The term "vulcanizing agent" refers to a product capable of converting 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, and sulfur donors such as bis[(trialkoxysilyl)propyl]polysulfide, thiuram, dithiodimorpholine, and caprolactam disulfide.

[0075] The term "vulcanization accelerator" means a compound capable of reducing the duration and / or operating temperature of the vulcanization process, such as sulfur donors such as TBBS, sulfenamides in general, thiazoles, dithiophosphates, dithiocarbamates, guanidines, and thiurams.

[0076] The term "vulcanization activator" refers to a product that can further accelerate vulcanization, making it possible for vulcanization to occur in a shorter time and, in some cases, at a lower temperature. One example of an activator is a stearic acid-zinc oxide system.

[0077] The term "vulcanization retarder" refers to a product capable of delaying the initiation of the vulcanization reaction and / or suppressing undesired secondary reactions, such as, for example, N-(cyclohexylthio)phthalimide (CTP).

[0078] The term "vulcanization package" is meant to refer to vulcanizing agents and one or more vulcanization additives selected from vulcanization activators, accelerators, and retarders.

[0079] The term "reinforcing filler" is meant to refer to reinforcing materials typically used in the tire rubber sector to improve the mechanical properties, preferably chosen from among carbon black, conventional silica, preferably amorphous, such as silica from sand precipitated with strong acids, diatomaceous earth, calcium carbonate, titanium dioxide, talc, alumina, aluminosilicates, kaolin, silicate fibers, and mixtures thereof.

[0080] The term "white fillers" is meant to refer to conventional reinforcing materials used in the sector, selected from among the conventional silicas and silicates such as sepiolite, palygorskite (also known as attapulgite), montmorillonite, alloysite, etc., possibly modified and / or derivatized by acid treatment. Typically, white fillers have surface hydroxyl groups.

[0081] The expression "reinforcing cord", or more simply "cord", means a thread-like element consisting of one or more elongated elements (also called "yarns") optionally covered by or embedded in a matrix of elastomeric material. [Brief explanation of the drawings]

[0082] [Figure 1] 1 is a schematic diagram of a radial section of a rear motorcycle tire according to the present invention, in which the tread band is shown without grooves and blocks for ease of illustration, and the arrangement of the cap (8a) and base (8b) layers is highlighted. [Figure 2] 1 is a perspective view of a typical big enduro knobby rear tire according to the present invention, in which the central annular portion (A) and annular shoulder portion (B) can be seen in dotted lines. DETAILED DESCRIPTION OF THE INVENTION

[0083] In the remainder of this specification and in the appended claims, even if not expressly stated, any numerical value will be understood to be modified by the term "about" to further indicate any numerical value that deviates slightly from the stated numerical value, for example to take into account typical dimensional tolerances of the reference sector.

[0084] Furthermore, when reference is made to any range of values ​​between a minimum and a maximum value, said minimum and maximum values ​​are understood to be included within said range, unless expressly stated otherwise.

[0085] Furthermore, unless expressly specified otherwise, all ranges include any combination of the recited maximum and minimum values, and include any intermediate ranges.

[0086] The tire according to the invention is characterized by one or more of the following features, taken individually or in combination:

[0087] The tire according to the invention comprises a tread band (8) of total radial thickness S.

[0088] The total radial thickness S of the tread band (8) and the radial thicknesses S1 and S2 of the rolling layer (8a) and the underlayer (8b) relate to the tire after molding and vulcanization.

[0089] 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, e.g., 14.5 mm, to allow for adequate tread life and tire integrity. Furthermore, the thickness of the tread band must be sufficient to ensure that the grooves do not come too close to the carcass ply and / or belt structure after vulcanization.

[0090] 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.

[0091] 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 110% to 120% of the total radial thickness S of the annular shoulder portions (B).

[0092] Preferably, the 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.

[0093] The thickness S2 of the lower layer (8b) in the central annular portion (A) is not uniform overall, as it is subject to lateral sliding during vulcanization and particularly during the molding process, as well as deformation caused by molding to define the blocks and grooves.

[0094] Preferably, the thickness S2 of the lower layer (8b) in the central annular portion (A) is 0.8 mm to 4 mm, more preferably 1.0 mm to 3 mm, and even more preferably 1.0 mm to 2.0 mm to provide adequate support.

[0095] In the annular shoulder portion (B), the thickness S2 of the lower layer (8b) instead corresponds to the total radial thickness S of the tread band.

[0096] In the tire of the invention, the sum of the width of the axial development of the two shoulder sectors (B) and the width of the axial development of the central annular sector (A) corresponds to the width of the axial development of the tread band (8).

[0097] Preferably, the central annular portion (A) extends axially over a width that is 75% to 85% of the width of the tread band.

[0098] Preferably, each annular shoulder portion (B) extends axially over a width of 7.5% to 12.5% ​​of the width of the tread band.

[0099] Preferably, the axial developments of the two annular shoulder sectors (B) have the same width.

[0100] In the tire of the present invention, the rolling layer (8a) is preferably formed entirely of the first elastomer compound and / or the lower layer (8b) is formed entirely of the second elastomer compound.

[0101] In the tire of the present invention, the first compound of the rolling layer of the central annular portion (A) has a dynamic modulus of elasticity E' in compression (measured at 70°C and 10 Hz according to the method described in the experimental part) that is greater than the modulus of elasticity E' (70°C and 10 Hz) of the second compound of the annular shoulder portion (B).

[0102] Preferably, the first and second compounds are selected so that the finished (vulcanized) tire has a vulcanized elastomeric material in the annular shoulder portions (B) having a dynamic modulus of elasticity E' (measured at 70°C and 10 Hz) that is 75% to 90%, more preferably 80% to 85%, of the dynamic modulus of elasticity E' (measured at 70°C and 10 Hz) of the vulcanized elastomeric material of the rolling surface of the central annular portion (A).

[0103] Preferably, said first elastomeric compound is characterized by an elastic modulus E' (measured at 70°C and 10 Hz) of less than or equal to 6.50 MPa, more preferably less than or equal to 6.00 MPa.

[0104] Preferably, said first elastomeric compound is characterized by an elastic modulus E' (measured at 70°C and 10 Hz) of 5.00 to 6.00 MPa, more preferably 5.00 to 5.50 MPa.

[0105] Preferably, said first elastomeric compound is characterized by an elastic modulus E' (measured at 70°C and 10 Hz) of greater than 5.00 MPa, more preferably greater than 5.50 MPa.

[0106] Preferably, said second elastomeric compound is characterized by an elastic modulus E' (measured at 70°C and 10 Hz) of less than or equal to 4.60 MPa, more preferably less than or equal to 4.50 MPa, even more preferably less than or equal to 4.40 MPa.

[0107] Preferably, said second elastomeric compound is characterized by an elastic modulus E' (measured at 70°C and 10 Hz) of greater than 4.00 MPa, more preferably greater than 4.20 MPa.

[0108] Preferably, said second elastomeric compound is characterized by an elastic modulus E' (measured at 70° C. and 10 Hz) of 4.00 to 4.50 MPa, more preferably 4.20 to 4.40 MPa.

[0109] In one embodiment, the first elastomeric compound is characterized by an elastic modulus E' (measured at 70°C, 10 Hz) of greater than 5.00 MPa, more preferably greater than 5.50 MPa, and the second elastomeric compound is characterized by an elastic modulus E' (measured at 70°C, 10 Hz) of less than or equal to 4.60 MPa, more preferably less than or equal to 4.50 MPa, even more preferably less than or equal to 4.40 MPa.

[0110] Preferably, the difference between the elastic modulus E' of the first compound and the elastic modulus E' of the second compound (measured at 70°C and 10 Hz) is 0.3 to 2.3 MPa, more preferably 0.4 to 1.5 MPa, and even more preferably 0.6 to 1.1 MPa.

[0111] In the tire of the present invention, the first compound of the rolling layer of the central annular portion (A) and the second compound of the underlying 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), a vulcanized elastomeric material having a loss tangent (measured at 70°C and 10 Hz) that is greater than the loss tangent (tan delta) (measured at 70°C and 10 Hz) of the vulcanized elastomeric material of the annular shoulder portions (B).

[0112] Preferably, the first and second compounds are selected so that the finished (vulcanized) tire has a vulcanized elastomeric material in the annular shoulder portion (B) having a loss tangent (measured at 70°C and 10 Hz) that is 45% to 65%, more preferably 50% to 60%, of the loss tangent (measured at 70°C and 10 Hz) of the vulcanized elastomeric material of the rolling surface of the central annular portion (A).

[0113] Preferably, said first elastomeric compound is characterized by a loss tangent (measured at 70° C., 10 Hz) greater than 0.220, more preferably greater than 0.230.

[0114] Preferably, said first elastomeric compound is characterized by a loss tangent (measured at 70° C. and 10 Hz) of 0.220 to 0.280, more preferably 0.230 to 0.270.

[0115] Preferably, said second elastomeric compound is characterized by a loss tangent (measured at 70° C., 10 Hz) of 0.180 or less, more preferably 0.170 or less.

[0116] Preferably, said second elastomeric compound is characterized by a loss tangent (measured at 70° C. and 10 Hz) of 0.120 to 0.180, more preferably 0.135 to 0.150.

[0117] Preferably, said first elastomeric compound is characterized by an IRHD hardness measured at 23°C of less than 78, more preferably less than 75, and / or greater than 66, more preferably greater than 68.

[0118] Preferably, said first elastomeric compound is characterized by an IRHD hardness measured at 23°C of 66-76, more preferably 68-74.

[0119] Preferably, said second elastomeric compound is characterized by an IRHD hardness measured at 23°C of less than 73, more preferably less than 71 and / or greater than 63, more preferably greater than 65.

[0120] Preferably, said second elastomeric compound is characterized by an IRHD hardness measured at 23°C of 63-73, more preferably 65-71.

[0121] In the tire, the first compound preferably has a load CA3 at 300% elongation that is lower than the load CA3 (measured at 23° C. according to the UNI6065:2001 standard) of the second compound.

[0122] Preferably, said first elastomeric compound is characterized by a load CA1 at 100% elongation of 1.7 to 2.3 MPa, more preferably 1.9 to 2.1 MPa, and / or a load CA3 at 300% elongation of 7.7 to 10.5 MPa, more preferably 8.6 to 9.5 MPa, measured at 23°C according to the UNI 6065:2001 standard.

[0123] Preferably, said second elastomeric compound is characterized by a load CA1 at 100% elongation of 1.7 to 2.3 MPa, more preferably 1.9 to 2.1 MPa, and / or a load CA3 at 300% elongation of 8.6 to 11.7 MPa, more preferably 9.7 to 10.7 MPa, measured at 23°C according to the UNI 6065:2001 standard.

[0124] In a preferred embodiment of the tire of the present invention, the first compound of the rolling layer of the central annular portion (A) of the tread band (8) has a load value CA3 of 7.7 to 10.5 MPa measured at 23°C, a dynamic modulus of elasticity E of 5.00 to 6.00 MPa measured at 70°C and 10 Hz, a loss tangent of 0.220 to 0.280 measured at 70°C and 10 Hz, a dynamic modulus of elasticity E' of 6.60 to 10.00 MPa measured at 23°C and 10 Hz, and a loss tangent of 0.320 to 0.431 measured at 23°C and 10 Hz.

[0125] More preferably, the first compound has a load value CA3 measured at 23°C of 8.6 to 9.5 MPa, a dynamic elastic modulus E' measured at 70°C and 10 Hz of 5.00 to 5.50 MPa, a loss tangent measured at 70°C and 10 Hz of between 0.230 and 0.270, a dynamic elastic modulus E' measured at 23°C and 10 Hz of 7.00 to 8.60 MPa, and a loss tangent measured at 23°C and 10 Hz of 0.337 to 0.412.

[0126] In a preferred embodiment of the present invention, the second compound of the lower layer has a load value CA3 of 8.6 to 11.7 MPa measured at 23°C, a loss tangent of 0.120 to 0.180 measured at 70°C and 10 Hz, a dynamic elastic modulus E' of 4.00 to 4.50 MPa measured at 70°C and 10 Hz, a dynamic elastic modulus E' of 4.80 to 6.50 MPa measured at 23°C and 10 Hz, and a loss tangent of 0.262 to 0.354 measured at 23°C and 10 Hz.

[0127] More preferably, the second compound has a load value CA3 of 9.7 to 10.7 MPa measured at 23°C, a loss tangent of 0.135 to 0.150 measured at 70°C and 10 Hz, a dynamic elastic modulus E' of 4.20 to 4.40 MPa measured at 70°C and 10 Hz, a dynamic elastic modulus E' of 5.10 to 6.30 MPa measured at 23°C and 10 Hz, and a loss tangent of 0.277 to 0.339 measured at 23°C and 10 Hz.

[0128] In this preferred embodiment, the first compound has an IRHD hardness of 69-73 at 23°C, while the second compound has an IRHD hardness of 65-69.

[0129] Typically, for the preparation of tire compounds according to the invention, the raw materials listed below, as well as other raw materials typically used in the tire industry sector, can be used.

[0130] In particular, for the preparation of the compounds of the lower layer (8b) and of the rolling layer (8a), elastomer compositions can be used that contain at least one elastomer diene polymer, chosen for example from elastomer diene polymers commonly used in sulfur-crosslinkable elastomer compositions (vulcanization), peroxides, or other systems known to those skilled in the art and that are particularly suitable for the production of tires, or chosen from elastomer polymers or copolymers with unsaturated chains that usually have a glass transition temperature (Tg) below 20°C, preferably in the range of -110°C to 0°C.

[0131] The compounds of the lower layer (8b) and the rolling layer (8a) each contain 100 phr of at least one diene elastomer polymer, preferably at least one styrene-butadiene rubber selected from solution-polymerized styrene-butadiene rubber (S-SBR), emulsion-polymerized styrene-butadiene rubber (E-SBR), or a combination thereof. The styrene-butadiene rubber may be present in an amount ranging from 20 to 90 phr, for example.

[0132] Commercial examples of SBR polymers useful in the present invention are Tufden E581 and E680 polymers from Asahi Kasei® (Japan), SPRINTAN SLR4602, SLR3402, and SLR4630 from Trinseo (Germany), HPR620 from JSR Corporation (Japan), BUNA SL-4518, BUNA SE1502, and BUNA CB22 from Arlanxeo (Germany), Europrene 5543T, Europrene 1739, and Intol 1789 from ENI (Italy), HP755 from Japan Synthetic Rubber Co., Ltd. (Japan), and NIPOL NS522 from Zeon Corporation (Japan).

[0133] The compounds of the underlayer (8b) and of the rolling layer (8a) may contain at least one butadiene polymer (BR), preferably a low cis-functionalized BR, for example in an amount of 10 to 50 phr.

[0134] The compounds of the underlayer (8b) and of the rolling layer (8a) may comprise one or more liquid polymers, for example in an amount of 1 to 40 phr, selected from liquid polymers and copolymers based on alkylene, preferably based on butadiene (BR), isoprene (IR), isoprene / butadiene rubber (IBR), styrene / butadiene rubber (SBR), optionally hydroxy- or epoxy-functionalized, or from depolymerized liquid natural polymers (NR).

[0135] The compound of the lower layer (8b) and the compound of the rolling layer (8a) may contain at least one resin.

[0136] The 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 (phenols).

[0137] Examples of commercial terpene-based natural resins are Piccolyte F90 and Piccolyte F105 resins 2495 manufactured by PINOVA, Dercolyte A115 and Dercolyte M115 manufactured by DRT.

[0138] The at least one resin may be a hydrocarbon resin, for example selected from resins derived from coumarone-indene resins, resins derived from styrene-indene resins, resins derived from styrene-alkylstyrene resins, and resins derived from aliphatic resins.

[0139] A specific example of a commercially available hydrocarbon resin is NOVARES C resin (indene-coumarone synthetic resin) manufactured by RUTGERS CHEMICAL GmbH.

[0140] Examples of commercially available styrene-indene hydrocarbon resins are UNILENE A100 manufactured by Braskem and Novares TT90 manufactured by Ruetgers.

[0141] The at least one resin may be present in an amount of, for example, 0 to 50 phr.

[0142] The compounds of the underlayer (8b) and of the rolling layer (8a) according to the invention may contain at least one plasticizing oil.

[0143] The term "plasticizing oil" means a process oil derived from petroleum, a process oil derived from mineral oil, a process oil derived from vegetable oil, a process oil derived from synthetic oil, or a process oil derived from a combination thereof.

[0144] The plasticizing oil may be a petroleum-derived process oil selected from paraffins (saturated hydrocarbons), naphthenes, polycyclic aromatics, and mixtures thereof.

[0145] Examples of suitable petroleum-derived process oils are aromatic, paraffinic, naphthenic oils, such as Mild Extract Solvated (MES), Distillate Aromatic Extract (DAE), Treated Distillate Aromatic Extract (TDAE), Treated Residual Aromatic Extract (TRAE), and Residual Aromatic Extract (RAE), as known in the art.

[0146] The plasticizing oil may be an oil of natural or synthetic origin derived from the esterification of glycerol with fatty acids, including glycerol triglycerides, diglycerides, monoglycerides, or mixtures thereof.

[0147] Examples of suitable vegetable oils are sunflower oil, soybean oil, linseed oil, rapeseed oil, castor oil, and cottonseed oil.

[0148] The plasticizing oil may be a synthetic oil selected from among alkyl or aryl esters of phthalic or phosphoric acid.

[0149] An example of an oil used in the compound is Lanxess tri-(2-ethylhexyl)-phosphate (TOF).

[0150] Preferably, the oils, whether of natural (e.g., plant) or synthetic origin, have a glass transition temperature (Tg) of less than -70°C (according to the ISO28343:2010 standard).

[0151] Examples of suitable commercial plasticizing oils are petroleum-derived oils such as NYTEX 4700 sold by Nynas, EXTENSOIL 1471 sold by Repsol, and VIVATEC 500 sold by H&R, and vegetable oils such as RADIA 6132 sold by Oleon, Agripure AP18, and Agripure AP75 sold by Cargill.

[0152] The total amount of oil, including both added oil and oil that may already be present as a diluent for the elastomeric polymer, may be, for example, 10 to 70 phr.

[0153] The compound of the lower layer (8b) and the compound of the rolling layer (8a) may contain at least one reinforcing filler, for example in an amount of 10 phr to 150 phr.

[0154] The reinforcing filler may be selected from carbon black, white filler, silicate fibers, or mixtures thereof.

[0155] In one embodiment, the reinforcing filler is a white filler selected from hydroxides, oxides and hydrated oxides, salts and hydrated salts of metals, silicate fibers, or mixtures thereof. Preferably, the white filler is silica.

[0156] Commercial examples of suitable conventional silicas are Zeosil 1165MP from Solvay and Ultrasil 7000GR from Evonik.

[0157] In one embodiment, the reinforcing filler is carbon black.

[0158] Preferably, the carbon black has a specific surface area of ​​20 m (measured by statistical thickness surface area (STSA) according to ISO 18852:2005). 2 / g or more, preferably 50m 2 The carbon black is selected from carbon blacks having a surface area of ​​greater than 1 / g.

[0159] The carbon black may be, for example, N234, N326, N330, N375, or N550, N660 sold by Birla Group (India), or CRX1391 by Cabot Corporation.

[0160] The reinforcing filler may also include a mixture, for example a mixture of carbon black and silica.

[0161] The compounds of the lower layer (8b) and the rolling layer (8a) may contain at least one vulcanizing agent, for example in an amount of 0.5 to 7 phr.

[0162] The at least one vulcanizing agent is preferably selected from sulfur or, alternatively, sulfur-containing molecules (sulfur donors), such as, for example, bis[(trialkoxysilyl)propyl] polysulfides and mixtures thereof.

[0163] Preferably, the vulcanizing agent is sulfur, preferably selected from soluble sulfur (crystalline sulfur), insoluble sulfur (polymeric sulfur), (iii) oil-dispersed sulfur, and mixtures thereof.

[0164] Commercial examples of vulcanizing agents suitable for use in the elastomeric compositions of the present invention are Rhenocure® IS90P from RheinChemie or sulfur Redball Superfine from International Sulfur Inc.

[0165] In the present elastomeric compounds, the vulcanizing agent may be used in conjunction with adjuvants such as vulcanization activators, accelerators, and / or retarders known to those skilled in the art.

[0166] The compounds of the underlayer (8b) and the rolling layer (8a) may contain at least one vulcanization activator.

[0167] Suitable vulcanization activators for use in the present elastomeric compounds are zinc compounds, specifically ZnO, ZnCO3, zinc salts of saturated or unsaturated fatty acids containing 8 to 18 carbon atoms, which zinc salts are preferably formed in situ in the elastomeric compound by reaction of ZnO with a fatty acid or a mixture thereof. For example, zinc stearate, preferably formed in situ with ZnO and a fatty acid, or magnesium stearate formed with MgO, or mixtures thereof, may be used.

[0168] Vulcanization activators may be present in the elastomeric compounds of the present invention in an amount of, for example, 0.2 phr to 15 phr.

[0169] A preferred activator results from the reaction of zinc oxide with stearic acid.

[0170] Examples of activators are Aktiplast ST from Rheinchemie and zinc bis-neodecanoate VALIKAT Zn1910 from Umicore.

[0171] The compound of the lower layer (8b) and the compound of the rolling layer (8a) may contain at least one vulcanization accelerator.

[0172] The primary and secondary vulcanization accelerators typically used may be selected from, for example, dithiocarbamates, guanidines, thioureas, thiazoles, sulfenamides, sulfenimides, thiurams, amines, xanthates, or mixtures thereof.

[0173] Preferably, the accelerator is selected from mercaptobenzothiazole (MBT), N-cyclohexyl-2-benzothiazole-sulfenamide (CBS), N-tert-butyl-2-benzothiazole-sulfenamide (TBBS), dibenzothiazole disulfide (MBTS), and mixtures thereof.

[0174] Commercial examples of accelerators suitable for use in the present elastomeric compounds are N-cyclohexyl-2-benzothiazyl-sulfenamide Vulkacit® (CBS or CZ) and N-tertbutyl-2-benzothiazyl-sulfenamide Vulkacit® NZ / EGC sold by Lanxess, tetrabenzyl thiuram disulfide (Perkacit® TBzTD), dibenzothiazole disulfide Rhenogran MBTS80, N-tert-butyl-2-benzothiazyl-sulfenamide TBBS from Huatai Chemicals.

[0175] The vulcanization accelerator may be employed in an amount of, for example, 0.05 phr to 10 phr.

[0176] The compounds of the lower layer (8b) and the rolling layer (8a) may contain at least one vulcanization retarder.

[0177] The vulcanization retarder may be selected from urea, phthalic anhydride, N-nitrosodiphenylamine, N-cyclohexylthiophthalimide (CTP or PVI), and mixtures thereof.

[0178] A commercial example of a suitable retarder is VULKALENT G, N-cyclohexylthiophthalimide from Lanxess.

[0179] The vulcanization retarder may be present in an amount of, for example, 0.05 phr to 2 phr.

[0180] The compounds of the lower layer (8b) and the rolling layer (8a) may contain at least one silane coupling agent in an amount of, for example, 0.5 to 10.0 phr.

[0181] Preferably, the coupling agent is an agent selected from agents having at least one hydrolyzable silane group, such as those represented by the following general formula (III): (R')3Si-C n H 2n -X (III) wherein the R' groups, equal to or different from one another, are selected from alkyl, alkoxy, or aryloxy groups, or from halogen atoms, provided that at least one of the R' groups is an alkoxy or aryloxy group; n is an integer from 1 to 6; and X is selected from nitrose, mercapto, amino, epoxide, vinyl, imide, chloro, -(S) m C n H 2n A group selected from -Si-(R')3, and -S-COR', where m and n are integers from 1 to 6, and the R' group is as defined above.

[0182] Preferred silane coupling agents are bis(3-triethoxysilylpropyl)tetrasulfide and bis(3-triethoxysilylpropyl)disulfide. The coupling agents may be added by themselves or mixed with an inert filler (such as carbon black) to facilitate incorporation into the elastomeric compound.

[0183] An example of a silane coupling agent is TESPT bis(3-triethoxysilylpropyl) tetrasulfide Si69 sold by Evonik.

[0184] The compounds of the underlayer (8b) and of the rolling layer (8a) may contain additional ingredients customarily used in the sector, such as, for example, antioxidants and / or antiozonants (anti-aging agents), waxes, adhesives, etc.

[0185] The compounds of the underlayer (8b) and of the rolling layer (8a) may contain at least one wax, such as a mixture of petroleum waxes or paraffins, for example in an amount of 0.1 phr to 20 phr.

[0186] Commercial examples of suitable waxes are Repsol's N-paraffin mixture and Rhein Chemie's Antilux® 654 microcrystalline wax.

[0187] The compounds of the underlayer (8b) and the rolling layer (8a) may contain at least one antioxidant, for example in a total amount of 0.1 phr to 20 phr.

[0188] The antioxidants were 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, N,N'-diphenyl-p-phenylenediamine, N,N'-bis-(1,4-dimethyl-pentyl) ... N,N'-di-β-naphthyl-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.

[0189] A commercial example of a suitable antioxidant is Solutia / Eastman's 6PPD.

[0190] In a preferred embodiment, the first elastomeric compound is obtained by vulcanization of an elastomeric composition, the elastomeric composition comprising: At least one liquid polymer 0-30 phr; At least one resin 0-20 phr; and 10 to 60 phr of at least one plasticizing oil; The total of liquid polymers and resins, if present, and plasticizing oils is 20 to 90 phr; The elastomer composition comprises: 100 phr of a mixture of solid diene elastomeric polymers, The mixture of polymers is 10 to 50 phr of at least one solid polybutadiene (BR), a weight average molecular weight Mw of 300,000 g / mol to 600,000 g / mol, and at least one solid polybutadiene having a cis double bond content of at least 95%, The elastomer composition comprises: 10 to 70 phr of at least one emulsion-polymerized solid styrene-butadiene copolymer (E-SBR), Tg of -60℃ to -20℃ Mooney viscosity between 30 and 70 MU at 160°C, and at least one emulsion-polymerized solid styrene-butadiene copolymer having a styrene content of 15% to 50%; 10 to 80 phr of at least one solution-polymerized solid styrene-butadiene copolymer (S-SBR) chain-functionalized with a hyperbranched coupling agent; a weight average molecular weight Mw of more than 500,000 g / mol, and / or A styrene content of 25% to 50% and a vinyl content of 10% to 50%; and / or a Tg of -50°C to -20°C, and / or at least one solution-polymerized solid styrene-butadiene copolymer having a Mooney viscosity of 60 to 100 MU 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.

[0191] In a preferred embodiment, the second elastomeric compound is obtained by vulcanization of an elastomeric composition, the elastomeric composition comprising: At least one liquid polymer 0-20 phr; At least one resin, 5 to 40 phr; and 10 to 60 phr of at least one plasticizing oil; The total of liquid polymers and resins, if present, and plasticizing oils is 15 to 120 phr; The elastomer composition comprises: 100 phr of a mixture of solid diene elastomeric polymers, The mixture of polymers is a weight average molecular weight Mw of 200,000 g / mol to 600,000 g / mol, and containing 10 to 40 phr of at least one solid polybutadiene (BR), preferably having a cis double bond content of at least 30%, The elastomer composition comprises: 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 of more than 500,000 g / mol, preferably more than 800,000 g / mol, more preferably more than 900,000 g / mol, a styrene content of 25% to 50% and a vinyl content of 10% to 70%, preferably 10% to 50%, a Tg of -50°C to -10°C, and / or a Mooney viscosity at 100°C of 50 to 100 MU; at least 50 phr of at least one reinforcing filler; and at least 1.0 phr of at least one vulcanizing agent.

[0192] Description of the tire according to the present invention 1 and 2, reference numeral 1 designates a motorcycle tire according to the present invention.

[0193] Tire 1 is a rear tire, but the following description applies equally to front tires, except when specific reference is made to rear tires.

[0194] Tire 1 is (for example, 1000 cm 3 The term "big enduro" refers to motorcycle tyres defined as big enduro type having a high engine displacement (e.g. equal to 100 hp), a large power output (e.g. equal to 100 hp) and a mass of the motorcycle in riding position (e.g. equal to 200 kg or more).

[0195] Tire 1 is generally intended to be mounted on a wheel having a maximum radial section width of 90 to 170 mm (e.g., 90 mm to 120 mm for a front tire and 130 mm to 170 mm for a rear tire) and a seating diameter of about 17 inches (43.18 cm) to about 21 inches (53.34 cm) (e.g., 19 inches (48.26 cm) to 21 inches (53.34 cm) for a front tire and 17 inches (43.18 cm) to 18 inches (45.72 cm) for a rear tire).

[0196] An equatorial plane "XX" (Figure 1) and a rotation axis R (Figure 2) are defined for the tire 1. A circumferential direction, which is arranged according to the direction of rotation of the tire 1 and is therefore parallel to the equatorial plane XX, and an axial direction r, which is perpendicular to the equatorial plane "XX" and / or parallel to the rotation axis R, are also defined.

[0197] The tire 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 woven textile material, not shown.

[0198] In the tire of FIG. 1, the carcass structure 2 is of the radial type, i.e. the reinforcing cords of said at least one carcass layer 3 are arranged substantially parallel to one another in the radial direction, i.e. according to an angle of between 70° and 110°, more preferably between 80° and 100°, relative to the circumferential direction.

[0199] In one embodiment not shown, the carcass structure comprises at least two radially superimposed carcass plies, in which the reinforcing cords are essentially parallel to one another in each carcass ply and are oriented in each carcass ply in an oblique direction (for example at least 45°) relative to the equatorial plane of the tire and in the opposite direction relative to the cords of the radially adjacent carcass ply 3 (cross-ply carcass).

[0200] The carcass structure 2 is typically coated on its inner wall with a sealing layer 100, or so-called liner, consisting essentially of a layer of air-impermeable elastomeric material adapted to ensure an airtight seal of the tire 1 itself once inflated.

[0201] The (or each) carcass ply 3 is shaped according to a substantially toroidal form and has axially opposite lateral edges 3a directed towards respective annular reinforcing structures 4 intended to retain the tire 1 on a corresponding mounting rim (not shown), the annular reinforcing structures 4 being typically called bead cores.

[0202] A tapered elastomeric filler 5 is added to the outer peripheral edge of the bead core 4, and such tapered elastomeric filler 5 occupies the space defined between each carcass ply 3 and the corresponding turned-up lateral edge 3a of the carcass ply 3.

[0203] In a further alternative embodiment, not shown, each carcass ply is associated at its opposite lateral edges with a specific annular reinforcing structure provided with two annular metal inserts and without flaps.

[0204] The area of ​​the tire 1 comprising the bead core 4 and the elastomeric filling 5 forms a so-called bead 9, which is intended to secure the tire 1 to a rim, not shown.

[0205] Preferably, a carcass reinforcing structure may be advantageously provided at the radially outer position of the carcass (whether radial or with cross-plies). This reinforcing structure comprises, at least for the crown portion, a crown ply arranged radially outermost with respect to the radially outer carcass ply. Such crown ply is made of reinforcing elements arranged parallel to one another and arranged at an opposite angle to the reinforcing elements of the radially outermost carcass ply with respect to the equatorial plane. Optionally, the carcass reinforcing structure comprises two plies arranged transversely to the crown ply, axially facing each other with respect to the equatorial plane and not associated with the respective beads.

[0206] In one embodiment thereof, the (or each) carcass ply 3 is made by joining together a plurality of strips of elastomeric material reinforced by the aforementioned cords.

[0207] A belt structure 6 is applied circumferentially at a radially outer position to the carcass structure 2, the belt structure 6 comprising at least one belt layer 6a typically formed from rubberized textile or metal cords.

[0208] 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, forming a plurality of turns, such turns being oriented substantially according to the circumferential direction (typically at an angle between 0° and 5°), such a direction being usually called "zero degree" with reference to its laying relative to the circumferential direction of the tire 1.

[0209] Preferably, the belt layer 6a, typically known as "zero degree", may comprise axially aligned wraps of a single cord or a band of rubberized fabric comprising axially aligned cords.

[0210] The cords of the zero-degree belt layer 6a are typically metal cords made of high-carbon steel wires, i.e., steel wires having a carbon content of at least 0.6 to 0.7%. Preferably, these metal cords have high elongation (HE).

[0211] To improve the adhesion between the belt structure 6 and the carcass structure 2, an adhesive layer 7 of elastomeric material may be provided sandwiched between the two aforementioned structures.

[0212] In a different embodiment, the belt structure 6 comprises two or more radially superimposed belt layers, each layer made of an elastomeric material reinforced with cords arranged parallel to one another. The layers are arranged so that the cords of a first belt layer are oriented obliquely relative to the equatorial plane of the tire, while the cords of a radially adjacent belt layer have an oblique but crossed orientation relative to the cords of the first layer (so-called cross belts), and similarly for any other belt layers. The cross belts are typically accompanied by textile cords.

[0213] The tread band (8) is circumferentially superimposed on the belt structure 6 and, after a molding operation carried out simultaneously with the vulcanization process of the tire 1, the tread band (8) typically has circumferential and transverse grooves arranged to separate a plurality of blocks according to the geometric shapes detailed elsewhere in this specification.

[0214] According to a preferred embodiment, the tread band (8) (and other components of the tire) are made using an elastomeric material as defined above.

[0215] The tread band (8) comprises a central annular portion (A) arranged symmetrically across the equatorial plane (XX), and a pair of annular shoulder portions (B) arranged symmetrically on both sides of the central annular portion (A) and adjacent to the central annular portion (A).

[0216] The central annular portion (A) extends over a width comprising 70% to 90%, preferably 75% to 85% of the width of the tread band.

[0217] The tread band (8) is of the cap and base type and has as a whole a total radial thickness S which may vary between the center and the shoulders, and comprises a rolling ply (8a) (cap) having a radial thickness S1 at its radially outermost position, and a lower ply (8b) (base) of radial thickness S2 adjacent to the rolling ply (8a) and located at its radially innermost position. The tread band (8) has a total radial thickness S=S1+S2.

[0218] The rolling layer (8a) extends axially across the entire width of the central annular portion (A), and the lower layer (8b) extends axially across the entire width of the tread band, i.e. across the entire width of said central annular portion (A) and across the entire width of each annular shoulder portion (B).

[0219] Each annular shoulder portion (B) extends axially over a width of 5% to 15%, preferably 7.5% to 12.5%, of the width of the tread band, and the entire total radial thickness S of the tread band is made up of said underlayer (8b).

[0220] Table 1 below provides some example cap extension and base extension measurements for several types of tires according to the present invention.

[0221] [Table 1]

[0222] The tire 1 may further comprise a pair of sidewalls 10 applied laterally on either side of said carcass structure 2 .

[0223] Referring to FIG. 1, the tire 1 has a section height "H" measured on the equatorial plane "XX" between the top of the tread band (8) and the seating diameter identified by the reference line "r" passing through the bead 9 of the tire 1.

[0224] The tire 1 further has a maximum radial section width "C" defined by the distance between the lateral ends "E" of the tread band 8, and a deflection "f" defined by the distance of the top of the tread band (8) from a line passing through said lateral ends "E", measured on the equatorial plane "XX" of the tire 1. The lateral ends "E" of the tread band (8) may be formed with corners.

[0225] The tire 1 has a "camber ratio" (f / C) defined by the ratio between the deflection "f" and the maximum radial section width "C" mentioned above.

[0226] 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".

[0227] The reference symbols quoted ("H", "XX", "r", "C", "f", "E") are shown for the rear tires in Figure 1, but the reference symbols are similar for the front tires.

[0228] Preferably, the deflection "f" of the tire 1 is between about 40 mm and about 60 mm.

[0229] The tire 1 has a camber ratio "f / C" of between about 0.25 and about 0.35, for example equal to about 0.26.

[0230] The tire 1 has a deflected height to overall height ratio "f / H" of between about 0.40 and about 0.60, for example equal to about 0.43.

[0231] For the 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.

[0232] Furthermore, for the front tire, the ratio of deflection height to overall height "f / H" is between about 0.40 and about 0.60, and is equal to, for example, about 0.53.

[0233] As shown in FIG. 2, the tire 1 according to the invention is of the knobbed type, i.e. the tire 1 comprises a plurality of transverse and circumferential grooves which separate a plurality of mutually spaced blocks.

[0234] The blocks and grooves define a tread pattern having a void / full ratio of 0.40 to 0.65, preferably 0.50 to 0.6, for example equal to 0.51 for a rear tire that is 170 / 60 / R17 and 0.56 for a rear tire that is 150 / 70 / R18.

[0235] Experimental Part Evaluation method The static mechanical properties (load CA1 at 100% elongation, load CA3 at 300% elongation) according to the UNI6065:2001 standard were measured at 23°C on samples of the elastomeric material vulcanized at 170°C for 10 minutes.

[0236] Dynamic mechanical properties E', E", and loss tangent were measured using an Instron Model 1341 dynamic device in tension-compression mode as described herein. Test specimens of cross-linked materials (170°C for 10 min) with a cylindrical geometry (length = 25 mm, diameter = 14 mm) preloaded to a maximum longitudinal strain of 25% relative to the initial length and maintained at a predetermined temperature of 23°C or 70°C throughout the test were subjected to dynamic sinusoidal strain at a frequency of 10 Hz or 100 Hz with an amplitude of ±3.5% relative to the preloaded length. Dynamic mechanical properties were expressed as dynamic elastic modulus (E'), dynamic viscous modulus (E"), and loss tangent (loss factor). The loss tangent value was calculated as the ratio between the dynamic viscous modulus (E") and the dynamic elastic modulus (E'). The hardness in IRHD degrees (23°C) was measured according to the ISO 48:2007 standard on samples of the above-mentioned elastomeric materials vulcanized at 170°C for 10 minutes.

[0237] Preparation of compounds Base compounds MB1(INV), MB2(REF) and cap compounds MC1(INV) and MC2(REF) were prepared starting from the compositions detailed in Table 2 below.

[0238] [Table 2]

[0239] NR is natural rubber (Thaiteck Rubber's standard Thai rubber STR20).

[0240] Tufden E680 (S-SBR) is a solution polymerized styrene butadiene polymer extended with 37.5 parts TDAE oil per 100 parts dry polymer (107.3 phr of Tufden E680 contains 78 phr dry polymer).

[0241] SBR1739 is Schkopau's Buna® SB1739, an E-SBR produced by low-temperature emulsion polymerization using a mixed rosin / fatty acid soap. SBR1739 is plasticized with 37.5 parts TDAE oil relative to the solid rubber (60.5 phr and 76 phr of Buna® SB1739 contain 44 phr and 55.3 phr of dry polymer, respectively).

[0242] YB03 Asaprene is a low cis-functionalized polybutadiene polymer.

[0243] SBR1723 is an emulsified styrene butadiene polymer with a Tg of about -50°C, obtained by low-temperature polymerization using a mixture of rosin acid and fatty acid soap as emulsifier, extended with 37.5 parts of TDAE oil.

[0244] HPR620 is a styrene-butadiene polymer prepared in solution as described in SG10201800553S(A) in a continuous process, functionalized in-chain with a polyorganosiloxane hyperbranched coupling agent, having a weight average molecular weight of about 1,000,000 g / mol, a styrene content of about 40%, about 25% vinyl, a Tg of about -33°C, and a Mooney viscosity of about 80 MU (Mooney viscosity ML(3+4) 160°C), extended with 25 parts TDAE oil relative to the solid rubber (32.5 phr of HPR620 contains 26 phr of dry polymer).

[0245] BR is Europrene® Neocis BR60, a polybutadiene with a high cis content (minimum 97%) produced in solution using a neodymium organometallic catalyst.

[0246] N234 is a high surface area carbon black (STSA112m 2 / g).

[0247] CRX1391 is a high surface area carbon black (STSA156m 2 / g).

[0248] PERKASIL408 has a high surface area (BET175m 2 The silica is PERKASIL® KS408, a precipitated silica with a solubility of 1 / g.

[0249] ZEOSIL 1165MP has a high specific surface area of ​​165m 2 / g of silica microbeads.

[0250] ULTRASIL7000 has a high surface area (BET175m 2 / g) precipitated silica.

[0251] RICON 100 is a low molecular weight (Mn 4500) liquid (25% styrene) butadiene styrene copolymer (PBS) with a Tg of -57°C.

[0252] TDAE is a processed distilled aromatic extract that is an aromatic oil plasticizer, Vivatec® 500 (plasticizer).

[0253] POLYVEST 130 is a stereospecific, low-viscosity, non-saponifiable 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 approximately 12,000 g / mol.

[0254] TOF is the plasticizer tri-(2-ethylhexyl)-phosphate.

[0255] RESIN2495 is a terpene-based resin.

[0256] RASINA CUMARON is a coumarone resin.

[0257] RHENOSIN TT90 is a tackifying and dispersing hydrocarbon resin.

[0258] NOVARES TT30 is a hydrocarbon resin produced by the polymerization of C9 / C10 unsaturated aromatic hydrocarbons.

[0259] α-Methylstyrene resin is a thermoplastic resin.

[0260] Zinc Neodecanoate 50 is the zinc salt of neodecanoic acid.

[0261] RHENOGRAN ZNO is zinc oxide.

[0262] Acid Gras Sare de Zinc is a zinc salt of a fatty acid.

[0263] The liquid silane is SI69, bis[3-(triethoxysilyl)propyl]polysulfide.

[0264] The wax is BMO1, a mixture of N-paraffins and isoparaffins.

[0265] 6PPD is N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine, an antiozonant.

[0266] The sulfur is Lanxess's Rhenocure® IS90-20, a 90:10 ratio mixture of insoluble / soluble sulfur plus 20% oil.

[0267] TBBS is N-tert-butyl-2-benzothiazylsulfenamide.

[0268] MBTS80 is dibenzothiazyl disulfide.

[0269] DURALINK TS is hexamethylene-1,6-bis(thiosulfate) disodium salt.

[0270] TBZTD is tetrabenzylthiouram disulfide (Perkacit® TBzTD).

[0271] The elastomeric compounds were prepared according to the following process.

[0272] The ingredients were mixed in two stages using an internal mixer (Banbury, Intermix, or Brabender).

[0273] In the first step (1), all ingredients were introduced except for the vulcanizing agents and accelerators. Mixing was continued for a maximum time of 5 minutes, allowing the temperature to reach approximately 145°C. Then, in the second step (2), again using the internal mixer, the vulcanizing agents and accelerators were added, and mixing was continued for approximately 4 minutes, maintaining the temperature below 100°C. The compound was then removed. After cooling and at least 12 hours after preparation, some samples of the compound were pressed and vulcanized at 170°C for 10 minutes to obtain specimens useful for mechanical characterization.

[0274] Compound properties The main static and dynamic properties and hardness of the aforementioned elastomer compounds measured by the above methods are shown in Figure 3 below.

[0275] [Table 3]

[0276] The compounds used to make the tires according to the invention were MB1 and MC1: MC1 constituted the radially outer central annular portion (A) of the tread band, while MB1 constituted the radially inner lower layer occurring on the surface of the annular shoulder portion (B) (see comparative test below).

[0277] From Table 3 it can be seen that compounds MB1 and MC1 suitable for making the tire of the invention had significantly different properties compared to the previous compound MB2 in the underlayer and the previous compound MC2 in the rolling layer used in the conventional cap and base tread bands (see tire REF1 below).

[0278] Specifically, it can be seen that base compound MB1 and cap compound MC1 had significantly lower IRHD hardness and elastic modulus values ​​E' compared to compounds MB2 and MC2, respectively, under all test conditions.

[0279] Applicant has realized that the tread band of the present tire behaved rather homogeneously in use, as if formed from a single material with the various portions of the tread having moduli and hysteresis equivalent to each other under operating conditions, despite the simultaneous presence of different compounds.

[0280] This phenomenon was highlighted by measurements of the modulus and hysteresis of different compounds, carried out under real conditions where the different compounds acted in the specific parts of the tread band where they were located, as evidenced by the values ​​of E' and loss tangent in the various regimes shown in Table 3.

[0281] In this regard, the dynamic mechanical properties of the compound were evaluated at different levels of dynamic stress (sample stress at frequencies of 10 Hz and 100 Hz) and at different temperatures (23°C and 70°C) to reproduce the conditions experienced by the compound in road and off-road driving.

[0282] Specifically, considering road operation, it was possible to identify the following possible thermal regimes during operation, and relative measurement conditions of the module, as schematized in Table 4 below:

[0283] [Table 4]

[0284] As can be seen from Table 3, under these conditions (i.e., 100 Hz, 23°C for the shoulder and 10 Hz, 23°C for the core), the shoulder compound (MB1) and the core compound (MC1) had practically identical elastic moduli E' (7.77 vs. 7.79).

[0285] Instead, considering off-road operation, it was possible to identify the following possible thermal regimes during operation, and relative measurement conditions of the module, as schematized in Table 5 below:

[0286] [Table 5]

[0287] In off-road operation, the central annulus was hot, but the stresses were macro (engaging blocks) and not micro (lateral fluctuations), so the measurement frequency was 10 Hz.

[0288] As can be seen from Table 3, under these conditions (i.e., 100 Hz, 70°C for the shoulder and 10 Hz, 70°C for the core), the shoulder compound (MB1) and the core compound (MC1) had very similar elastic moduli E' (4.90 vs. 5.20).

[0289] Comparative Test The applicant has produced an exemplary rear tire 1 according to one embodiment of the present invention, which is 170 / 60 R17 and specifically has the cap and base configuration illustrated in FIG. 1 and the tread pattern illustrated in FIG. 2.

[0290] The cap layer was made of MC1 compound while the base layer was made of MB1 compound, this tire being designated INV below.

[0291] Two additional reference rear tires were constructed, designated REF1 and REF2. - In REF1, the cap and base layers extended annularly and axially across the full width of the tread band and consisted of MC2 and MB2, respectively. In REF2, the cap and base layers were arranged according to the invention and consisted of MC2 and MB1, respectively.

[0292] Outdoor tests were carried out to compare the tire of the invention with tires REF1 and REF2.

[0293] The REF1 tyre is a big enduro type made by the Applicant and has been highly praised by customers for its excellent off-road behaviour, as well as its behaviour on dry and wet roads which is considered to be satisfactory.

[0294] The REF2 tire was a prototype created for comparison purposes to evaluate the effect of the properties of the cap and base compounds on the performance of a tire having the same tread structure (cap and base arranged in accordance with the present invention).

[0295] The relevant measurements of the tread band and its components of the tire INV of the invention and the comparative tires REF1 and REF2 are given in Table 6 below.

[0296] [Table 6]

[0297] Tests were carried out on a BMW GS1250R motorcycle with a tire (inflated to the same inflation pressure) mounted on the rear wheel and an identical tire mounted on the front wheel under substantially identical environmental conditions.

[0298] The front tires were 120 / 70R19 with 3.00x19 rims and had an inflation pressure of 2.0 bar for off-road tests and 2.5 bar for road tests. The rear tires were 170 / 60R17 with 4.50x17 rims and had an inflation pressure of 2.0 bar for off-road tests and 2.9 bar for road tests.

[0299] The behavior of the INV, REF1, and REF2 tires both on road (dry and wet) and off-road was evaluated by asking drivers for their opinions. Specifically, the items listed in Tables 7, 8, and 9 below, which also show the opinions given by the drivers, were evaluated. Road tests were conducted on both dry and wet roads along straight stretches and routes with curves. Off-road tests were conducted by running several straight stretches of preset length on prepared mud and sand surfaces that replicated conditions that might be found in the natural environment, keeping the surface as homogenous as possible after each test. The straight stretches were equipped with two sensors to determine when the motorcycle entered and exited, the latter equipped with suitable instrumentation (GPS sensor, engine throttle valve opening sensor, and speed sensors for both wheels).

[0300] Table 7 relates to dry road testing, Table 8 relates to wet road testing, and Table 9 relates to off-road testing.

[0301] In Tables 7 to 9, "=" indicates a rating equivalent to that obtained with the REF1 tire, and "+" and "-" indicate an improvement or deterioration compared to the REF1 tire.

[0302] [Table 7]

[0303] [Table 8]

[0304] [Table 9]

[0305] Tables 7 and 8 show how the INV tire unexpectedly and generally produced improved road performance compared to that of the REF1 tire, particularly in terms of comfort and handling with respect to dry contact and wet road grip, with behavior consistent with that of the REF1 tire in the other aspects evaluated. On the other hand, the REF2 tire, whose capping compound MC2 did not have the characteristics of the inventive capping compound MC1, was found to be pejorative.

[0306] Thus, the applicant has demonstrated that the use of certain compounds in combination with the specific construction employed in the tire of the present invention does in fact make it possible to obtain surprising improvements in performance on both dry and wet roads.

[0307] Instead, Table 9 also highlights the unexpected improvement in off-road performance for all items tested, an improvement that was not predictable and far exceeded the expectations of the applicant, who set out with the objective of maintaining the excellent off-road behavior of the reference tire (REF1).

Claims

1. A tire (1) for a road / off-road motorcycle (big enduro), comprising a tread band (8) of total radial thickness S, said tread band (8) including a plurality of blocks and grooves defining a void / solid ratio in said tread band (8) of between 0.40 and 0.65, said tread band (8) comprising a central annular portion (A) symmetrically disposed across an equatorial plane (X-X), and a pair of annular shoulder portions (B) adjacent to said central annular portion (A) and symmetrically disposed on either side of said central annular portion (A), - said central annular portion (A) extends axially over a width between 70% and 90% of the width of said tread band and comprises a rolling layer (8a) of radial thickness S1 at its outermost radial position and a lower layer (8b) of radial thickness S2 adjacent to said rolling layer (8a) and located at its innermost radial position, said tread band (8) having a total radial thickness S=S1+S2; the rolling layer (8a) extends axially over the entire width of the central annular portion (A), and the lower layer (8b) extends axially over the entire width of the central annular portion (A) and over the entire width of each annular shoulder portion (B); each annular shoulder portion (B) extends axially over a width between 5% and 15% of the width of said tread band and is made from said underlayer (8b) over said total radial thickness S of said tread band; A tire (1) for a road / off-road motorcycle (big enduro), wherein the rolling layer (8a) comprises a first elastomer compound characterized by an elastic modulus E' of 5.00 to 6.50 MPa, and the lower layer (8b) comprises a second elastomer compound characterized by an elastic modulus E' of 3.50 to 4.60 MPa, wherein the elastic modulus E' is measured using a dynamic device in tension-compression mode at 70°C and 10 Hz on specimens crosslinked at 170°C for 10 minutes, and the percentage ratio between the elastic modulus E' of the second elastomer compound of the lower layer (8b) and the elastic modulus E' of the first elastomer compound of the rolling layer (8a) is 70% to 90%.

2. A tire according to claim 1, wherein said total radial thickness S of said tread band (8) is between 10 mm and 20 mm.

3. 3. The tire according to claim 1, wherein the thickness S1 of the rolling layer (8a) in the central annular portion (A) is 9 mm to 17 mm, and the thickness S2 of the lower layer (8b) in the central annular portion (A) is 0.8 mm to 4 mm.

4. 2. The tire of claim 1, wherein said central annular portion (A) extends axially over a width of between 75% and 85% of the width of said tread band, and each annular shoulder portion (B) extends axially over a width of between 7.5% and 12.5% ​​of the width of said tread band.

5. 2. The tire of claim 1, wherein the percentage ratio of the modulus of elasticity E' of the second elastomeric compound to the modulus of elasticity E' of the first elastomeric compound is between 75% and 90%.

6. 2. The tire of claim 1, wherein the difference between the modulus of elasticity E' of the first elastomeric compound and the modulus of elasticity E' of the second elastomeric compound is between 0.3 and 2.3 MPa.

7. 2. The tire of claim 1, wherein said first elastomeric compound is characterized by a modulus of elasticity E' of 5.00 to 6.00 MPa and said second elastomeric compound is characterized by a modulus of elasticity E' of 4.00 to 4.50 MPa.

8. 2. The tire of claim 1, wherein said first elastomeric compound is characterized by a loss tangent of 0.220 to 0.280 and said second elastomeric compound is characterized by a loss tangent of 0.120 to 0.180, said loss tangents being measured at 70°C and 10 Hz.

9. 10. The tire of claim 1, wherein said first elastomeric compound is characterized by an IRHD hardness of 66 to 76 and said second elastomeric compound is characterized by an IRHD hardness of 63 to 73, said IRHD hardnesses being measured at 23°C.

10. said first elastomeric compound is characterized by a load CA1 at 100% elongation of between 1.7 and 2.3 MPa and / or a load CA3 at 300% elongation of between 7.7 and 10.5 MPa; 2. Tire according to claim 1, in which said second elastomeric compound is characterized by a load CA1 at 100% elongation of between 1.7 and 2.3 MPa and / or a load CA3 at 300% elongation of between 8.6 and 11.7 MPa, said load CA1 and said load CA3 being measured at 23°C according to the UNI 6065:2001 standard.

11. The first elastomer compound for the rolling layer (8a) is obtained by vulcanization of an elastomer composition, the elastomer composition comprising: 0 to 30 phr of at least one liquid polymer; 0 to 20 phr of at least one resin; and 10 to 60 phr of at least one plasticizing oil; the total of said liquid polymers and resins, if present, and plasticizing oils is from 20 to 90 phr; The elastomer composition 100 phr of a blend of solid diene elastomeric polymers, said blend of polymers comprising: 10 to 50 phr of at least one solid polybutadiene (BR), a weight average molecular weight Mw of 300,000 g / mol to 600,000 g / mol, and at least one solid polybutadiene having a cis double bond content of at least 95%; The elastomer composition 10 to 70 phr of at least one emulsion-polymerized solid styrene butadiene copolymer (E-SBR), Tg of -60°C to -20°C, a Mooney viscosity of 30-70 MU at 160°C, and at least one emulsion-polymerized solid styrene butadiene copolymer having a styrene content of 15% to 50%; 10 to 80 phr of at least one solution-polymerized solid styrene-butadiene copolymer (S-SBR) chain-functionalized with a hyperbranched coupling agent; a weight average molecular weight Mw of more than 500,000 g / mol, and / or a styrene content of 25% to 50% and a vinyl content of 10% to 50%; and / or a Tg of -50°C to -20°C, and / or at least one solution-polymerized solid styrene-butadiene copolymer having a Mooney viscosity of 60-100 MU at 160°C; at least 40 phr of at least one reinforcing filler; 10. The tire of claim 1 comprising at least 1.0 phr of at least one vulcanizing agent.

12. The second elastomer compound for the lower layer (8b) is obtained by vulcanization of an elastomer composition, the elastomer composition comprising: 0 to 20 phr of at least one liquid polymer; 5 to 40 phr of at least one resin; and 10 to 60 phr of at least one plasticizing oil; the total of said liquid polymers and resins, if present, and plasticizing oils is 15 to 120 phr; The elastomer composition 100 phr of a blend of solid diene elastomeric polymers, said blend of polymers comprising: comprising 10 to 40 phr of at least one solid polybutadiene (BR); The elastomer composition 60 to 90 phr of at least one continuously produced, end-functionalized, solution-polymerized, solid styrene-butadiene copolymer (S-SBR); at least 50 phr of at least one reinforcing filler; 10. The tire of claim 1 comprising at least 1.0 phr of at least one vulcanizing agent.

13. The at least one solid polybutadiene (BR) has a weight average molecular weight Mw of 200,000 g / mol to 600,000 g / mol and a cis double bond content of at least 30%; 13. The tire of claim 12, wherein the at least one continuously produced, end-functionalized, solution-polymerized, solid styrene-butadiene copolymer (S-SBR) has a weight average molecular weight Mw of greater than 500,000 g / mol, a styrene content of 25% to 50% and a vinyl content of 10% to 70%, a Tg of -50°C to -10°C, and / or a Mooney viscosity at 100°C of 50 to 100 MU.

14. 10. Tire according to claim 1, primarily for off-road use.

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