Bicycle tyre

Abstract

A bicycle tyre (100) comprising a pair of bead cores (8), a carcass structure (2) turned around said pair of bead cores (8) and a tread band (4) located radially outside said carcass structure (2); at each bead core (8) there is provided an elastomeric material filler (12) extending in a radial direction for a first length (H1) from the bead core (8), wherein the first length (H1) is at least 20% of a distance (H4) measured in the radial direction between the bead core (8) and a radially outermost portion of said carcass structure (2).

Description

TECHNICAL FIELD

[0001] The present application relates to a bicycle tyre.

[0002] Preferably, the bicycle equipped with the tyre of the present application is a mountain bike, an electrically assisted bicycle (also commonly referred to as "e-bike" or "e-bike"). BACKGROUND

[0003] In the present description and in the following claims, the following definitions apply.

[0004] The term "electrically assisted bicycle" means a bicycle provided with an auxiliary electric motor capable of developing a maximum continuous nominal power of 0.25 KW.

[0005] The term "mountain bike" means a bicycle intended to travel on typically rough or irregular terrains, i.e. terrains very different from each other and from asphalt (for example, muddy terrain, sandy terrain, rocky terrain, compacted terrain, soft terrain, etc.). Such bicycles include bicycles that meet the regulations established by the International Cycling Union (UCI), including in particular "mountain bikes" (MTB), all-terrain bikes (ATB), BMX, downhill bikes, fat bike, cross-country bikes and climbing bikes.

[0006] The term "equatorial plane" of a tyre means a plane perpendicular to the rotation axis of the tyre and dividing it into two symmetrically equal parts.

[0007] The terms "radial" and "axial" and the expressions "radially inner / outer" and "axially inner / outer" are used with reference to a direction perpendicular and parallel, respectively, to the rotation axis of the tyre.

[0008] The expressions "axially inner" and "axially outer" mean, respectively, a position closer to and further from the equatorial plane.

[0009] The expressions "radially inner" and "radially outer" mean, respectively, a position closer to and further from the rotation axis of the tyre.

[0010] The terms "circumferential" and "circumferentially" are used with reference to the annular extension direction of the tyre, i.e. the rolling direction of the tyre, which corresponds to a direction lying on a plane coincident or parallel to the equatorial plane of the tyre.

[0011] The term "elastomeric material" means a composition comprising at least one elastomeric polymer and at least one reinforcing filler. Preferably, such composition also comprises additives, such as cross-linking agents and / or plasticizers. Such material can be cross-linked by heating due to the presence of cross-linking agents.

[0012] The term "cord" or the expression "reinforcing cord" means an element composed of one or more thread-like elements (hereinafter also referred to as "wires") which are optionally coated with or incorporated in an elastomeric material matrix.

[0013] The term "diameter" of a cord or wire means the thickness of the cord or wire as measured according to the BISFA E10 method (Internationally Agreed Methods For Testing Steel Tyre Cords, 1995 edition).

[0014] The term "thread count" of a layer or ply or fabric means the number of reinforcing cords per unit length present in such layer / ply / fabric. The thread count can be measured in TPI (threads per inch).

[0015] The term "linear density" or "count" of a cord or wire means the weight of the reinforcing cord per unit length. The linear density can be measured in dtex (grams per 10 km length).

[0016] The term "bicycle tyre" means a tyre having an assembled diameter not less than about 300 mm (which corresponds to an outer diameter of about 15 inches), preferably less than or equal to about 650 mm (which can correspond to a specific outer diameter of about 28, 29 or 30 inches depending on the width of the tyre), and a width of the tyre not greater than about 120 mm, preferably greater than about 18 mm.

[0017] The term "assembled diameter" of a tyre means the diameter of the tyre as measured according to the ETRTO (European Tyre and Rim Technical Organisation) or ISO (International Organisation for Standardisation) at the inner diameter of the bead core anchoring the tyre to the wheel rim.

[0018] The term "width" of a tyre means the maximum axial extension (or "maximum cord") of the tyre as measured according to the ETRTO standard. The width of the tyre corresponds to the projected width of the tyre on a plane perpendicular to the equatorial plane of the tyre and tangent to the maximum diameter of the tyre, such width corresponding to the dimension of a segment having as extremities the two axially outermost positions of the tyre.

[0019] In the rest of the present description and in the following claims, when certain values are mentioned, these values refer to absolute values, i.e. both positive and negative values.

[0020] A bicycle tyre typically comprises a carcass structure turned up around a pair of bead cores and a tread band arranged in radially outer position with respect to the carcass structure.

[0021] The carcass structure is intended to withstand the inflation pressure and the weight of the bicycle and the cyclist. It comprises one or more carcass plies, each comprising a plurality of appropriately oriented reinforcing cords. In the case of a plurality of carcass plies, they are inclined with respect to each other to form a cross structure.

[0022] The tread band is intended to ensure the adhesion of the tyre to the asphalt.

[0023] The task of the bead core is to ensure anchoring of the tyre to the wheel rim.

[0024] In a radially inner position to the carcass structure, a chamber is usually provided into which pressurised air is introduced. However, tyres exist which are known as "tubeless", i.e. without a chamber. In such tyres, the pressurised air acts directly on the carcass structure. The carcass structure and the wheel rim are configured in such a way that their mutual anchoring ensures airtight sealing.

[0025] Prior art

[0026] CN 202806223U describes a bicycle tyre comprising a crown portion, two sidewalls arranged on the sides of the crown portion, and a carcass arranged inside the crown portion and the sidewalls. The carcass comprises a first inner carcass ply wound around a first bead core and folded on itself at a first sidewall of the tyre. A second inner carcass ply is wound around a second bead core and folded on itself at a second sidewall of the tyre. The first and second carcass plies extend at a height comprised between 30% and 60% of the height of the corresponding sidewall of the tyre. The carcass further comprises an outer carcass ply wound on the first and second carcass plies and symmetrically folded on itself at the crown portion. A wear insert is arranged outside the outer carcass ply, encircles the corresponding bead core, and extends less than 30% of the height of the corresponding sidewall of the tyre. SUMMARY

[0027] The Applicant has observed that, when high loads are transmitted to the tyre, for example in the case of electric bicycles, in which the driving torque applied by the cyclist is added to that given by the electric motor, or in the case of off-road bicycles used on particularly rough terrain, the tyre is subjected to great stresses which generate torsional deformations (which tend to deform the tyre along a plane parallel to the plane passing through the rotation axis of the tyre), longitudinal deformations (which tend to deform the tyre in the direction of travel, perpendicular to its rotation axis), vertical deformations (which tend to deform the tyre in the direction pointing towards the centre of the tyre) and transverse deformations (which tend to deform the sidewalls of the tyre during a turn).

[0028] The Applicant has observed that the performance of the tyre (acceleration and braking response, handling, controllability in straight or in curves, grip and safety given by stability in curves) is closely associated with the deformation of the tyre caused by the load supported by the tyre.

[0029] The Applicant has realized that the performance of the tyre can be improved by increasing the torsional stiffness, the longitudinal stiffness, the lateral stiffness and / or the vertical stiffness of the tyre.

[0030] The Applicant has also realized that by increasing the torsional stiffness, the longitudinal stiffness, the lateral stiffness and the vertical stiffness of the tyre in the portion immediately radially adjacent to the bead core, the tyre itself is able to experience a lower degree of deformation in the areas of the bicycle wheel rim where forces and torques are transmitted.

[0031] The Applicant believes that in this way the acceleration and braking response, the handling, the controllability in straight or in curves, the grip and the safety given by stability in curves of the bicycle are increased.

[0032] The Applicant has found that this effect can be obtained by axially interposing an elastomeric material filler between the carcass plies, in particular by radially bringing an elastomeric material filler to each bead core.

[0033] The present application therefore relates to a bicycle tyre comprising a pair of bead cores, a carcass structure turned around the pair of bead cores and a tread band radially external to the carcass structure.

[0034] Preferably, an elastomeric material filler is provided at each bead core, which extends in the radial direction from the bead core for a first length.

[0035] Preferably, the first length is at least about 20% of the distance measured in the radial direction between the bead core and the radially outermost portion of the carcass structure.

[0036] The Applicant believes that when the elastomeric material filler has a very limited extension in the radial direction, for example less than about 20% of the distance measured in the radial direction between the bead core and the radially outermost portion of the carcass structure, the performance improvement of the tyre can be reduced due to an insufficient increase in the torsional stiffness, the longitudinal stiffness, the lateral stiffness and the vertical stiffness of the tyre.

[0037] The Applicant also believes that when the elastomeric material filler has a very long extension in the radial direction, for example extending up to where it joins the tread area, the performance improvement of the tyre can be reduced due to an excessive increase in the torsional stiffness, the longitudinal stiffness, the lateral stiffness and the vertical stiffness of the tyre.

[0038] The present application can have at least one of the following preferred features, which can be taken individually or in combination with any other described preferred feature.

[0039] Preferably, the first length is less than the distance measured in the radial direction between the bead core and the radially outermost part of the carcass structure.

[0040] Preferably, the first length is less than about 80% of the distance measured in the radial direction between the bead core and the radially outermost part of the carcass structure.

[0041] Applicants believe that the effectiveness of the elastomeric material filling can be better when the elastomeric material filling extends between about 20% and about 80%, preferably between about 30% and about 70%, including the end values, of the distance measured in the radial direction between the bead core and the radially outermost part of the carcass structure, even more preferably about 50%.

[0042] Thus, the elastomeric material filling preferably engages a portion of the sidewall of the tire.

[0043] Preferably, the elastomeric material filling extends from the radially outer surface of the bead core. Preferably, the elastomeric material filling is not present radially inside the bead core.

[0044] Preferably, the first length is greater than about 10 millimeters.

[0045] Preferably, the first length is less than about 50 millimeters.

[0046] Preferably, the first length is between about 10 millimeters and about 50 millimeters, including the end values, more preferably between about 20 millimeters and about 40 millimeters, including the end values, even more preferably between about 30 millimeters and about 35 millimeters, including the end values.

[0047] Preferably, the thickness of the elastomeric material filling measured in the axial direction at the portion radially adjacent to the bead core is equal to or less than the thickness of the bead core measured in the same axial direction.

[0048] Preferably, the elastomeric material filling has a thickness measured in the axial direction greater than about 0.5 millimeters.

[0049] Preferably, the elastomeric material filling has a thickness measured in the axial direction less than about 4 millimeters.

[0050] Preferably, the thickness of the elastomeric material filling measured in the axial direction is between about 0.5 millimeters and about 4 millimeters, including the end values, more preferably between about 1 millimeter and 3 millimeters, including the end values, even more preferably between about 1.3 millimeters and 2.5 millimeters, including the end values.

[0051] Preferably, the elastomeric material filling has a constant thickness along its entire extension.

[0052] Preferably, the elastomeric material filler is made of a material having an ultimate tensile strength greater than about 15 MPa.

[0053] Preferably, the elastomeric material filler is made of a material having an ultimate tensile strength less than about 40 MPa.

[0054] Preferably, the elastomeric material filler is made of a material having an ultimate tensile strength between about 15 MPa and about 40 MPa, inclusive, more preferably between about 20 MPa and about 30 MPa, inclusive.

[0055] Preferably, the elastomeric material filler is made of a material having an ultimate tensile strength greater than about 15 MPa.

[0056] Preferably, the elastomeric material filler is made of a material having an ultimate tensile strength less than about 40 MPa.

[0057] Preferably, the elastomeric material filler is made of a material having an ultimate tensile strength between about 15 MPa and about 40 MPa, inclusive, more preferably between about 20 MPa and about 30 MPa, inclusive.

[0058] Preferably, the elastomeric material filler is made of a material having a dynamic elastic modulus E'(23°C - 10 Hz) greater than about 3 MPa.

[0059] Preferably, the elastomeric material filler is made of a material having a dynamic elastic modulus E'(23°C - 10 Hz) less than about 35 MPa.

[0060] Preferably, the elastomeric material filler is made of a material having a dynamic elastic modulus E'(23°C - 10 Hz) between about 3 MPa and about 35 MPa, inclusive, more preferably between about 3 MPa and about 10 MPa, inclusive.

[0061] Preferably, the elastomeric material filler is made of a material having a dynamic elastic modulus E'(70°C - 10 Hz) greater than about 2.2 MPa.

[0062] Preferably, the elastomeric material filler is made of a material having a dynamic elastic modulus E'(70°C - 10 Hz) less than about 25 MPa.

[0063] Preferably, the elastomeric material filler is made of a material having a dynamic elastic modulus E'(70°C - 10 Hz) between about 2.2 MPa and about 25 MPa, inclusive, more preferably between about 2.2 and about 10 MPa.

[0064] Preferably, the elastomeric material filler is made of a material having a load at 50% elongation greater than about 0.5 MPa.

[0065] Preferably, the elastomeric material insert is made of a material having a load at 50% elongation of less than about 10 MPa.

[0066] Preferably, the elastomeric material insert is made of a material having a load at 50% elongation of between about 0.5 MPa and about 10 MPa, inclusive, more preferably between about 0.5 MPa and 8 MPa, inclusive.

[0067] Preferably, the elastomeric material insert is made of a material having a load at 100% elongation of greater than about 0.7 MPa.

[0068] Preferably, the elastomeric material insert is made of a material having a load at 100% elongation of less than about 15 MPa.

[0069] Preferably, the elastomeric material insert is made of a material having a load at 100% elongation of between about 0.7 MPa and about 15 MPa, inclusive, more preferably between about 0.7 MPa and about 13 MPa.

[0070] Preferably, the elastomeric material insert is a monolithic insert.

[0071] Preferably, the carcass structure comprises at least one carcass ply comprising a plurality of reinforcing cords inclined at a first angle with respect to the equatorial plane.

[0072] Preferably, the carcass ply is turned around the bead core so as to generate at least two superimposed carcass plies; the elastomeric material insert is interposed between the two superimposed carcass plies.

[0073] Preferably, the carcass ply is turned around the bead core so as to generate two carcass plies at two opposite first portions of the tire and three superimposed carcass plies at a second portion of the tire, arranged between the two opposite first portions; the elastomeric material insert is arranged in the two opposite first portions of the tire.

[0074] Preferably, the two opposite first portions of the tire in which the two carcass plies are juxtaposed coincide with at least a portion of the two sidewalls.

[0075] In some embodiments of the application, a further carcass ply can be provided.

[0076] Preferably, the reinforcing cords of the carcass ply are inclined at the first angle of between about 30° and about 60°, inclusive.

[0077] Preferably, the first angle is greater than or equal to about 30°, more preferably greater than or equal to about 40°.

[0078] Preferably, said first angle is less than or equal to about 60°, more preferably less than or equal to about 50°.

[0079] In a preferred embodiment, said first angle is comprised between about 40° and about 50°, including the extreme values, for example equal to about 45°.

[0080] Preferably, the reinforcing cords of said at least one carcass ply are made of textile material, so as to limit the weight of the tyre as much as possible.

[0081] Preferably, the number of threads of the carcass ply or of each carcass ply is greater than or equal to about 15 TPI, more preferably greater than or equal to about 30 TPI, even more preferably greater than or equal to about 60 TPI, even more preferably greater than or equal to about 120 TPI.

[0082] Preferably, the number of threads of the carcass ply or of each carcass ply is less than or equal to about 360 TPI, more preferably less than or equal to about 300 TPI, even more preferably less than or equal to about 240 TPI, even more preferably less than or equal to about 200 TPI.

[0083] In a preferred embodiment, the number of threads of the carcass ply or of each carcass ply is comprised between about 15 TPI and about 360 TPI, including the extreme values, preferably comprised between about 30 TPI and about 300 TPI, including the extreme values, more preferably comprised between about 60 TPI and 240 TPI, including the extreme values, even more preferably comprised between about 120 TPI and about 200 TPI, including the extreme values, for example equal to about 60 TPI.

[0084] Preferably, the diameter of the reinforcing cords of the carcass ply or of each carcass ply is less than or equal to about 0.55 mm, more preferably less than or equal to about 0.35 mm.

[0085] Preferably, the diameter of the reinforcing cords of the carcass ply or of each carcass ply is greater than or equal to about 0.10 mm, more preferably greater than or equal to about 0.12 mm.

[0086] In a preferred embodiment, the diameter of the reinforcing cords of the carcass ply or of each carcass ply is comprised between about 0.10 mm and about 0.55 mm, including the extreme values, preferably comprised between about 0.12 mm and about 0.35 mm, including the extreme values, for example equal to about 0.30 mm.

[0087] Preferably, the reinforcing cords of the carcass ply or of each carcass ply have a thread density greater than or equal to about 110 dtex, more preferably greater than or equal to about 230 dtex.

[0088] Preferably, the reinforcing cords of the or each carcass ply have a linear density less than or equal to about 1300 dtex, more preferably less than or equal to about 940 dtex.

[0089] In a preferred embodiment, the reinforcing cords of the or each carcass ply have a linear density comprised between about 110 dtex and about 1300 dtex, including the extreme values, preferably comprised between about 230 dtex and about 940 dtex, including the extreme values, for example equal to about 450 dtex.

[0090] Preferably, at each bead core a ring is provided, interposed between the carcass structure and the elastomeric material filling and turned around the bead core so as to define a first flap located axially outside the elastomeric material filling and a second flap located axially inside the elastomeric material filling.

[0091] Preferably, the first flap extends in a radial direction from the bead core for a second length and the second flap extends in a radial direction from the bead core for a third length.

[0092] The Applicant believes that this ring is able to connect and keep together in a substantially integral manner the bead core and the relative elastomeric material filling, thus making it possible to further improve the stiffening of the bead and sidewall region of the tyre. In the Applicant's view, since the ring is interposed between the carcass structure and the elastomeric material filling, this at least partially avoids the possible sliding between the carcass plies which would transmit different stresses to the elastomeric material filling and to the bead core, causing a relative movement between the bead core and the elastomeric material filling. In fact, the Applicant believes that the turning of the ring around the bead core and the extension of the ring radially away from the bead core make it possible to couple and keep together the bead core and the elastomeric material filling and make it possible to act as an interface between the carcass structure and the bead core-elastomeric material filling assembly, thus mitigating or at least partially eliminating the possible decoupling effects of the carcass structure tending to transfer to the bead core and to the elastomeric material filling.

[0093] Preferably, the second length and the third length are less than or equal to the first length.

[0094] The Applicant has observed that the retaining effect of the bead core on the elastomeric material filling is particularly improved when the two flaps of the ring do not close on themselves, in other words when the two flaps of the ring do not touch each other. The Applicant believes that by avoiding the mutual contact of the two flaps of the ring, the two flaps of the ring are prevented or in any case limited to slide with respect to each other and with respect to the elastomeric material filling. By arranging the second length and the third length, in other words the radial extension of the first and second flaps of the ring, to be less than or equal to the first length, in other words the radial extension of the elastomeric material filling, the two flaps of the ring cannot touch each other since they are hindered by the presence of the elastomeric material filling axially interposed between the two flaps.

[0095] Preferably, the second length and the third length are at least about 30% of the first length. Therefore, preferably, the two flaps of the ring extend between about 30% and about 100% of the radial extension of the elastomeric material filling.

[0096] Preferably, the second length and the third length are substantially equal to each other. In this way, the ring extends substantially symmetrically on the two axially opposite surfaces of the elastomeric material filling.

[0097] Preferably, the ring is arranged in direct contact with the elastomeric material filling.

[0098] The Applicant has observed that in this way the ring maximizes the grip and retaining action on the elastomeric material filling. The Applicant believes that the direct contact between the ring and the elastomeric material filling counteracts or in any case significantly reduces the possible relative sliding between the ring and the elastomeric material filling, thus maximizing the stable coupling effect between the elastomeric material filling and the bead core.

[0099] Preferably, the ring is made of the same material as the manufacturing of the carcass structure.

[0100] Preferably, the ring is made of a ply comprising a plurality of reinforcing cords made of textile material, which can all be parallel to each other or can be made in a square fabric structure, i.e. with warp reinforcing cords and weft reinforcing cords.

[0101] Preferably, the number of threads of the reinforcing cords of the ply of the ring is equal to or greater than the number of threads of the reinforcing cords of the carcass plies.

[0102] Preferably, the number of threads of the reinforcing cords of the ply of the ring is twice the number of threads of the reinforcing cords of the carcass plies.

[0103] Preferably, at each bead core a wear-resistant strip element is provided, which is arranged outside the carcass structure.

[0104] Preferably, the wear-resistant strip element is turned around the bead core.

[0105] Preferably, the wear-resistant band-like element is a ply comprising reinforcing cords or an elastomeric polymer strip.

[0106] In case the wear-resistant band-like element is a ply comprising a plurality of reinforcing cords, the reinforcing cords are preferably made of textile material.

[0107] Preferably, the reinforcing cords of the wear-resistant band-like element can all be parallel to each other or can form a square weave structure (i.e. with warp reinforcing cords and weft reinforcing cords).

[0108] Preferably, the reinforcing cords are arranged obliquely with respect to the equatorial plane.

[0109] Preferably, the wear-resistant band-like element extends radially for a distance smaller than the second and third distances. In other words, the wear-resistant band-like element extends radially for a length smaller than the length of the first and second flaps of the ring.

[0110] Preferably, a bead-to-bead ply (BTB) is provided, which is arranged radially outward of the carcass structure and radially inward of the tread band.

[0111] The bead-to-bead ply has the function of preventing or, in any case, limiting the possibility that the sharp body can penetrate the carcass ply.

[0112] Preferably, the bead-to-bead ply extends from one bead to the other bead.

[0113] Preferably, the bead-to-bead ply does not turn around the beads.

[0114] Preferably, the bead-to-bead ply is a ply comprising a plurality of reinforcing cords. Preferably, the reinforcing cords of the bead-to-bead ply can all be parallel to each other or can form a square weave structure (i.e. with warp reinforcing cords and weft reinforcing cords).

[0115] Preferably, the reinforcing cords are arranged obliquely with respect to the equatorial plane.

[0116] Preferably, the reinforcing cords of the bead-to-bead ply are made of textile material. More preferably, the reinforcing cords of the carcass structure and the reinforcing cords of the bead-to-bead ply are made of the same textile material.

[0117] In a preferred embodiment, the number of threads per inch of the bead core to bead core ply is comprised between about 15 TPI and about 360 TPI, inclusive, preferably comprised between about 30 TPI and about 300 TPI, inclusive, more preferably comprised between about 60 TPI and about 240 TPI, inclusive, even more preferably comprised between about 120 TPI and about 200 TPI, inclusive, for example equal to about 60 TPI.

[0118] In a preferred embodiment, the diameter of the reinforcing cords of the bead core to bead core ply is comprised between about 0.10 mm and about 0.55 mm, inclusive, preferably comprised between about 0.12 mm and about 0.35 mm, inclusive, for example equal to about 0.30 mm.

[0119] In a preferred embodiment, the linear density of the reinforcing cords of the bead core to bead core ply is comprised between about 110 dtex and about 1300 dtex, inclusive, preferably comprised between about 230 dtex and about 940 dtex, inclusive, for example equal to about 450 dtex. BRIEF DESCRIPTION OF DRAWINGS

[0120] Further features and advantages of the tyre of the present application will become more apparent from the following detailed description of some preferred embodiments thereof, given by way of example and made with reference to the attached drawings. In these drawings:

[0121] - Figure 1 a perspective cross-section of an embodiment of a bicycle tyre according to the present application is schematically shown;

[0122] - Figure 1A a detail of Figure 1 is shown;

[0123] - Figures 2-15 possible construction solutions representative of alternative embodiments of the tyre of the present application are shown. DETAILED DESCRIPTION

[0124] In Figure 1 , reference 100 as a whole denotes a bicycle tyre according to the present application. The tyre is intended to be mounted on a wheel of a bicycle, in particular on a wheel of an electric bicycle or of an off-road bicycle.

[0125] The tyre 100 comprises an axis of rotation O and an equatorial plane X perpendicular to the axis of rotation O. A circumferential direction is also defined, arranged according to the direction of rotation of the tyre 100, and an axial direction perpendicular to the equatorial plane X and / or parallel to the axis of rotation O.

[0126] Figure 1The tyre 100 comprises a carcass structure 2 comprising a crown portion 2a, preferably arranged symmetrically with respect to the equatorial plane X, and opposite lateral portions 2b arranged on axially opposite sides with respect to the crown portion 2a.

[0127] In radially outer position with respect to the carcass structure 2, a tread band 4 is provided, by means of which the contact of the tyre 100 with the road surface occurs.

[0128] The tread band 4 comprises a central portion 5 and two lateral portions 6 (or side walls 6) arranged on axially opposite sides with respect to the central portion 5.

[0129] The central portion 5 can comprise (as in the example shown in Figure 1 ) a plurality of blocks 7.

[0130] In the example shown in Figure 1 , the carcass structure 2 comprises a single carcass ply 3, but other embodiments exist (like those schematically shown in Figure 4 , 7 , 8, 11, 14, 15) in which the carcass structure 2 comprises two carcass plies indicated with 3, 3a in Figure 4 , 7 , 8, 11, 14 and 15.

[0131] Unless explicitly stated otherwise, what is described below with reference to the carcass plies shown in the accompanying drawings applies both to the single carcass ply 3 of the tyre and to each carcass ply 3, 3a of the tyre having a plurality of plies.

[0132] The carcass ply 3 is turned around a respective annular anchoring structure, called "bead core", 8.

[0133] The carcass ply 3 is turned around the bead core 8 so as to generate a plurality of layers of carcass ply 3 radially juxtaposed to each other.

[0134] In the embodiment schematically shown in Figure 2 , 5 , 9 and 12, the carcass ply 3 is turned around the bead core 8 so that two layers of carcass ply 3 are arranged at two opposite first portions 9 of the tyre, which are preferably at least partially juxtaposed at the side walls 6 of the tread band. The carcass ply 3 has a single layer of ply at a second portion 10, which is axially arranged between said two opposite first portions 9 and is preferably at least partially coincident with the crown 2a.

[0135] The carcass ply 3 has two end edges 11 which define two separation areas between said portion with a single layer of ply of the carcass ply 3 and said two portions with two juxtaposed layers of ply of the carcass ply.

[0136] In another alternative embodiment, illustrated in Figures 10 and 13, the carcass ply 3 is turned around the bead core 8 so that two layers of carcass ply 3 are arranged at two opposite first portions 9 of the tyre, which are preferably at least partially juxtaposed at the sidewall 6 of the tread band. The carcass ply 3 has a single layer of plies at a second portion 10, which is axially arranged between said two opposite first portions 9 and is preferably at least partially coincident with the crown 2a. Figure 3 、 6

[0137] The carcass ply 3 has two end edges 11 which define two separation areas between said portion with a single layer of plies of the carcass ply 3 and said two portions with two juxtaposed layers of plies of the carcass.

[0138] In another alternative embodiment, illustrated in Figures 11 and 14, there are two carcass plies 3, 3a, wherein each carcass ply 3, 3a is turned around the bead core 8 so that two layers of plies of each carcass ply 3, 3a are arranged at two opposite first portions 9 of the tyre, which are preferably at least partially juxtaposed at the sidewall 6 of the tread band. The two carcass plies 3, 3a each have a single layer of plies at a second portion 10, which is axially arranged between said two opposite first portions 9 and is preferably at least partially coincident with the crown 2a. Figure 4 、 7

[0139] The two carcass plies 3, 3a have two end edges 11 which define two respective separation areas between said portion with a single layer of plies of each carcass ply 3, 3a and said two portions with two juxtaposed layers of plies of each carcass.

[0140] According to this embodiment, the carcass structure 3 has four layers of carcass plies (two layers for each carcass ply 3, 3a) juxtaposed at two opposite first portions 9 of the tyre and two layers of carcass plies (one layer for each carcass ply 3, 3a) juxtaposed at a second portion 10 of the tyre.

[0141] In another alternative embodiment, illustrated in Figures 10 and 13, the carcass ply 3 is turned around the bead core 8 so that two layers of carcass ply 3 are arranged at two opposite first portions 9 of the tyre, which are preferably at least partially juxtaposed at the sidewall 6 of the tread band. The carcass ply 3 has a single layer of plies at a second portion 10, which is axially arranged between said two opposite first portions 9 and is preferably at least partially coincident with the crown 2a. Figure 8 15

[0142] ​​​​Both carcass plies 3, 3a have three plies at the second portion 10, which is axially arranged between two opposite first portions 9 and preferably at least partially coincides with the crown 2a.

[0143] Both carcass plies 3, 3a have two end edges 11, which define two respective separation areas between the portion with three juxtaposed plies of each carcass ply 3, 3a and the two portions with two juxtaposed plies of each carcass ply.

[0144] According to this embodiment, the carcass structure 3 has four plies of carcass ply (two plies for each carcass ply 3, 3a) juxtaposed at the two opposite first portions 9 of the tyre and six plies of carcass ply (three plies for each carcass ply 3, 3a) juxtaposed at the second portion 10 of the tyre.

[0145] The bead core 8 is preferably made of textile fibres with high modulus of elasticity, like for example aramid fibres (generic name of fibres of aromatic polyamide), or of metal wires, like for example steel.

[0146] In radially outer and adjacent position to each bead core 8, there is an elastomeric material filling 12, which is preferably monolithic.

[0147] The elastomeric material filling 12 extends from the radially outer surface of the bead core 8. As Figure 1 shown, the elastomeric material filling 12 is not present radially inside the bead core 8, in other words it extends only from the radially outer surface 8a of the bead core 8 in radially outer direction.

[0148] As shown in these figures, the elastomeric material filling 12 is axially interposed between the respective layers of the carcass ply 3. The elastomeric material filling 12 is axially arranged between the carcass plies 3, preferably in radially inner position to the two end edges 11 of the carcass ply 3, so that each elastomeric material filling is arranged at the two portions with two juxtaposed plies of the carcass ply 3, respectively.

[0149] The area of the tyre 100 comprising the bead core 8 and the elastomeric material filling 12 forms the so-called "bead", which is intended to anchor the tyre 100 on the corresponding mounting rim 101 (partially shown in Figure 1 ) by elastic forced assembly.

[0150] As shown in these figures, at each bead core 8, in particular in axially outer positions of the carcass structure 2, a wear-resistant strip element 13 can be applied. This wear-resistant strip element 13 interposes between the carcass ply 3 and the rim 101 of the wheel when the tyre 100 is mounted on such a rim 101. The wear-resistant strip element 13 has the function of ensuring grip and friction with the rim 101 of the wheel, thus avoiding damage that could be caused by abrasion following friction of the carcass ply 3 with the rim 101.

[0151] Instead of the wear-resistant strip element 13, a single reinforcing cord that can be laid after the adhesive treatment can be used.

[0152] With reference to Figure 1 , 2 , 3, 4, 9, 10 and 11, a bead-to-bead ply 14 is shown that can optionally be present in the tyre 100.

[0153] The bead-to-bead ply 14 is associated with the carcass structure 2 in radially outer positions and preferably extends from one bead core 8 to the other bead core 8, without turning around the bead core. Alternatively, the bead-to-bead ply 14 extends only at the crown 2a of the carcass structure 2.

[0154] The bead-to-bead ply 14 is arranged radially inboard of the tread band 4. The function of the bead-to-bead ply 14 is to prevent the tyre 100 from being possibly pierced.

[0155] Figure 5 , 6 , 7, 8, 12, 13, 14 and 15 show a tyre structure without the bead-to-bead ply 14.

[0156] In some embodiments of the application, as shown in Figure 1 and 9 - 15, at each bead core 8 and in positions axially between the elastomeric material filler 12 and the carcass ply 3, there is a ring 15 that turns around the bead core 8. The ring 15 defines a first flap 15a and a second flap 15b respectively located axially outboard and axially inboard of the elastomeric material filler 12, which extend radially away from the bead core 8.

[0157] The function of the ring 15 is to keep the elastomeric material filler 12 and the bead core 8 together in a substantially unitary manner. As shown in Figure 1 and schematically represented in Figures 9-15 , the flaps 15a, 15b of the ring are in direct contact with the elastomeric material filler 12.

[0158] Both the annular 15 (if any) and the elastomeric material filler 12 extend circumferentially along the entire extension of the tyre 100.

[0159] As shown in the enlarged view of Figure 1A , the elastomeric material filler 12 extends in a radial direction from the bead core 8 for a first length H1. The first length H1 is less than a distance H4 (shown in Figure 1 ) measured in a radial direction separating the bead core 8 from a radially outermost portion of the crown 2a of the carcass structure 2, in other words, the elastomeric material filler 12 engages less than half of the carcass structure 2. In a preferred embodiment of the application, the first length H1 is comprised between about 20% and about 80% of the distance H4, including the extreme values, preferably between about 30% and about 70% of the distance H4, including the extreme values, even more preferably about 50% of the distance H4.

[0160] In absolute terms, the first length H1 is comprised between about 10 mm and about 50 mm, including the extreme values, more preferably between about 20 mm and about 40 mm, including the extreme values, even more preferably between about 30 mm and about 35 mm, including the extreme values.

[0161] The elastomeric material that can be used as the elastomeric material filler 12 according to the present application can have the following mechanical properties (static and dynamic properties measured according to the standards given below):

[0162] Ultimate tensile strength equal to or greater than 10 MPa, preferably comprised between about 15 MPa and about 40 MPa, including the extreme values.

[0163] Elongation at break equal to or greater than about 120%, preferably equal to or greater than about 150%, even more preferably comprised between about 200% and about 800%, including the extreme values, even more preferably comprised between about 300% and about 800%, including the extreme values.

[0164] Load at 50% elongation equal to or greater than about 0.4 MPa, preferably equal to or greater than about 0.5 MPa.

[0165] Load at 50% elongation preferably equal to or less than about 10 MPa, preferably equal to or less than about 8 MPa.

[0166] Load at 100% elongation equal to or greater than about 0.6 MPa, preferably equal to or greater than about 0.7 MPa.

[0167] Load at 100% elongation equal to or less than about 15 MPa, preferably equal to or less than about 13 MPa.

[0168] Dynamic modulus of elasticity E' (23°C - 10 Hz) equal to or greater than about 2 MPa, preferably comprised between about 3 MPa and about 35 MPa, including the extreme values.

[0169] Dynamic modulus of elasticity E' (70°C - 10 Hz) equal to or greater than about 2 MPa, preferably comprised between about 2.2 MPa and about 25 MPa, including the extreme values.

[0170] In the following, an example of elastomeric material and preparation of the elastomeric material filling 12 for the elastomeric material filling 12 is shown (the amounts of the individual components are expressed in phr, i.e. parts per hundred of rubber).

[0171] All the components, except sulphur, accelerator (TBBS) and anti-scorching agent (PVI), were mixed in a Banbury mixer (Pomini model PL 1,6) for about 5 minutes (first step). As soon as the temperature reached 145 ± 5°C, the elastomeric composition was discharged. Sulphur, accelerator (TBBS) and anti-scorching agent (PVI) were added and mixed in an open roll mixer (second step).

[0172]

[0173]

[0174] IR: high cis-1,4-polyisoprene synthetic rubber, SKI-3, Lee Rubber.

[0175] CB: carbon black, N375, Cabot.

[0176] Stearic acid: Sogis.

[0177] Zinc oxide: Zincol Ossidi.

[0178] Tackifying resin: octylphenol resin, SP1068, Si Group.

[0179] Oil: MES (mild extract solvate), ENI SPA.

[0180] Silica: 1165 - Solvay.

[0181] Supported silane: 50% bis[3-(triethoxysilyl)propyl]tetrasulphide, 50% carbon black, Evonik-Degussa.

[0182] TBBS: N-tert-butyl-2-benzothiazylsulphenamide, NZ / EGC, Lanxess;

[0183] PVI: cyclohexylthiophthalimide, Santogard PVI, Flexsys

[0184] Vulcanizing agent: sulfur, Redball Superfine, International Sulfur Inc.

[0185] The elastomeric material can be characterized by the following parameters:

[0186] The static mechanical properties (CA05 load at 50% elongation and CA1 load at 100% elongation) were measured on the above elastomeric material samples vulcanized at 170°C for 10 minutes at different elongations (50%, 100%) according to the standard UNI 6065. The results obtained are given in Table 2.

[0187] The rheological analysis MDR was performed using a MDR Monsanto Rheometer. The test was performed at 170°C for 10 minutes, with an oscillation frequency of 1.66 Hz (100 oscillations per minute) and an oscillation amplitude of ±0.5°. The minimum torque (ML) value and the maximum torque (MH) value were measured.

[0188] The dynamic mechanical properties E' and Tan delta were measured according to the following method using an Instron model 1341 dynamic device in traction-compression mode. A test piece of crosslinked material (10 minutes at 170°C) having a cylindrical shape (length = 25 mm; diameter = 14 mm), preloaded under compression until a longitudinal deformation of 25% with respect to the initial length and kept at a predetermined temperature (23°C, 70°C) during the entire test, was subjected to a dynamic sinusoidal stress with an amplitude of ±3.5% with respect to the length under pre-load and a frequency of 10 Hz. The dynamic mechanical properties were expressed in values of dynamic elastic modulus (E') and Tan delta (loss factor). The Tan delta value was calculated as the ratio between the viscous dynamic modulus (E") and the elastic dynamic modulus (E'). The thermoplastic behavior was evaluated as the difference delta E' between the values of elastic dynamic modulus measured at the two reference temperatures.

[0189] Table 2

[0190]

[0191] The thickness of the elastomeric material filling 12, measured in the axial direction, is less than or equal to the thickness of the bead core, measured in the same direction. Preferably, the elastomeric material filling 12 has a thickness, measured in the axial direction, greater than about 0.5 millimeters. Preferably, the elastomeric material filling 12 has a thickness, measured in the axial direction, less than about 4 millimeters. Preferably, the thickness of the elastomeric material filling 12, measured in the axial direction, is comprised between about 0.5 millimeters and about 4 millimeters, including the extreme values, more preferably between about 1 millimeter and about 3 millimeters, including the extreme values, even more preferably between about 1.3 millimeters and about 2.5 millimeters, including the extreme values.

[0192] In preferred embodiments of the application, the elastomeric material filling 12 has a constant thickness along its entire extension, while in other embodiments of the application the elastomeric material filling 12 tapers along its extension in the radial direction, so that the thickness of the elastomeric material filling 2, measured in the axial direction, of the portion of the elastomeric material filling 2 radially adjacent to the bead core 8 is greater than the thickness of the elastomeric material filling 12, measured in the axial direction, of the portion of the elastomeric material filling 12 radially distant from the bead core 8.

[0193] In any case, the thickness of the elastomeric material filling 12, measured in the axial direction, at the portion radially adjacent to the bead core 8 is equal to or less than the thickness of the bead core 8, measured in the axial direction.

[0194] With reference to the embodiment provided with the ring 15 and as shown in Figure 1A , the first flap 15a extends radially away from the bead core 8 for a second length H2. The second flap 15b extends radially away from the bead core 8 for a third length H3, as shown in the enlarged view of Figure 1A .

[0195] The second length H2 and the third length H3 are preferably equal to each other.

[0196] The second length H2 and the third length H3 are less than or equal to the first length H1. The second length H2 and the third length H3 are comprised between about 20% and about 80% of the first length H1, including the extreme values, preferably between about 40% and about 60% of the first length H1, including the extreme values, even more preferably they are about 50% of the first length H1.

[0197] In all embodiments, the carcass ply 3 of the tyre 100 is preferably made of elastomeric material and comprises a plurality of reinforcing cords arranged substantially parallel to each other.

[0198] The reinforcing cords are preferably made of textile material selected from nylon, rayon, PET, PEN, lyocell, aramid or combinations thereof, in single or multi-ply, preferably in single or double ply.

[0199] The diameter of the reinforcing cords is preferably comprised between about 0.10 mm and about 0.55 mm, more preferably between about 0.12 mm and about 0.35 mm, including the extreme values, for example equal to about 0.13 mm.

[0200] The linear density of the reinforcing cords is comprised between about 110 dtex and about 1300 dtex, more preferably between about 230 dtex and about 940 dtex, including the extreme values, for example equal to about 450 dtex.

[0201] Specific examples of textile materials that can be used for the above-mentioned reinforcing cords are the following:

[0202] Nylon 930 dtex / 1

[0203] Nylon 470 dtex / 1

[0204] Nylon 230 dtex / 1

[0205] Aramid 470 / 1

[0206] Where the number 1 after dtex indicates the number of strands.

[0207] The reinforcing cords are inclined with respect to the equatorial plane of the tyre 100 by an angle comprised between about 30° and about 60°, preferably between about 40° and about 50°, including the extreme values.

[0208] Preferably, the number of threads of the carcass ply 3 is comprised between about 15 TPI and about 360 TPI, more preferably between about 30 TPI and about 300 TPI, even more preferably between about 60 TPI and about 240 TPI, even more preferably between about 120 TPI and about 200 TPI, including the extreme values, for example equal to about 60 TPI.

[0209] Figure 1 The tyre 100 shown does not comprise a belt arranged in a radially outer position with respect to the carcass structure. However, different embodiments can be provided comprising a belt or comprising more than one belt.

[0210] The ring 15, if present, can be made of the same material as the carcass ply 3.

[0211] In any case, the ring 15 is made of a ply 16 comprising a plurality of reinforcing cords, preferably parallel to each other and inclined with respect to the equatorial plane by a second angle. Alternatively, the reinforcing cords of the ply 16 can be made in a square fabric structure (i.e. with warp reinforcing cords and weft reinforcing cords).

[0212] The reinforcing cords of the ring 15 are preferably made of a textile material selected from nylon, rayon, PET, PEN, lyocell, aramid or combinations thereof, in a single or multi-ply, preferably single or double-ply.

[0213] The diameter of the reinforcing cords of the ring 15 is preferably comprised between about 0.10 mm and about 0.55 mm, more preferably between about 0.12 mm and about 0.35 mm, including the extreme values, for example equal to about 0.13 mm.

[0214] The linear density of the reinforcing cords of the ring 15 is comprised between about 110 dtex and about 1300 dtex, more preferably between about 230 dtex and about 940 dtex, including the extreme values, for example equal to about 450 dtex.

[0215] Specific examples of textile materials that can be used for the above-mentioned reinforcing cords of the ring 15 are as follows:

[0216] Nylon 930 dtex / 1

[0217] Nylon 470 dtex / 1

[0218] Nylon 230 dtex / 1

[0219] Aramid 470 / 1

[0220] Where the number 1 after dtex indicates the number of plies.

[0221] The reinforcing cords of the ring 15 are inclined with respect to the equatorial plane of the tyre 100 by an angle comprised between about 30° and about 60°, preferably between about 40° and about 50°, including the extreme values.

[0222] Preferably, the number of threads per inch of the plies 16 of the ring 15 is equal to or greater than the number of threads per inch of the carcass plies 3 of the carcass structure 2. Preferably, the number of threads per inch of the plies 16 of the ring 15 is comprised between about 15 TPI and about 360 TPI, more preferably between about 30 TPI and about 300 TPI, even more preferably between about 60 TPI and about 240 TPI, even more preferably between about 80 TPI and about 200 TPI, including the extreme values, for example equal to about 120 TPI.

[0223] As an example, the carcass plies 3 can have a number of threads per inch of about 60 TPI, the plies 16 of the ring 15 can have a number of threads per inch of about 120 TPI.

[0224] As Figure 1As shown, the inclination of the reinforcing cords of the ring 15 is opposite to the inclination of the reinforcing cords of the carcass ply 3 of the carcass structure. As an example, when the reinforcing cords of the carcass ply 3 are inclined by 45°, the reinforcing cords of the ply 16 of the ring 15 are substantially perpendicular to the reinforcing cords of the carcass ply 3.

[0225] The distance H5 over which the wear-resistant strip-like element 13 extends radially is smaller than the second distance H2 and the third distance H3. In other words, the length over which the wear-resistant strip-like element 13 extends radially is shorter than the length of the first flap 15a and of the second flap 15b of the ring 15. Figure 1A

[0226] The bead-to-bead ply 14 is a ply comprising reinforcing cords inclined by a third angle with respect to the equatorial plane. The third angle of inclination of the reinforcing cords of the bead-to-bead ply 14 is comprised between about 30° and about 60°, including the extreme values, preferably between about 40° and about 50°, including the extreme values, for example equal to about 45°.

[0227] Alternatively, the reinforcing cords of the bead-to-bead ply 14 can be made in a square fabric structure (i.e. with warp reinforcing cords and weft reinforcing cords).

[0228] The reinforcing cords of the bead-to-bead ply 14 are made of a textile material. The reinforcing cords of the carcass structure and the reinforcing cords of the bead-to-bead ply are made of the same textile material.

[0229] In a preferred embodiment, the bead-to-bead ply 14 has a thread count comprised between about 15 TPI and about 360 TPI, including the extreme values, preferably between about 30 TPI and about 300 TPI, including the extreme values, more preferably between about 60 TPI and about 240 TPI, including the extreme values, even more preferably between about 120 TPI and about 200 TPI, including the extreme values, for example equal to about 60 TPI.

[0230] In a preferred embodiment, the diameter of the reinforcing cords of the bead-to-bead ply 14 is comprised between about 0.10 mm and about 0.55 mm, including the extreme values, preferably between about 0.12 mm and about 0.35 mm, including the extreme values, for example equal to about 0.30 mm.

[0231] In a preferred embodiment, the linear density of the reinforcing cords of the bead-to-bead ply 14 is comprised between about 110 dtex and about 1300 dtex, including the extreme values, preferably between about 230 dtex and about 940 dtex, including the extreme values, for example equal to about 450 dtex.

[0232] As Figure 1 ​As shown, in the case where the reinforcing cords of the carcass ply 3 and the reinforcing cords of the bead-to-bead ply 14 are substantially parallel, the inclination of the reinforcing cords of the bead-to-bead ply 14 is opposite to the inclination of the reinforcing cords of the carcass ply 3 of the carcass structure 2. For example, when the reinforcing cords of the carcass ply 3 are inclined by 45°, the reinforcing cords of the bead-to-bead ply 14 are substantially perpendicular to the reinforcing cords of the carcass ply 3.

[0233] Preferably, the building of the tyre 100 is carried out according to processes known to the person skilled in the art.

[0234] Some tests were carried out to evaluate the performance of the bicycle tyre according to the present application.

[0235] In particular, three tyres were tested - a reference tyre (tyre 1), a tyre with filler (tyre 2) and a tyre according to the present application (tyre 3), respectively.

[0236] The three tyres had dimensions 27.5 x 2.6 (ETRTO 65-584).

[0237] The three tyres were each mounted on a rim having dimensions 584 x 21 C. The rigidity of the rim was such that, by applying any load to the wheel, the contribution of the rim to the total deformation of the wheel was less than 1%.

[0238] The three tyres differed only in the following features:

[0239] - in addition to the reference tyre, the tyre with filler also had a filler of elastomeric material of the type having a thickness in the axial direction equal to that of the bead core and an extension in the radial direction of about 35 mm at each bead core;

[0240] - in addition to the tyre with filler, the tyre according to the present application also had a ring of the type having a number of threads of the reinforcing cords twice that of the carcass ply and extending at each bead core up to about half the radial extension of the filler of elastomeric material.

[0241] All three tyres were provided with the same bead-to-bead ply of the type described, the same carcass structure (of the type shown), the same tread band and the same wear-resistant band-like element. Figure 1 and 2 of the type shown).

[0242] For the stiffness tests on the tires, each wheel (rim and tire) is mounted on a fixed hub. The tires are inflated to 2 bar. Each tire has possible blocks removed from the tread band and the tire is set in contact with a flat surface. The wheel is subjected to a fixed vertical load and then alternating longitudinal, lateral and twist torques are applied at the contact area of the tire with the flat surface. A force sensor placed on the hub measures the forces and moments transmitted to the wheel. The vertical stiffness is calculated as the ratio between the vertical force applied and the vertical displacement of the wheel. The lateral stiffness is calculated as the ratio between the lateral force applied and the lateral displacement of the wheel. The longitudinal stiffness is calculated as the ratio between the longitudinal force applied and the lateral displacement of the wheel. The twist stiffness is calculated as the ratio between the twist torque applied and the rotation of the wheel.

[0243] From the comparative stiffness tests on the tires it can be seen that:

[0244] - the vertical stiffness of tire 2 is increased by about 6% with respect to tire 1 and the vertical stiffness of tire 3 is increased by about 10% with respect to tire 1 ;

[0245] - the lateral stiffness of tire 2 is increased by about 5% with respect to tire 1 and the lateral stiffness of tire 3 is increased by about 8% with respect to tire 1 ;

[0246] - the longitudinal stiffness of tire 2 is increased by about 6% with respect to tire 1 and the longitudinal stiffness of tire 3 is increased by about 10% with respect to tire 1 ;

[0247] - the twist stiffness of tire 2 is increased by about 8% with respect to tire 1 and the twist stiffness of tire 3 is increased by about 12% with respect to tire 1.

[0248] For the obstacle impact tests, the tires are inflated to 1.5 bar and each wheel (rim and tire) is subjected to a vertical load of 600 N. The wheels are made to pass over a fixed obstacle, increasing the speed in increments of 5 km / h until the carcass structure breaks.

[0249] From the comparative obstacle impact tests it can be seen that:

[0250] - the carcass breakage speed of tire 1 is 20 km / h;

[0251] - the carcass breakage speed of tire 2 is 25 km / h;

[0252] - the carcass breakage speed of tire 3 is 35 km / h.

[0253] For the rideability test, the double-suspension E-MTB bicycle was equipped in turn with the tyres of types 1, 2 and 3 described above. The tyres were inflated to about 1.5 bar. A test rider rode the bicycle on a route with alternating uphill, downhill, flat, fast, slow sections, gravel, compact ground, bends with inclination, bends with counter-gradient and sudden braking.

[0254] The table below summarises the sensations perceived by the tester, where the term "rideability" means the ability to maintain a set trajectory, the term "reactivity" indicates the speed of transmission of the drive torque to the ground, and the term "safety" means the progressive behaviour in the turns. The symbol "+" indicates a slight improvement in performance with respect to the reference value given by the bicycle equipped with the tyre of type 1, the symbol "++" indicates a significant improvement in performance with respect to the reference value given by the bicycle equipped with the tyre of type 1, and the symbol "+++" indicates a great improvement in performance with respect to the reference value given by the bicycle equipped with the tyre of type 1.

[0255] Riding quality Reactivity Safety Tire 2 + ++ + Tire 3 ++ +++ ++

[0256] The application has been described with reference to some preferred embodiments. Different modifications can be made to the above-described embodiments, while still remaining within the scope of protection of the present application, as defined by the appended claims.

Claims

1. Bicycle tyre (100) comprising a pair of bead cores (8), a carcass structure (2) turned around said pair of bead cores (8) and a tread band (4) located radially outside said carcass structure (2); at each bead core (8) there is provided an elastomeric material filler (12) having a constant thickness throughout its extension, made of a material having an ultimate tensile strength greater than or equal to 15 MPa and less than 40 MPa, extending in a radial direction from said bead core (8) for a first length (HI) comprised between 20% and 80% of a distance (H4) measured in a radial direction between said bead core (8) and a radially outermost portion of said carcass structure (2).

2. Bicycle tyre (100) according to claim 1, wherein, said first length (HI) is comprised between 30% and 70% of a distance (H4) measured in a radial direction between said bead core (8) and a radially outermost portion of said carcass structure (2).

3. Bicycle tyre (100) according to claim 1, wherein, said elastomeric material filler (12) extends from a radially outer surface of said bead core (8).

4. Bicycle tyre (100) according to claim 1, wherein, said first length (HI) is greater than or equal to 10 mm and less than or equal to 50 mm.

5. Bicycle tyre (100) according to claim 1, wherein, a thickness of said elastomeric material filler (12) measured in an axial direction at a portion radially adjacent to said bead core is equal to or less than a thickness of said bead core (8) measured in the same axial direction.

6. Bicycle tyre (100) according to claim 1, wherein, said elastomeric material filler (12) is made of a material having an elongation at break greater than 120% and less than 800%.

7. Bicycle tyre (100) according to claim 1, wherein, said elastomeric material filler (12) is made of a material having a dynamic modulus of elasticity E' greater than 3 MPa and less than 35 MPa at 23°C, 10 Hz.

8. Bicycle tyre (100) according to claim 1, wherein, said elastomeric material filler (12) is made of a material having a dynamic modulus of elasticity E' greater than 2.2 MPa and less than 25 MPa at 70°C, 10 Hz.

9. Bicycle tyre (100) according to claim 1, wherein, at each bead core (8) there is provided a ring (15) interposed between said carcass structure (2) and said elastomeric material filler (12), turned around said bead core (8) so as to define a first flap (15a) located axially outside said elastomeric material filler (12) and a second flap (15b) located axially inside said elastomeric material filler (12), wherein said first flap (15a) extends in a radial direction from said bead core (8) for a second length (H2) and said second flap (15b) extends in a radial direction from said bead core (8) for a third length (H3).

10. Bicycle tyre (100) according to claim 1, wherein, said elastomeric material filler (12) has a thickness measured in an axial direction greater than 0.5 mm and less than 4 mm.

11. Bicycle tyre (100) according to claim 1, wherein, said elastomeric material filler (12) is a single-piece insert.

12. Bicycle tyre (100) according to claim 1, wherein, said carcass structure (2) comprises at least one carcass ply (3) comprising a plurality of reinforcing cords inclined at a first angle with respect to the equatorial plane.

13. Bicycle tyre (100) according to claim 12, wherein, Said carcass ply (3) is turned up around said bead core (8) so as to create at least two superimposed carcass plies; said elastomeric material filler (12) is interposed between said at least two superimposed carcass plies.

14. Bicycle tyre (100) according to claim 12, wherein, Said carcass ply (3) is turned up around said bead core (8) so as to create two carcass plies at two opposite first portions (9) of said tyre and three superimposed carcass plies at a second portion (10) of said tyre, said second portion being arranged between said two opposite first portions (9); said elastomeric material filler (12) is arranged in said two opposite first portions (9) of said tyre.

15. Bicycle tyre (100) according to claim 9, wherein, Said second length (H2) and third length (H3) are less than or equal to said first length (H1).

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