Studded tyre having reduced road wear
A tyre ( 200 ) includes a tread ( 210 ) and multiple studs ( 100 ) in the tread ( 210 ) such that at least pins ( 110 ) of the studs ( 100 ) are exposed on the tread ( 210 ). The tyre ( 200 ) is configured such that a load index (LI) of the tyre ( 200 ) as defined in The European Tyre and Rim Technical Organization Standards Manual (2023) table G.7 is from eighty-six to one hundred sixteen (from 86 to 116). The tyre ( 200 ) is further configured such that a road wear of the tyre ( 200 ) as measured according to the standard SFS7503:2022:en is less than the value calculatable by the polynomial formula −0.000139×LI 2 +0.0431×LI−1.90.
1 . A tyre comprising:
a tread;
a metal belt extending circumferentially around a rotational axis of the tyre,
a textile belt comprising a strand running around the metal belt a plurality of rounds such that the textile belt is arranged between the tread and the metal belt,
an underlayer comprising a first rubber compound, the underlayer being arranged radially outside the textile belt,
a cap layer forming at least part of a running surface of the tyre, and
an intermediate layer made of a second rubber compound, the intermediate layer being arranged, at least partially, between the underlayer and the cap layer,
wherein a first round of the plurality of rounds of the strand is spaced apart from a second round of the plurality of rounds of the strand such that:
a first spacing is arranged between the first round of the strand and the second round of the strand in an axial direction of the tyre, the first spacing having a width of 5% to 50% of a width of the strand;
the strand comprises fibres, the fibres having a diameter of 0.4 mm to 0.7 mm, having a longitudinal direction forming a right angle with a direction of the width of the strand, and being made of polyamide; and
a plurality of studs in the tread;
wherein:
the plurality of studs are arranged at least partly on the underlayer,
the underlayer has a hardness between 45 ShA and 60 ShA,
the intermediate layer being arranged, at least partially, on locations of the studs,
a dynamic stiffness of the underlayer is at least 100% higher than a dynamic stiffness of the intermediate layer at a temperature of 0° C., and the dynamic stiffness of the intermediate layer is higher than the dynamic stiffness of the underlayer at a temperature of at least 5° C., the dynamic stiffnesses of the underlayer and the dynamic stiffness of the intermediate layer being determined according to the standard ISO 4664-1:2011 in a compression test,
the plurality of studs include a first group of studs, each stud of the first group of studs comprising a base flange, wherein each stud of the first group of studs is arranged such that the base flange of each stud of the first group of studs comprises a portion of the base flange such that no part of the strand is arranged between the part of the base flange and the metal belt,
at least pins of the studs are exposed on the tread, the tyre being configured such that:
a load index of the tyre as defined in The European Tyre and Rim Technical Organization Standards Manual (2023) table G.7 is from eighty six to one hundred sixteen, and
a road wear of the tyre as measured according to the standard SFS7503:2022:en is less than the value calculatable by the formula −0.000139×LI 2 +0.0431×LI−1.90.
2 . The tyre of the claim 1 , wherein:
the road wear of the tyre as measured according to the standard SFS7503:2022:en is less than 1.00 g and the load index of the tyre is 99 or more; or
the road wear of the tyre as measured according to the standard SFS7503:2022: en is less than 0.91 g and the load index of the tyre is 93 or more; or
the road wear of the tyre as measured according to the standard SFS7503:2022: en is less than 1.09 g and the load index of the tyre is 105 or more.
3 . The tyre of claim 1 , wherein:
a mass of each one of the studs is 0.4 g to 3 g.
4 . The tyre of claim 1 , wherein:
an average of protrusions of studs from the tread is between 0.6 mm and 2.0 mm.
5 . The tyre of claim 1 , wherein:
a central line of the tread defines a first half of the tread and a second half of the tread, wherein:
the first half comprises a first number of studs and
the second half comprises a second number of studs such that:
a ratio of the first number to the second number is 90% to 110%.
6 . The tyre of claim 1 , wherein:
the tread has a first width and a first circumference,
the tread comprises a total number of studs, and
a ratio of the total number of studs to the product of the first width and the first circumference is more than 5.6 pieces per square-decimetre.
7 . The tyre of claim 1 , wherein:
the tread comprises tread blocks such that grooves are arranged between the tread blocks, and
at least some of the grooves are inclined such that the at least some of the grooves define a V-shape or a half of a V-shape, the V-shape or the half of a V-shape defining a direction of rotation of the tyre when used driving forwards, the direction of rotation being reverse to a direction to which the V-shape or the half of a V-shape opens.
8 . The tyre of claim 1 , wherein:
the dynamic stiffness of the underlayer is configured to be less than 25 MPa, determined at 20° C., and
the dynamic stiffness of the underlayer, determined at 0° C., is configured to be at least 2 times the dynamic stiffness of the underlayer determined at 20° C.,
determined according to the standard ISO 4664-1:2011.
9 . The tyre of claim 1 , wherein:
an axial edge of the strand is arranged closer to the first round than to the second round or the first round forms the axial edge of the strand; and
the first round is arranged a distance apart from the axial edge of the strand, the distance being at most five times the width of the strand or
the first round forms the axial edge of the strand;
the distance is at most three times the width of the strand or the first round forms the axial edge of the strand.
10 . The tyre of claim 1 , wherein:
the width of the strand is 6 mm to 18 mm and/or
the first spacing between the first round of the strand and the second round of the strand is 10% to 40% of the width of the strand.
11 . The tyre of claim 1 , wherein the first spacing is 15% to 25% of the width of the strand.
12 . The tyre of claim 1 , wherein an average thickness of the underlayer is 1.0 to 6.0 mm.
13 . The tyre of claim 1 , wherein a thickness of the intermediate layer, determined at a location wherein the intermediate layer is surrounding a stud, is 0.4 mm to 7 mm.
14 . The tyre of claim 1 , wherein a hardness of the intermediate layer is 66 to 80 ShA.
15 . The tyre of claim 1 , wherein one or more studs of the plurality of studs each comprises:
a base flange,
a second part, the second part being joined to the base flange and extending in a longitudinal direction of the stud from the base flange, and
a pin protruding from the second part in the longitudinal direction of the stud, the pin comprising metal or ceramic, wherein:
the base flange has a first cross-section on a plane to which the longitudinal direction of the stud is normal, the first cross-section having a first area,
the pin has a second cross-section on a plane to which longitudinal direction of the stud is normal, the second cross-section having a second area, and
the first area is 20 mm 2 to 80 mm 2 .
16 . The tyre of the claim 15 , wherein in each one of the one or more studs of the plurality of studs:
a ratio of the first area to the second area is 6.5 to 21.
17 . The tyre of claim 15 , wherein in each one of the one or more studs of the plurality of studs:
the pins protrude a first height from the second part of the stud in the longitudinal direction of the stud, wherein a ratio of the first area to the first height is 20 to 50 mm 2 /mm.
18 . The tyre of claim 15 , wherein in each one of the one or more studs of the plurality of studs:
the second cross-section has at least one and at most three axes of symmetry.
19 . The tyre of claim 1 ,
wherein;
a position of a tan delta maximum of the underlayer and/or the first rubber compound is configured to be between −10° C. and +15° C., determined according to ISO 4664-1:2011 in compression.
20 . The tyre of claim 19 , wherein:
the dynamic stiffness of the underlayer is configured to be less than 25 MPa, determined at 20° C., and
the dynamic stiffness of the underlayer, determined at 0° C., is configured to be at least 2 times the dynamic stiffness of the underlayer determined at 20° C.,
determined according to ISO 4664-1:2011 in compression;
the dynamic stiffness of the underlayer determined at −25° C., is configured to be at least 20 times the dynamic stiffness of the underlayer determined at +20° C.,
determined according to the standard ISO 4664-1:2011.
21 . The tyre of claim 1 , wherein:
the plurality of studs include a second group of studs, each stud of the second group of studs comprising a base flange, and
each stud of the second group of studs is arranged such that a part of the strand is arranged radially inward from at least a part of the base flange of the stud of the second group.
22 . The tyre of claim 21 , wherein at least a part of the studs of the second group belong to the first group of studs.
23 . The tyre of claim 1 , wherein the strand comprises fibres made of polyamide 6 or polyamide 6.6.
24 . The tyre of claim 23 , wherein the first spacing is 15% to 25% of the width of the strand.
25 . An arrangement comprising:
a first tyre according to claim 1 , and
a second tyre comprising a second tread and a plurality of studs in the second tread such that at least pins of the studs are exposed on the second tread, the second tyre being configured such that:
a second load index of the second tyre as defined in The European Tyre and Rim Technical Organization Standards Manual (2023) table G.7 is from eighty six to one hundred sixteen and
a second road wear of the second tyre as measured according to the standard SFS7503:2022:en is less than the value calculatable by the formula −0.000139×LI 2 2 +0.0431×LI 2 −1.90, wherein
the second load index is not equal to the load index of the first tyre.