The invention relates to an asymmetric tread for a tire comprising a plurality of basic patterns, for each of which there is defined a sipes density corresponding to ∑ i li P * Wm where i is the number of sipes in the pattern, li is the length of the i th sipe on the tread surface, P is the pitch of the basic pattern and Wm is the width of the basic pattern, a sipes orientation level corresponding to ∑ i li * α i P * Wm , where αi is the positive or negative angle formed on the tread surface by the i th sipe with the transverse direction and |αi|≤45 degrees and a steering pull criterion for the basic pattern corresponding to ∑ i li * α i ∑ i li * α i . The sipes density is greater than or equal to 60 μm/mm 2 , the sipes orientation level is greater than or equal to 1.5 degrees/mm and the steering pull criterion for the pattern is less than or equal to 0.2. The tread comprises an inboard half-tread adjacent to an inboard sidewall of the tire, the sipes orientation level relating to the inboard half-tread being greater than 2 degrees/mm.
1. An asymmetric tread for a tire adapted to be fitted to a motor vehicle in a predetermined direction of fitting, comprising:
a tread surface adapted to be in contact with a roadway when the tire is being driven, and comprising an in-board half tread adjacent to an inboard sidewall of the tire and an outboard half-tread adjacent to an outboard sidewall of the tire;
a sequence of basic patterns arranged in the circumferential direction (X), each basic pattern extending over at least 80% of the width (W) of the tread;
each basic pattern comprising a plurality of raised elements provided with sipes opening onto the tread surface, each sipe having a width less than 1 mm and a depth of at least 3 mm;
wherein:
the following are defined for each basic pattern:
a sipes density (D) corresponding to
∑
i
li
P
*
Wm
where i is the number of sipes in the pattern, li is the length of the i th sipe on the tread surface, P is the pitch of the basic pattern and Wm is the width of the basic pattern;
a sipes orientation level (NO) corresponding to
∑
i
li
*
α
i
P
*
Wm
,
where αi is the positive or negative angle formed on the tread surface by the i th sipe with the transverse direction and |αi|≤45 degrees;
a steering pull criterion for the basic pattern (CT) corresponding to
∑
i
li
*
α
i
∑
i
li
*
α
i
wherein the sipes density (D) is greater than or equal to 60 μm/mm 2 , the sipes orientation level (NO) is greater than or equal to 1.5 degrees/mm, and the steering pull criterion (CT) is less than or equal to 0.2, and
wherein the sipes orientation level (NO) of the inboard half-tread is greater than 2 degrees/mm, such that the sipes of the inboard half-tread are inclined more steeply with respect to the transverse direction than the sipes of the outboard half-tread.
2. The asymmetric tread according to claim 1 , wherein the steering pull criterion (CT) is less than 0.1.
3. The asymmetric tread according to claim 1 , wherein the steering pull criterion (CT) is less than 0.05.