Tyre slits (on the wets)

[djones]

I have noticed these small cuts in the blocks on a lot of winter tyres for the road.

What do they acheive?

[Just_a_fan]

They're called "sipes" after John Sipe (he invented them in the 1920s).

I think they work because the leading edge of a tread block helps to clear the water and bite in to the tarmac. With sipes, the number of leading edges increases massively. This improves grip.

Winter tyres have huge numbers of sipes,

[xpensive]

That could very well be JAF, simply making a more compliant tread without using too soft a rubber is another theory?

[Jersey Tom]

JAF is spot on.

It does make the tread as a whole more "compliant" in shear, but it doesn't make the rubber any more compliant or hysteretic which would increase grip.

You'll see sipes all over consumer tires.

[xpensive]

Compliant? I think that's what I said? Yes, I'm certain I used the xpression compliant? Didn't I say compliant?

[n_anirudh]

The video on the first post in the URL shows how the wet weather tires are made

http://www.thescuderia.net/forums/showt ... cia.-Video

[Jersey Tom]

Compliant? I think that's what I said? Yes, I'm certain I used the xpression compliant? Didn't I say compliant?

It is, but to me it sounded like you meant it made the tread more compliant as in higher grip.. higher loss modulus that is. Like running a "softer" compound.

In reality, water evacuation notwithstanding, sipes hurt handling and make it less responsive and precise. Squirmy.

[xpensive]

Compliant? I think that's what I said? Yes, I'm certain I used the xpression compliant? Didn't I say compliant?

It is, but to me it sounded like you meant it made the tread more compliant as in higher grip.. higher loss modulus that is. Like running a "softer" compound.

In reality, water evacuation notwithstanding, sipes hurt handling and make it less responsive and precise. Squirmy.

I did mean compliant as in higher grip, which I belive is the name of the game when driving in snow or wet, isn't it?