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Summer And Winter Tyre Ratings

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I really do not understand the new A.B.C.D.E.F.G tyre ratings when it comes to wet weather performance. On one hand we have the tyre salesman carping on about forking out for winter tyres and when you look at the wet weather braking performance of these highly recommended winter tyres they aren't as good as some of the B rated summer tyres. Are winter and summer tyres tested under different temperature conditions?

I watched a recently posted propaganda film about winter tyres and saw how the wonderfully almost saintly winter tyre outperformed the "terrible stinky public enemy baddie ne'er do well" summer tyre. I wondered how easy it would be to fit the most slippery summer tyre and compare it to the most sticky winter tyre in order to improve winter tyre sales.

I do not doubt that softer compounds have a much higher coefficient of friction when compared to hard compounds but I had perhaps wrongly assumed that anything which showed itself to grip well in the wet would be a good winter tyre too due to its higher coefficient of friction under wet weather conditions.

When all is said and done, the formula one cars do not have differing compounds of wet weather tyres unlike their dry weather tyres which have quite varying characteristics from one dry compound to the next.

Has anyone been able to find anything which actually makes sense? Like I say, the propaganda video I saw wasn't really very informative at all other than to illustrate high coefficient of friction verses low coefficient of friction.... a simple experiment I remember carrying out at school as a 12 year old in a physics lesson with a polished wooden block and a rubber block of similar weight being towed along the desktop by a spring balance.

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Hi Geoff, I skipped over from the Rav forum when i saw your post. I ran my last Rav over two winters on Continental winter tyres and they totally transformed an already very capable vehicle. I'm not sure which video you have seen, maybe this helps.

Regards Paul .

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TBH I take the tyre ratings with a grain of salt anyway; The Conti PC2E and PC5 have very differing ratings but feel almost identical.

That said, wet weather performance isn't just about rubber compound, but also tread design, as the tyres need to be able to cut through the water and also get rid of it; Often, the winter tyre tread patterns are designed with snow grip in mind, which isn't necessarily optimal for removing water.

You can have as grippy a compound as you want but it ain't gonna make a bit of difference if the tyre is aquaplaning because it can't shift/cut through the water.

The coefficient of friction thing is slightly misleading; The two main differences between summer and winter tyres is the tread pattern and the rubber compound being designed to stay flexible in colder temps where a summer tyre would be harder.

This means the winter tyre will retain its coefficient of friction in the colder temps where the summer tyre would lose some to hardening, but above those optimal temps the summer tyre would have better traction, esp. on motorway runs and multi/heavy braking situations where it can get up to operating temperature, while the winter tyre would likely start to overheat and lose traction..

TBH we still haven't even gotten close to the quoted 7C optimal winter tyre temp down here so the topic has so far been pretty moot :lol:

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