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#5: 05-18-2011, 08:11 PM
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Originally Posted by outahere View Post
Here is another good article on the Summer vs UHPAS tire debate:

"..........Consumers and a shockingly high number of tire company sales staff are under the mistaken belief that all-season tires offer better damp-road grip than summer tires.
The truth: All-season tires trade damp and dry grip in exchange for some (albeit limited) mobility on snowy roads and in well-below freezing temperatures..........."
The basic points that Mac is making in the article are somewhat valid, but there's some assumptions & generalizations being made that need to be clarified. Evreyone needs to decide on their individual needs / mix of operating conditions and make a more informed decision... (ie AS traction or max summer performance).

The compound choices on summer only tires are making the tire optimized for temps above freezing, and as a result they are able to take advantage of improved damp & dry grip. Also remember that there's a difference in damp grip & hydroplaning resistance: damp surfaces have a very thin water layer on the surface which doesn't require lateral tread features or sipes (simple or complex shaped biting edges) to break through that subtle layer, the actual "grip" qualities of the rubber allow it to adhere to the road quite well. The other situation involving deeper water or hydroplaning resistance comes into play with both compound choice & water evacuation: if the tread pattern can clear the water, then the rubber can make contact and go to work, but if it can't make contact, then grip will suffer.

I don't necessarily agree that there's only a handful of days in SC that summer tires would be better than AS tires. Different needs for diff drivers of course, but in my experience I'm dependent on my UHP AS tires to provide adequate traction & control in more than a handful of snow/ice days during the year. I frequently visit the local mtns where lingering snow/ice is around and summer tires would not do the job, both because of the compound & temp limitations, but also based on tread design. I also frequent areas for kayaking during the summer or winter that require a bit more soft soil / dirt road / mud traction than a more summer oriented tire is meant for (summer designs typically use high surface area designs = mostly solid tread surface for more road contact instead of lateral grooves / sipes / circumferential grooves such as in AS tires.
As I stated, a tread compound with a lower glass transition temperature (ie lower temp operating range) is more helpful to me year round vs swapping tires in later spring / summer. Mac mentioned the glass trans temp, but fails to identify the overall shape of the rubber response curve as it approaches it's glass trans temp. It's not a subtle change for grip vs temp as it approaches the low temp pt, it's a bit gradual as the temp drops and then goes more exponential (ie steep dropoff) so the change is significant & noticeable when you attempt to use the tire beyond it's intended temp range. I needed single digit Farenheit temp performance this past winter & summer tires would not have provided it. The year round mixed condition traction needs & treadwear mileage requirements dictate my choices in tires more so than anything.
Any other questions, feel free to fire away. If I don't know something, then I'm not going to give a crap answer. Let the facts speak for themselves, and read as much as you can to make an informed decision based on your tire choice needs.