[quote author=pkoko link=topic=73415.msg1305438#msg1305438 date=1175475928]
Summary: Grand touring all-season < Performance all-season < High performance all season < High performance Summer < Ultra High peformance summer. That is 4 levels of upgrades. That is extreemely significant improvement in handling/braking/ dry traction. My personal opinion- Stock Michelins to Kuhmos; there is 20% improvement in braking/accleration. 30-40% improvement in handling. I know the Kuhmos are a little wider (20mm or 1 inch); A wider aspect tires improves handling as well. Getting a bigger rim size will only reduce wheel flex ( improves handling by a small margin. It only comes into play at limits of car suspension & tires traction ). Bigger rims don't improve handling; Better tires do.
Good luck
sorry for long post.
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Hi pkoko. :wavey: Almost all of what you say in your post is 100% true. However, I just wanted to address your above estimates (from #3 in your post) as to the percentage of improvement you feel can be achieved by going to an "Ultra High Performance Summer" tire. Please believe me that this is not to start a debate with you or anyone else, just to put things into perspective for those with less automotive knowledge than you.
Let me state up front, that I understand you were just trying to quote some numbers off the top of your head (and I know how hard that is to do) to help others. The only reason I am replying is due to the fact that some forum members will take the numbers that you (a respected and knowledgeable forum member) posted, and truly believe them as achievable by just replacing their tires, only to be greatly disappointed.
Just so we have a baseline, I will take the figures from a Motor Trend test of the 2006 Fusion V-6 SEL: 0-60 time of 7.2 seconds, and a quarter mile time of 15.5 seconds. A stopping distance from 60 mph of 137 feet. And an average lateral skidpad performance of .80g's.
If a Fusion owner were to buy "Ultra High Performance Summer" tires and get a 20% improvement in braking and acceleration, their car would now accelerate 0-60 in 5.76 seconds, and do the quarter mile in 12.4 seconds. Their braking performance from 60 mph would improve to 109.6 feet. The Fusion's skidpad performance (granted, just one measure of handling) at a 30-40% improvement figure, would improve to .96 - 1.12 g's.
As you can see, it would be impossible to see anywhere near an improvement of that magnitude by merely replacing the tires. Some of those numbers are now in "Supercar" territory (quarter mile, braking and handling)
In closing, I felt I should put the numbers into perspective, so no other members pay for "Ultra High Performance Summer" tires, and then wonder why they don't see the type of improvements cited (I agree 100% that better tires will noticeably improve braking, acceleration and handling, just not that dramatically).
Please take this post in the friendly manner it was meant (informational, not confrontational at all).
Good luck! :cheers: