AndersA

I have run my GT2 on MPSC tires for some time. Today I changed to my 19" wheels with Yokohama AVS tires. In addition to the expected differences in traction and comfort I also noticed a big difference in stability at higher speeds (above 130mph). The car felt "floating" and inprecise. With the MPSC it is rock stable up to at least 190 mph.

What is your experience with this? Can this be a issue with the AVS tires in particular or would any "road-tyre" behave in the same way? Any suggestions on a tyre with better stability than my AVS?


_____________________

Anders
996 GT2

Sweden

GT3 Chuck

since you say you changed to your 19" wheels I'm assuming your MPSC tires are on 18"s...besides 12.7mm more air under the car you might have changed the front and/or rear toe enough to affect handling/high speed stability...a fresh alignment for the 19"s might be the order of the day..would be surprised if it's a tire problem at that speed...any Y/Z rated tire should be fine...

AndersA

Sorry, I forgot to mention that I use lower profile 19" tires to keep the same wheel diameter. So the ride height is almost identical. I run 315/30-18 and 235/40-18 MPSC om the stock rims and 315/25-19 and 235/35-19 AVS on "Gemballa Racing" rims.

I think that the alignment is OK but it is something I need to check. I also should check if the wheels are warped, but my own guess is that the stiff sidewalls of the Cup tires gives the increased stability.

bora

If the tires are brand new, give it at least 500 miles to get rid of the release compound on the tire.
Also what are the tire pressures at?

edpurplett

.... I second the tire pressure issue.... sometimes a lb or two of too much pressure can cause your issue.... i have new MPS's on and had 2 lbs too much almost changed out suspensions... :-)... car was scaring me above 120.... lowered pressure and ..viola, perfect...