325/25/20 on M6?

[brad850csi]

Originally Posted by BlackBear

Front Pirelli P-Zero 265/35/20

Rear Michelin Pilot Super Sport 295/30/20

All tires have very good tread.

The sizes are correct factory sizes. Both tires are approved by BMW.

I know that the straight line traction issues are caused by too much power.

My question really is if anyone has had issues with the two brands mixed on an M5 or M6 like I'm having with traction control intervening in mildly aggressive turns?

I have had this problem on a Porsche Turbo when I mixed brands. The only remedy was to switch to Michelins all around. After I did that there was no more premature traction control intervention in turns.

Some cars are more sensitive than others.

I've got 305/30r20 PS4S on stock wheels and they are great with my original 265/35r20 PZero's. Perhaps it is the PS4S or the extra width helps slightly, possibly due to the width or the rolling radius...let me expand on this:

One thing I have seen a lot of in the F80 forums is that they have a taller tyre in the rear - their stock sizes are all 20mm wider at the rear with the same aspect ratio. This means that if someone runs square all round or goes up wider at the rear and lowers the aspect ratio such as going from 255/35r19 and 275/35r19 to 295/30r19 in the rear only without changing the fronts they go from 2.1% taller in the rear to being 0.3% shorter in the rear. This confuses the hell out of the traction control when you're accelerating hard, even if you're not actually losing grip.

Perhaps if your PZero's are new and the PSS are old and you're running stock sizes this could be a problem? With the stock sizes assuming brand new tyres the car has 1.3% shorter rear tyres which it is programmed for but with the 305's at the rear that drops to only 0.3% difference which may help more with traction systems - not so much traction itself