What Tyre's?

[swanvesta]

on my 328 coupe i have got standard m sport wheels, with 7.5j x 17 on the front, and 8.5j x 17 on the back, what size tyres should i have on the front and what on the back? i had 235 40 17 on both and the asc light came on occasionally, (and stayed on) but now i've got 235 40 17 on the back, and 225 45 17 on the front. the light comes on all the time above 50 mph! they have got 16mm difference in diameter and i think this is why my traction control keeps coming on and staying on. HELP! i ts driving me crazy!!

[jshearer]

I have 235/40/17 all around and have no problems at all. Inside my door jam and in the manual this size is listed as the optional size from BMW.

[jllphan]

I could be wrong, but I'm not sure that tire size is why your ASC is going off. I had 235-45's front and back until recently, and replaced with 225-45's up front and 255-40's in the back, and have never had the ASC light come on (unless of course it's doing it's job). Of course my current tire set up is ideal, because I only have a difference of .3" or 2 revolutions per mile which is pretty good considering the offset.

You might have your code read or do the pedal dance, to see if it's an ECU error.