Originally Posted by llis
I have the 235/40R18 and 255/40R18 on my E92 (Dunlop Wintersport 3Ds), and it is riding what seems like an inch or more lower, and my speedometer, pretty close on the ZCP wheels & Conti tires, is now 4mph off at 65mph.
If one were to believe that actually lowering the car for winter is probably non-ideal, how would one adjust this package to get back to decent clearance for winter?
If all you changed were the width of the tires, the car should only sit 0.3" lower. A 245/40-18 tire (stock for the M3) is only 0.3" taller than the 235/40-18. If the car is riding 1" lower, something else is going on. Also, the speedo should only be out 0.7 mph at 60.
See this link for the calculation... http://www.rimsntires.com/rt_specs.jsp
I think going 235 front and 255 rear will only have a nominal difference on ride height and on the speedo. I went 245/40 all around, myself. This kept the front at stock height and the rear slightly off. Seems fine so far.