Quote:
Originally Posted by jackliu0527
I have X-drive yes, why wouldent I run 255/285? its the same factory ratio of 245/275, i know the fronts are slightly larger, but factory does run that set up
So if 295 no good on 9" how about 285? maybe I can run 245/285 which is same diameter
|
A 295/30/20 tire is 27" tall. So is a 255/35/20, which is why they are a perfect match.
A 285/30/20 is only 26.7" tall, so you are starting out with a difference of just over 1% when the tires are brand new.
Tread depth is 10mm. At half wear on the 285/30, the tire will only be 26.3-26.4" tall. If the front are wearing half as fast at the rears, the front tire is now 26.8-26.9" tall. The difference is around half an inch, which is approximately 2%.
The generally accepted limits in tire height difference for the x drive system is 1%. But this applies at every point during the life cycle of the tires. So if you start out with a 1% difference, you need to know what will happen to that percentage over time. On the 6 series, the height difference will increase over time because the rears wear faster than the front, and on the setup you are using the rear is already the smaller tire.
I've run through 3 sets of rears and one set of fronts on my car with 255/35 front and 295/30 rear with no issues.
Several people have tried running 255/35 and 285/30 and have reported issues. Its your car, though, so do what you want.
the 245/35/20 and 285/30/20 are only off by .1 inch and are probably the best solution if you want to use the 373 wheels.
I can't explain why BMW sells the 245/275 set up. They are violating their own recommendations. Unless that set up doesn't come on x drive vehicles? I honestly don't know if it is only on RWD vehicles or both RWD and xdrive.