I recently purchased an '07 E350 CPO with Sport Package. I was happy the dealer installed four new tires (Continentals). However, the next day I noticed the front and rear tires are the same size (245/40R18), but the car calls for 265/35R18 XL (extend load) in rear. The dealer said there was no issue with the tires being the same size. Moreover, the dealer claimed I could rotate the tires given they are the same front to back. That evening I got a chance to read the manual. I learned the front wheels are 8.5J x 18 and the rear are 9J x 18, the offsets are 30mm and 39mm front to back, respectively- meaning the tires cannot be rotated.

I stated the above to the dealer and reached out to MB USA for their recommendation. Is there anyting else I should be doing? Or should I even be concerned?

 

I should think you would want to address this situation with the dealer immediately and see if he will put the proper tires on the rear. IMO, and with previous experience with improper tires on several types of vehicles, you could very well experience a stabilty problem in the rear, especially at extreme limits. Cars like the MB's with the sports packages are very sensitive to tire sizes and any time you have a vehicle designed for a larger tire in the rear the suspension dynamics are tuned to match the wheel/tire combo. I've even had experiences where I purchased same size tires for the front and tried to put the used ones on the rear and experienced stability problems on a HONDA. You can imagine what that may do to a car with a tuned suspension. Your OD is probably close to the same with the taller than stock (40 vs 35) in the rear which may make it less noticeable. I would call a tire expert like the tire rack and get their take and then go to the dealer armed with a "professional" opinion. I suspect if you hear back from MB they would stand by the recommended tire sizes from the factory.

 

Specauto -

Thanks for the insight. The dealer is installing the correct size and type tires. The service manager could not answer why the specified were installed from the beginning.