Forgive me if this topic has already been addressed.

My 2008 550i with sport package will soon need replacement tires. I would like to increase the sidewall when I replace the OEM tires. Has anyone tried to upgrade the stock 245/35/19 front and 275/30/19 rear to 245/40/19 front and 275/35/19 rear? There is a little change in the width of the tires and the overall diameter increases by one inch. If you have tried this did you encounter any problems? Any input welcome.

 

I have no personal experience with this size change. But, aside from speedometer error the increased diameter might cause some rubbing problems. Did you use this site http://www.miata.net/garage/tirecalc.html to determine the new size dimensions?

 

Thanks for the website there is certainly some good information there. My real concerns are rubbing and potential traction/stability control issues.

 

I am not sure on the specifics on that one, but I upgraded my 530i to 550i wheels (245/275). I called tirerack and asked them, and to be sure I also called my local dealer and asked to speak with a technician. In my case they both gave me the same answer so it was a relief!

When you call tirerack just pretend you're considering buying some of their tires, and at the dealer pretend you intend to have them installed there...

 

You could take a set of measurements using your current tires and see if you have sufficient clearance under full load and with the suspension deflected at the max. It's fair to assume that with the OEM tire size set-up you should have at least one full inch of clearance. But, with the diameter increased by almost one full inch you may be close. Look for rubbing interference in the suspension area (around the lower cushion of the strut) and in the wheel arch area.

I know that many set-ups have moved up in wheel diameter - but that was accompanied by a lower tire aspect ration. You're taking it up in the opposite direction. I do understand looking to consider a higher tire sidewall. Potholes are a killer of low profile tires.