In an attempt to "accuratize" the speedometer on my 540i, I put 275-40 ZR18 tires on the back of my 540i. I am using staggered wheels with 9.5" wide rears. That solved my speedo situation; instead of reading 75 or 76 at 70 mph the reading was 70 or 71. Since I enjoy driving a little north of the speed limit I like to know my speed. 73 mph and 85 mph feel about the same in a 540i. 85 mph costs $125 since the limit here is 65. BUT! one of the tires rubbed the fender (right side) and my DSC, brake and ABS lights all came on in the dash after driving a short distance. I don't know if the DCS and ABS were disabled but I don't want to have the lights on. Since the rubbing tire only made contact over a good sized bump I think the cause was the difference in speed of the front and rear tires. Any information on this would be interesting and appreciated. Anyway, using my standard sized winter wheels on the back solves this problem so I am going to go back to 265's in the rear. I don't want to start grinding off the wheel well. ggondek
The sensors picked up the differential sizes front and rear. If you're changing the diameter at one end, you need to change it by the same amount on the other end.
I am looking to bump up in size from the stock 17" wheels to 19" staggered rim set up. Will this through my spedo off?
Not if you do it properly and use tires that are the same overall diameter. This is called a "Plus Two" fitment and it requires a much lower profile tire sidewall to be correct.
