Thanks for the reply. The reason for the staggered sizes is because I already have a different set of rims from my other E46. I'm getting ready to trade it in and want to keep the wheels for the xi. The tires are slightly different in width because I didn't quite like the feel when I was running a completely square set up. Steering feel and response is more to my liking running the 215/40 up front. Also, I should have mentioned that wheels are 18 x 8 all around. As for problems with my speedo... That is not the concern. The issue with running staggered sizes is that side wall hight typically varies front to back...meaning overall diameter is different. The difference in diameter means that each wheel takes a different number of revolutions to travel the same distance. This puts a slight strain on the differentials depending on how far off the diameters are. Overall this can lead to excessive drivetrain wear and eventually failure. Ideally... All four wheels and tires would have the exact same diameter leading to a perfect distribution of torque and power and even wear on the differentials. But manufacterers realize this is not realistic due to uneven tire wear... Flats... Etc. Therefore there is a certain range of variation that is acceptable per the manufacterer specifications.
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