If alignment does not explain it, driving conditions might. By your use of 'tyre' and 'cheers' I guess that you may be in a right hand drive country. So then you're driving on the left side of the road, most exit ramps will probably circle left, so if you take all the ramps with extreme gusto, maybe it is eating the right side tire (tyre). You would have to be hitting them fairly hard to make that big of a difference, but that is the sort of thing the M3 encourages....
To credit the forum, click through one of the banners in my signature and the top of the page, or call me direct at 877.522.8473 ext 660. Email:firstname.lastname@example.org