i know this is not timely as the OP was back in 01 Nov. but here it is. i recently sold my Audi Quattro for my 335xi. i had a similar incident w/ my audi, cut a tire down (FR) at 5K miles. Audi measured the rubber and said no problem w/ butting a new tire at this mileage. and anyone knowing Quattro, their tolerances are much tighter then BMW x drive. so by default a good guess is yes you are ok to replace a new tire. Audi had to measure all 3 other tires.
maybe the OP can let us know how he made out.
