I recently found out that I have to replace a bad tire on the rear of my 2000 A6Q, and would rather not buy 4 new tires, but instead two, or just replace the one with a used one of similar tread depth. How bad is it to be off a few MM's in depth/overall diameter? I know it's bad to be way off for the health of the differentials, but how bad is it to have the front matched, and the rear matched, but not the front AND rear matched? Thanks in advance!

 

anything more than 4/32's (1/8 of and inch) of difference will damage your AWD. BTW this really isnt the correct place to be posting something like this.