My 2008 MINI Cooper S w/ JCW package has worn the front tires down to the wear bars (in 12k miles). The rear tires still look almost new (I haven't measured, but I'd guess they have at least 6/32s left). I imagine this is due to my "spirited" driving style. The wear on the fronts is even, so I don't suspect any suspension problems.
My question is will I cause any extra wear or damage by replacing only the worn-out fronts? I would move the existing rears to the front and put the new tires on the back. Tire size matches, but brand and model would be different.