This is exaggerated for runflats. I've been through 2 sets of Goodyear F1 asymetricals on the rear and they wore pretty evenly accross the whole tyre. The runflats I took off were awful, loads of tread on the outside,naff all on the inside edge,didn't spot it until I took the wheels off to clean the alloys ( 18"). Don't expect much more than 12,000 miles out of the rears,but the fronts are at 22,000 and showing loads of tread ( AND that's with 2 trackdays on them too).