My car is in having its 24k service and the garage say the rear discs need replacing. But they have mentioned that its only half of one disc that is worn. Is there any reason this would be the case, would I be wasting my time pushing for it warranty saying the pads and one disc are perfectly fine. Should they not wear at an even rate. Also nearly died when they quoted me £370 just for the discs and thats without fitting. Advice would be appreciated.