Hi there Im new to this forum and have a question. have searched precious threads for an answer but i am stumped. I picked up some 18" sline alloys for my A6 quattro sport. The tyre profile was the wrong size to fit under the front wishbones 50 series instead of 40. So i decided to fit the rear wheels with the 50 series tyres, as there is room to fit them ok. Then drive to the tyre shop to change the fron 2 to 40 series tyres. All sounds straight forward, rear wheels fitted ok with no clearance problems. Set of to the tyre shop, but only got a couple of hundred yards down the road when the abs warning lit up on the DIS. Confused i took the wheels of again to check i hadn't damaged the abs sensors. All ok, refitted the 18"'s. Again the abs lights up. Now here is the weird thing, i put the old 16" wheels back on, took it for a test drive and all is fine???? Any thoughts?