my 2 front had really bad thread and the rear probably had 40%. Didnt want to chuck them yet since they were still pretty good. The sales rep warned me (though not proven) that my driveshaft could damaged if i didnt buy all 4. I thought that was BS. because the fronts usually get worn out much more than the rears anyways and we are all essentially driving with different thread life in front vs back. When he told me that i thought it was just a ploy to buy 4 tires now. He even had me sign a waiver if anything happened to my car they wouldnt be responsible. Anyone have any thoughts on this?