generally I put the new ones on the back, because the ones that were on the back look nearly new(FWD)! With enthusiastic driving, the sides peel a bit but in terms as water dissapation they are as good as new ones, (better as they are scrubbed in). However if the fronts were on the limit, and the rears were quite worn I think I would have the good ones on the front as they have to turn and handle the power. But I have a full set of adjustable Konis and 215/40/17 so my car does little oversteer or understeer, just grips forever, in the wet it goes a little out of shape at the front but as long as you on the gas the rear end goes nowhere. (however lift of oversteer is nice and easy to acheive but I wouldent condone that) She cocks the inside rear up occaisonally to!