Tires, ok to just buy 2?

My rear Pilot sports are starting to lose their tread, while the fronts show little wear. Any major problems to consider buy just buying 2 new rear tires? Car (99 - 996 cab 7/99 build) is on original tires, 14k miles. No plans to track or even autocross this year.

Art, Same happened to me i had to order two new S02's to ship over (that size not available here).. The problem I had was tramlining seriously for the first 1,000km or so.. Even now after about 2,000km I can still feel the tramlining. I strongly suggest that you change all four if you can, otherwise you have to endure a bit on disturbance from tramlining. What is tramlining: it is the feeling that you car is on rails and if you want to maneouver thru the lanes at high speeds (above 100km/hr) you will feel that the car will kind of resist and sway against your little steering instructions.. which will make you steer a tad more, and eventually the opposite happens when you want to stop your lane changing maneouvre.. so there your car will start going left and right without your control (it is even dangerous above the 200km/hr mark) Waz

I have had the opposite experience. I wear out two sets of rears (on both cars) for each set of fronts. In over 10 years of driving P cars I have just made sure to match the brand and durometer when changing out the rears. Your experience may vary. My driving habits rarely include highly agressive driving, but I do occasionally find my own limits if not the car's.

Absolutely no problem replacing only 2 tires (on the same axle of course) on a C2. It's advisable to replace with the same type as the fronts to ensure balanced handling. On a C4, Porsche claims all 4 tires must be changed together to avoid damage to the 4wd differential. The 4wd center diff is apparently very sensitive even to small differences in tire radius front to rear.

I've always advocated changing all 4 tires each time. I just bought a set of 4 last fall for DE, and kept the old ones for the street until truly worn. My rears are down if not beyond the wear bars, while the front still has maybe 60-70%!!! So, here's my thinking. For the last few hundred miles or so, I've been running a tire wear difference between front and rear of about 50-60%. If I change only the rear tires, the wear difference will actually be less, about 40-50%, between the old front at 60% tread and the new rear at 100% tread. What's wrong with that? Nothing at all, as far as I'm concerned. Why would it be OK to have significantly less tread in the rear vs the front, as frequently happens near the end of the life cycle of the tires, but not OK for the front to have significantly less than the rear? Unless somebody has a good answer to that one, my next purchase of street tires is for just one pair of rears. BTW, for all you C4S owners, Michellin Pilot Sport Cup tires, R-compound DOT, are now available in the C4S and Turbo rear tire sizes. One set of 4 tires will soon be on order <img border="0" alt="[jumper]" title="" src="graemlins/jumper.gif" /> .

Thanks for the responses, but somewhere someone mistook what I said. My rears are almost bald, and my fronts are pretty new. The plan is to replace the rears, leave the front alone. Thanks. Art

Palting, I have to agree with your logic - I have always thought the same thing. But I believe the official word from Porsche is to change all 4 on 4wd models. Maybe there is some other reason. Is it possible the nature of the viscous diff is such that it is more sensitive to the fronts being worn more than the rears than visa-versa? I dunno, I've not heard a convincing argument. It's just a bit difficult to imagine a few millimeters of wear being so important.

Art, As Speedgeek said, at least with a C2 there is no problem changing two rears without changing the fronts. We all do it both on the street and on the track. Jim

I have to express the same sentiment as speedgeek. The rears just naturally wear faster than the fronts (under normal conditions). Such wear causes a differential in the fron to rear tire diameters. On most dry road conditions there is as little as 5% of the power applied to the front wheels, and it is not a mechanical coupling. The Porsche recommendation is belt and suspenders and I might add is not enforced by at least some of their dealers.

I thought that on AWD Porsche specified maxium wear differences between the front and the back but that they didn't call for an automatic change of all four tyres. In any case, I go through a little more than two sets of rears for each set of fronts. Unlike Pelting though, I have two sets of rims and keep the well worn tyres for use on the track and try to save the nice new tyres for use on the road. Stephen