jay827

had the alignment on my '96 993 targa done last year. since then i've tracked the car a bit and have put 10000 miles on it. the outer 1 inch of my rear tires are now worn to zero tread, while the inner edge is 50% worn. i've run tire pressure of 31 lbs (these are 17" wheels) front and rear. recently i've come to believe the uneven wear is due to underinflation and not alignment. has anyone had similar experience?

Jim Michaels

Jay: It might help the experts (I'm not in that group) to speculate if they knew what the alignment specs are and what kind of tires you have. Ok, I'll speculate anyway. 31 psi cold might be a little low (but not by much) for most street tires for your car. Although I haven't run street tires on track for over 10 years, I'd think something closer to the 36 psi factory recommendation for 17" wheels (maybe 34 psi?) might be better; but I don't think you'd want to get them over 42 psi hot. So if you run on a hot day, maybe you'll need only 32 psi. I'm thinking that alignment may have more to do with your uneven wear. Excessive outside wear could be due to insufficient negative camber, or to excessive toe-in. Even on street tires, I'd want a little over 1 deg negative camber for the track. If you run close to zero camber and corner hard, the outside edges will certainly wear more. Camber settings are usually a compromise for street/track cars, but I have 1.3/1.4 deg neg camber in my triple duty car. The way your tires are worn now, you could put lots of neg camber in to use the excess on the inside.

tom_993

It's possible that your alignment has gotten out of spec in the year since you've had it done.