My car is going single as we speak, would like to know what is the biggest tire I can put on the back with stock rims on a 94 tt.? I have 255 now. Just got done spending allot of money for me and would like to wait on buying rims.
When I bought my Supra - it had mismatched Goodyear 275's in the rear. I think that's probably pretty decent for a 9.5" rim. I'm a bit surprised Toyota put 255's on it as OE, and I did put 265s Pilot MXX3's when I replaced the mismatched Goodyears.
I think you probably could do a 285 on a 9.5" rim - but that's about as far as I'd take it... Think the general rule of thumb is rim width (in mm) ~ 90% of tire width. If you go much less than that, I'd think you'd get a significant amount of sidewall flex.