Thanks! I'll go with the 275's for the rear...Steve Theodore said:315's can physically be done on the back with stock rims, but it's not a good idea if you like to turn.
An 11" wheel is the minimum recommended for a 315 tire. The 255 front you mentioned is also too wide for a stock front 17x8 TT rim.
A 275/40/17 is OK for the rear stock rim, as a 9.5 inch width does qualify at the low end for a 275. I've run them with no issues in the past, but your handling may deteriorate a bit overall. Stick with a 235/45/17 on the front if you're keeping 17x8's up there.
1995 Supra TT hardtop