I have 18 X 10s on the back of my car with a 275 tire, they don't stick out, I've run up to 315s without issue of clearance and my car is lowered about 2", it's the front you need to watch out for, without mods to the suspension a 255 is about as wide as is practical so as not to have deteriorated handling
1995 Mustang GT Cnv 427 stroker
1996 Cobra with Kenne Bell 2.1 Supercharger dynoed at 12psi: makes 412whp/424wtq on E85: 250K miles on stock engine
2003 Infiniti M45 V8 340 hp
"What do you do besides drive fast?" "Have fun...."