fancyvpp

I have an 09 GTCS which came with 18/8.5 and i was running 255/45/18 in front and 275/40/18 in rear. i just bought shelby wheels 20*9 front and 20*11 in rear. my question is, what would be the widest tires i can run on them with all factory suspension currently and maybe upgrading the suspension later with some lowering spring and eibach pro kit. i have had some people say they are running 305 in rear and some say 315. and also for front they said 275 or 295.

akiba17

I run 275's all around on 19's and it seems pretty tight in the front, 295's should work fine in the rear, not too sure about stepping it to 300's though, you may run into clearance issues once you lower it.