With a mini tube I was able to get 28x10.5 under my 90 stang. I think I could also fit a 12.5 under it, but damn it would be close. Click on "my car" for a pic... My stang is low to the ground, none of that Mickey Mouse jacked up in the rear crap to fit a big tire stuff.

I'm running 5's in the 1/8 mile, after a few suspension adjustments it now hooks up fine on a 10.5 tire.