no idea on the TJs, might be better to ask the same Q in the TJ forum
on stock rims (15x7) you can safely go as big as 31x10.5... but with no lift or any other mods (fender trimming) a 31 will rub.
without rubbing, you should be good with 235/75r15
most commercially made body lifts are even inch measurements... 1", 2" or 3". most will recommend not going bigger than 1" on a body lift
if you're thinking 2.5", that would most likely be a suspension lift
Sean B. - Schenectady, NY - 95 YJ, 350/700r4/NP241, JB Shorty SYE, 8.8 rear, 2" BDS, 1" homebrew shackles, Daystar 1" BL, TJ flares, 31x10.50 Cooper Discoverer STT, Polyshield polycarbonate windshield, HD over/under crossover steering
swap/build thread: http://www.jeepforum.com/forum/f22/a...hread-1542284/