ok im askin this for a friend. he is putting a 2 inch lift on his 90 sammi and he wants to know big of tire he can run. (ps he will be running thornbirds if that makes a difference)

well i have a friend with a LWB sammi and he squished 31's in it stock so i dunno prob liek 31's woth no rubb maybe

if his lwb was a sj the weel wells r bigger....

we have almostr decided on 29's

ok heres our math. 4 inches of lift you can run 31's right?right

so minus 2 from both and you have 2inches of lift and 29

am i right or am i wrong?

if his lwb was a sj the weel wells r bigger....

we have almostr decided on 29's

ok heres our math. 4 inches of lift you can run 31's right?right

so minus 2 from both and you have 2inches of lift and 29

am i right or am i wrong?

A 29" tall tire is only 1" smaller in the radius from a 31" tire. This is important because your reference point or the part your going to lift is the axle or the center of the tire so it would be better to thing of the differences between tires, for fitment purposes, using a radius concept. ANYWAY I've have or know of several different Samurai on 2" shackle reverse lifts running 29 inch and 235/75/15 tires very successfully. The front of the bumper needs a little trimming and you might, although I haven't had to as of late, have to fold the body seam in the back of the front wheel well over. This rig below has the bumper trim but not the seam fold and does not rub even at full compression and steering lock with the 29x8.5 Super Swampers



You also can consider how much tire rub you can stand. If lugs going clunk-clunk-clunk don't bother you, than a 31" will work but if you want rub free motion, I'd say 29 inchers...

I'd also steer your friend away from the Thornbirds. They are an AT tire despite their aggressive look and don't work to well, unless cut, in mud, snow, and pretty much everywhere. Of course this is just another tire opinion and everybody has one of those.  

Good Luck, Eric

he says thanke hes going with 30 thorbirds he know they AT its his daily driver and he doesnt whell to  much its all more show then go (personnally id go with 31 ltb's and learn to ignore the rub.)