31 inch tires would fit on a 91 Wrangler, but only for casual driving. It would limit your off road capabilities greatly because you will not have the clearance in the fenders.
4 inch lift
A few variables come into play (wheel width, wheel offset, tire width), but the general rule for the Wrangler YJ is... 0 inch lift will fit 30-inch tires 1 inch of lift to fit 31-inch tires 2 inches of lift to fit 32-inch tires 3 inches of lift to fit 33-inch tires
You will need a minimum 3" lift to have 33" tires clear when making tight turns. 31" tires will fit with not modifications.
None.
You can go as large as 31" tires without having to lift it.
A few variables come into play (wheel width, wheel offset, tire width), but the general rule for the Wrangler YJ is... 1 inch of lift to fit 31-inch tires 2 inches of lift to fit 32-inch tires 3 inches of lift to fit 33-inch tires
I got a 4 inch suspension lift under my tj with 33 12.50 tires it looks great!
I think 32's will be too big without a lift, you can add a cheap shackle extension lift and fit them in.
What year Jeep for one. Does it have a lift kit? My 3" lifted Jeep Wrangler fits 33s easy with no scrub.
Putting a lift in a 2013 Jeep Wrangler and using 33 inch tires depends on what size tires you are using now. You can get 33 inch tires to fit any size rim. If the Jeep is already lifted you may not need anything else but tires. A 2003 Jeep Wrangler, Rubicon Edition, has a 2 inch suspension and uses 33 inch tires.
the lift kit is worth putting in it but with out it 33''s
31" tires with no lift required, if you are planning on going "off road" consider at least a 1" body lift or shakle lift