Like he ^^^^ said. Tons of posts on this subject. I use Google to search the forums: 'FJ Cruiser Forums what size tire' (no quotes)
What size wheel? I had no issue with 275/70R17 with no lift and stock wheels. I now have 2-3 inch lift with upper control arms replaced and 285's (stock wheels). Some say 285 'SHOULD' work without lift but it has to depend on the tire. Get a test fit. I did not try 285s before the lift.