I just recently bought a 2001 dodge 1500 sport "off road" I was wondering if anyone knew what size tire could be fit on the truck without having to trim the fenders.

Thanks for the responses  

33 or 285s the offroad editions are a little taller then the regular 4x4s  

You'll probably still rub on the inside frame rail a bit, but you won't have to trim the fenders.  the 01 sport off road editions had a 3 inch advantage over the stock 4x4s, and I had 34's on my old dodge with a small 2 1/2 lift on it...couldn't go too much more in the front, because dodge front tires tend to sit further back in the fenderwell than I think they should be, and you can't trim it back there, because that's where the cab starts, right underneath the splash guard.  

Please be advised that that model year truck has a weakened front axle by design as it is notched out near diff on passenger side for a axle shaft disconnector in 2wd. I have seen many of these trucks with bent/sagging front axle with lift and big tires that have been played hard with. I strongly suggest that you truss front axle if you plan to run some bigger rubber on it because the axle can bend/warp fairly easily if pushed hard.