i have a stock 97 f150 xlt shortbox and it came with 255/75/16 and i have bought a set of harley rims 20" and currently run 275/4520. i am wondering what the biggest tire sizei can run without changing speedo gears. was thinks maybe 285 or something in that range. any ideas. i do not want to do any mods to make any larger fit. they must fit under the truck with out changing things! please let me know as the tires are shot and i wouldnt mind a little wider!!

 

You don't HAVE to recalibrate the speedometer but it is always a good idea. If your truck is a 4x2, you could fit 285/50-20's, 295/50-20's or 305/50-20 at stock height.

 

just wonderin if i am going to rub with that size