I have an 03' Fat Boy and it is just about time to change the rear tire. What is the largest size tire that can be put on without any mods to the bike?

 

I put a 160 on mine with no problem - Metzler 160x18 50cm profile -- I had room to go to 180 with no mods. I also went from the heavy solid wheels to 18" PM wheels.

Cheers --

Front went from 130 to 140 - again a 150 would fit. If you Fat Boy is 2000 or older you may have some work using larger tires.