Does anyone know what the largest wheels you can go to on a fat bob without moding front or rear?

 

The chart on this web page has a Fat Bob listing. Maybe it will help.

 

By largest, do you mean wheel diameter or wheel width? I know there are few on the board that have fit a 200 tire in the rear and I believe someone did a 160 tire in the front. As far as diameters, you could definitely do a 21 in the front and an 18 in the rear.