rigid "swingarms" are way wider than the normal maxi.
normal maxi swingarm 2.25 is MAXIMUM and its a tight fit.
on my rigid freespirit, i tried sliding my mb5 wheels in with 2.75 18" gazelles on them. they were a really tight squeeze, and i couldnt fit it in with the axle, but the tire itself fit right in there. i think you could run 2.75s in there if you had 16" wheels no problem. 17s would be a stretch.