I've made a huge improvement to this bike, simply by adding an 18 tooth BMX freewheel. 21 on the chain ring gives copious amounts of climbing ability and the down low to grunt through mud and snow (the whole reason I bought this bike) and now being a free wheel, you can actually use gravity in your favor every now and then. Rather than having to resist the affects of gravity on a 35lb bike, you can enjoy it as the big fat fatties roll over anything and everything in their way. This bike is a really hoot at speed. Yes, I said hoot.
new freewheel installedRH side clearance
LH side clearance
Chain to tire clearance
This frame was definitely not designed around the Endomorph tire, but I think it will do the job and just sneak by.