Just based on my eye-balling from the clearance my road tire had i think it'd fit at least a 25c which is not anymore than i'd want..... basically what i'm looking to do here is trade wheel size/knobby tires for bigger wheel/slimmer tires... Oh and i brought up ksyrium because everyone i've talked to who has used them has never had a problem even in rough conditions for road bikes. I'd run it up front but i just don't know about the hub... seems like it'd be fine based off popular review though.