I used a bbso2 on a Framed mtb 68mm and on a Schwinn Axum 73mm Framed bike can use 36 t chainring has about an inch of clearance from chain stay . Axum needed 42t inset chainring which put it right next to the chainstay . Riding the Axum in muddy conditions just puts tons of crap right into the chain and sprocket making it basically a dry weather bike. Just some more stuff you should think about when picking a bike.