Left crank arm hitting the frame? Fat tire bikes, trikes, and bikes with funky frames may need a little extra clearance. Try this bafang offset crank arm on your BBS02 or BBSHD mid drive motor to gain more space and eliminate the crank arm from hitting your frame. The image shows the offset crank arm above a normal crank arm. A standard Bafang crank arm is marked with AC08-2. A offset crank arm is marked AC08 or AC08-170. The offset is approx 13mm, the thickness of the crank arm itself at the pedal end. The photo shows a standard crank arm on the bottom and the offset above.