Join Date: Mar 2002
Location: Fairfield, NorCal USA
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The cassett that you have on your wheel now, and a freewheel for a hub motor are different. Your cassette slides onto a splined ratchet. The freewheel threads directly onto the hub motor, and the ratchet portion is built into the freewheel.
For many years people have not made 9 speed freewheels because there is no bearing at the outer end of the freewheel, as there is in the cassette ratchet. The fear is that with a great amount of force on the chain, the axle, supported only to the width of the motor, would be damaged.
With the advent of hub motors and the demand to electrify 27 speed bikes, one manufacture (Sun, I believe) ha started producing the 9 speed freewheels. Since we recumbent riders do not usually apply the force of a mountain biker standing on the pedals, the rear axle is safe. And because the motor power comes from the wheel itself, no motor force is transmitted through the chain.
The 13-32 will work perfectly with your bike; basically the highest gear will just be two teeth lower. And many people change the cassette to suite their own style , so nothing radical there.