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Old 08-13-2014, 12:39 PM
FFV8 FFV8 is offline
Motorized Bicycle Elite Member
Join Date: Oct 2013
Location: Spring Valley NV
Posts: 545
Default Re: Gear ratios for HF bike -- please help!

Sprocket choices depend on how much fabrication skill you have, and what soer of equipment you have to use.

You should do most of your reduction i the first stage. You are planning on using the bottom bracket bearings for a jackshaft, and they are not high speed items. I would really recommend replacing them with sealed ball bearings.

The 28T final sprocket limits you to a few choices, none of them easy bolt up stuff.

12/65 > 10/28 just makes it. A 65T #35 chain sprocket would have to be fitted to the jackshaft input, and a 10T sprocket on the output.

12/72 > 12/28 works too, but the 72T #35 sprocket is over 9" OD with a chain wrapped around it.

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