Pulley calculation

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May 20, 2010 | 10:06 AM

Surfit

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From: Oxnard CA

Pulley calculation

I am going to Sturgis this year and I was thinking about dropping a tooth or two for higher cruising speeds. How many mph do you gain per tooth?
Thanks.

May 20, 2010 | 10:12 AM

xFreebirdx

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From: Landrum, SC , elevation 986'

Wouldn't you want to increase your front pulley by a tooth or 2?

May 20, 2010 | 10:18 AM

Surfit

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From: Oxnard CA

Quote:

Originally Posted by xFreebirdx

Wouldn't you want to increase your front pulley by a tooth or 2?

I was thinkin rear pulley.

May 20, 2010 | 10:48 AM

cHarley

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From: Boynton Beach, FloriDuh

If you're decreasing the number of teeth on the rear pulley, divide the original tooth count by the new tooth count to get the correction factor, then multiply your cruise speed by the correction factor. Example; changing from a 60 to a 55 tooth and using a speed of 70 mph, then 60/55=1.09 so, 70 x 1.09=76.4 mph.

If you are increasing the tooth count on the front pulley, use the same process as above, except you divide the New tooth count by the Original tooth count.

May 20, 2010 | 10:57 AM

BikerV

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From: South Jersey

I would go for the 34 tooth front instead of dropping the rear. If I remember correctly, I had to change a drive belt also when I put the 65 tooth rear in place of the 70. I believe you can just pop in the 34 front and use the same drive belt. As far as a stock 32/70 set-up goes, dropping to a 65 rear gives you a 2:03 ratio or adding a 34 tooth front gives you the 2:06 ratio. Stock ratio is 2:19 (rounding the numbers).

Last edited by BikerV; May 20, 2010 at 11:00 AM.