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[QUOTE="BRush, post: 524598, member: 18729"]
On a bike (well, at least on my KDX) the final, or overall ratio is calculated like this:

Final Ratio = Chain Ratio * Trans Ratio * Primary Ratio

The primary ratio is the reduction before the transmission.  You’ll have to determine by what the spreadsheet is doing to see if “total reduction” corresponds to chain (e.g. sprocket) ratio or not.

On my ’96 H model . All the data for the primary and trans ratios were found in the service manual.

Example:

Primary reduction ratio. This is 63/22 or 2.864

Transmission ratio, which of course depends on which gear you are in:

1st gear = 35/13 = 2.692
2nd gear = 28/14 = 2.000
3rd gear = 23/15 = 1.533
4th gear = 21/17 = 1.235
5th gear = 25/24 = 1.042
6th gear = 20/23 = 0.870

Chain ratio, which depends on your sprockets. Stock is:

47/13 = 3.615

Final Ratio = 3.615 * 0.870 (6th gear) * 2.864  = 9.007

If you know the final ratio, your engine rpm, and your rear tire diameter then you can calculate the  theoretical **  speed for that gearing.

MPH = (RPM * PI * D) / (Final Ratio *1056)

Where D = wheel diameter in inches

** (“theoretical” is code for saying that we’re just having fun with math here and you ain’t never gonna get your KDX to do 110 no matter what size sprockets you slap on    :confused: )
[/QUOTE]

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