Keith,
The way I approached it is that I determined how fast I wanted to go. My
gear selections are limited so I got the highest ratio available and then
determined how large a tire I needed to the MPH to work out right.
That equates to 205 mph with a 3.08 rear gear, a overdrive at .80 and a
27.5 diameter tire at 6,172 engine rpm. Now all I have to do is build
enough power to get the motor to spin that fast.
We have all watched the discussions on comparing types of rear ends but
there hasn't been much on the horsepower losses between different ratios.
I suspect, that the mathematical transmission losses between a higher ratio
and lower ratio AFTER the wheel diameter are insignificant. The variable
will be the calculated friction between the gears and bearings.
I myself would favor a slightly lower ratio and a larger diameter tire,
believing that it's better to have the largest tire diameter possible.
Less rolling resistance and slower turn speed at the tire surface.
So if you have two different combos, find the chassis dyno and run a low
gear/big tire and high gear/small tire test. Back to back runs with quick
gear changes so the atmospheric changes are minimal. That is the only way
we will really know how the combos affect rear wheel horsepower.
I'll take an XL.
GH
--- Gene Halvorson
--- ghalvorson@earthlink.net
--- EarthLink: It's your Internet.
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