Tjackson82@aol.com wrote:
>
> I believe there is a formula for roughly figuring your top speed that
> involves computing the size of the tire, the rear axle ratio and the engine
> RPMs. Can anyone help?
And there have been a couple of good responses using Excel and a basic
program, but if all you have is a calculator, here is the method:
Speed in mph = .002975 x Wheel dia in inches x rpm
-------------------------
axle ratio x gear ratio
The formula is derived as follows:
Speed = wheel circumference in miles x wheel revs per hour
where: wheel circumference in miles = Pi (3.1418) x diameter in inches
-------------------------------
12 x 5280
(inches per foot) (feet per mile)
and: wheel revs per hour = engine revs per min x 60 (engine revs per hr)
------------------------
axle ratio x gear ratio
You derive the wheel diameter from the tire data using the aspect ratio or
measure it with a tape to get a rough result. I think it is most accurate
if you measure from the center of the axle to the ground and double it.
Peter Ross
|