While both these equations may come up with the same figure, I suspect that
they are based on the gearbox having a top gear of 1:1 ratio. What about
my gearbox that has 2 more gears that are both overdrive?
Inquiring minds want to know!
Joe (C)
BillDentin@aol.com wrote:
>
> In a message dated 08/08/2002 3:45:54 PM Central Daylight Time,
> mjb@autox.team.net writes:
>
> > Tire Diameter (in) x RPM x 188.5
> > Speed (mph) = -------------------------------------------
> > final drive ratio x gearbox ratio x 63360
> >
> > I just have this spreadsheet I wrote up years ago where you plug in a few
> > bits of info and you get the chart of speeds in the various gears. I
> > haven't
> > actually sat down with a calculator and the equation for quite some time.
> >
>
> Mark:
>
> We have similar to the above on a spread sheet as well, for the several
> different tires sizes and drive trains we run. I am not very secure about
> matters mathematical (although I like to multiply), but I am interested. We
> normally get our tires from SASCO SPORTS, and the formula they gave us was:
>
> MPH=(((ENGINE RPMs*TIRE DIA.)*0.002975)/(DRIVE RATIO*RING&PINION RATIO))
>
> Seems to be a variation. I've not tried the two equations yet to see if they
> come up with a similar answer, but 188.5 divided by 63360 = .002975, so I
> guess both would get similar answers.
> .
> At one time BFG had given me an equation that involved tire revolutions per
> mile. I seem to follow the logic on that one a little better, but I've
> misplaced the equation.
>
> Bill Dentinger
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