Let's see. Should be :
RPM * tire diameter(inch) * pi / gear ratio = speed in inch/minute
MPH = inch/minute * (1 mile / 63360 inch) * (60 min / hour)
tire diameter(inch) = section width(mm) * aspect ratio * 12.7 + wheel
diameter(inch)
(gear ratio is the product of all gears, so would be the tranny ratio * OD
ratio * diff ratio)
So, MPH = RPM * ((section width * aspect ratio / 12.7) + wheel diameter) *
0.002975 / gear ratio
A TR3 with 145/90-15 tires, 1.0 tranny (4th gear), no OD (1.0) and a 3.70
rear, turning 3000 RPM is doing 3000 * ((145 * .90 / 12.7) + 15) * .002975
/ (1.0 * 1.0 * 3.70) = 61 mph.
Randall
59 TR3A
"Just beneath the surface of the mud, there's more mud, here." CSN
"Anything at all"
On Friday, July 30, 1999 10:57 AM, Tom Ambrose [SMTP:tambrose@tir.com]
wrote:
>
> Can anyone point me to a formula that converts RPM to MPH using tire
size,
> tranny gear ratio, and diff ratio? What'd I forget?
>
> TIA
>
> Tom
> My Spit is on the road, yuck
>
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