Re: RPM calculator

[Doug Ahern <D170A833@xxxxxxxxxxxxxxxxxxx>]

On 23 04/30/07, ledman_70@xxxxxxxxxxx wrote:
> 
> Can anybody tell me how to figure the rpm's at a give mph? I have no 
> idea what the final ratio is for my 66 A833, either.

1:1 direct drive on non-OD A-833s


example with 3.23:1 and 24" dia. tire.

PI ( ) = 3.14159 
1 mile = 63,360 inches

tire circumference in inches is distance travelled with one revolution
of the tire,

PI * diameter (inches) = tire circumference 
3.14159 * 24" = 75.39816" 
tire circumference = 75.39816" 

to go 1 mile a 24" tire turns ( 63360/75.398 ) 840.03 times
with a 3.23:1 rearend ratio, 
thats 3.23 * 840.03= 2714.3  engine revolutions

40 miles * 2714.3 = 108,572 engine revolutions to go 40 miles

put a timer on it.  40 miles in 1 hour, or 40 miles / 60 minutes.
108,572 / 60 minutes = RPM = 1809

1809 RPM @ 40MPH.

substitiute your tire dia., rear end ratio, and MPH...


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