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Equation For Finding Mph At Any Given Rpm


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#1 missouri_guy1973

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Posted 11 September 2007 - 05:03 PM

Here's the equation for finding what your car's MPH will be with any given RPM, given gear ratio, tranny ratio, and tire height:

(RPM x Tire Height) / (Rear Gear ratio x Tranny gear ratio x 336) = MPH

And it's pretty simple to find what your RPM will be at any give MPH also by solving for the RPM:

(MPH x Rear gear ratio x Tranny gear ratio x 336) / Tire Height = RPM


Example: a car at 75mph with a 4.10 gear and a .62 overdrive in 5th gear and 26" tires=

(75 x 4.10 x .62 x 336) / 26 = 2463 RPM

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#2 96sohc

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Posted 11 September 2007 - 07:13 PM

thanks for the info
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#3 Lethal President

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Posted 03 February 2009 - 07:58 PM

To get your final gear ratio you take rpm x tire dia./ mph x 336 in fourth gear (1:1) to get the final gear ratio

Effective ratio old tire dia/ new tire dia.x ratio=effective ratio

equivalent ration new tire dia./ old tire dia. x ratio=equivalent ratio
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#4 zzims98

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Posted 27 April 2010 - 07:22 PM

good to know

#5 8 YURGM

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Posted 14 January 2012 - 08:51 PM

THANKS

Here's the equation for finding what your car's MPH will be with any given RPM, given gear ratio, tranny ratio, and tire height:

(RPM x Tire Height) / (Rear Gear ratio x Tranny gear ratio x 336) = MPH

And it's pretty simple to find what your RPM will be at any give MPH also by solving for the RPM:

(MPH x Rear gear ratio x Tranny gear ratio x 336) / Tire Height = RPM


Example: a car at 75mph with a 4.10 gear and a .62 overdrive in 5th gear and 26" tires=

(75 x 4.10 x .62 x 336) / 26 = 2463 RPM






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