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Old 05-08-2020, 05:04 PM   #1
whizzernick
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Default A question of R.P.M.

1934 ford --- New 3.54 gears --- New 5.25 - 5.50 17in firestone tires --- speedometer just rebuilt .
what should the R.P.M. be at 60 MPH ?
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Old 05-08-2020, 05:15 PM   #2
Mart
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Default Re: A question of R.P.M.

2500 ish.

https://spicerparts.com/calculators/...rpm-calculator
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Old 05-08-2020, 06:43 PM   #3
earlyride
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Default Re: A question of R.P.M.

RPM=mph x gear ratio x 336 / tire dia.
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Old 05-08-2020, 07:40 PM   #4
JSeery
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Default Re: A question of R.P.M.

Just be sure you group all the numerator and divide by the denominator.

RPM=(mph x gear ratio x 336) / tire dia

Handy formula, you can also solve it for the MPH or to determine the effect of different Gear Ratios or Tire Sizes on MPH or RPM.
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Old 05-09-2020, 01:10 AM   #5
frnkeore
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Default Re: A question of R.P.M.

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The old Balloon tires where just as wide, as tall. So, your tire diameter is 5.50 + 5.50 + 17 = 28" tall.
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