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Old 08-21-2020, 09:49 PM   #1
gwmartin55
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Default RPm on open road

What is preferred rpm when on open road? Fresh 37, 21 stud engine 3:55 gears . Choice of tires open. Shift at 25 and 38 mph. Expect lots of open road driving. Don’t want to over rev it on long trips.
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Old 08-21-2020, 10:02 PM   #2
JSeery
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Default Re: RPm on open road

It is somewhat a matter of personal preference. 2500 isn't a bad starting point.
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Old 08-21-2020, 10:14 PM   #3
GB SISSON
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Default Re: RPm on open road

Do you have a tach?
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Old 08-22-2020, 03:44 AM   #4
CA Victoria
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Default Re: RPm on open road

Here is a calculator to give you an idea where you are with your car RPM.
600-16 bias tires are about 28-28.5” tall.
With 3.55 gears you will turn abt. 2350 @ 55, your engine should be happy.

The Columbia chart gives a close comparison too.

http://www.csgnetwork.com/multirpmcalc.html
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Old 08-22-2020, 05:28 AM   #5
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Default Re: RPm on open road

Quote:
Originally Posted by CA Victoria View Post

The Columbia chart gives a close comparison too.
Wonder if I am the only one who can't read the Columbia chart as posted?
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Old 08-22-2020, 06:56 AM   #6
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Default Re: RPm on open road

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I modified my chart for your 3.55 and 28.5" tall rear tires.
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Old 08-22-2020, 08:41 AM   #7
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Default Re: RPm on open road

I think it is easier to just run the numbers.

RPM = (Axle Ratio x MPH x 336) ÷ (Tire Dia)

Last edited by JSeery; 08-22-2020 at 09:38 AM.
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