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11-20-2020, 05:10 PM | #1 |
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Join Date: May 2010
Location: Powell, TN
Posts: 2,508
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rear axle gear ratio chart
Sometime in the past someone posted a chart that had rear axle ratios, tire sizes, rpms and road speed data. It included everything from Model A 19" rubber on up thru 15" stuff. I printed it off but its deep somewhere in my piles of paper. If you have such a animal, could you please post it. A friend has a 60 running a 3:78 in a T with 19" A tires and wants to get a more optimal ratio that will put the RPM range around 2500-3000 rpm at 60 to 65 mph.
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11-20-2020, 05:43 PM | #2 |
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Join Date: Nov 2012
Location: Wichita KS
Posts: 16,132
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Re: rear axle gear ratio chart
It is an easy formula, just calculate it for your parameters.
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11-20-2020, 06:02 PM | #3 |
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Join Date: May 2010
Location: Norfolk UK
Posts: 213
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Re: rear axle gear ratio chart
Here's a link to mine on google drive.
You can edit it online, or download it as an excel file. Works in Libre office too. https://docs.google.com/spreadsheets...gid=1208129397 |
11-20-2020, 06:54 PM | #4 |
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Join Date: May 2010
Location: Hancock, New Hampshire
Posts: 375
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Re: rear axle gear ratio chart
Here’s the one I use:
http://www.advanced-ev.com/Calculators/TireSize/ |
11-20-2020, 07:37 PM | #5 | |
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Re: rear axle gear ratio chart
Quote:
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11-21-2020, 08:27 AM | #6 |
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Re: rear axle gear ratio chart
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11-21-2020, 09:17 AM | #7 |
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Join Date: Nov 2012
Location: Wichita KS
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Re: rear axle gear ratio chart
There are a lot of calculators online, but I have seen several of them product incorrect results! I would at least check them against doing it by hand at least once to double check the fill in the blank calculators. It is a very simple formula:
RPM = (MPH X Axle Ratio X 336) / Tire Dia As an example 60 MPH 3.78 Axle Ratio 30 inch Tires RPM = (60MPH X 3.78 AR X 336) / 30 TD RPM = (76,204.8) / 30 RPM = 2,540 |
11-21-2020, 11:22 AM | #8 | |
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Join Date: Oct 2020
Location: Azalea, Oregon
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Re: rear axle gear ratio chart
Quote:
Thanks, this is eactly what I need to decide whether to change my 3.78 to 3.55 or 3.25. |
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