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Accelo · 06-01-2022, 10:39 AM

The 235/75R15 BFGoodrich All-Terrain T/A KO2 has a diameter of 28.9", a width of 9.3", mounts on a 15" rim and has 721 revolutions per mile.

Using the, factory provided, Rev. Per. Mile is more accurate. Because of the flat spot where the tires contact the pavement they act like slightly smaller tires.

My calculations show a 7.3% error with the 8 & 21 gears.
My calculations show a 2.4% error with the 8 & 20 gears.

I find it easier to do the % error and use that to correct the gears. However, one need both actual speed and the indicated speed at to calculate the % error.

Below are some other options using the gear ratios between the two speedometer gears:

06-01-2022, 10:39 AM	#7
Accelo Registered User Join Date: Mar 2015 Location: washington Posts: 2,162	Re: Saginaw 3 speed Speedo Drive Gear? The 235/75R15 BFGoodrich All-Terrain T/A KO2 has a diameter of 28.9", a width of 9.3", mounts on a 15" rim and has 721 revolutions per mile. Using the, factory provided, Rev. Per. Mile is more accurate. Because of the flat spot where the tires contact the pavement they act like slightly smaller tires. My calculations show a 7.3% error with the 8 & 21 gears. My calculations show a 2.4% error with the 8 & 20 gears. I find it easier to do the % error and use that to correct the gears. However, one need both actual speed and the indicated speed at to calculate the % error. Below are some other options using the gear ratios between the two speedometer gears: Attached Images Last edited by Accelo; 06-01-2022 at 10:47 AM.