Re: SPEEDO REVOLUTIONS PER MILE

Posted by TxGoat On 2024/3/30 9:53:17

If you keep the original rear axle ratio and tire diameter, the speedometer should remain accurate.
Otherwise, the speedometer drive gear on the transmission end of the cable may need changed. In most cases, several different drive gears were available. Generally, speedometers were not very accurate. One way to check on the true accuracy is to use a Garmin device that shows speed and mileage and compare what the Garmin shows to what the speedo shows. In the case of my'37 120 with correct size 7.00 X 16 bias tires, the speedo shows about 23 MPH at a true 25 MPH, and it is dead accurate at or near 50 MPH.
I suspect that that error and non-linearity is typical. To check odometer accuracy, I'd want to drive 30 miles or so on the open road at a moderate speed.