1928 Model A - Speedo

[Guest]

Have a model A, early 1928 which was years ago fitted with 19" wheels. As she looked a bit funny with the wings to large over the wheels, and to become more genuine, we put her back to the original 21" wheels. Of course the indicated speed differs now about 10%. The indicated speed before was correct, that means wheels and speedo was a matching set.<P>Does anybody know what I have to change now?<P>1) Do there exist two types of (oval!) speedos - different for 19" and 21" wheels?<BR>2) Is there something to adjust inside the speedo?<BR>3) Is the gear wheel for the speedo-cable to be changed and how should it look like?<P>What did Ford originaly as they changed from 21" to 19" wheels?<P>Thanks to everybody for hints.<P>Regards, Alfred

[Guest Hal Davis (MODEL A HAL)]

I did not realize that there was a difference in the tire circumference of a 19" or 21" tire. I thought that the O.D. was the same. <P>At any rate, I'm pretty sure the speedos were the same. There are different speedo drive gears for the speedo drive assembly that mounts to the torque tube. Bratton's lists two different ones; an 18 tooth for high speed rear ends (3.54:1) and a 19 tooth for standard 3.78:1 rear ends. <P>If you are reading 10% slow with a 19 tooth, an 18 tooth will get you to only 4% slow, if my math is correct. You can also have your speedo calibrated for about $75 plus shipping.

[Guest]

You might want to check the rear end to see if has been changed.Sometimes you can tell by the radius rods or maybe they din't change the speedo gear.

[Guest]

on some of the old speed there was a tension spring adjuster on the solid side of the speed wheel. seems like you could just decrease the tension but it would be trial and error.

[Guest]

One thing you did not mention was how acurate it measures a mile.

[Guest]

Hi<BR>There were diffently different speedometer driven gears, the MARC/MAFCA judging standards has an excellent chart. Also different speedometer cables were used.<P>Carl