Speedo gear

[shopratwoody]

Anyplace to get info on what gear and number of teeth I need with my gears and tires size?
Thanks, Ron

[57 Ford Kustom]

Ron 
  I  checked my speedo with a GPS and used the following formula for a new gear.  Add 1 tooth for every 5 to 7 MPH slow the speedo is or subtract 1 tooth for every 5 to 7 MPH over the speedo is. at 50MPH my sons GPS and my speedo matched. He could not believe that loose formula would work that good.



TOM

[CDN.SD]

I haven't actually tried using it yet, but I found this formula online a while back, and saved it for future reference.


Formula
(Trans. Drive Gear) X (Rear Axle Ratio) X (Tire Rev. per Mile) /1000

Example
((7 Tooth Gear) X (3.27 Ratio) X (815 TRPM))/ 1000 = 18.655


Hope it helps.

[shopratwoody]

Thanks for the replys Guys. See what I can do.
Ron