Calibrate Speedometer

[rweaver56]

Is there anyway to calibrate the speedometer on my '64. I replaced what I figured were oversized tires with a smaller tire and now my speedometer is about 8 mph off at highway speeds. Measured with GPS, my speedo is reading 63 at 55 mph.

My justification for the smaller tires:

• front tires rubbed on the inner fender when turning sharply
• original wheels were 14" and the car currently has 15" wheels
• speedo was already off by 4mph and i figured this might correct it (obviously I worked the ratios out incorrectly in my bald head

Thanks, for any help.

[phjohnso]

Wow - that's awesome - I believe you need to replace a gear on the housing but don't know any more specifics than that. Sorry!

[Darrellinceres]

You change it by changing the plastic gear on the end of the speedo cable that goes in the transmition tailshaft. I think you can still get them from the dealer.