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Speedo calibration

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ceedub

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I have installed an OD trans in my '73 B and replaced the speedo with a 1000 TPM model. With the original 1280 TPM speedo, the reading was about 25% slow. At least the 1000 TPM speedo is much closer to actual speed and I'm guessing that it is reading slightly faster than actual speed. Of course, my lower profile 195/60R/14 tires probably account for that faster reading. Anyway, some time ago, I stumbled across a website that equated tach RPM with speed using OEM tires. Anyone have access to that info? I'm not all that fussy that I'm going to have the speedo recalibrated but thought if there was some info out there that might help me determine appoximately how much over actual speed my speedo is reading I would be able to correct a little. Thanks.
 
Of course that assumes the tach rpm's are reading correctly. My experience, however, has shown that tach readings on LBC's to be somewhat unreliable.
 
Borrow a GPS unit, most of which will give you an MPH readout. Or have someone follow you at a steady, known speed.
 
Borrow a GPS unit, most of which will give you an MPH readout. Or have someone follow you at a steady, known speed.
 
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