Tony and all:
Speedo calibrations are very near and dear to my heart, since I spent 3 months
scratching my head why mine indicated me traveling at 90 MPH and I was getting
run over in a 60 MPH zone!
I've gone through the numbers many times verifying engine speed, time to travel
distance, pacing with a 'known' standard calibrated vehicle, as have a number of
others on the list. I believe that the 1120 turns/mile calibration is correct
for a stock TR6 with a 3.7:1 diff and 'stock' tire diameters (26.5" dia, ~83"
cir). 1180 turns/mile, I believe, would under indicate you speed by ~5%.
Based on the same calculations, I believe that the 1000 turns/mile speedo came
out of a 3.45 diff '6, but I have not been able to verify that yet.
Scott Mackay
Austin TX
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