Someone recently mentioned the ecstasy of driving an Alpine with overdrive
and a 3:89 rear. With this combination you can cruise at 80 MPH at under
4,000 RPM or loaf at 60 MPH under 3,000 RPM. Unfortunately the speedos are
way off base when doing the OD/3:89 combination.
Rootes never came up with a speedo drive/driven gear to accomodate this
combnation of drivetrain. What they did was build a special speedometer just
for the OD with a 4:22 rear. The Speedo has a stiffer hair spring which makes
the speedo worthless except for its intended application.
Fear not Bunky, there is salvation. Go visit your local speedo shop and ask
for an inline reducer with a ratio of .6740. This ratio applies to OD/3:89
combinations using series IV or V speedos. Tyre size and other factors may be
involved. So ask the shop to loan you a "rev counter" to put on your cable to
check the number of turns/mile.
With this info the shop can dial in the exact ratio you need. Now your next
question is....is the speedo accurate? If not calibrated for the past 10
years, there is a high probability that it is not on target.
Tiger Tom
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