I Just did this with my Speedo. I had taken it apart to repair the
odometer, so figure I may have messed it up. When I was on the highway
doing 65, everyone would be passing me. I never ran the car before the
speedo rebuild, so I don't know if it was wrong before.
I took an old speedo cable, and connected it to a DC motor with a reed
switch and magnet to clock RPM and a DC variable power supply to control
the speed.. I then used a electronic pulse counter to measure the speed
of the motor, and set the motor to 1180 RPM (19.66 pulses per second),
which should give 60 miles per hour on the speedometer (same as the
revs/mile figure on the speedo face). The speedo actually read more than
70. I just pulled the needle from the shaft and repositioned it bit by
bit until I got the correct speed, then rechecked it at 30 and 90 miles
per hour. It was only off by a few MPH at 90, so I left it.
You can get a magnet and reed switch at Radio Shack, and use an
electronic tachometer instead of the counter. The 4 cylinder setting
will read 1/4 of the actual RPM. If you've got an electric drill with
speed control, you can chuck the cable into it and use that.
Kinderlehrer wrote:
>
> Hi Gang,
> This should be the biggest problem with my TR3A, but I may as well ask
> anyway. My speedometer reads very high. It will be reading 80 mph (about
> 3500-4000 RPM) and everyone is passing me. I'm actually doing about 70
> according to my wife who was following me.
>
> I have 165R15 tires, no overdrive, and I have no idea what the CPO (CHEAP
> Previous Owner) did with the rear end but I am pretty sure he swapped
> transmissions.
>
> Is there anyway to calibrate the speedometer? I don't see any choices for
> different speedometer gears in Moss, are they available elsewhere?
>
> TIA,
> Bob
--
George Richardson
Wyvern - '57 Triumph TR3, TS15559LT -
http://www.merlingroupinc.com/tr3.htm
Griffin - '71 Triumph Stag - undergoing restoration
Pikachu - '75 Triumph TR6 - undergoing repair
Kitty - '83 Jaguar XJ6 Vanden Plas - Daily Driver
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