Hi,

Took my car for a test on a disused airfield this mornin which was pretty awesome but it highlighted the fact that my speedo isnt calibrated right.

I tested it against a sat nav reading, which is dead accurate and:

Actual speed- 37 Speedo Reading - 30
Actual speed- 26 Speedo Reading - 20

So its cosiderably out (the wrong way too!).

I can see 2 possible causes:

The engine and gearbox are out of a ford sierra and the rear axle and wheels are out of an escort. Not sure if the gearing in the diffs or the wheel sizes of the two cars are different?

Either that or the magnet or spring in the speedo is too strong/weak.

Is there any way you can adjust the calibration of cable driven speedos? If so how? Otherwise, I was thinking of printing my own rear plate on the computer with the markings in the correct position for my car.

Has anyone got any clever ideas?!

Thanks,

Matt

i think recalibration is a pro job.

if you can take it apart easy enough, printing a new backing for the speedo may be your easiest option

Depends how much time you have before SVA, recalibration would be best, another set of rims & tyres might get you round the problem. There are many calculators out there that you could work out what size you want. Reprinting the speedo face will work, or:-

Bit of a bodge, but as each is about 10mph off, take the unit apart, hold the needle at around 10mph, then with pointed nose pliers hold the spindle, pull needle off, put it back on at zero & reassemble. Then take it for another run.

Alan...

Speedo healer?? Not exactly a cheap option at around 50-60 squids, but definatly the easy way to sort the issue.

quote:

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Originally posted by iiyama
Speedo healer?? Not exactly a cheap option at around 50-60 squids, but definatly the easy way to sort the issue.

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change the cable driver gear in the gearbox, the one behind the metal cup. They come in three different colour, each giving a different drive ratio. I would suggest that you need one with two teeth more than the one you have in there already.

What did the speedo come out of ?
What diff ratio
What colour is thenylon speed drive gear --- normally you can see the colour with the speedo cable removed.


If it is a Smiths speedo the turns per mile is normally in a very small font near the base of the dial --- either about the 5 o'clock position or the 7 o'clock position look for a number between about 750 and 1400