The Simmonds
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| posted on 28/3/09 at 03:07 PM |
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Speedo Calibration
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
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blakep82
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| posted on 28/3/09 at 03:24 PM |
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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
________________________
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FEZ1025
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| posted on 28/3/09 at 03:35 PM |
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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...
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iiyama
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| posted on 28/3/09 at 04:24 PM |
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Speedo healer?? Not exactly a cheap option at around 50-60 squids, but definatly the easy way to sort the issue.
If its broke, fix it. If it aint broke, take it apart and find out how it works!
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adithorp
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| posted on 28/3/09 at 04:51 PM |
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quote:
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.
Won't work for a mechanical speedo.
"A witty saying proves nothing" Voltaire
http://jpsc.org.uk/forum/
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jollygreengiant
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| posted on 28/3/09 at 04:56 PM |
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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.
Beware of the Goldfish in the tulip mines. The ONLY defence against them is smoking peanut butter sandwiches.
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britishtrident
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| posted on 28/3/09 at 06:15 PM |
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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
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