GPS speedometers.

A friend has recently bought an imported Mercedes. Won't be used much, it's for "Sunday best". As an import, the car is LHD and the
speedometer is in kilometres per hour, not miles per hour. It'll be rather expensive to replace the speedometer with a one that shows MPH. So he was thinking of augmenting the speedometer with a car-specific GPS speedometer that shows MPH. I don't know a lot about such things. But a few moments googling comes up with:
http://www.he-mandualcontrols.co.uk/gps.html
which looks like it would do the job.
Does anyone have any other suggestions, recommendations, useful websites etc?
--
Dennis Davis, BUCS, University of Bath, Bath, BA2 7AY, UK
snipped-for-privacy@bath.ac.uk
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I'm not sure about MOT requirements. However, all you really need are a few chinagraph pencil marks on the glass for the important speeds like 30 and 70.
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Dave Plowman snipped-for-privacy@davenoise.co.uk London SW
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On 08/11/2011 11:23, Dave Plowman (News) wrote:

How would you suggest that an MOT station tests a speedo'?
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They might notice it has the wrong scale? There are lots of other things they check without the car moving.
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Dave Plowman snipped-for-privacy@davenoise.co.uk London SW
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On Tue, 08 Nov 2011 13:19:40 +0000, Dave Plowman (News) wrote:

AFAIK the only vehicles that have any sort of check on the speedometer are Class 5. Even then it's only a check that one is fitted, can be illuminated, and is not clearly inoperative.
Chris
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Chris Whelan wrote:

it could be calibrated in knots as far as the mot is concerned, it (ordinary car) does not need one at all (for mot)
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Dave Plowman (News) wrote:

There is no requirement for a speedo for the mot. you can buy a small digital display that just picks up from the existing wiring on the car. something like this: http://www.ebay.co.uk/itm/DANMOTO-NANO-Digital-Speedometer-Tachometer-NEW-SP6-/370321193014?pt=UK_Motorcycle_Parts&hash=item5638dcf836
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Mrcheerful presented the following explanation :

http://www.ebay.co.uk/itm/DANMOTO-NANO-Digital-Speedometer-Tachometer-NEW-SP6-/370321193014?pt=UK_Motorcycle_Parts&hash=item5638dcf836
You can also buy a little box of trick which recalibrates the speedo by intercepting the pulse and putting out to the speedo a slightly different one with the correction.
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Harry Bloomfield wrote:

The cheapest way is to remember that 30mph = 50 kph, 40 mph = 60 kph, 50 mph = 80 kph, 60 mph = 100 kph, and 70 mph = 110 kph. All rounded, but close enough that you'll not get pulled over for speeding.
Depending on the car, it may be possible to have a main dealer reprogram the speedo and odometer, or, if all else fails, speak to your local tachograph centre, who will be able to put a small gearbox on the speedo output from the main gearbox to do the job.
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John Williamson wrote :

Not unless it is an older car (pre-1990?) with a mechanically driven speedo. Most/ all nowadays are electrical impulse driven.
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On 10/11/2011 12:24 AM, Harry Bloomfield wrote:

My Merc '83 a 500sec has a dual scale on the speedo.
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My guess is it would be cheaper to source a UK speedo for that model from a breaker's yard etc. Unless the car is very rare. In which case keep an eye on Ebay. Instruments often get kept long after the rest of the car is gone.
Most cars these days don't have mechanical drives so a gearbox wouldn't work. Of course the OP didn't give the age of the car.
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Dave Plowman snipped-for-privacy@davenoise.co.uk London SW
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"Dave Plowman (News)" wrote:

Or just memorize four numbers
30mph = 48.3 km/h 40mph = 64.4 km/h 50mph = 80.5 km/h 60mph = 96.5 km/h
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johannes wrote:

Without conversion the car will not pass MOT requirements , lights will need to be corrected for the dip beam for starters speedo will need to show mph .
If its an electronic speedo then its possible a merc garage may be able to reprogramme the ecu
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steve robinson wrote:

I'm quite surprised why it should not pass MOT. I once had a LHD personal import car (admittedly, some years ago), and it definitely passed MOT. Why does it matter what units the speedo is in? The speedo still records the speed of the car. You can still figure it out.
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johannes wrote:

Because the units in the UK are MPH not KPH and not everyone could do the calculation .
With most modern cars its purely acedemic because the ecu are just reprogrammed to suite the specific marketplace , infact some electronic displays can be user changed now
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steve robinson wrote:

In that case it is fail-safe since km/h values > mph values. Just obey the numbers, whatever they are... Anyway, it's claimed somewhere else in the thread that it does not affect MOT.
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How many cars have electronic displays for speed? It is so '80s...
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Dave Plowman snipped-for-privacy@davenoise.co.uk London SW
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"Dave Plowman (News)" wrote:

Quite many, possibly smaller french cars. I can often read the digital speedo in a nearby car and compare with the speed I'm doing.
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Good grief. ;-)
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Dave Plowman snipped-for-privacy@davenoise.co.uk London SW
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