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Thread: Using a GPS Speedo. Legal in UK?

  1. #1
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    Using a GPS Speedo. Legal in UK?

    I am thinking of using a GPS Speedo on my car.
    I like the ease of install, accuracy and I want to minimise connections between body and chassis.

    I know they are not IVA compliant, however that's not an issue for me.
    I don't believe there are any issues MOT-wise? (correct?)
    However there seems to be some differing opinions as to whether they are legal in the UK..?
    (although I've yet to hear a compelling reason as to why; other than "it won't work in the Dartford Tunnel")

    Any thoughts?

  2. #2
    Quote Originally Posted by steve View Post
    .
    I don't believe there are any issues MOT-wise? (correct?)
    Speedometers of any description are not part of the MOT test (currently anyway). My car passed it's MOT before the speedo was calibrated.

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    Senior Member BlueNova's Avatar
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    Quote Originally Posted by Andrew View Post
    Speedometers of any description are not part of the MOT test (currently anyway). My car passed it's MOT before the speedo was calibrated.
    You're right Andrew. My daughter's car failed it's mot last summer on brakes and they mentioned the milometer wasn't working. They said they normally note the mileage on the mot but if it's not available they simply mark that box 'reading not possible'. Her car subsequently passed (after I'd fixed everything, including the milometer)

    Alistair

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    Senior Member BlueNova's Avatar
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    PS ....

    Steve, as you say, IVA isn't relevant in your case because you have a VW chassis with a V5C document. Speedos are not tested in the mot, so I would assume that just leaves the Construction & Use Regs which were in force when your chassis (or Nova) was originally built. As far as I can see, the 1986 Regs only say that a working speedo must be installed and maintained in working order. Unless there is more recent legislation that rules out GPS I'd reckon you're good to go! Here's the link to the C&U Regs 1986 ...

    http://www.legislation.gov.uk/uksi/1...on/35/made#top

    Alistair

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    ...and when you look at the next provision, it also mentions it must work at all material times, so if it doesn't work in the Dartford tunnel?
    http://www.legislation.gov.uk/uksi/1...on/36/made#top

    There are also issues with some, where they do not take into account changes in height, i.e. going up or down hill, but display speed over 'flat ground traversed', not all, but some apparently.

    Another possible issue is that speedos must never show a speed that is less than actual speed, and this may not be the case for gps speedo?

    Not saying its illegal to use gps, but it is a very grey area!

    lots of discussions about it on the internet, e.g. https://www.pistonheads.com/gassing/topic.asp?t=957174

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    You would have fun if you were stopped for speeding though and tried to challenge it. Or were involved in an incident where speed was a factor.
    Just saying !!

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    If memory serves, regardless of what MoT standards may be, you NEED to be able to tell how fast you're going, no matter what the environment. So, yes, you would need some way to tell your speed in tunnels and other area's which may affect the reliability of a gps speedometer.

    With this in mind, I believe that while a GPS speedo may be legal on a technicality, it wouldn't be reliable or accurate enough to cover all bases.

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    Quote Originally Posted by MartinB View Post
    Another possible issue is that speedos must never show a speed that is less than actual speed, and this may not be the case for gps speedo?
    True enough, showing less than the actual speed would be a concern and as I mentioned in my last post, I don't personally believe a GPS speedo is accurate or reliable enough to make it a viable option.

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    My mechanical speedo jumps around plus or minus 10mph the actual speed (its on my list of things to do) so I do generally relay on the GPS speedo, but do not think I would want to just rely on the GPS because other than the Dartford tunnel I can loose GPS in a very built up city and in very cloudy conditions, and the other big one is there is nothing stopping the Yanks switching off the satellites.

    Dirk

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    Dirk, that sounds like either the cable's loose or not socketing properly at one end or the other; I'd check the cable on each end to make sure its properly connected, if that doesn't cure it, try the spare speedo you have in your collection of spares.

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