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Thread: Speedometers

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    Fellow Frogger! tasie C5's Avatar
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    Default Speedometers

    Anyone know what the difference is between the indicated speedo reading and the actual in modern cars?
    I believed it to be 6 to 7% optimistic on most cars.

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    UFO
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    That has generally been my experience. Funny enough our CX has the most accurate speedo - checked against a GPS. The D and the C5 read a few km under true speed.
    Craig K
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    Fellow Frogger!
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    I ferry lots of rental cars & all speedos read a minimum constant error of at least 4 Km / Hr. with near new tyres, fully inflated. I have seen as much as 7 Km / Hr.optimism at 100 Km / hr..

    Richard

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    Fellow Frogger! tasie C5's Avatar
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    The reason for my question is that when on a longer trip I set the cruise at, say 106km at the 100km limit assuming, if I get pinged I should register 100km.People with GPS should be able to verify their speed. Then again, how accurate is a GPS?

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    1000+ Posts arunine's Avatar
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    Australian Design Rules disallow under-reading of speedometers but allow over-reading of up to 4% on new cars. This does not allow for worn tyres, rim size, inflation settings or load variation. amongst other things.
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    There was a change to the ADRs in 2003 ( I think) Anyway, there is a 10%! variance allowed but the speedo cannot show a speed SLOWER than the car is going. Manufacturers therefore err on the side of caution. GPS is incredibly accurate ( almost all of the time).
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    JBN
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    Quote Originally Posted by tasie C5 View Post
    The reason for my question is that when on a longer trip I set the cruise at, say 106km at the 100km limit assuming, if I get pinged I should register 100km.People with GPS should be able to verify their speed. Then again, how accurate is a GPS?
    Relax. If you are pinged, the notice will state what speed you were actually doing and you can adjust the cruise control accordingly.

    I am working on another theory. If I travel fast enough, the camera will only take a photo of where I was a millisecond ago. So far so good....

    John

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    UFO
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    Quote Originally Posted by JBN View Post
    Relax. If you are pinged, the notice will state what speed you were actually doing and you can adjust the cruise control accordingly.

    I am working on another theory. If I travel fast enough, the camera will only take a photo of where I was a millisecond ago. So far so good....

    John
    And if you get pinged it the 2CV it's a badge of honour.
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    the famous 18E pug206gti's Avatar
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    Quote Originally Posted by JBN View Post
    I am working on another theory. If I travel fast enough, the camera will only take a photo of where I was a millisecond ago. So far so good....
    John
    G'day,
    a few years ago, a newly installed speed camera in a village in Italy, from memory, was set to photograph the front of cars. A motorcycle went through but only the rear of the side was pictured, he was going so fast. However, there was only one of this model in the area, so he was caught.
    Moral... go really really fast, and you might not be recognised.

    The reason for my question is that when on a longer trip I set the cruise at, say 106km at the 100km limit assuming, if I get pinged I should register 100km.People with GPS should be able to verify their speed. Then again, how accurate is a GPS?
    I doubt, but don't quote me, that you be booked for 106k/h in a 100k/h zone. Unless it was by one of the new outsourced camera cars.
    regards,
    Les W.


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  10. #10
    Fellow Frogger! tasie C5's Avatar
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    My son got pinged in my new C5 at 134km/h so I guess his indicated speed was 142km/h. His excuse was the lack of sensation of speed the car gave. Mind you his car gives a sensation of rapid speed at 50km/h.

    My friends (poor old codgers) complain about anyone going above 80 km on the highway. They all, generally, drive very BOOOOOOORING cars.

  11. #11
    bob
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    G'day,

    land cruiser at factory, when the coopers were nice and new, was a real money trap - read around 10% under !

    cheers,
    Bob

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    Bottom line is that you should do some checking (even of the GPS/Car speed) Most highways have one kilometre markers sequentially numbered, so you can set your vehicle on 100 kph cruise and check it between the markers - if correct the reading on a stopwatch will be 36 seconds,

    Do enough of these check to satisfy yourself (after tyre change etc) and cross check with your GPS and that should be sufficient even at a court of law. (depending upon the way your laws are constructed to protect the speed cameras!!)

    Some states have official marked section on the road, (usually over 5 km) just work out the travel time using the 36 second to 1 km traveled at 100 kph.

    There used to be a calculator on the internet.

    Or you could get a friendly cop with a "hairdryer" to check your speed.

    Good luck!!

  13. #13
    Fellow Frogger!
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    Bottom line is to Love and respect yourself and others not to speed on the roads then when speed cameras go broke you will have achieved something positive in your lives. But if your pinged at a couple of k's over then go to fight fines and learn how to deal with the matter instead of just paying up.

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    Quote Originally Posted by tasie C5 View Post
    Anyone know what the difference is between the indicated speedo reading and the actual in modern cars?
    I believed it to be 6 to 7% optimistic on most cars.
    I'd check it by GPS. Our Xantia is pretty accurate. However, the Renault R8 registers around 35-40 mph for 60 kph, 45 mph for 70 kph and 55 mph for 80 kph. Believe no speedometer I say!
    JohnW

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