Ds23 speedo reads 10kph under
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Thread: Ds23 speedo reads 10kph under

  1. #1
    Fellow Frogger!
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    Default Ds23 speedo reads 10kph under

    My DS. A 5 speed Pallas running the hankook tyres it came with consistently reads under the actual speed. Thoughts?

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    So does my D special with standard xvs's

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    10% is at the extreme end of the range when it comes to standard under calibration, but it is not uncommon. 3-7 % under is the norm for non calibrated brand new cars by all manufacturers. Reason being manufacturers are not interested in helping defend speeding fine arguments.

    You can either get it recalibrated (almost nobody does this, even in heavy trucks) or get used to compensating for error.
    In a pile of trucks I have driven with calibrated speed restriction at 100 real kmh, none has read 100- all are 103-107.5

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    1000+ Posts Kim Luck's Avatar
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    How do you measure your speed is the first thing I'd like to know? Not telling anyone how to suck eggs but when I was a little younger and rallying, it was important to do a speedometer check before every event. You can still do this by finding a likely and generally old mile/kilometer post on the side of the road, resetting your odometer and taking a trip up the road to an 10 mile/kilometer post further up. If your odo doesn't read exactly the same distance between the posts, your speedo is likely to be out by exactly the same margin.
    Don't it always seem to go that you don't know what you've got 'til it's gone............

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    Tadpole
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    In most capitals cities there is at least one digital readout government provided set up somewhere. Melbourne has only one remaining, on the Princess Westgate freeway northbound from Geelong. Otherwise an accurate GPS on your phone will do it. Should be able to find an app easy enough. Or just do 100kmh for 1 minute on the freeway & measure GPS distance travelled- longer sample straight line travel works better of course.

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    Little doubt on the speed. Have used a gps and the overheads as some have said. Just seems to be a big over read when most seem to under read. Anyway. Looks like I just compensate as suggested

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    Working like it should! They've all been this way since new.

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    Quote Originally Posted by PeterMol View Post
    My DS. A 5 speed Pallas running the hankook tyres it came with consistently reads under the actual speed. Thoughts?
    Are you saying that with an indicated speed of 100 kph on the speedo you are actually going 110 kph? If you are then others have misinterpreted your question. From the factory the speedo's are set to indicate that you are going a bit faster than actual speed for the reasons stated.

    Steve

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    How do you know how fast you're going in the first place without being pedantic?
    Ok I'm being pedantic..

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    Quote Originally Posted by forumnoreason View Post
    How do you know how fast you're going in the first place without being pedantic?
    Ok I'm being pedantic..
    Reminds me of a boss I oncew had who raced his Mini Cooper (a real one!). Across the speedo he had a Dymo label saying "Ignore it, just go faster".
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    My D Specials have consistently under read, reading 50mph (80kmh) when I am actually doing over 90kph And reading around 55mph when over 100kmh. The current car speedo wobbles around a bit too.

    I actually use the tachometer more when in fourth on the flat - 2500rpm = 80kph, 3000rpm = 100kph - to gauge my speed!

    is it difficult to calibrate them? How is it done?

    AM

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    Speed cameras have a 9% error ' tolerance' on them don't they?

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    I keep my GPS in front of the speedo. I have checked it against one of the highway overheads and it is far more acurate

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    Quote Originally Posted by 405 SRTD Owner View Post
    In most capitals cities there is at least one digital readout government provided set up somewhere. Melbourne has only one remaining, on the Princess Westgate freeway northbound from Geelong. Otherwise an accurate GPS on your phone will do it. Should be able to find an app easy enough. Or just do 100kmh for 1 minute on the freeway & measure GPS distance travelled- longer sample straight line travel works better of course.
    Don't trust them ... there about as accurate as sticking a wet finger out of the window to check your speed. On the rear occasion they actually see one of my cars they are usually wrong. My uncle even had one ping his bulldozer as going faster them him (he was driving the truck that was towing the bulldozer on a trailer......).

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    1000+ Posts Greg C's Avatar
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    Is everyone reading the first post correctly? I read it as the speedo reading is lower than the actual speed the car is doing. I find this very unusual, most speedos over read, i.e. say the car is going faster than it actually is. It is possible to calibrate it, just take to an automotive instrument repairer and get it calibrated.

    I had the CX speedo recalibrated, but to the standard stamped on the speedo, so it overheads with 195/70 tyres. According to the iPhone GPS speed tracker 130km/hr equals 115km/hr real
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    I read the first post the same way i.e. as the speedo reading being lower than actual speed. Certainly this has been my experience with two D Specials...

    Quote Originally Posted by Greg C View Post
    Is everyone reading the first post correctly? I read it as the speedo reading is lower than the actual speed the car is doing. I find this very unusual, most speedos over read, i.e. say the car is going faster than it actually is. It is possible to calibrate it, just take to an automotive instrument repairer and get it calibrated.

    I had the CX speedo recalibrated, but to the standard stamped on the speedo, so it overheads with 195/70 tyres. According to the iPhone GPS speed tracker 130km/hr equals 115km/hr real

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    The mechanical speedo is a friction device of some sort as far as I am aware. If it read lower than true speed, then start by checking the odometer. It ticks over as the cable turns, so it will help you know if the rolling diameter of the tyres is seriously wrong. It won't actually guarantee the speedo needle points to the correct number, so if it reads out by a different factor to the odometer, then the speedo part is faulty. Get it serviced by an instrument workshop perhaps?

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    1000+ Posts driven's Avatar
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    New cars you just plug in the computer, put in tyre size and BINGO, recalibrated

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    Quote Originally Posted by David S View Post
    The mechanical speedo is a friction device of some sort as far as I am aware.
    Not so. It is a rotating disc, driven by the speedo cable that reacts magnetically with the magnets supported on the shaft of the needle of the speedo. You calibrate by moving the disk closer or further away. The odometer is gear driven, directly, so the accuracies of both are not interconnected.
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    Yes, 'magnetic friction' ...

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    Quote Originally Posted by Greg C View Post
    Not so. It is a rotating disc, driven by the speedo cable that reacts magnetically with the magnets supported on the shaft of the needle of the speedo. You calibrate by moving the disk closer or further away. The odometer is gear driven, directly, so the accuracies of both are not interconnected.
    They are not interconnected that is true, however establishing the accuracy of the odometer allows you to check your average speed over an accurate distance. Anyone remember using a tachymeter?
    Don't it always seem to go that you don't know what you've got 'til it's gone............

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    1000+ Posts robmac's Avatar
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    Does it also measure 10% under on the odo?

    This will let you ascertain if it's speedo error or speedo/ odo gearing.

    If both are under you can use a ratio box to adjust . Something like this:

    Speedo Corrector - Cable Driven +10%

    However you may need adapters to suit the speedo cable.
    Last edited by robmac; 7th August 2015 at 08:09 PM.

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    Thanks all good feedback. Will do a check on the odo as suggested and see if it is calabration issue or the gearing on he cable. From the sound of some posts (yes it is actually showing a speed that is slower than actual speed and I have verified with gps). I suspect answer will be to have speedo adjusted. Any knowledge of a good place to go in Melbourne ?

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    Quote Originally Posted by PeterMol View Post
    Thanks all good feedback. Will do a check on the odo as suggested and see if it is calabration issue or the gearing on he cable. From the sound of some posts (yes it is actually showing a speed that is slower than actual speed and I have verified with gps). I suspect answer will be to have speedo adjusted. Any knowledge of a good place to go in Melbourne ?

    Peter,
    Have a good look at the condition of the cable, if it's outer is broken it could cause drag. Make sure the connections are good, one at the speedo head, one at the join (cable is in two parts) just below the suspension sphere and the one at the gearbox.

    Roger Parker will have replacement cables.

    Cheers
    Chris
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    Quote Originally Posted by PeterMol View Post
    Thanks all good feedback. Will do a check on the odo as suggested and see if it is calabration issue or the gearing on he cable. From the sound of some posts (yes it is actually showing a speed that is slower than actual speed and I have verified with gps). I suspect answer will be to have speedo adjusted. Any knowledge of a good place to go in Melbourne ?
    vdo gauges tachometer smiths chronometric marine speedometer instrument repairs dials speed limiting

    You could speak to this company. A friend who is besotted with real (Issigonis era) Minis uses them and has had good results.
    However, I have no first hand experience.

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