Calibrating a speedo/odemeter ?

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Mark

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#108132 24-Aug-2012 11:11

Hi there,

Does anyone know where in Auckland is one of those measured out roads ? (they measure out something like 5km and have signs every 500meters or so) I need to check the accuracy of an aftermarket speedo on my motorbike and adjust if required.

Thanks!

Mark

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Vocus

#676346 24-Aug-2012 11:14

If you head south on the SH1, there is one. I can't recall exactly where it is, but someone else might.

minigopher17

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#676347 24-Aug-2012 11:18

On the Ramarama straight before you get to the slow vehicles lane heading south towards Bombay.

gzt

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#676350 24-Aug-2012 11:32

Alternatively use a GPS and use a long straight level road.

Some phone GPS might be ok but some might not be up to it. It's an option.

There's a legal WOF definition/standard for speedo accuracy somewhere. IIRC you can read over by as much as 10% but if it reads under the current speed at all - that is a fail.

floydbloke

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#676379 24-Aug-2012 12:17

gzt:

There's a legal WOF definition/standard for speedo accuracy somewhere. IIRC you can read over by as much as 10% but if it reads under the current speed at all - that is a fail.

How can they check this when you take it in for the WOF check?
Or is it simply a case of potentially getting ticketed if you get caught speeding and you tell the cop "but my speedo said I was driving at the speed limit?"

Sometimes I use big words I don't always fully understand in an effort to make myself sound more photosynthesis.

gzt

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#676382 24-Aug-2012 12:38

floydbloke:
gzt: There's a legal WOF definition/standard for speedo accuracy somewhere. IIRC you can read over by as much as 10% but if it reads under the current speed at all - that is a fail.

How can they check this when you take it in for the WOF check?

My mistake. Looks like there is no WOF definition for accuracy. It is covered by other standards.

http://www.consumer.org.nz/news/view/speedometer-accuracy

minigopher17

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#676387 24-Aug-2012 12:52

What about the odometer? Is there a standard there? My Mitsubishi Cedia, doing the odometer test on the Southern Motorway, appeared to had done 5.2km on the 5km. So that means I really haven't done all those many kilometres on my car. Is it worthwhile fixing? Or is it too expensive to fix?

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floydbloke

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#676396 24-Aug-2012 13:18

gzt:

My mistake. Looks like there is no WOF definition for accuracy. It is covered by other standards.

http://www.consumer.org.nz/news/view/speedometer-accuracy

Good find, thanks GZT.
FWIW, comparing my car speedo against a a GPS, it tends to 'overvalue' by about 6-7% (i.e it shows a 106 when I'm doing a 100).

Sometimes I use big words I don't always fully understand in an effort to make myself sound more photosynthesis.

gzt

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#676397 24-Aug-2012 13:19

minigopher17: What about the odometer? Is there a standard there? My Mitsubishi Cedia, doing the odometer test on the Southern Motorway, appeared to had done 5.2km on the 5km. So that means I really haven't done all those many kilometres on my car. Is it worthwhile fixing? Or is it too expensive to fix?

No idea. That is good accuracy for a car odo btw. I've seen closer to 10%.

As the tyre gets smaller with wear, the number of turns for the same distance will increase.

[Edit: If you are driving a small diesel with RUC calculated on the odo that is going to have n% financial implications]

minigopher17

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#676406 24-Aug-2012 13:28

gzt: No idea. That is good accuracy for a car odo btw. I've seen closer to 10%.

As the tyre gets smaller with wear, the number of turns for the same distance will increase.

[Edit: If you are driving a small diesel with RUC calculated on the odo that is going to have n% financial implications]

If it's acceptable and within the normal range found on cars, I can live with it.

Mark

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#676413 24-Aug-2012 13:56

Thanks for that .. I'll go find it this weekend :-)

davisg

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#676466 24-Aug-2012 15:37

Just blow past a speed camera at an indicated 120 km/h and you will receive a calibration report in the post within a few days together with a photograph to prove it and an invoice for the service!

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scuwp

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#676474 24-Aug-2012 15:45

Most speedo's now comply with European standards which is within +/-8 km. There are so many variables it's impossible to get then 100% accurate 100% of the time as they are based on such a rudimentary mechanical process of rotation, either of wheels or gearbox.

My vote is on grabbing a GPS, and doing some test runs on a straight level section of highway at 50, 80, and 100 and noting the difference.

There is no accuracy standard for WOF (yet) only that it has a working speedometer. The odometer is not a mandatory requirement. Only vehicles that need the odometer for road user charges (diesel tax) must have one that is working and recording accurately.

Lazy is such an ugly word, I prefer to call it selective participation

floydbloke

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#676482 24-Aug-2012 15:54

scuwp: ... The odometer is not a mandatory requirement. ...

That's the 2nd thing I've learnt from this thread today. Although they do take a reading when you take your car in for a WOF check (or is it only VTNZ that do this, and not all garages?)
Is it not a requirement for selling a vehicle?

Sometimes I use big words I don't always fully understand in an effort to make myself sound more photosynthesis.