Speedo Inaccurate

[Topend]

Hi,

Had our first long drive yesterday in my wife's new Golf VI. I fitted my GPS to check the speedo accuracy. It turns out the speedo is out by -7%, ie at an indicated 100km/h we are only traveling at 93km/h.

Does anyone know if the VW service guys would be able to correct this?

Cheers,
Dave.

[gregozedobe]

Does anyone know if the VW service guys would be able to correct this?

Cheers,
Dave.

Welcome aboard Dave. Lots of useful info here.

The short answer is "No". Some of the more switched on techs probably could, but I doubt that any of them would be willing to do it for you. This under-reading error is common on many modern cars due to ADR requirements.

If you want lots more info try the search facility, as there have been many threads covering this issue and discussing what options are available.

[The_Hawk]

This under-reading error is common on many modern cars due to ADR requirements.

There is no good reason for this, the ADR says you CANT read under, but you can read over by up to 10% (7% in your case). If you run the numbers of all the standard wheel and tyre combo's there are available (and I have for the Mk5) there is about 1% difference in rolling diameter across the range. So even if you set the speed right for the largest wheel, it should only be out by 1% for the smallest.
Add to this that tyre wear will only ever make you go slower (as the tyre wears it gets a smaller rolling diameter) and even then it's only about 4%.

Why all the speedo's are so wrong is beyond me, especially when there are so many reports of people bringing up the speed on the digital readout and it's much closer to reality :S

[Topend]

Thanks for the responses. I should add that my speedo and MFD don't read the same either. There is a 2 or 3 km/h difference.

It is annoying that in order to travel at 100km/h the speedo has to indicate 108km/h and for 110km/h the speedo has to indicate 119km/h. We have 130km/h limits up here (use to be unlimited) so it will be interesting to see what the speedo indicates at that speed.

Cheers,
Dave.

[brad]

It will pretty much be 7% all the way through.

On my Octavia, I have to do 120kmh to maintain a true 110kmh. It must be an endemic thing among the car manufacturers because I'm constantly having to flash cars on the M5 to get out of my way & they think I'm being aggro - all I want to do is get to work and stick to the speed limit.

[Coaster]

Thanks for the responses. I should add that my speedo and MFD don't read the same either. There is a 2 or 3 km/h difference.

Is the MFD more accurate than the analogue (speedo) display?

[Topend]

Is the MFD more accurate than the analogue (speedo) display?

Yes, 2km/h closer to the true speed.

[Topend]

I tested at a true 130km/h this morning. The speedo indicates 141km/h.

[Zeke]

Probably better for your licence that it over reads.

If you were travelling to the nearest star in our galaxy that 8kph difference would probably count.

Going down to the shops it probably won't.

[scheps]

its to get you to think you are going from 0-100 in shorter time

[Treza360]

Should be able to be corrected slightly with VAG-Com
Threads here: http://www.vwwatercooled.org.au/newf...ad.php?t=22508
and here: http://www.vwwatercooled.org.au/newf...ad.php?t=21307
with further links inside the last one. I imagine there will be some changes in the procedure and settings for the MkV and MkVI but nothing too dramatic.
Cheers,
Trent

[Zeke]

Basically at the speed of light as indicated on your speedo and factoring in the the 7% overread you would be approx 4 months late for your appointment at Alpha Centauri.

Equates to 1/100 of a Nano second late to your local Woolworths/Coles not factoring in delays at red lights.

4months late at Alpha Centauri assumes there are no traffic lights between Earth and Alpha Centauri

[Umai Naa!!]

^^ Nice one!

Basically, VW regards their speedos as accurate. As long as they're within the ADRs guidlines, they wont do anything about it.

[hoi polloi]

^^ Nice one!

Basically, VW regards their speedos as accurate. As long as they're within the ADRs guidlines, they wont do anything about it.

Although Australia is not a member of the ECE (Economic Commission for Europe) they are a signatory of their agreement for the harmonisation of vehicle certification standards. A lot of countries (like the US and Canada) are not... This is good for us as it makes it easy for European manufacturers (like VW) to certify cars for sale here as there is (I understand) reciprocal certification...

Beacuse of this, the speedo error that in the old days was ±10% does not apply to current models...

Be grateful for the fantastic choice we have in new cars bearing in mind we are a small market...

The certification requirements for speedometers are here -

http://www.unece.org/trans/main/wp29/wp29regs/r039r1e.pdf

and largely repeated here -

http://rvcs-prodweb.dot.gov.au/files/ADR%201803.pdf

From this it appears that a speedometer cannot under read but can over read by 10% + 4km/h (para. 5.3)

Regards,
- Anthony.

[Deano]

i hav a copy of a bulletin from VW about customer complaints on incorrect speedo's, i will try and find it and post it up. IMO the GPS unit will be more incorrect than the speedo.