Speedo reading accuracy

[Lemonskin]

Hi all

I'm sure this has been discussed but I couldn't find it in a forum search so here goes... Sorry if this is a duplication.

Does anyone have any solid idea on how accurate the speedo in the Polo is? Travelling back from Adelaide to Sydney I was using my GPS a fair bit and there was a fair discrepancy between what was on my speedo and what my GPS was tracking me at. In a good way though, as the speedo readout was a fair bit lower than the GPS.

Generally, the Polo's speedo seemed roughly about 8-10% slower than the GPS said. For instance, I did a lot of cruising at 100-110km/h. Where the Polo's speedo said I was doing 118km/h, the GPS was tracking me at dead on 110km/h.

Similarly, at lower speeds, when I was doing 65km/h on the speedo, GPS said it was more like 60km/h

Anyone got any thoughts on this? I don't know which is more accurate, the speedo or the GPS?

[Candyman]

Speedo reading accuracy

All speedos are designed to read over by up to 10%

Has its advantages

[ATYPIC]

Generally most cars speedos are set from factory 6-8% faster than 100kmh or the legal limit... and these cars are no different.

[Lemonskin]

All speedos are designed to read over by up to 10%

Has its advantages

Kind of, but I've just adjusted and now I drive up to 10% faster

[ill0gitech]

Speedo reads 117, GPS reads 110 on the dot, so about the same as you mate.

[GTD_XU1]

If you have the time you could read the guff on ADR 18/03 Vehicle Standard (Australian Design Rule 18/03 - Instrumentation) 2006.
Section 5 - Specifications. Subsection 5.2 ....
Vehicle Standard (Australian Design Rule 18/03 - Instrumentation) 2006
I'm sure that will make it all clear as crystal.
( Ex-Shire myself).

[Guest001]

Basically the rule is that speedos can be up to 10% fast plus or minus 4kph

They cannot legally read under

Our Polo is 7 k over at 100kph Checked with GPS and VCDS plugged in . Couldnt correct it due to limited control

The Passat is 6 k over at 100k checked with GPS and with the Canbus reading Havent tried to correct it yet

Cant fix either with tyres as would need to be to big to be legal 40mm for the Polo and 25mm legal oversize

[MGV]

What i personally find disconcerting now is that there's a couple of speed cameras where the Hume freeway north of Melbourne goes from 100 to 110 kph limit, I have my GPS reading 109, car speedo reading 117 & the camera still fires as i drive through!
Apprehensively checking the mailbox each arvo... I think there was an issue with these cameras a year or so back, & they turned them off for a while, but they're back on now & have a photo of me...

[bigfoot]

GPS 100 v Speedo 103 for me (aftermarket wheels)

[Bflat]

What i personally find disconcerting now is that there's a couple of speed cameras where the Hume freeway north of Melbourne goes from 100 to 110 kph limit, I have my GPS reading 109, car speedo reading 117 & the camera still fires as i drive through!
Apprehensively checking the mailbox each arvo... I think there was an issue with these cameras a year or so back, & they turned them off for a while, but they're back on now & have a photo of me...

The Hume cameras go off regardless, I wouldn't lose sleep.

[LunchboxVRS]

With my MDF reading 110k the speedo needle is just a little over the mark and GPS is 103km. So I had a police friend bring his gun and he clocked me at 107. A week later when he had a different gun we did the same thing on the same road in identical conditions and he got me at 109.

So you can go with what ever you thinks best but there guns and fixed cameras are never spot on. There tolerances are tighter but the can still be about 3% off and be legal. as you can see if i went by GPS and increased by 7km with the second gun on me I'd get book for going 116km in tas it problem get of but from experience in Victoria I'd be pinged for sure. Had to tickets there for 4km over 5km over in a 110 zone on the Hume.

[DETROITCANDY]

I've found the same results, 117-118km/h = 110km/h, 106-107km/h=100km/h when measured against GPS, I haven't tried switching the snow tyre option on the MFD to correct it either.

As Bflat said, the cameras go off regardless with a barely visible flash of infrared light.

Be careful on the Hume, a few of the average speed cameras have now been upgraded to instantaneous cameras also (maybe one standalone camera has been added inbound?), always good idea to reset average speed on your MFD if you have one as you go past each camera to make sure your average speed isn't too high.

[Candyman]

Speedo reading accuracy

Meh, just stop for a piss a few times and then drive like an idiot and average speed will be just fine

[trauts]

Same with my Polo
118km/h = 110km/h
106km/h = 100km/h
87km/h = 80km/h
All checked with GPS, It's highly frustrating. I've looked into places that will calibrate speedometers, but have had no luck.

[Ryan_R]

Displayed speed is 8% for me, those with larger rims (Golf GTI, R) have less variance.

I now have a Polar FIS+ which displayed the OBD speed which is the traditional 2kph out, much better. Also has a quicker refresh rate.