Speedo shows way off

[matsa71]

Hi all,

A newbie from Sweden here.
Recently got my second Scirocco, a 2009 GT, the first one was a 1975 TS
I'm wondering if any of you have tried to measure the accuracy of your speedo?
When measuring the speed using two different GPSes I found that my speedo is showing almost 13% more than the GPS speed.
I.e. when doing 140 km/h on the speedo, the GPSes shows 122 km/h
I know most speedos shows more than the real speed, but 13% feels a bit high.
The tires are 235/40R18 which should have 1% larger circumference than the standard 225/45R17 so that doesn't really explain it either.
I'm taking it back to the stealership to get it recalibrated, but would appreciate your input if you have noticed anything similar.
Cheers,
/Mat

[jc74]

hi i recently had a fiscon installed which displays a digital speed read out which i assume to be the actual speed. This displays 77 when speedo reads 83. So not as bad as yours!

[peter.vw]

Hi yes mine is out but not as much as yours with the GPS showing 70 the speedo will show 74. dont know that changing wheel size from 17 to 18 would make the difference as the overal diameter of the wheel would not change as the rim is bigger but the depth of the tyre wall gets smaller

[peter.vw]

Hi all,

A newbie from Sweden here.
Recently got my second Scirocco, a 2009 GT, the first one was a 1975 TS
I'm wondering if any of you have tried to measure the accuracy of your speedo?
When measuring the speed using two different GPSes I found that my speedo is showing almost 13% more than the GPS speed.
I.e. when doing 140 km/h on the speedo, the GPSes shows 122 km/h
I know most speedos shows more than the real speed, but 13% feels a bit high.
The tires are 235/40R18 which should have 1% larger circumference than the standard 225/45R17 so that doesn't really explain it either.
I'm taking it back to the stealership to get it recalibrated, but would appreciate your input if you have noticed anything similar.
Cheers,
/Mat

hi are you liveing in Sweden now or are you from Sweden now living in the UK? the reason i ask is if you have a UK Scirocco the speedo will be in MPH not Km/h. KMH will be in the read out in the middle.

[rhcp128]

Mine seems to be of by about 7-8%. Bear in mind that the GPS may not be a 100% accurate either (especially going up or down a slope)

[pat15312]

If you have 2zone climate control, there is a little trick to get into the vehicle diagnostics. One of the parameters you can view is actual road speed.
Press AC and fan direction up (picture of the person sitting down and the up arrow) at the same time to open diagnostics.
With the left hand 2zone control knob, turn the dial to 19
With the middle 2zone control know, turn the dial to 1
The road speed will now be shown digitally (in mph) on the right hand LCD display screen on the climate control panel.
You can also view it in kph, i think its 19,0 or 19,2...

[matsa71]

Wow, that's a realy neat trick. Thanks!
Looks like 19.0 was the speed readout in km/h and 19.1 in mph
(you don't by any chance have a listing of all the other readouts?)
The speed readout is much more accurate in the diagnostic menu than on the main speedo.
Only about 5% of when doing 140 km/h, an acceptable error in my opinion.
Makes you wonder why the dial speedo is so wrong when the car obviously have a better reading.

/M

EDIT:
Found this link for the climate control diagnostic
http://www.my-gti.com/224/volkswagen-cl ... iagnostics" onclick="window.open(this.href);return false;
Looks to be the same.

[rimshot]

VW probably don't wanna have to deal with "My speedo said i was below the speed limit but i got in trouble with the law "lawsuits?

[bianco]

You can change how optimistic the speedo is with VAG-COM

I got mine to within 1-2% of the readout from two different GPS's

[rhcp128]

Do you have any idea if the car is using the speedo reading or the internal reading to calculate the distance traveled, consumption, etc.

[bianco]

As far as I know, the setting to alter the speedo reading only affects that.

I try to keep tap on how much gas (petro) I burn, per the trip counter, and that figure did not change when I change the speedo reading setting.

[lancs_lad]

Legally speedos need to be within 10% but cannot read under the actual speed. Thats the case in the UK anyway, not sure about Sweden.

[leekb]

My speedo shows 119 Km/h when GPS is 113 Km/h. About 5% error. Acceptable I think.

[PGN]

I heard a rumour thath te speedo can be recalibrated via VAGCOM. Can anybody confirm this?

[bianco]

You can change how optimistic the speedo is with VAG-COM

I got mine to within 1-2% of the readout from two different GPS's

Is this the rumor You are talking about

[matsa71]

Couldn't get a clear answer from the dealer, they said something about it not being adjustable. I find that hard to beleive.
They will give it a try beginning of December.
Hoping to get the speedo to less than 5% off, basically to the same reading as I can read out on the clima controll.
I'll keep you updated on how it works out.
/M

[bianco]

If You have VAG-COM, then its a no-brainer.
There is a setting for it, 1 through 7.
Mine was originally at 5, set it to 1 and now it is 1-2% optimistic.

[ZephyR]

So how accurate are the GPS units themselves in measuring your speed. My satnav struggles to get your position to with several yards when I'm stationary so I don't see how it can be that accurate in calibrating your speed. Perhaps the speedo is right the GPS is wrong ?

I've noticed that when driving past some of those roadside advisory speed cameras when I think I'm doing 31-32 mph they tend to say I'm doing 27-29 mph. But I don't how how accurate they are either. Now that could be more than a 10% error.
I wonder if I can get the dealer to check and improve the speedo's accuracy.

@matsa71 - do you know how that percentage difference varies across different speed ranges. Does it make a difference how fast you are going or is it always 13% out ?

[bianco]

Did You wait 20 min.?

Principly the GPS can take up to 20 min. to acquire a 100% correct possition.

As for accuracy, they are used to detect five cm movement
gps-may-provide-early-earthquake-warning

[AgaZaKa]

Found this link for the climate control diagnostic
http://www.my-gti.com/224/volkswagen-cl ... iagnostics" onclick="window.open(this.href);return false;
Looks to be the same.

Great link, thanks.