speedo accuracy

[zaker]

Excactly how accurate are golf speedos ?  I have a Talex speed camera detecter which also gives a mph readout. At 90 mph (speedo reading) the talex is showing 82mph. Of course it could be the Talex which is inacurate ??  but i had it in my TT and the discrepency was only about 3 or 4 mph.
Has anyone else experienced this ?

Cheers Z

[Teutonic_Tamer]

GPS speedos are only really accurate on long, straight flat roads.

I was under the impression that VAG speedos were pretty accurate.  My S4 is only 1mph out at 70mph.  Maybe your speedo has been incorrectly coded/calibrated.

Is your car an import??

[zaker]

GPS speedos are only really accurate on long, straight flat roads.

I was under the impression that VAG speedos were pretty accurate.  My S4 is only 1mph out at 70mph.  Maybe your speedo has been incorrectly coded/calibrated.

Is your car an import??

No its not an import. Think i might let the dealer have a look

[illyun]

My 06 Mk5 GTI and 56 Mk5 R32 were exactly the same as yours - speedo reading starts to lose accuracy past 40mph and the figures you've given tally with what I found when I compared it with the speed on my tomtom.  I tested my wifes Mk4 1.8T GTI with the tomtom and the readings matched to 1mph so that car is fine.  There is definitely an error there with the Mk5's - and before anyone points out the error on a gps signal, htats true that there is one but it is constant (introduced by the Americans) and therefore does not affect speed measurements.   On a positive note, its saved me from a few speeding tickets and points 

[Creepy Coupe]

I have a TomTom Go and a Road Angel, and if I use them together at say 73 mph they both read the same, but the car reads 80 MPH, I read on an American forum that VW issued a service bulletin for this problem, however my dealer knew nothing of it.

Corrected..

[wantmygti]

I thought 10% was a generally accepted difference between actual and speedo readings?

[dalgleish00]

I treat it is a nice safety measure!

[laney]

I have a TomTom Go and a Road Angel, and if I use them together at say 80 mph they both read the same, but the car reads 73 MPH, I read on an American forum that VW issued a service bulletin for this problem, however my dealer knew nothing of it.

So are you saying that the speedo reads 73 when you are actually doing 80 - surely this is the wrong way round? 

[Creepy Coupe]

I have a TomTom Go and a Road Angel, and if I use them together at say 80 mph they both read the same, but the car reads 73 MPH, I read on an American forum that VW issued a service bulletin for this problem, however my dealer knew nothing of it.

So are you saying that the speedo reads 73 when you are actually doing 80 - surely this is the wrong way round? 

Laney, your right, I got it the wrong way round, speed reads 80 and Sat Nav- Road Angel 73 mph 

[farina]

The US TSB can be found at http://vonx.homeip.net:81/~twb/carwork/speedo/vw.tb.90-06-01.pdf

There's also a trick to show your speed on the climate temp display (I suspect people already know this).

Press Econ and Up arrow (top right of the four) at the same time
Use the left dial to set the left figure to 19
Use the middle dial (fan) to set the left figure to 19.1
Read your speed in the right temp display
Click Econ to reset

There are some other readings you can get:

* 1.0 : Temp as read by sensor in middle fan speed knob
* 1.4 : light intensity falling on same sensor
* 4.0 : Outside temp - front bumper
* 4.1 : Outside temp - roof?
* 15.0 : Oil temp
* 19.0 : Uncorrected speed (Kmh)
* 19.1 : Uncorrected speed (Mph)
* 19.2 : Coolant temp
* 19.3 : Revs
* 19.4 : Oil pressure?
* 25.0 : Voltage