Speedo shows way off

[rhcp128]

using the climatronic diagnostic display. the km/h reading is practically the same as the gps (+/- 1 km/h). So the car seems to have a very accurate idea of the speed... kind of a mystery why the hell VW chose to create such a big discrepancy (my spedo is about 7% over that reading)

[bianco]

Because they have to be right, even when tires are worn down and underinflated.

[matsa71]

I Just got my car back from the dealers.
They have had if for two days to retrofit parkingsensors, electric engine heater, and to most importantly, to sort out the speedo problem.
The parking sensors and engine heater worked out great, but they couldn't adjust the speedo.
They claim to have checked this with VW in Sweden and got the answer that a 13% error was within the acceptable range and claiming that the speedo is analogue and therefore not adjustable.
All in all, I'm satisfied with the accuracy of the read-out in the climate controll, but I want the speedo to be at least the same as the climate controll.
If any of you guys with access to VAG-COM can check if you can see where this adjustment can be done, it would be highly appreciated
I'm not letting this rest as I want an accurate speedo, but knowing where to change this would give me good leverage when kicking and screaming at VW
I would just love to tell VW how to change this!
Thanks,
Mat

[dkfsk]

here you can se how to ajust the speedo using VCDS;

http://www.my-gti.com/140/volkswagen-sp ... correction" onclick="window.open(this.href);return false;

[matsa71]

Thanks dkfsk!
That's great info!
Brgds,
Mat

[dkfsk]

you're welcome

[tucker101uk]

Personally I dont see the big problem.

Every car I have had since i got my first tomtom, the speedo has read less than the GPS. I've always taken it for granted that the speedo is slightly under calibrated to prevent the whole "my speedo says im doing 30 officer" scenario.

Seriously guys, enjoy your cars and stop picking faults that aren't really there!?!?!?!?!!?!!?!?!?!?!!?!

[dkfsk]

it is not a question of picking faults but a question of knowning that what you see is what you get and also the fun you have by optimizing the car your self.

[lancs_lad]

EU legislation:
Error
Most speedometers have tolerances of some 10% plus or plus due to wear on tires as it occurs. Additional sources of error are; tire diameter variations due to temperature, pressure, vehicle load, and nominal tire size.

Modern speedometers are said to be accurate within 10% but as this is legislated accuracy, this may not be entirely correct. This can make it difficult to accurately stay on the speed limits imposed; most countries allow for this known variance when using RADAR to measure speed, although levels of some 3 km/h or 3% are also used in areas of tough enforcement. This causes many arguments due to motorists complaining that they were not doing the speed as reported. Revenue[3] is being increasingly blamed for these stricter measures. There are strict United Nations standards in place but it seems not being enforced leaving this matter in limbo for many countries. Excessive speedometer error after manufacture can come from several causes but most commonly is due to nonstandard tire diameter, in which case the

percent error = 100x("standard diameter"/"new diameter" - 1).
Nearly all tires now have their size shown as "T/A_W" on the side of the tire (See: Tire code), and the tire's

diameter in inches = TxA/1270 + W.
For example, a standard tire is "185/70R14" with diameter = 185x70/1270 + 14 = 24.20 in. Another is "195/50R15" with 195x50/1270 + 15 = 22.68 in. Replacing the first tire (and wheels) with the second (on 15" wheels), a speedometer reads 24.19/22.68 = 1.0670 times the correct speed or 6.7% too high.

[edit] International agreements
In many countries the legislated error in speedometer readings is ultimately governed by the United Nations Economic Commission for Europe (UNECE) Regulation 39[4] which covers those aspects of vehicle type approval which relate to speedometers. The main purpose of the UNECE regulations is to facilitate trade in motor vehicles by agreeing uniform type approval standards rather than requiring a vehicle model to undergo different approval processes in each country in which it is to be sold.

European Union member states must also grant type approval to vehicles meeting similar EU standards. The ones covering speedometers [5] [6][7] are similar to the UNECE regulation in that they specify that:

The indicated speed must never be less than the actual speed, i.e. it should not be possible to inadvertently speed because of an incorrect speedometer reading.
The indicated speed must not be more than 110 percent of the true speed plus 4 km/h at specified test speeds. For example, at 80 km/h, the indicated speed must be no more than 92 km/h.
The standards specify both the limits on accuracy and many of the details of how it should be measured during the approvals process, for example that the test measurements should be made (for most vehicles) at 40, 80 and 120 km/h, and at a particular ambient temperature. There are slight differences between the different standards, for example in the minimum accuracy of the equipment measuring the true speed of the vehicle.

The UNECE regulation relaxes the requirements for vehicles mass produced following type approval. The upper limit on indicated speed is increased to 110 percent plus 6 km/h for cars, buses, trucks and similar vehicles, and 110 percent plus 8 km/h for two or three wheeled vehicles which have a maximum speed above 50 km/h (or a cylinder capacity, if powered by a heat engine, of more than 50 cc). European Union Directive 2000/7/EC, which relates to two and three wheeled vehicles, provides similar slightly relaxed limits in production.

[matsa71]

Personally I dont see the big problem.

Every car I have had since i got my first tomtom, the speedo has read less than the GPS. I've always taken it for granted that the speedo is slightly under calibrated to prevent the whole "my speedo says im doing 30 officer" scenario.

Seriously guys, enjoy your cars and stop picking faults that aren't really there!?!?!?!?!!?!!?!?!?!?!!?!

and I can't recall asking for you opinion about this being a problem or not
Basically my questions has been, is this problem seen on other Sciroccos and can it be fixed since my VW dealer sais it's not adjustable.
I've had several cars and all have shown too much on the speedos, but never 13% more than the actual speed.
Not even my 1975 Scirocco.