Can speedo reading be calibrated in VIDA?
 

Can the speedo reading be calibrated in VIDA?

As my 2002 v70 speedo calibration seems consistently off by about 5mph ( under reading )

I've checked the speedo reading with an mobile GPS speed app and those road side signs that show your speed, both show the same 5mph under-read.

Pretty much the standard for all cars, it is usually about 4mph under, it is maybe because of your tyre choice that yours seems a little low.

My wife's VW reads 40 when in fact it is doing 36. It's quite handy actually as it lets you think you are going a little faster but not really. I once went through a speed trap (copper jumped out of a bus stop with a laser aimed gun) and I was doing 38mph on the clock when I started to brake, so in actual fact it was only 34 when I started to brake and thus when I approached the "stopper" car they didn't even look at me. Had I been in my Volvo with police calibrated speedo, I would have been doing 38 and would have probably only got down to 35 by the time they clocked me.

So, moral of the story, live with it and drive a bit over the limit - because even though I know the speedo in my wife's car is over by 4, I still usually only drive about 30-33 on the clock, thus I am doing fine.

The other irritating thing about having an exact speed is that you will get frustrated with everyone then doing 46 in a 50 etc. I find in roadworks with Avg. speed cams I will sit on the nail at say 50 - but I often get stuck behind people sitting at 46 - that is because they all sit on what they think is 50!

No it can NOT,
Dave

you might find an option for setting tyre sizes in the DIM .. experiment and see , choose the smallest tyre .

another thing , if the difference is always 5mph at any speed just pull the needle off and refit it a bit clockwise as I did on my 340 and it's now perfect .

What's the full set of tyre profile numbers?

Edited.

Apologies to TRIvolvo for my earlier post.

Despite the reference to under-reading, the OP is actually complaining about an over-reading speedo.

Hi I find that the obd2 port sends the speed data spot on with the gps reading,
but the speedo in the DIM reads % high,
Dave

@ TDIvolvo
I understand where you are coming from, but would much prefer to just have the correct speed shown.

To clarify, my speedo is for example indicating 40mph when in fact the car is only traveling at 35mph.
Apologies for any confusion.

@Clan
Checking the DIM for tyre sizes sounds like a good shout.
Moving the actual needle is much too much work, but thanks for the suggestion!

@cheshired5
Tyre sizes: 205/55/ R16

So he is!

Well ignore my post above folks!

That's pretty normal. At a real speed of 35 mph the speedo must show between 35 mph and 38.5 mph. Given parallax errors and human judgement and various inaccuracies such as tyre pressures, you may be reading 38.5 mph as 40 mph.

Wiki details it quite well:

https://en.wikipedia.org/wiki/Speedometer
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,[6] which covers those aspects of vehicle type approval that 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 where it is sold.

European Union member states must also grant type approval to vehicles meeting similar EU standards. The ones covering speedometers[7][8][9] 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 and road surface. 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. At Conformity of Production Audits 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 that have a maximum speed above 50 km/h (or a cylinder capacity, if powered by a heat engine, of more than 50 cm³). European Union Directive 2000/7/EC, which relates to two- and three-wheeled vehicles, provides similar slightly relaxed limits in production.