Speedo Calibration

[Clan]

Originally Posted by Photomad2

Hi, yesterday I passed 2 speed signs which tell you what speed you are doing, both showed, at 30mph, that I was doing 2mph less than my speedo was showing (XC60, 2020). I know that there are manufacturers tolerances for vehicles, and these road signs, and it's better that your car is doing a little less than what your speedo is showing. Also there may be differences when swapping wheels, eg. summer to winter. I'd like to know how or where I can get my speedo calibrated and the cost. It would be useful to know what speed I am actually doing, at different speeds. Does anyone have any recommendations?

Just about ALL volvo speedos going right back to the 340 are 2 to 3 mph fast ... i take the needle off and move it round a touch. It is a very accurate expensive electronic instrument and can read correctly . However it is illegal for a speedo ever to read low so that's why there is the 2 to 3 mph discrepancy .

[EssexExile]

I fear the OP has a 2020 model so he won't have a "needle" to pull off, perhaps he needs a tech wizard to modify the electronic jiggery pokery.

[Clan]

Originally Posted by EssexExile

I fear the OP has a 2020 model so he won't have a "needle" to pull off, perhaps he needs a tech wizard to modify the electronic jiggery pokery.

or just take it as accurate and forget about it and save some fuel 😊

[inchindown]

I pass a roadside speed sign every day with the cruise control set to 30 MPH and the sign always reads 27 MPH.

[Clan]

Originally Posted by inchindown

I pass a roadside speed sign every day with the cruise control set to 30 MPH and the sign always reads 27 MPH.

Exactly , those signs seem to be very accurate..

[Whyman]

Yes they are my constantly shows 3mph over the sign mph.

Nice to know and it explains why if you set the cruise control at 50mph in roadworks the lorries with their calibrated Speedos will overtake you.

[xsaab]

Use a stand-a-lone Sat Nav in the car and compare the indicated speed versus the car speedo speed - always there is a 2 to 3 mph difference.

So use it as a way of driving a litle bit faster knowing that you are not exceeding the speed limit.

[Ian21401]

Originally Posted by xsaab

Use a stand-a-lone Sat Nav in the car and compare the indicated speed versus the car speedo speed - always there is a 2 to 3 mph difference.

So use it as a way of driving a litle bit faster knowing that you are not exceeding the speed limit.

That’s what I did. On the infrequent occasions when I took the satnav on a trip to an unfamiliar location, (as a back up to my map, not instead of ) I found that may car speedo. was reading 10% fast across the range. (ie: speedo = 30mph, satnav = 27mph, speedo = 70mph, satnav = 63mph.)

[green van man]

Originally Posted by Clan

Exactly , those signs seem to be very accurate..

Those signs are set by a bloke with a computer and can be anything he wants. I assisted one such bloke on a solar powered sign job, this one was a bend warning at the top of a hill. He had to change batteries as the panel was unable to keep pace with the sign usage.
His solution was simple, fit new batteries then adjust the aproach sensor to 60 mph so that it never, unless aproached by a camacazi pilot triggered the sign.

I questioned if the speed reminder signs could also be programmed, yes he says, they are all the same gubbins and we usually set them 2 or 3 mph under the limit.

Please do not confuse speed reminder signs with ANPR cameras as they are accurate and I know of a lad prosecuted because the elapsed time between 2 cameras indicated an average speed of 80 mph.
He privately admitted to reaching 140mph in places so did not contest the fine and points.

Paul.

[Bashy]

I am sure i heard/read that they are doing/done away with the 10%, of which is totally wrong as not all speedos a accurate, plus, the smaller the tyre becomes due to wear, the slower the car is compared to the speedo.

I have always used my GPS speed as a guideline, if the GPS says 50 yet my speedo says 52, thats what i will drive at, its always about 2mph out, i have never had a car where the speedo is the same as GPS. and i would say that the GPS is more accurate than your speedo unless calibrated of course and as long as the car has a good view of the sky, no dense forest or surrounded by tall buildings or tunnels etc....