How accurate is your speedo?

[g3org3y]

Yesterday on the way to work went past a Police van on the A127 parked on the hard shoulder, rear doors open to approaching traffic.

Can only assume it was a speed camera set up jobbie? (unless given the position more likely ANPR?) Was doing a speedo indicated 80km/h, which ime of the E30, is more like 75.

Do speedos lose accuracy over time?

How accurate do you estimate yours to be?

Edited by g3org3y on Saturday 17th April 10:59

[z06tim]

You can check it against a GPS system, which I believe are pretty accurate. I find they vary enormously, some over read by as much as 10% whilst others are quite accurate.

[minipower]

They vary quite a bit. From looking at the GPS, my mini is about 9mph out, MX5 is 5mph and the vette is 2mph out. If you were doing the speed you have indicated I probably would not worry. You are probably within the 10% allowance.

[1337n00b]

afaik, all speedos are engineered to give faster readings than you're actually going. And, the faster you go, the more inaccurate the reading.

[Andy M]

My E60 5 series reads 53mph at a true 50mph, and 74 at a true 70.

[Ricky_M]

Van reads 3-4 MPH faster than what the sat nav says, Puma about 4-5 MPH below. Had a friend with a K10 Micra that read 10MPH below a GPS reading!

Edited by Ricky_M on Saturday 17th April 11:07

[Dale19]

mines fairly accurate, at an indicated 100kph, i`m doing 60mph, 50kph is 30mph, so its not far off at lower speeds, but at an indicated 100mph its about 5 out.

[Pints]

75mph speedo reading at 70mph GPS reading.

[CaptainAhab]

My speedo is 5mph over during general driving (compared to GPS). As the speed increases, the error increases. On a private road of course.

[dunclane]

Mines bang on 10% Lexus IS220d

[knight]

Speedo in the Cerbera is almost exactly the same as through the GPS, whereas in my Primera it is about 10% out.

[Mroad]

I believe the legal requirements from the factory are that speedos can read up to 10% over but definitely never under your true speed.

[insanojackson]

the focus at work read under by approx 8%

[kambites]

Not very, it reads about 76mph at 70.

[EDLT]

Hopefully not very, this will be confirmed some time over the next couple of weeks

[Maxym]

Dale19 said:

50kph is 30mph

31.25 (give or take the odd decimal).

[Dogwatch]

insanojackson said:

the focus at work read under by approx 8%

Mine appears to overread by 2mph throughout compared to GPS. Very frustrating when you're stuck behind some cautious soul who is driving 2-3 mph under the limit 'to be safe' and you can see that they are actually 4-5mph or more below the limit.

[Futuo]

1337n00b said:

afaik, all speedos are engineered to give faster readings than you're actually going. And, the faster you go, the more inaccurate the reading.

Same here with my Volvo T5, 30 ish seems pretty spot on, but starts to get further away at about 90, so if the clocks reading 90 I'm fairly certain I'll be doing something like 86 and plod won't hassle me at that.

In the new virtual roadworks (cones, lamps, signs but no actual workmen) stick the the cruise control on around 55 and have a smoke, ring a mate etc.

[V8mate]

My Citroen C5 is bang on at 70mph - the Satnav cycles 70-70-69 with the cruise control set at 70mph and the needle is dead on.

Above 70 the accuracy starts to diverge though (allegedly).

[chr15b]

I often wonder, do we put too much trust in the accuracy of tomtom etc?