Mr Carlos Snr ( ex cheif engineer for Land Rover) also confirmed this when I spoke to him last night - car speedo's GENERALLY under read by about 10% - according to him, the faster you go (i.e. into silly speeds) the more inaccurate they become, ie. an indicated 130mph may only be 120 mph

I'm ex-Ricardo, Lotus Engineering, Torotrak & JCB..........;)

One of the first thing's that struck me about my MINI is the accuracy of the speedo (compared with my New Road Angel). Even at silly speeds (and I do mean silly), the difference between the two readings was never more than 2mph! :cool:

James

i did this in my car, my mums and my dads.

at 70mph on the speedo it was flickering between 68 and 69mph. therefore having tried it at higher and lower speeds i have concluded that the speedo is about 2% over opptimisic. i have tried it aswell on my 16" and 17" wheels and it seemed the same on the speedo.

incidently on my mums car, a Golf, at an indicated 70mph she was only doing 62mph :eek: at 10% over accurate it means that instead of the 10k miles shes done its actually done 9k which is a bit cheeky of VW!

Speedo accuracy isn't necesarrily the same as milage accuracy... Speedos are deliberately kept inaccurate to stop them from underreading, resulting in speeding tickets and possible claims for the manufacture (I imagine modern cars are more accurate because of smaller tolerances, i.e. manufacturers can afford making them more accurate without risking the incidental under-reading).

OTOH, for milage counters it is a lot more important that the reading is about accurate, and not so important if any fault is positive or negative (as long as it is not too big).

I tried this out wit the G-Trex GPS tracker a few weeks back. Figures are something like this:

Speedo vs GPS:

30 - 29
40 - 39
50 - 48
60 - 57
70 - 66
80 - 75

I'm running 16 run flats.

Incidentally, I also tried this out on my Dad's Escort and when his speedo read 40, he was actually only doing 33 :eek:

I tried this out wit the G-Trex GPS tracker a few weeks back. Figures are something like this:

Speedo vs GPS:

30 - 29
40 - 39
50 - 48
60 - 57
70 - 66
80 - 75

I'm running 16 run flats.

Incidentally, I also tried this out on my Dad's Escort and when his speedo read 40, he was actually only doing 33 :eek:
Wow, those are the lowest results ive seen at 80 mph on a test track ;)

[QUOTE=Hickster]I tried this out wit the G-Trex GPS tracker a few weeks back. Figures are something like this:

Speedo vs GPS:

30 - 29
40 - 39
50 - 48
60 - 57
70 - 66
80 - 75

yep, that looks about right, my road angel and tomtom are very nearly identical, at 30 on the speedo, the gps shows 29, and at 70 on speedo the gps shows 67 ...

Martin

The document that controls the MINI speedo design and layout for the entire world (except the Ozzie MINI) is UNECE REGULATION NO 39/00

This Regulations states the following on display of the vehicle speed in a SPEEDOMETER EQUIPMENT.

The speed indicated shall not be less than the true speed of the vehicle. There shall be the following relationship between the speed displayed (V1 ) and the true speed (V2).

0 ≤ (V1 - V2) ≤ 0.1 V2 + 4 km/h

This is why it the speedo will read high and will read higher the faster you go.

Now why does the hidden speed display in the tacho read the correct speed? The regulation states that this is not a speedo for needs of the regulation. I.e. it does not have to have this inbuilt error as this is not the main speedo that the driver will use to get his speed from.

Conclusion the MINI knows exactly how fast it is going but the government makes it lie to you. :rolleyes: :D

Yes, i agree, it is at the disgression of the officer and not only that, i know someone who was done for doing 32 in a 30, as apparently in north wales, the margin doesnt count and 31 is speeding! whether they would actually do u at 31 is another story but, something to bear in mind when ur counting on the 10% margin!

I was doing slightly above the speed limit on my Speedo one day and my GPS Radar Detector was telling me I was below the limit :eek:

i dont condone speeding at all - these were done under test conditions


:D suuuuuuuuuure

heres mine on snooper s5neo

speedo (mph) gps
30 27
50 48
70 68
130 127
150 145


i dont condone speeding at all - these were done under test conditions

Not done it under test conditions but that would probably be roughly the same as mine, may compare it with the speed on Tom Tom, just for interest :hmph:

i was on a rolling road doing 130 and my gps said i was doing 0 all the way......

i think my gps is broke :D :D :D :D:biggrin: :biggrin: :biggrin: :biggrin: :D :D :D :D :biggrin: :biggrin: :biggrin: :biggrin:

I think something more important in everyday driving in the mini is paralax error (spelling is tough for me). That means as we dont sit directly in frount of the speedo we will miss read it all the time: for example (I hope this looks the same for everyone else)

10:20:30:40:50:60:70
..........|..................
.........a...b.............


So if you look from (a) you read 30, but if you look from (b) the needle looks like it is in frount of 20. This is an exageration but I think you get the idea

The only speed diff i can remember using a road angel is that when the speedo reads 80 im doing 76. Might be more wayward than standard set up due to my 215/40/17s being slightly smaller overall.