Baiting of motorists?

mcwhirter

SteveC wrote: »

Sorry for being pedantic but that wikipedia stuff is slightly inaccurate. Those type approval regulations, as far as I can see, were never adopted here.
AFAIK Irish law points to 75/443/EEC + 97/39/EC as the legal basis for speedometer accuracy.

The test figures / allowances are the same though.

Is that the same calculation as stated earlier in your link paragraph 4.4.

Cionád

Just for a spot of empirical data, I tested my car with a GPS for speed during the summer:

Real Speed .. Speedo Reading
50km/h .. 55km/h
60km/h ..... 66km/h
80km/h ..... 89km/h
100km/h ..... 111km/h
120km/h ..... 133km/h
130km/h ..... 144km/h

Car was an Almera, 1998.

So around the 10% off the mark at all speeds over 50km/h, didn't test any lower.

Steve

mcwhirter wrote: »

Is that the same calculation as stated earlier in your link paragraph 4.4.

The only difference in the one I linked is that the test equipment accuracy allowance is 1% as opposed to 0.5% in Rovi's link.

That's not to say that there hasn't been a revision to the schedule in an as yet unpublished Irish SI, the EU directive I linked is current though.

Quint

I think most people with a GPS realise their speedo is wrong. In my car, if you travel on a nice empty motorway at 120kph on the GPS (constant speed for a decent lenght of time so it'll be accurate) the car speedo says about 124-125. Thats in a BMW, but in my mates honda, do 120kph with the gps and the car says you're doing 132kph! Slightly different in a suzuki, mazda and toyota I've used it in too. They're definitely not all the same and accurate, that's for sure. And none say you're actually going faster.

Mellor

Alun wrote: »

They also are not legally allowed to read slow

Well thats pretty obvious from the rules given above

mcwhirter wrote: »

The article below states the requirements, I can't imagine any manufacturer designing their speedometer to read 100% accurate due to wear and tear etc, although if anyone can find any who do then I'll eat my hat:p

I imagine its down to tolerance. say they make speedo that are accurate to +/- 2%. Then they likely would go to -3 or 4%. So that they are never over, resulting in a recall or individual testing etc

My point still stands that there is no law that states they have to fast by 10% as was stated above.

eringobragh

Cionád wrote: »

Just for a spot of empirical data, I tested my car with a GPS for speed during the summer:

Real Speed .. Speedo Reading
50km/h .. 55km/h
60km/h ..... 66km/h
80km/h ..... 89km/h
100km/h ..... 111km/h
120km/h ..... 133km/h
130km/h ..... 144km/h

Car was an Almera, 1998.

So around the 10% off the mark at all speeds over 50km/h, didn't test any lower.

I did a similar test with my GPS on my 95 Primera and a ford escort and it gave similar results

However i tested my GPS on a 06 ****roen Berlingo Van and it was always within a few kms on the actual reading like 50 might be 49 and 120 would be 118 maybe some newer cars are more accurate??

Alun

eringobragh wrote: »

... maybe some newer cars are more accurate??

It's got little to do with "accuracy" as such these days. The days of wobbly cable driven induction motor speedos with the need to calibrate them are long, long gone, and most speedos (whether they have a digital or analogue display) are all electronic taking their feed from sensors in the gearbox. These send electronic pulses to an on board computer which translates these into some kind of a display. Analogue speedos are driven by precision stepper motors, so no inaccuracies (apart from a possible small parallax error) there either. Any significant difference between the real and displayed speed is down to either fitting the "wrong" sized tyres, i.e. a different size to what the software is assuming, incorrectly inflated or worn tyres (although the difference generated here can be shown to be very small) or the in-built "fudge factor" the manufacturer built in to comply with the EU regulations quoted earlier.