basingwerk wrote:
Oscar wrote:
A little margin up over is in order, as manufacturers must not supply a vehicle, which has a speedo that reads low
AFAIK, even modern speedos are not absolute instruments, and are subject to calibration errors. I reckon these should be quite small, the main areas of error probably coming from wheel circumference change (read tyre size and wear) and clock inaccuracies (assuming they use a clock or capacitor circuit to integrate the wheel rev readings, which, for example, may be read by sensor from a toothed wheel or other similar set-up). 10% seems a little high, but I get the idea. Clocks (can be) accurate, so it comes down to change in tyre circumference. Rough calculations suggest to me a tolerance band of around 6% in the maximum variation. If this were offset on a worst-case basis so that the speedo reads high, you would, worst case, be doing around 28 mph when your speedo says 30 mph. These are very rough calcualtions, of course, but this seems a respectable speed to me, quite close to the absolute limit, so this is no reason for the
Pratnerships to allow 10%, because the speedo inaccuracy over stating the speed, thus working in the drivers favour anyway.
On the other had, I wonder what tolerance margins are published for the camera measurement instruments themselves?
Basingwerk mate - we agree that they are
Prat nerships then.
They can set tolerance margins on scams - but with talivans - can depend on mood and target set by paymasters. We have not guarantee as to fair play settings - and suspicions are further aroused by the hullaballoo over getting to see the evidence. When they make mistakes - and they do - it is up to victim to find out and challenge - which is made impossible - M4 fiasco last year is a case in point. This only came to light when a couple of victims challenged because they remembered exactly where they were on the road at the time.
But this was not given huge highlights in media and there are still number of unaware convicted motorists who were legal all the time.
Both Jags are 3mph out - both under actual speedo - across speed range - according to useful gadgets in the car. The Stag
one of first manufactured - speedo is not at all accurate
discrepancy increases to as much as 20% on higher speeds. Unfortunately - a replacement part is like gold dust - which is why that voluptuous vamp only goes out to owners' club meets. She still performs on track
Lovely husky - sultry engine hum ..... No idea exactly how fast she is going - but she can certainly turn in a good performance - and does not blow a gasket (original engine - always been prone to overheat and throw tantrums!
This "cor blimey" car has thrown some strops in her time - but that is another story ....)
The Moggies - one (Wildy's convertible version) - speedo - 10% error margin - above speedo , and the saloon one -
- same problem as the Stag. Problem - is getting hold of parts - and no guarantee that replacement will be any more accurate than existing part.
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. Are we turning him into a petrolhead? Resistance is futile, basingwerk, you will be assimilated. 
Round dangly things, I agree, but I don't see the partnerships coming out and saying that a margin is necessary because the cameras can get it wrong. That'd be suicide for them.
. In the end, I believe it's up to the person sending you the NIP to decide.