Speed Camera And Speedometer Calibration
Discussion
Is it true speed cameras are set to catch you 10% over speed limit so for a 60 limit its 66mph and 30 its 33mph and which cameras does this aplly to? mobil, laser, GATSO or all?
and is it also true that all european cars speedos are set 10% low i tink, so if it reads 30 your actually doing 27 and at 60 your actually doing 54?
need some clarification please =]
and is it also true that all european cars speedos are set 10% low i tink, so if it reads 30 your actually doing 27 and at 60 your actually doing 54?
need some clarification please =]
steven182 said:
Is it true speed cameras are set to catch you 10% over speed limit so for a 60 limit its 66mph and 30 its 33mph and which cameras does this aplly to? mobil, laser, GATSO or all?
and is it also true that all european cars speedos are set 10% low i tink, so if it reads 30 your actually doing 27 and at 60 your actually doing 54?
need some clarification please =]
There is an 'allowance' for error, as there is with the breath/blood tests for drink driving. and is it also true that all european cars speedos are set 10% low i tink, so if it reads 30 your actually doing 27 and at 60 your actually doing 54?
need some clarification please =]
With regard to the setting of speedos, you have to accept that these too have an error margin. The most one can hope for is that, when it shows 30mph, one is not travelling at over that speed.
You can so easily affect the accuracy of speedo readings. Different section tyres for instance and, I've been told, there is a measurable, and significant, difference in the reading given by new tyres and those that have just the legal minimum tread. With the lowering of limits (see below) it is, evidently (I can't work the maths), easy to drift into points territory.
Up until the early 2000s process units ran on the 10% +2mph over the limit as the minimum before accepting process although most took 10mph over the limit unless there were aggravating factors - multiple offences, failing to stop, failed the attitude test, that sort of thing. Nowadays the borderlines are more prescribed and many stick to just 10%. There some who, against ACPO guidelines, take the start of process as the 10% limit. I've had a NIP for 55 in a 50 although I wasn't prosecuted.
[quote=Derek Smith.
Different section tyres for instance and, I've been told, there is a measurable, and significant, difference in the reading given by new tyres and those that have just the legal minimum tread. .
[/quote]
If you change tyre section you should try to keep the rolling raduis the same as standard? How much difference to speed will just over half a centimetre of tread make I can't be bothered to do the maths but it can't be very much.....
Different section tyres for instance and, I've been told, there is a measurable, and significant, difference in the reading given by new tyres and those that have just the legal minimum tread. .
[/quote]
If you change tyre section you should try to keep the rolling raduis the same as standard? How much difference to speed will just over half a centimetre of tread make I can't be bothered to do the maths but it can't be very much.....
All my cars for donkeys I have "calibrated" the speedo. OK not exactly calibrated in the truest sense of the word but made a variation chart.
Drive out to the measured miles which are near our local traffic unit base. Drive up and down at various steady speeds timing how long it takes to cover one mile. Best done when tyres are new thus any effect from tyre wear will only make the speedo read slightly faster.
Plot results on a graph, from that it is possible to draw a line which best fits the data. Not always a straight line but usually not far off.
Only once have had a vehicle which was actually 10% fast more or less across the range, a Vauxhall Nova.
Have had vehicles which are bang on accurate, Citroens in particular.
Mostly vehicles are around 4-5% fast in my experience, which is logical as manufacturers are thus aiming at the middle of the -0+10% range.
Every so often drive down the traffic unit mile at 60 mph and note the time just to keep the check current.
Why? Well you might ask that, and yes it is anal, but in my view it means that you can drive through a specs monitored section at an indicated 52 mph, knowing that you are cock-on 50, whereas everyone else sits there at around 45-47. Likewise the traffic car sitting in lane one at 65, you just drive past knowing you are Persil.
Drive out to the measured miles which are near our local traffic unit base. Drive up and down at various steady speeds timing how long it takes to cover one mile. Best done when tyres are new thus any effect from tyre wear will only make the speedo read slightly faster.
Plot results on a graph, from that it is possible to draw a line which best fits the data. Not always a straight line but usually not far off.
Only once have had a vehicle which was actually 10% fast more or less across the range, a Vauxhall Nova.
Have had vehicles which are bang on accurate, Citroens in particular.
Mostly vehicles are around 4-5% fast in my experience, which is logical as manufacturers are thus aiming at the middle of the -0+10% range.
Every so often drive down the traffic unit mile at 60 mph and note the time just to keep the check current.
Why? Well you might ask that, and yes it is anal, but in my view it means that you can drive through a specs monitored section at an indicated 52 mph, knowing that you are cock-on 50, whereas everyone else sits there at around 45-47. Likewise the traffic car sitting in lane one at 65, you just drive past knowing you are Persil.
esselte said:
Derek Smith. said:
Different section tyres for instance and, I've been told, there is a measurable, and significant, difference in the reading given by new tyres and those that have just the legal minimum tread. .
- * by worn I don't mean legal min but worn to the point at which clean wet road grip would be seriously compromised i.e. <3mm
Flat in Fifth said:
All my cars for donkeys I have "calibrated" the speedo. OK not exactly calibrated in the truest sense of the word but made a variation chart.
Drive out to the measured miles which are near our local traffic unit base. Drive up and down at various steady speeds timing how long it takes to cover one mile. Best done when tyres are new thus any effect from tyre wear will only make the speedo read slightly faster.
Plot results on a graph, from that it is possible to draw a line which best fits the data. Not always a straight line but usually not far off.
Only once have had a vehicle which was actually 10% fast more or less across the range, a Vauxhall Nova.
Have had vehicles which are bang on accurate, Citroens in particular.
Mostly vehicles are around 4-5% fast in my experience, which is logical as manufacturers are thus aiming at the middle of the -0+10% range.
Every so often drive down the traffic unit mile at 60 mph and note the time just to keep the check current.
Why? Well you might ask that, and yes it is anal, but in my view it means that you can drive through a specs monitored section at an indicated 52 mph, knowing that you are cock-on 50, whereas everyone else sits there at around 45-47. Likewise the traffic car sitting in lane one at 65, you just drive past knowing you are Persil.
A good method but....Drive out to the measured miles which are near our local traffic unit base. Drive up and down at various steady speeds timing how long it takes to cover one mile. Best done when tyres are new thus any effect from tyre wear will only make the speedo read slightly faster.
Plot results on a graph, from that it is possible to draw a line which best fits the data. Not always a straight line but usually not far off.
Only once have had a vehicle which was actually 10% fast more or less across the range, a Vauxhall Nova.
Have had vehicles which are bang on accurate, Citroens in particular.
Mostly vehicles are around 4-5% fast in my experience, which is logical as manufacturers are thus aiming at the middle of the -0+10% range.
Every so often drive down the traffic unit mile at 60 mph and note the time just to keep the check current.
Why? Well you might ask that, and yes it is anal, but in my view it means that you can drive through a specs monitored section at an indicated 52 mph, knowing that you are cock-on 50, whereas everyone else sits there at around 45-47. Likewise the traffic car sitting in lane one at 65, you just drive past knowing you are Persil.
......thank **** for GPS devices with a speedo!
steven182 said:
Is it true speed cameras are set to catch you 10% over speed limit so for a 60 limit its 66mph and 30 its 33mph and which cameras does this aplly to? mobil, laser, GATSO or all?
and is it also true that all european cars speedos are set 10% low i tink, so if it reads 30 your actually doing 27 and at 60 your actually doing 54?
need some clarification please =]
I don't think there are any rules are there? Guidelines maybe.... :sarcastic:and is it also true that all european cars speedos are set 10% low i tink, so if it reads 30 your actually doing 27 and at 60 your actually doing 54?
need some clarification please =]
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