06 ST1300A, speedo shows wrong speed by about 5 kph (3 mph)

Andrew Shadow said:
Most jurisdictions would require that the police vehicles speedometer have current calibration certification to be authorized for this purpose.
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Dunno about US regs in this, but on EC P-spec the instruments must then have a (white) sticker on, showing [calibration: institution/date/person responsible | next calibration due: date]
 
ST1100Y said:
Dunno about US regs in this, but on EC P-spec the instruments must then have a (white) sticker on, showing [calibration: institution/date/person responsible | next calibration due: date]
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Which strongly suggests that police spec vehicles have a speedo that can be calibrated. Ie different from the standard. They are still affected by the diameter of the tyre - ie tyre tread and air pressure. So displayed speed will still vary during the life of a tyre and changes in tyre pressure due to temperature.
 
A speedometer I disassembled many years ago had a spinning magnet-and-cup "clutch" that rotated the needle against a spring. If the magnetic engagement can be adjusted, the speedo can be calibrated.

For electronic speedometers, I'm sure there is a simple trimmer (variable) resistor to adjust.

The point is that, if they can be mis-calibrated intentionally, they can be accurate intentionally.
 
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Simple solution. Take the dash out and remove the glas. Pull the needle off.
Go ride with your gps and the open dash.
Do this on a straight road with no Traffic.
Put the needle on while driving on the correct gps speed. Maybe 20mph
I did this after i changed the leds.
Perfect calibration afterwards.
 
jfheath said:
Which strongly suggests that police spec vehicles have a speedo that can be calibrated. Ie different from the standard. They are still affected by the diameter of the tyre - ie tyre tread and air pressure. So displayed speed will still vary during the life of a tyre and changes in tyre pressure due to temperature.
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Yes, they are different. The police spec speedometers are scaled in smaller increments- I think that it is two MPH increments instead of the five for civilian.
They can be calibrated. In most jurisdictions, if the speedometer reading is to be used for speed enforcement, in addition to being calibrated they must also have current calibration certification for that speedometer. Police departments that are using their vehicles speedometer reading for the actual issuance of a fine must also use the vehicle with the equipment that it was certified with. i.e. They can not change tire size without getting the speedometer re-calibrated to that new standard if they want to use that speedometer reading for speed enforcement.

This level of speedometer accuracy is all academic anyway for the most part. Police won't be issuing fines for exceeding the speed limit by one or two MPH based on what they say they saw on their speedometer. They had better have more accurate and verifiable readings like radar or LIDAR if they want to be that ridiculous with their speed enforcement efforts. Anyone who wants to take this to court will have a pretty easy time of it as the police officer just can not guarantee beyond any reasonable doubt that a driver was going one MPH over the speed limit based on what he said that he saw. This, of course, excludes the judges who are in cahoots with the police to use speeding fines as a means of involuntary tax collection.
 
Larry Fine said:
Actually, my Accord is less than 1mph off of my Garmin.
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I can look up specs on same size tire, two different brands and one tire will have 810 rev per mile and the other will have 785. The manufacture know the speedo will not be accurate. My 07 accord was 3-4 mph off of gps and my 99 was off 5 mph.
 
Al st1100 said:
I can look up specs on same size tire, two different brands and one tire will have 810 rev per mile and the other will have 785. The manufacture know the speedo will not be accurate. My 07 accord was 3-4 mph off of gps and my 99 was off 5 mph.
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Our 1999 Odyssey was off 10 mph at 60! Honda wouldn’t do anything about it at the time saying that it was an “instrument not a gauge” and instruments can allow more tolerance than a gauge. I was pretty mad for a while, but we liked everything else about that van so I got over it.
 
Interestingly, if you use a gps for your speed and compare the route distance (from a .gpx file) to your odometer, they will not match. The gps calculates distance as a series of straight lines and adds them up. All this will drive you crazy.
 
r2c9y said:
Does anyone have some good advices for fixing this? It's only an annoyance, I know, but I would like it fixed regardless if possible.
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Very typical of Honda's. All 4 of my bikes are the same. It's done intentionally by Honda,,, and they have been prosecuted for it in the past,, on their automotive products of the last century. I use my gps speedo,,, cheers,, CAt'
 
Andrew Shadow said:
It has to be if it will be used in police duty service. In many jurisdictions police are authorized to use the speed that their vehicles speedometer indicates as a means to determine if other drivers are speeding and use that data to issue a fine. Most jurisdictions would require that the police vehicles speedometer have current calibration certification to be authorized for this purpose.
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Yeah, that's pretty much what I was hinting at.

It just reinforces the fact that they could easily make them accurate, but choose not to.
 
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