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Commander
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- May 31, 2002
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Re: Ticketed in Louisiana
Actually, it's highly likely that her odometer is off to the high side, so she was going slower than she thought she was:
Add all that up, it means your speedo on your American car can easily be 10% off. If it says you're going 70 MPH, you could easily really going 64.
If she was driving a european car, if her speedo is working right it is garuanteed to be high. A european speedo must NEVER read slow, even if the tires are worn or you change tire sizes. Your european speedo is perfectly fine if it reads 70 when you're really doing 61.5 MPH (1/10 over plus 4 km/h):
My 2003 Buick speedo is 3 MPH fast at 70. 70 on the speedo is 67 on the GPS.
This law was enacted precisely because of drivers like Jay_Merrill. They seem to feel that it is their right to drive in the left lane at 60 MPH and block following traffic, causing dangerous traffic situations behind them, because "I'm not breaking the law". Now you are, and the cops can do something about it.
jay_merrill said:Unless the girl was driving an old "hoopty," its highly unlikely that her speedo was off.
Actually, it's highly likely that her odometer is off to the high side, so she was going slower than she thought she was:
In the U.S., manufacturers voluntarily follow the standard set by the Society of Automotive Engineers, J1226, which is pretty lax. To begin with, manufacturers are afforded the latitude to aim for within plus-or-minus two percent of absolute accuracy or to introduce bias to read high on a sliding scale of from minus-one to plus-three percent at low speeds to zero to plus-four percent above 55 mph. And those percentages are not of actual speed but rather a percentage of the total speed range indicated on the dial. So the four-percent allowable range on an 85-mph speedometer is 3.4 mph, and the acceptable range on a 150-mph speedometer is 6.0 mph. You're allowed another plus-or-minus two percent near the extremes of 20-to-130-degrees Fahrenheit. Take another plus-or-minus one percent if the operating voltage strays two volts above or below the normal rating. Tire error is excluded from the above.
Normal wear and underinflation reduce the diameter of the tire, causing it to spin faster and produce an artificially high reading. From full tread depth to baldness, speeds can vary by up to about two percent, or 1.4 mph at 70 mph. Lowering tire pressure 5 psi, or carrying a heavy load on the drive axle, can result in about half that difference.
Start at 4% for a 100 MPH speedo, add 2% figuring it'll see 20 degrees sometime in it's life, add another 1% cause the battery will probably die before the car is junked. Add 2% for tire wear, and another 1% if your tires are 5 PSI low.
Add all that up, it means your speedo on your American car can easily be 10% off. If it says you're going 70 MPH, you could easily really going 64.
If she was driving a european car, if her speedo is working right it is garuanteed to be high. A european speedo must NEVER read slow, even if the tires are worn or you change tire sizes. Your european speedo is perfectly fine if it reads 70 when you're really doing 61.5 MPH (1/10 over plus 4 km/h):
The European regulation, ECE-R 39, is more concise, stating essentially that the speed indicated must never be lower than the true speed or higher by more than one-tenth of true speed plus four kilometers per hour (79.5 mph at a true 70). Never low. There's your explanation of high-reading European speedometers, with the highest readings on Porsches and BMWs that are most likely to lure owners inclined to fool with tire sizes.
My 2003 Buick speedo is 3 MPH fast at 70. 70 on the speedo is 67 on the GPS.
jay_merrill said:What I do object to, is a situation where a driver who is obeying the law, may not drive in a particular lane and make full use of a roadway. Even more so, I object to a law that turns a person who is obeying the law, into a "criminal" (moving violations are criminal), so that others can break another law.
This law was enacted precisely because of drivers like Jay_Merrill. They seem to feel that it is their right to drive in the left lane at 60 MPH and block following traffic, causing dangerous traffic situations behind them, because "I'm not breaking the law". Now you are, and the cops can do something about it.