Robert
Buffalo,#2Consumer Comment
Fri, October 26, 2007
What you're reporting about is a built-in error to consumer vehicles speedometers that are built to be sold in the U.S. This has been going on for at least 30 years that I know of. Don't blame VW. Blame congress, the insurance company lobbyists, and the Department of Transportation for not requiring more accurate speedometers. I learned about this back in the late 70s when I was stationed at Plattsburgh AFB. I had a friend in the NY State Police who told me about this. My experience has been that the speedometer has an approximate 6% error. If it indicates I'm going 65 mph, I'm actually going about 61. In the US, speedometers are required by federal regulation to be accurate to 5% of the reading. Please note that TIRE SIZE will effect the accuracy. If you change your tire size to something other than the OEM recommended tire size (sticker on inside support rail rear of the driver's door) it will effect speedometer accuracy. A larger tire diameter will cause the speedometer to "under-report" (indicate your going SLOWER than your actual speed) and a smaller tire will cause it to "over-report" your speed. You can check this yourself by driving on an interstate at a steady spead, say 60 mph, and use a stopwatch to time how long it takes to go from one mile marker to the next mile marker. At 60 mpg, it should take 60 seconds. If it takes longer, your going slower and vice-versa. For a more accurate estimate, you can time how long it takes to traverse 10 mile markers and calculate the seconds to travel 1 mile.