AMajor

2005 Audi A4 Cabriolet 3.0L, stock wheels and tires, inflated to recommended pressure. Speedometer consistently displays 5 mph faster than GPS at 60 mph, i.e. over 8% faster. Tested GPS in Murano and Acura at same speed and GPS was accurate within +- 1 mph with both test vehicles' speedometer. Asked Audi Dealer in Syracuse NY about discrepancy and was told that all Audis are calibrated to show speed faster by 5 mph, purportedly for safety reasons. I assume the speedometer and odometer are linked. The yet to be answered question from Audi is: Will my 50,000 mile warranty be extended to 54,000 miles? Any comments?

paulroad

dealer is full of crap. ask heim to fix it or find another dealer.

Stardog

German cars tested were consistently calibrated 3-5 mph over actual speed. Japanese and American cars were all closer to actual speed. My own experience with several late model Audis is the same. There is an easy way to test this. Although the speedo is calibrated 3-5 mph fast, the odometer is spot on. Next time you are on an empty stretch of freeway, run a consistent speed, say, 60 mph. Then reset your trip computer on the average speed function. The average speed will show about 56-57 mph. I don't know if there is a way to fix the problem. I think it is just part of the baggage you accept with a German car.

paulroad

I've seen 1-2 mph variations but not that much.

Confirmed via GPS as well as the AVG button, and TSD with a stopwatch.

whn you have an 03 with 163,000 miles on it you tend to find many things to keep you busy while you drive.

Stardog

Below is a part of the article explaining European speedo regs:

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. Not even if somebody swaps a big set of 285/35R-18s for stock 255/45R-16s.

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. Of course, only the speedometer must conform. Trip computers are free to report average speed honestly. Try setting your BMW or Porsche cruise control and then resetting the average-speed function. Unless you've screwed up the tires, the trip computer should show a nearly accurate reading. Even General Motors, whose domestic speedometers are the best, must skew its readings slightly high on vehicles exported to Europe.

paulroad

I don't think so,

Wiki is wonderful:


As of 1997, Federal standards in the United States allowed a maximum 5% error on speedometer readings (per "Auto Tutor", American Automobile Association of California magazine, Oct. 17, 1997). Aftermarket modifications, such as different tire and wheel sizes or different differential gearing, can cause speedometer inaccuracy.

Stardog

That's not what I say--that's what Car & Driver says.

TwoSeven

The odometer works fine. Try testing it against a mileage counter on your GPS. I noticed the 5mph bump too, and measured it against both the trip computer and the GPS to test the accuracy. End result is, the computer knows how fast it is going, it just lies to you about it.

I drive "5mph faster" than I normally would now - woo hoo!!!