Speedometer Accuracy
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New Member
Joined: Jan 2006
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Speedometer Accuracy
Guys,
I am new owner (2004 A8L). My first Audi after 15 years of Mercedes'. I have learned a lot already from reading this forum over the past month. It helped me decide on the car and to feel confident in my purchase. Thank you all.
I picked up my car last weekend...still under warranty with only 13,000 miles and I had asked the dealer to ensure that all factory recalls and upgrades were applied prior to taking delivery...all seems fine and I have to say that I love this car.
One question however is the accuracy of the speedo. I live on the North Shore of Boston and drive Route 128 every day...the unofficial speed limit seems to be about 75MPH and I would regularly enjoy 80 plus in my E430. So now I find that 80 does not seem so fast, and either everyone else on the road has suddenly decided to drive at least 5MPH faster, or there is some inaccuracy in the Audi speedometer (or maybe the Benz speedo was wrong and all of this time I was really driving much faster than I thought!)
The A8 has factory 19" wheels and Bridgstone Potenza 255/40R19 tires.
Any thoughts or similar experience?
I am new owner (2004 A8L). My first Audi after 15 years of Mercedes'. I have learned a lot already from reading this forum over the past month. It helped me decide on the car and to feel confident in my purchase. Thank you all.
I picked up my car last weekend...still under warranty with only 13,000 miles and I had asked the dealer to ensure that all factory recalls and upgrades were applied prior to taking delivery...all seems fine and I have to say that I love this car.
One question however is the accuracy of the speedo. I live on the North Shore of Boston and drive Route 128 every day...the unofficial speed limit seems to be about 75MPH and I would regularly enjoy 80 plus in my E430. So now I find that 80 does not seem so fast, and either everyone else on the road has suddenly decided to drive at least 5MPH faster, or there is some inaccuracy in the Audi speedometer (or maybe the Benz speedo was wrong and all of this time I was really driving much faster than I thought!)
The A8 has factory 19" wheels and Bridgstone Potenza 255/40R19 tires.
Any thoughts or similar experience?
AudiWorld Super User
Joined: Aug 2003
Posts: 2,384
Likes: 0
It reads about 5% high
There's a graph in my pic poster that shows the error.
You can test yours by resetting the average speed display shown on the dash. When the speed is displayed after the reset, it will be the true speed. You can then see how much different the speedo is to this 'instant average'.
You can test yours by resetting the average speed display shown on the dash. When the speed is displayed after the reset, it will be the true speed. You can then see how much different the speedo is to this 'instant average'.
AudiWorld Super User
Joined: Jan 2006
Posts: 6,310
Likes: 123
From: Las Vegas, Nevada USA
Re: It reads about 5% high
Every Audi & water cooled VW I have owned (seven, as of now) reads about 5 mph faster than true at speeds above 45 mph. Below that, about 3 mph fast.
I checked one car with a calibrated radar gun on the high speed track at TRC in East Liberty, Ohio. That's a 7 1/2 mile oval. Too bad it was not my A8L!
I checked one car with a calibrated radar gun on the high speed track at TRC in East Liberty, Ohio. That's a 7 1/2 mile oval. Too bad it was not my A8L!
AudiWorld Senior Member
Joined: Aug 2005
Posts: 622
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I believe there is a law...
When I questioned why the speedo on my BMW motorcycle was overly optomistic, I found out (I think...it was years ago) that there are gov't regulation about speedometers that they must not read too low with fines if they do...therefore they car calibrated toward the "upper end of acceptible". ...and the penalties are much stiffer in Europe than in the US. Therefore the manufacturers tend to set them "too too" high on Euro cars.
...I believe this is accurate, but I will stand corrected if anyone has better info.
(E)
...I believe this is accurate, but I will stand corrected if anyone has better info.
(E)
New Member
Joined: Jul 2001
Posts: 48
Likes: 0
Re: I believe there is a law...
I, too, have heard that the error limits are set by law (and engineering standards) so that the speedometer reading can be "+", but not "-" (e.g., show 55 mph, but not 45, in a 50 zone).
However, mine reads 10% high--not 5 mph, which really becomes obvious at high freeway speeds (such as showing 72 mph in a 70 mph zone--as on the 5 freeway down California's central valley--when actually doing 65 mph, and cars zooming by like you're standing still!).
It really is pathetic that, with all the "gee whiz" electronics and computational power on the 2004 A8L, Audi cannot get something as simple as a speedometer reading accurate! (Each time I ask my service advisor, his reply is that there is still no service bulletin about the problem. I wonder if there will ever be one.)
PS: The car came with 19" wheels, which I have changed out once with the same size, so it's not a matter of a change in wheel size causing this horrendous deviation from the correct speed. It's been a problem from day one with the car.
However, mine reads 10% high--not 5 mph, which really becomes obvious at high freeway speeds (such as showing 72 mph in a 70 mph zone--as on the 5 freeway down California's central valley--when actually doing 65 mph, and cars zooming by like you're standing still!).
It really is pathetic that, with all the "gee whiz" electronics and computational power on the 2004 A8L, Audi cannot get something as simple as a speedometer reading accurate! (Each time I ask my service advisor, his reply is that there is still no service bulletin about the problem. I wonder if there will ever be one.)
PS: The car came with 19" wheels, which I have changed out once with the same size, so it's not a matter of a change in wheel size causing this horrendous deviation from the correct speed. It's been a problem from day one with the car.
AudiWorld Super User
Joined: Dec 2000
Posts: 7,597
Likes: 3
Re: I believe there is a law...
I had my speed control set at 83MPH coming out of Oklahoma this past New Years, the Arkansas Hwy Patrolman "GOT ME", the officer said, "sir, did you realize you were doing 79MPH"?, I said, YES SIR. He did let me go with a "please slow down a bit, so you'll get back to Atlanta safely". I said "Thank you, sir".
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