SPEEDO ERROR

[hridge06]

My speedometer is reading around 5mph faster than I'm actually going. I purchased the car (95 318ti) used and there doesn't appear to be any drivetrain modifications. Does anyone have any suggestions?

[angel318ti]

Originally Posted by hridge06

My speedometer is reading around 5mph faster than I'm actually going. I purchased the car (95 318ti) used and there doesn't appear to be any drivetrain modifications. Does anyone have any suggestions?

Not even wheels were modified? maybe its just your instrument cluster thats off then

[Micaoct]

Take a look at this article from CarAndDriver, it helps explain it. All speedometers have a percent error, and Cars are required to show the % error on the higher side (to prevent people that are unaware of the error from speeding). If your reading 50mph your probably actually doing 49mph or so. It depends on other factors too, but this is a small reason why your speedo might be not so accurate

[1996 328ti]

BMWs always read higher.

[Will'sBimmer]

mine reads over more. i noticed when i passed one of those speed readers that is set up by cops and it told me i was going slower than what my speedo told me i was doing. only off by maybe one or two miles

[John Firestone]

Originally Posted by Micaoct

Take a look at this article from CarAndDriver, it helps explain it....

It helps and is a fun read, but their explanation blaming European law for grossly overreading speedometers on some German imports is bogus. It is an American projection onto Europe of an American solution to an American problem.

As far as I can tell from this distance, BMW NA calibrated their speedometers to more generously overread because they have much less control over the tires the customers put on their cars. They feared some would slap on larger outside diameter tires that would otherwise cause the speedometer to underread.

I happened to be discussing this issue with a German engineer yesterday, and why the speedometers on European E36s are more accurate and can all use the same "K-factor".

[Bozola]

The interesting part is that the car knows the true speed..

(it can be displayed in the AVG speed on the OBC).

Try it.
Set the cruise to 60 on a flat road.
Reset the AVG speed.
Drive one minute.

Your avg speed will be 58.x..

Weird huh??
________
growing marijuana

[Tyler]

Originally Posted by Will'sBeamer

mine reads over more. i noticed when i passed one of those speed readers that is set up by cops and it told me i was going slower than what my speedo told me i was doing. only off by maybe one or two miles

Those are never really accurate unless your the only one on the road and there is nothing moving around it.

[m-technik_ti]

My radar detector runs by GPS plus it also displays your true speed and it’s always a bit lower than my speedometer readout.

[pnosker]

Mine runs +3/4 also. The AVG speed thing does work. I've synchronized it via GPS a few times. It's kind of annoying though as for some reason the MPG calculator relies on the indicated speed on the speedo.

[weezer]

Originally Posted by hridge06

My speedometer is reading around 5mph faster than I'm actually going. I purchased the car (95 318ti) used and there doesn't appear to be any drivetrain modifications. Does anyone have any suggestions?

What size tires are you using.
Mine's of because I'm wearing 225 45 16 instead of 225 50 16 on 16x7 wheels.
My speedo always reads 5 miles higher.

[John Firestone]

Originally Posted by Bozola

The interesting part is that the car knows the true speed....Weird huh??

American lawyer-ing.