[acizek]

my speedometer is not very accurate... when I go 130 km/h it's off by about 8 km/h, in 160 it's off by 11 km/h and over 200 km/h it's off by almost 20 km/h!!
any idea on how to fix it?

[Dankim10]

how did you find out that your speedometer is not accurate?

[Antinontoxic]

about -5km/h here...

[acizek]

I have a TomTom GPS navigation device which shows actual speed...

[FirstClass]

Most car makers do this. Get used to it.

[nmulax]

Originally Posted by FirstClass

Most car makers do this. Get used to it.

+1

There's usually around a 5% error in the speedometer reading. Just deal with it.

[DrPowers]

if you get it documented you could get out of some tickets.

I had a friend that got a ticket reduced because he recently put new wheels on his car which made his speedometer inaccurate.

[FirstClass]

Originally Posted by DrPowers

if you get it documented you could get out of some tickets.

I had a friend that got a ticket reduced because he recently put new wheels on his car which made his speedometer inaccurate.

Won't work. Your friend's speedometer read low, ours read high. This happened because your friend put wheels that were bigger than stock on his car. A high reading speedometer won't get you out of any tickets.

[encryption]

mine is off by 4 miles/hour

a buddy of mine said its a mandate which requires auto manufacturers to set the speedo a little faster than the car is actually going in order to ensure no wildcats are out breaking records (or at least doing it a tad slower).

dont know how true this is (and I haven't googled to check for accuracy of this info either).

My 97 TL is off by 2 miles/hour.

I have a Garmin navigation unit and it gives me a fairly accurate mph reading

[bmwexecutive]

Mine is accurate until 30MPH. At that point it starts to go off by 2MPH. At 100MPH the speedometer on my 330i is off by 3.9MPH. Not too bad in my opinion. I tested it against a Garmin GPS unit.

[web1b]

How far off can the speedometer be off before it is a warranty issue that needs to be corrected? Is there some standard that says 5 mph or 10 mph error is OK?
Mine is off by several MPH and I have stock tires and wheels.

[Orient330iNYC]

Originally Posted by web1b

How far off can the speedometer be off before it is a warranty issue that needs to be corrected? Is there some standard that says 5 mph or 10 mph error is OK?
Mine is off by several MPH and I have stock tires and wheels.

10% +2.4mph is within spec
so at 80mph indicated, 10.4mph off is within spec

[web1b]

Originally Posted by Orient330iNYC

10% +2.4mph is within spec
so at 80mph indicated, 10.4mph off is within spec

Wow! Does that mean the odometer may also be off by the same as the speedometer?
Why is it so sloppy? Can't they fix it?

[Firepriest]

it's intentional, there is a European regulation stating that the speedometer can not read slower then the car is actually going. The error is built into the display. If you access the secret menu (search the forum for "secret menu") you can get to a display that shows the actual speed of the car, so the car knows how fast it's really going, it's just lying to you.

[web1b]

Originally Posted by Firepriest

it's intentional, there is a European regulation stating that the speedometer can not read slower then the car is actually going. The error is built into the display. If you access the secret menu (search the forum for "secret menu") you can get to a display that shows the actual speed of the car, so the car knows how fast it's really going, it's just lying to you.

Who said it should read slower than the actual speed instead? How about accurate or 1 or 2% off instead of 10%?

Does the odometer compensate so it doesn't say 90,000 miles when the car was really driven more than 100K miles?

[Orient330iNYC]

Originally Posted by web1b

Who said it should read slower than the actual speed instead? How about accurate or 1 or 2% off instead of 10%?

Does the odometer compensate so it doesn't say 90,000 miles when the car was really driven more than 100K miles?

the computer takes the real speed (your actual distance over time) and biases it upward to ensure that the speedometer can never read less than actual. EU law requires this. this is why there's a fairly large margin built in, to account for tire wear and the various tire sizes used as parts of different options. EU law is very clear, it can NEVER read lower than actual speed for OE wheel and tire fittaments.
the raw real speed is used for the odometer, so the odometer is correct, the speedometer is just biased to read high.

European Union member states must also grant type approval to vehicles meeting similar EU standards. The ones covering speedometers [5] [6][7] are similar to the UNECE regulation in that they specify that:

* The indicated speed must never be less than the actual speed, i.e. it should not be possible to inadvertently speed because of an incorrect speedometer reading.
* The indicated speed must not be more than 110 percent of the true speed plus 4 km/h at specified test speeds. For example, at 80 km/h, the indicated speed must be no more than 92 km/h.

The standards specify both the limits on accuracy and many of the details of how it should be measured during the approvals process, for example that the test measurements should be made (for most vehicles) at 40, 80 and 120 km/h, and at a particular ambient temperature. There are slight differences between the different standards, for example in the minimum accuracy of the equipment measuring the true speed of the vehicle.

The UNECE regulation relaxes the requirements for vehicles mass produced following type approval. The upper limit on indicated speed is increased to 110 percent plus 6 km/h for cars, buses, trucks and similar vehicles, and 110 percent plus 8 km/h for two or three wheeled vehicles which have a maximum speed above 50 km/h (or a cylinder capacity, if powered by a heat engine, of more than 50 cc). European Union Directive 2000/7/EC, which relates to two and three wheeled vehicles, provides similar slightly relaxed limits in production.

[purplewidow]

wow i put 19 inch morr vs8's on and at 70mph only off by 2mph on speed guns.

[Mooreski]

Like someone said, go into the secret menu. 8.00 is the real speed, 8.01 is the speed shown on the speedo. Neat little trick