[Kabrich]

There is a spot several miles from my home that has a stationary radar displaying your current speed. Its been there for years.

In my past cars and vehicles, as well as every vehicle i have ever been in, the radar would display either 44 or 45 MPH (same speed always for the same car) when the vehicle is displaying 45 MPH.

On my new F30, when the speedometer is displaying 47 MPH the radar says its actually 44MPH.

Has anyone else seen a descrepancy of this nature with the Speedometer on the F30s?

Quite frankly, on a 1,000 mile / month lease, 3 MPH, the 8% overage means one would only drive 925 miles a month while the odometer would show 1,000 miles.

[Frogman]

BMW speedometers read artificially high on purpose, up to 5% or so. Something about a Germany law that requires that the speedo not ever read lower than actual.

The odometer is accurate.

[F30SD]

My speedo definitely reads higher by about 3mph.

[760Lifan]

That's (3mph above radar) how it was on my former E60 M5, too.

[Steve33]

Same with the F10 I'm in right now, also confirmed with a phone GPS speedometer

[kobechrome]

I did a similar experiment with my E90 with my Garmin GPS and found there to be a discrepancy of 3-4 mph (E90 showing higher).

[KellerKiller]

Mine only reads about 3 KM/H above what the radar shows. I hope that means it'll only read about 1.5-2 mph over. It'd be kind of messed up if it's set to read 3 higher regardless of the unit of measurement...

[Kabrich]

Originally Posted by Frogman

BMW speedometers read artificially high on purpose, up to 5% or so. Something about a Germany law that requires that the speedo not ever read lower than actual.

The odometer is accurate.

How can the odometer be accurate if the speed is off by 8%?

Met with JParker82 today. He speculated that perhaps the issue was that I had 19" wheels and the electronics were still calibrated for 18" wheels.

From the posts here, it sounds like this is a known bug, not a tire size/calibration issue (which made sense as a possibility).

[DarkTrigger]

Originally Posted by KellerKiller

Mine only reads about 3 KM/H above what the radar shows. I hope that means it'll only read about 1.5-2 mph over. It'd be kind of messed up if it's set to read 3 higher regardless of the unit of measurement...

I was about to say, I can drive 5 mph faster now... 80 now instead of 75!

[Frogman]

Originally Posted by Kabrich

How can the odometer be accurate if the speed is off by 8%?

Met with JParker82 today. He speculated that perhaps the issue was that I had 19" wheels and the electronics were still calibrated for 18" wheels.

From the posts here, it sounds like this is a known bug, not a tire size/calibration issue (which made sense as a possibility).

The instrument cluster reads the actual speed from the car and adds a correction factor to it before the value is shown (Speedo, HUD, etc).

There's a coding variable you can change to disable the corrector if you want. Refer to the to coding forum for details.

The issue of changing the wheel size is a different matter! It's not the wheel size (18" or 19"), but the outside diameter of the tire that matters. If that changes significantly, then the speedo will be off even more.

[Frogman]

Originally Posted by DarkTrigger

I was about to say, I can drive 5 mph faster now... 80 now instead of 75!

Mine reads 2mph fast at 70 mph (tested with a portable GPS).

I was also worried about the odometer being off, so when I did a long trip (a straight 300+ mile leg on I-5), I used the odometer feature on the GPS and after 300 miles the car odometer read within 0.2 miles of what the GPS said. I'm not worried anymore.

[CirrusSR22]

Every BMW has done this since at least the late 1980s / early 1990s.

[Kabrich]

Originally Posted by Frogman

The instrument cluster reads the actual speed from the car and adds a correction factor to it before the value is shown (Speedo, HUD, etc).

There's a coding variable you can change to disable the corrector if you want. Refer to the to coding forum for details.

The issue of changing the wheel size is a different matter! It's not the wheel size (18" or 19"), but the outside diameter of the tire that matters. If that changes significantly, then the speedo will be off even more.

Are you saying there is a coding variable to disable the incorrect speed - or odometer, as I would like to get the speed correct, if possible.

[Frogman]

Originally Posted by Kabrich

Are you saying there is a coding variable to disable the incorrect speed - or odometer, as I would like to get the speed correct, if possible.

It changes the adjusted speed shown.

It's called BC_V_KORREKTUR in KOMBI. I have not coded it myself, so I can't attest to it being effective or not.

[DarkTrigger]

Originally Posted by Frogman

It changes the adjusted speed shown.

It's called BC_V_KORREKTUR in KOMBI. I have not coded it myself, so I can't attest to it being effective or not.

Dang, we should try it next time!

[Frogman]

Originally Posted by DarkTrigger

Dang, we should try it next time!

I'll let you experiment on your car all you want!

[Mahzari]

In Germany, it is illegal for a speedometer to read slower than the car is driving. This would cause legal problems when it comes to speeding. Because of this, BMW builds in a safety margin (of up to 10%) into their speedometers. When I pass my the electric signs that tell me my speed, it can be 1-2mph higher or as much as 5mph in a 55mph zone.

[slaaw]

That can easily be corrected by using slightly larger diameter tires.

Originally Posted by Kabrich

There is a spot several miles from my home that has a stationary radar displaying your current speed. Its been there for years.

In my past cars and vehicles, as well as every vehicle i have ever been in, the radar would display either 44 or 45 MPH (same speed always for the same car) when the vehicle is displaying 45 MPH.

On my new F30, when the speedometer is displaying 47 MPH the radar says its actually 44MPH.

Has anyone else seen a descrepancy of this nature with the Speedometer on the F30s?

Quite frankly, on a 1,000 mile / month lease, 3 MPH, the 8% overage means one would only drive 925 miles a month while the odometer would show 1,000 miles.

[Kabrich]

Originally Posted by slaaw

That can easily be corrected by using slightly larger diameter tires.

I have 19" on 403M rims. If this is a "corrected" number, I'd hate to see it on 18" or 17".

[Stillhart]

I know that most motorcycles I've ever ridden have the same feature. I assumed all cars had it as well. It's a 7-8% overage on the displayed speed. That's why I'm never concerned when I pass a cop going 5 over.

[Steve33]

I've changed it in my car via coding and it makes it the actual speed now.

Originally Posted by Kabrich

I have 19" on 403M rims. If this is a "corrected" number, I'd hate to see it on 18" or 17".

The rim size doesn't matter, the outside diameter of the tires is what matters

[BavarianFanatic]

Another speedo error thread.

Here's why:

Directive 75/443/EEC - Reverse and speedometer of motor vehicles

"4.4 The speed indicated must never be less than the true speed. At the speeds specified for the test in 4.3.5 above and between these speeds, there shall be the following relationship between thespeed indicated on the dial of the speedometer (V1) and the true speed (V2):

0<= V1 - V2 <= V2/10 + 4km/h"


The reason BMW (and others) use a conservative error is to account for variations in overall tire circumference from manufacturer to manufacter and even model to model. Even though a tire has the same advertised tread width, rim diameter and aspect ratio as another, it can have a different overall diameter and thus circumference. THIS is why they build in the error.