[S6F]

This is my 8th BMW. All overestimated the car's speed, usually by 3mph. This latest one, a 340i, is off by 4mph. This is really rediculous. Any other car I've ever owned (roughly 25 of them) was right on.

[hollandog]

wonder why is this a big deal?

[tgmsocal]

From the F30 Coding Reference Guide v1.7:

KOMBI
3000
BC_V_KORREKTUR
nicht_aktiv
aktiv
Turns off speed correction and displays actual speed.

Maybe that's what you're looking for? Agree with prev post, no idea why 3-4mph matters. Also because the table doesn't show - "aktiv" is default, you'd code to "nicht_aktiv".

-tgm

[Beowulf65]

If your car under estimates the speed...that is an issue. You could be stopped for speeding without knowing you were over the limit. Over estimating your speed is an intentional design decision to mitigate against customer complaints. As noted above this can be adjusted by coding.

[CLittle]

I can understand why it would be annoying to have this safety factor/error.

If you try to drive the speed limit using the speedometer, then you're going 4 mph under. Or you have to adjust like me and using the HUD, I'm always driving 37, 47, & 57 mph on city streets.

[XRAVE]

All BMWs are like 6% off, not exactly 4 mph. I actually like it because I always know I'm not speeding, especially when cruise controlling on the highway.

[AudiA4]

Originally Posted by XRAVE

All BMWs are like 6% off, not exactly 4 mph. I actually like it because I always know I'm not speeding, especially when cruise controlling on the highway.

One would assume it's a percentage, but every time I've checked, it's always 2-3 MPH off whether I'm going 25 (actually 22-23) or 80 (measures 77). Either way, like you, I don't mind since I know the actuals.

[mtx450]

After hours and hours of research on this topic, I'm 99% sure coding those values above DO NOT do anything. The odometer will always read true, but the speedometer has a built in correction factor to increase it by around 4-6%.

[RoundelM3]

Originally Posted by mtx450

After hours and hours of research on this topic, I'm 99% sure coding those values above DO NOT do anything. The odometer will always read true, but the speedometer has a built in correction factor to increase it by around 4-6%.

The "built in correction factor" is turned off by coding as mentioned above. Checking speed against my GPS after coding the "correction" to "nicht aktiv", it's within 1 MPH of what the GPS reads. There are also portable radar trailers that the local PD sets up around town and every single time I go past one, its readout matches that of my analog and digital speedometer readouts (coded that, too).

[Billfitz]

Originally Posted by AudiA4

One would assume it's a percentage, but every time I've checked, it's always 2-3 MPH off whether I'm going 25 (actually 22-23) or 80 (measures 77). Either way, like you, I don't mind since I know the actuals.

True. Mine reads about 2MPH low at 30 and at 60. I also don't mind. Like most I tend to drive around 15% above the limit. The 'error' gives me a buffer that prevents speeding tickets.

[mtx450]

Originally Posted by roundel335

The "built in correction factor" is turned off by coding as mentioned above. Checking speed against my GPS after coding the "correction" to "nicht aktiv", it's within 1 MPH of what the GPS reads. There are also portable radar trailers that the local PD sets up around town and every single time I go past one, its readout matches that of my analog and digital speedometer readouts (coded that, too).

Wow, I'll have to try coding this then! I haven't gotten around to it, so my claims were based upon what I've read. A lot of people were saying that it didn't work after coding (F30 specifically).

[RoundelM3]

Originally Posted by mtx450

Wow, I'll have to try coding this then! I haven't gotten around to it, so my claims were based upon what I've read. A lot of people were saying that it didn't work after coding (F30 specifically).

Most definitely works. I code the correction off and the digital readout (an addition to the list of selectable items in the "bc" area between tach and speedo). I've done this since 2011 on previous E-series cars and now on both of my F-series cars.

[mtx450]

Originally Posted by roundel335

Most definitely works. I code the correction off and the digital readout (an addition to the list of selectable items in the "bc" area between tach and speedo). I've done this since 2011 on previous E-series cars and now on both of my F-series cars.

BC_V_KORREKTUR = Correction for Analog Speed
BC_DIGITAL_V_KORREKTUR = Correction for Digital speed

I'll give this a shot!

[Vitoco]

Or you could just step up the profile on the tires a notch like I did, and now my speedo matches the GPS speed.

[AudiA4]

Originally Posted by Billfitz

True. Mine reads about 2MPH low at 30 and at 60. I also don't mind. Like most I tend to drive around 15% above the limit. The 'error' gives me a buffer that prevents speeding tickets.

I always thought it was dumb when people set their watches ahead by 5 minutes, so I'm not sure why I give this a pass! LOL!

[Billfitz]

Originally Posted by AudiA4

I always thought it was dumb when people set their watches ahead by 5 minutes, so I'm not sure why I give this a pass! LOL!

It helps to know how cops work. If they're sitting on the side of the road with a hand held radar gun they can zoom in on individual cars and clock them. That's a lot of work. It's easier to use a window mounted gun that clocks every car, and set an alarm that goes off at a specified speed reading. But if they stopped every speeder that would be too much work too, so they set the alarm speed about 15% above the limit. If the limit is 65 they set it at 74. If you're doing 73 the alarm won't sound. If the limit is 65 I set my cruise at 73, knowing that will give me some leeway just in case I go by a cop who's more aggressive in his settings or has a badly calibrated radar gun. That all goes out the window in heavy traffic, there I just go with the flow. On the Jersey Pike that tends to be about 85.

[RoundelM3]

Originally Posted by mtx450

BC_V_KORREKTUR = Correction for Analog Speed
BC_DIGITAL_V_KORREKTUR = Correction for Digital speed

I'll give this a shot!

Latest "cheat sheet" for 2-series shows "unable to find BC_DIGITAL_V_KORREKTUR". Also looked in BMW Coding Database and didn't find it. May not be an option on newer cars?

[KGB_123_99]

Based on my phone's GPS, my car not only over-estimates the speed but also distance traveled. Can anyone else confirm?

[tgmsocal]

Originally Posted by KGB_123_99

Based on my phone's GPS, my car not only over-estimates the speed but also distance traveled. Can anyone else confirm?

Well that's interesting. If that's true, I'd be curious if it is more accurate after coding out the correction.

When you say "distance traveled" do you mean odometer, trip, or nav unit?

- tgm

[ScarecrowBoat]

Who cares if it overestimates speed by a couple %, it's doing you a favor. Your odometer is not affected in anyway by altering the coding of the car. There are federal guidelines for weights and measures that the car must adhere to.

[Vegetable]

I personally would rather my speedo read the correct speed. I don't need or want any buffer. But.. I do appreciate my 435i being only about 2-3 MPH off at 80 MPH (optimistic) vs my e92 which was 4-5 MPH optimistic at the same speed.

[Vegetable]

Originally Posted by hollandog

wonder why is this a big deal?

Because we want our gauges to give us correct information