[pixlplague]

Hi all,

I have a question for y'all: how accurate is your speed reading on your G30??

You see, I have a 2017 540i with the HUD and the digital cluster (can't remember the option... 6W something something) and have noticed a persistent 4 to 6 km/h error on my speed reading in both.

I always show a slower speed than acutally travelling, which is driving me absolutely mad! The slower I go, the less the margin is but it's still almost always around 5 km/h (or around 3 mph). I know this through GPS and with radar (didn't get a ticket, just the warning ones around town ).

What really gets me is when I told the dealership they answer "it's normal, BMW are like that to keep you from speeding".

WHAT?! So first, that's stupid. Second, the cheap a** Hyundai Sonata I got for work shows me the EXACT speed I'm travelling, how is it BMW doesn't. And lastly, that's STUPID. I've had three 3 series before that and never noticed such a difference, except if I have the wrong wheel size...

So, before I blow a gasket at them (first time buying from them, not impressed) is there truth to that? And if there is, is there any way to fix it?!?

I can go in details on why I don't trust them anymore, but suffice to say they better give me one damn good price on a car to buy from them again.

[lnaukkar]

afaik bmw speedo always shows 3 more (real speed is 3 less)

for europe thats 3 km less [the real speed] (this has always been the case in a bmw for me atleast)
and for US 3 mph less (I suppose, i think I've read it somewhere)

this is of course assuming you use the correct oem wheel + tire size

[Mach550]

mine always reads 2 to 3 mph faster than what I'm actually going. All the speed reading signs on the side of the road read 35 when I'm going 37-38 and so does waze.

[Skyrider01]

Originally Posted by Mach550

mine always reads 2 to 3 mph faster than what I'm actually going. All the speed reading signs on the side of the road read 35 when I'm going 37-38 and so does waze.

I agree with this. Both my G30 and F10 show about 2mph faster than actual. (I compare the speed with the GPS speed readout on my radar detector).

My understanding is that speedometers are calibrated to display a faster speed than actual to prevent you from speeding. If the indicated speed is lower than actual and you get pulled over for speeding, the car manufacturers could be liable because your speedometer indicated you were going slower than you actually were.

[Qsilver7]

Uhh...here we go again.

The accuracy of the speedometer (as discussed for DECADES across multiple forums)...is altered due to European regulations. It's easy to find by just googling it because it has been asked a million times.

And no...it does not affect your odometer.

Japanese & American made cars usually follow the 4% rule:

The four percent rule

For ordinary passenger vehicles, there’s no law in the U.S. that regulates speedometers, but U.S. manufacturers (and most Japanese as well) subscribe to a standard called SAE J1226. Your speedometer reading must be within a range of plus or minus four percent off, but that’s four percent over the entire range of the speedometer, and that range can then be shifted in what’s called a bias.

European made cars follow a different formula:

The European formula

Now it gets really crazy. The European Union requires adherence to UN ECE Regulation 39. It’s a lot of math, but the simple version is that no speedometer can read slower than the actual speed. On the high side, it’s allowed to read up to 10% above the actual speed plus four or six kilometers per hour, depending on the type of vehicle.

[pixlplague]

Originally Posted by Qsilver7

Uhh...here we go again.

The accuracy of the speedometer (as discussed for DECADES across multiple forums)...is altered due to European regulations. It's easy to find by just googling it because it has been asked a million times.

And no...it does not affect your odometer.

Ok ok jeez sorry didn't mean to stir up anything. I just thought that's what forums were for: discussing things.

I did do a search on the forum, and nothing turned up. As for google, I must have simply missed it... too narrow a search I guess. Going on my asessment of other cars (hindsight Korean and American) I didn't think regulations could be an actual thing.

Case closed.

[SteveinArizona]

One final comment. If you don't like it, you can code it to actual.

[pixlplague]

Originally Posted by SteveinArizona

One final comment. If you don't like it, you can code it to actual.

THAT! That was the essence of my question! Thank you, I will investigate how to do this, and if it's possible through Bimmercode.

Thank you kind stranger.

[Bimmertrashjr]

Originally Posted by Mach550

mine always reads 2 to 3 mph faster than what I'm actually going. All the speed reading signs on the side of the road read 35 when I'm going 37-38 and so does waze.

+1

[enigma01]

Originally Posted by pixlplague

Hi all,
I always show a slower speed than acutally travelling, which is driving me absolutely mad! The slower I go, the less the margin is but it's still almost always around 5 km/h (or around 3 mph). I know this through GPS and with radar (didn't get a ticket, just the warning ones around town ).

If it's truly showing a slower speed than actual, then you should talk to your dealer again.

A typical BMW, as the others painfully pointed out already, shows a faster speed (by about 5%) than actual. So, at a highway speed of 65mph (as shown by your speedometer), you are actually traveling at roughly 62mph.

[MysticBlue]

Originally Posted by pixlplague

Ok ok jeez sorry didn't mean to stir up anything. I just thought that's what forums were for: discussing things.

I did do a search on the forum, and nothing turned up. As for google, I must have simply missed it... too narrow a search I guess. Going on my asessment of other cars (hindsight Korean and American) I didn't think regulations could be an actual thing.

Case closed.

Well, you were pretty adamant, "blowing a gasket", lot's of exclamation points, etc. Just as another data point, yes, this is totally normal. Speedo's from Europe reading 3 or 4 or even 5% high is normal. Think about it this way. If they are going to error, they need to error on the side of safety. If they tried to make it right on, some number of them would read too low. Even if it was 1 or 2%, it wouldn't take very long before a class action suit would be brought by people who were involved in accidents and/or got speeding tickets.

[ezaircon4jc]

Originally Posted by SteveinArizona

One final comment. If you don't like it, you can code it to actual.

Please expound. I've searched and coded something that said it was a correction but had no effect.

[AP]

Maybe you coded the fuel consumption adjustment? Believe you can do that so the fuel consumption figures report are accurate

[ezaircon4jc]

Originally Posted by AP

Maybe you coded the fuel consumption adjustment? Believe you can do that so the fuel consumption figures report are accurate

Don't think so. I coded something like speed-correction with ESys.

[cartaozinho]

When I've driven by those "Your Speed Is X mph" signs, my speedometer reads about 1.05X. That is, my speedo reports about 5% higher speed than actual speed (assuming the signs are accurate).

Some vectors: (Speedometer Reading, Actual Speed)

(84, 80)
(63, 60)
(42, 40)
(21, 20)

[SteveinArizona]

Originally Posted by ezaircon4jc

Don't think so. I coded something like speed-correction with ESys.

I don't do my own coding so I can't tell you how.