[txm550i]

Hey all, wondering if this is a common issue, something easily corrected by the dealer etc..

After buying my M550i (2018 with 26k miles) I had a nice 4-hour drive on the interstate to get it home. My wife was following behind in our 2015 Expedition. We noticed there was a 3-4 mph difference in what the BMW was telling me I was doing and what the speedo in the truck was telling us. For example I would set the cruise in the BMW to 80mph and my wife would tell me she had to set her cruise to 76-77mph to not run up on me. We took cruise off on both vehicles and no matter what speed I chose in the BMW, the truck always reported 3-4mph slower.

For more evidence we've noticed that any nav application we're using usually reports were doing 3-4mph slower than what the BMW is telling me its doing. Example, I use Waze a lot and did some driving this last weekend. When I was doing 80mph, Waze showed I was doing anywhere from 75-77mph.

[Joe-BMW33]

BMW's have always had a 3-5 generous discrepancy. Every one I have ever had, beginning with my E30. It's a known thing.

[beerman80]

Originally Posted by txm550i

Hey all, wondering if this is a common issue, something easily corrected by the dealer etc..

After buying my M550i (2018 with 26k miles) I had a nice 4-hour drive on the interstate to get it home. My wife was following behind in our 2015 Expedition. We noticed there was a 3-4 mph difference in what the BMW was telling me I was doing and what the speedo in the truck was telling us. For example I would set the cruise in the BMW to 80mph and my wife would tell me she had to set her cruise to 76-77mph to not run up on me. We took cruise off on both vehicles and no matter what speed I chose in the BMW, the truck always reported 3-4mph slower.

For more evidence we've noticed that any nav application we're using usually reports were doing 3-4mph slower than what the BMW is telling me its doing. Example, I use Waze a lot and did some driving this last weekend. When I was doing 80mph, Waze showed I was doing anywhere from 75-77mph.

When I bought my first BMW I noticed this as well. My speed was consistently 3mph slower than what the speedo showed. After googling it I found that European regulations are very strict for going over the speed limit, so they set them to read faster than what you are actually going.

[ezaircon4jc]

Originally Posted by txm550i

Hey all, wondering if this is a common issue, something easily corrected by the dealer etc..

After buying my M550i (2018 with 26k miles) I had a nice 4-hour drive on the interstate to get it home. My wife was following behind in our 2015 Expedition. We noticed there was a 3-4 mph difference in what the BMW was telling me I was doing and what the speedo in the truck was telling us. For example I would set the cruise in the BMW to 80mph and my wife would tell me she had to set her cruise to 76-77mph to not run up on me. We took cruise off on both vehicles and no matter what speed I chose in the BMW, the truck always reported 3-4mph slower.

For more evidence we've noticed that any nav application we're using usually reports were doing 3-4mph slower than what the BMW is telling me its doing. Example, I use Waze a lot and did some driving this last weekend. When I was doing 80mph, Waze showed I was doing anywhere from 75-77mph.

BMW purposely calibrates their speedometers to run 3 mph slow above about 40mph. I think I remember reading somewhere it has something to do with the way speeding tickets are issued in Germany. I just set my cruise at 3 over what I want.

[txm550i]

Originally Posted by beerman80

When I bought my first BMW I noticed this as well. My speed was consistently 3mph slower than what the speedo showed. After googling it I found that European regulations are very strict for going over the speed limit, so they set them to read faster than what you are actually going.

Interesting lol. I should have known. Welp, guess I'll drive by what the Nav tells me then.

[AP]

Yeh last thing you want is driving at the speed limit only to find out a speed camera "gets you"

Also allow for tyre wear and minor variations.

Believe police speedometers are calibrated to be more accurate, any police on this forum to confirm that?

[LogicalApex]

This is the case for all the German makes. The EU has a law or regulation that prohibits manufacturers from ever under reporting the speed. In the US I believe our laws allow for this, but it has to be right 95% or the time or something like that.

If it matters to you in a CC situation you can just add a few MPH to your set limit to work around it.

The difference between actual speed and the speed dial tends to get noticed more with German cars because their speedometers are designed to never report a speed lower than actual speed. European law (ECE-R39) says speedometers cannot show speeds less than the actual speed, and they must never show more than the 110 per cent of actual speed plus 4 km/h. So, under those rules, a car could be moving at 100 km/h, but the speedometer could legally display as high as 114 km/h.

Source: Globe & Mail

[HighlandPete]

European regs' go something like this... from GOV UK.

Speedometers

The Motor Vehicles (Approval) Regulations 1996

Speedometers

1. The vehicle shall be fitted with a speedometer capable of indicating speed in mph at all speeds mph. up the maximum design speed of the vehicle.

2. For all true speeds up to the maximum design speed of the vehicle, the true speed shall not exceed the indicated speed.

3. For all true speeds of between 25 mph and 70 mph (or the maximum design speed if lower), the difference between the indicated speed and the true speed shall not exceed—

V / 10 + 6.25mph

where V = the true speed of the vehicle in mph.

[Qsilver7]

As already mentioned...European cars fall under a regulation...UN ECE Regulation 39...which you can google for more details:

The European formula

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.

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.