[GL84]

Picked up our 2022 M240i

On the highway we noticed the 240 is 4mph faster than the WAZE GPS and my wife's Civic cruise control.

Is this normal on a BMW?

Can I fix it somehow?

[Pentland]

Originally Posted by GL84

Picked up our 2022 M240i

On the highway we noticed the 240 is 4mph faster than the WAZE GPS and my wife's Civic cruise control.

Is this normal on a BMW?

Can I fix it somehow?

Been discussed many times. All EU cars speedos read fast. They are not allowed to be under.

[GL84]

Originally Posted by Pentland

Been discussed many times. All EU cars speedos read fast. They are not allowed to be under.

You don't know what you don't know.
Thanks for the info, but this sounds ridiculous for someone who's never touched a EU car.


Still do you know if it digitally adds 3mph? If I got a different size tire will it affect the outcome or just get another 3mph added to it..?

[Pentland]

Originally Posted by GL84

You don't know what you don't know.
Thanks for the info, but this sounds ridiculous for someone who's never touched a EU car.


Still do you know if it digitally adds 3mph? If I got a different size tire will it affect the outcome or just get another 3mph added to it..?

Who said it digitally adds a set amount?
You need to buy tyres of the correct size and tolerance. Otherwise it will affect speedo.

[GL84]

Originally Posted by Pentland

Who said it digitally adds a set amount?
You need to buy tyres of the correct size and tolerance. Otherwise it will affect speedo.

It's the OEM tire and wheels. I read up on a different thread as you suggested, but it seems the spedo and the odometer aren't linked as the OBD port reads the same as the GPS speed. Hence it is possible that the dash shows a +3 no matter what the real speed is as affected by tire size.

[wb8164]

As noted, this is a common topic/complaint by new owners. To my knowledge, there's no way to code in any kind of re-calibration. However, fitting a different wheel/tire size combination should affect the speedo readout, so if you plan correctly, you could get a more accurate speedo reading. There are online wheel/tire calculators that can give you a hand in finding what wheel and tire size would work.



Here's a link to a wheel/tire calculator

https://tiresize.com/calculator/

Personally, I've learned to just live with it and mentally add 2-3 mph to the speedo reading.

[H00CH90]

My radar detector displays GPS speed, this has been my work around. Annoying but oh well. At least it's reading higher and not lower.

[eli371]

every single car I've ever driven with a digital speedo has been off by 3-8km depending how fast i've gone.

[Fronzdan]

The interesting thing about this is SOMETIMES the car speedo is 3-4 mph faster than the speed determined via gps in Waze. But sometimes they align. It’s weird. And this is while driving on the highway for over an hour. It’s dead on the same.

[Desert240]

Have measured mine several times against GPS and it seems to be consistently 6.7 % high. Pretty irritating. I've never driven a car that had a speedo this far off without aftermarket wheels. Haven't checked if the odometer is off by a similar amount

[RockCrusher]

Originally Posted by Desert240

Have measured mine several times against GPS and it seems to be consistently 6.7 % high. Pretty irritating. I've never driven a car that had a speedo this far off without aftermarket wheels. Haven't checked if the odometer is off by a similar amount

First encountered an optimistic speedo in my 2002 Porsche Boxster. Car came with 17" wheels/tires vs. the factory 16" wheels/tires. (Word was *no one* ever opted for the 16" wheels/tires.)

Had a Garmin GPS device and it displayed speed. Also had an OBD2 scan tool which could display real time speed. Based on the GPS speed and OBD2 speed the car speedo read ~5mph optimistic. Think I spoke with the dealer about this but my memory is nothing came of it. Word from some other owners was this anomaly arose from the larger than "factory" wheels/tires fitted.

And furthermore the word was a UK/European "law" prohibited speedos from reading less than actual speed.

(Don't know if there is a similar law here in the US but I seem to recall Honda got into some trouble when it was found speedos in some models read under the actual speed.)

I could live with an optimistic speedo but I was worried about the effects this might have on the odometer. In eastern KS I set out heading west on a flat/pretty darn ruler straight KS state highway. At the start of my drive I zeroed both the car's trip odometer and the GPS distance readout. 200 miles later the readings were within 0.2 of a mile! With a 50K mile warranty the odometer error could have been 50 miles. And I don't recall now if the error was in my favor or not.

Just lived with it. My 2002 VW Golf TDi speedo was optimistic, too, but I don't recall it being ~5mph optimistic.

Can't recall if my 2006 GTO manifested any speedo optimism, but my both my 2002 996 Turbo and 2008 Caymay S did but it was just 2mph. Both cars were fitted with the factory standard wheel/tire sizes: 18".

Since I moved on from my Porsche cars in Dec. 2017 and I have not bothered to precisely determine if there is any speedo optimism with my cars: Dodge Challengers, MINI S and JCW, M-B cargo van, 230i, 230xi and M2. However, a few times in my M2 on the freeway I have passed a speed radar sign and used this as an opportunity to check my M2's speedo. Based on my observations it reads 2mph high at 75mph.

[inevitab1e]

I have the US spec and my speedo reads about 4mph fast compared to waze gps.
Has anyone tried changing the tire size through iDrive to see if the speed changes?
My car has 19" wheels and I wonder what would happen manually setting 18"?
Could there be a mechanical problem arising from setting the wrong diameter and/or tire sizes?

[Pentland]

Originally Posted by inevitab1e

I have the US spec and my speedo reads about 4mph fast compared to waze gps.
Has anyone tried changing the tire size through iDrive to see if the speed changes?
My car has 19" wheels and I wonder what would happen manually setting 18"?
Could there be a mechanical problem arising from setting the wrong diameter and/or tire sizes?

Changing tyre size in idrive makes no difference as all sizes are within tolerance. i.e. if you changed to 18” wheels, the tyre has a bigger profile.
Smaller wheels/tryes (from standard) would make the speedo run faster assuming speed is calculated from wheel/tyres size.

[inevitab1e]

Originally Posted by Pentland

Changing tyre size in idrive makes no difference as all sizes are within tolerance. i.e. if you changed to 18” wheels, the tyre has a bigger profile.
Smaller wheels/tryes (from standard) would make the speedo run faster assuming speed is calculated from wheel/tyres size.

I see. So maybe the solution is to go to a thicker tire.
Instead of 225/40/19 up front, go to 225/45/19.
Same with the rear, 255/35/19 to 255/40/19.
That would probably affect the speedo, bigger diameter

[Rdurty2]

Honest question, why is it such a big deal? It’s only 3mph. It’s not like it’s 13

I’ve never had a car that was spot on. It was always off in either direction a bit.

I feel like people are making a mountain out of a mole hill with this.

[semox]

It helps you not get a speeding ticket

[inevitab1e]

Originally Posted by Rdurty2

Honest question, why is it such a big deal? It’s only 3mph. It’s not like it’s 13

I’ve never had a car that was spot on. It was always off in either direction a bit.

I feel like people are making a mountain out of a mole hill with this.

It's annoying. Let's say the speed limit is 45 and you're going 48. You're under the speed limit. I don't want to be under the speed limit and driving like I'm 90 years old.
It's like an all-day mental calculation added to the driving experience.
You have to always think about the mph difference.
My 135i was off by 2mph, that was somewhat bearable. 4mph is stupid.

[Pentland]

Originally Posted by inevitab1e

It's annoying. Let's say the speed limit is 45 and you're going 48. You're under the speed limit. I don't want to be under the speed limit and driving like I'm 90 years old.
It's like an all-day mental calculation added to the driving experience.
You have to always think about the mph difference.
My 135i was off by 2mph, that was somewhat bearable. 4mph is stupid.

With America being the litigatious country that it is, it’s no surprise manufacturers do this.

Put it this way, if you didn’t have GPS, you wouldn’t know.

In the UK, there is an unwritten tolerance the other way i.e. cops and cameras won’t be triggered by going over the speed limit by x% (varies depending on the region force)

Anyway, good drivers drive to the conditions, not the limits.

[Rdurty2]

Originally Posted by inevitab1e

It's annoying. Let's say the speed limit is 45 and you're going 48. You're under the speed limit. I don't want to be under the speed limit and driving like I'm 90 years old.
It's like an all-day mental calculation added to the driving experience.
You have to always think about the mph difference.
My 135i was off by 2mph, that was somewhat bearable. 4mph is stupid.

So you are concerned about appearing like a 90 year old due to driving a bit slow? Cmon that is just a ridiculous reason.

When is the last time you actually drove at EXACTLY the speed limit? I’m guessing almost never. Go with the flow of traffic

[inevitab1e]

Originally Posted by Rdurty2

When is the last time you actually drove at EXACTLY the speed limit? I’m guessing almost never. Go with the flow of traffic

I don't drive at the speed limit. Usually 5 over minimum.
My point is the constant thinking about calculations when looking at the speedo

[Pentland]

Originally Posted by inevitab1e

I don't drive at the speed limit. Usually 5 over minimum.
My point is the constant thinking about calculations when looking at the speedo

Well now you are 1mph over. Just keep driving at your +5mph and you don’t need to work anything out.
I think some just like to complain.

[inevitab1e]

Originally Posted by Pentland

Well now you are 1mph over. Just keep driving at your +5mph and you don’t need to work anything out.
I think some just like to complain.

In a 45 I need to drive 54 to be 5 over. It's insane.
The dealer should be able to calibrate these things, IMO