Speedo wildly inaccurate

[Powerflex]

Picked mine up on Saturday and within 5 minutes I could see the speedo was reading very fast so checked with GPS and it is displaying 50mph at a true 42mph, a long way outside of tolerances.

Has anyone else noticed this?

The dealer said they had no idea and would look into it.

I am sure it is a simple software fix but I am concerned the distance is inaccurate and therefore the range also, but have yet to check the accuracy of the distance display.

 

[woof]

Every BMW I've driven (and I got to drive a lot of different loaners over the 2 years of ActiveE ownership) has displayed speed exactly 3 MPH faster than the actual speed (as determined by iPhone GPS apps, as well as stop watch timings) above 25 MPH. Interestingly, the odometer was not off at all based on "mile post" counting.

But they were never off by 8 MPH as yours is showing.

Curious what happens if you switch to km/h?

--Woof!

 

[Surge]

my guess would be that it's a hardware issue not software

perhaps it's set for 19" wheels and you have the 20" ?

 

[mindmachine]

my guess would be that it's a hardware issue not software

perhaps it's set for 19" wheels and you have the 20" ?

I am not 100% sure on this, but I don't think the overall diameter with the tires mounted is any different between the 20 and 19's. I read about the Bridgestone tire development for the i3 and I believe the 20's are a lower profile tire. So they changed the aspect ratio in order to maintain the ability to switch between 19 and 20's without impacting drive ratios and speedo issues.

Even on the 19's where they use a wider rear wheel with 428 rim the tire aspect ratio is different so on the rear the contact patch is wider.

Tires: http://insideevs.com/bridgestone-release-details-on-the-bmw-i3-tires/

 

[Powerflex]

Apologies my error.

It is about 5% fast which is an acceptable tolerance.

The car is an absolute revelation and I am very pleased with it.

 

[i3burlington]

I don't have an i3 'yet'
My 1 series is the same. I had a software mod done so the digital display could show the REAL speed but the normal analogue dial and digital info all show a few % high.
I think all BMW's do this now.

Very annoying. I was hoping that going to an i3 would eliminate this.
It's a little thing but it always bugs me knowing it's wrong.

 

[agj]

Since I was intrigued by Powerflex's post, I made some experiments today and compared speedo display to my iPhone's Navigon.

Result is indeed that the car is little bit more "optimistic" than the actual speed (less than 5% according to my readings).

That being said I thought that this phenomenon was pretty common in the automotive industry (i.e., not limited to BMW cars).

Speedometer accuracy is a tricky question. Some aspects are fairly well described here : http://carnutgarage.com/technical/speedometer-accracy.html

For the braves, here is the full text of the UNECE Reg :shock:
http://www.unece.org/fileadmin/DAM/trans/main/wp29/wp29regs/r039r1e.pdf