[Sean Nugent]

OK, so my inner OCD is bugging me.
My speedo reads about 10% high. I am doing a GPS 45 and the car reads 50mph or thereabouts. I don't mind this except that all the speed camera warnings are based off the car reading and not a GPS reading. So I am doing actual 48 in a 50 and the car is bleeping at me.

So - how can I change the in car speed to read a more accurate number?
I went to Kia today and was told the reading comes from the ABS sensors, into the ABS ECU and from there to the cluster but that they have no mechanism to recalibrate the speedo.

Any ideas?

 

[prawlin]

The speedo over read is deliberate on most if not all EU compliant cars. The car will know the correct speed but it adds a bit on in the software.

The reason is the type approval rules specify that a Speedo can over read by some silly amount (8%??) but cannot under read by any amount whatsoever. So due to manufacturing tolerances of wheels, tyres and sensors etc (and tyre wear so rolling circumference changes) it is impossible to calibrate the plus/minus tolerance at the correct actual speed (with variations some will read over and some under which is unacceptable to the specification)

I'm not sure, but I think US cars don’t suffer this nonsense and they read correctly. Maybe someone can confirm/deny?
AFAIK there's nowt you can do about it.
Peter.

 

[80698]

I'm not sure, but I think US cars don’t suffer this nonsense and they read correctly. Maybe someone can confirm/deny?

My US LEAF was exactly the same as my UK model with the speedometer being very optimistic. For example on that car you have to do an indicated 76-77 to do a GPS 70.

 

[Todor]

Pump your tyres up? Or let some air out... Sorry can't remember which way it goes.

But difference like this is on the high side (not by much), and there is a reason for it. Your rims or tyres could be out of spec for the car, so you need to check those first.

 

[charleschas]

Feels like something odd - I have a soul, which has the same electrics/mechanics as the niro - I've got the GPS speed showing on the map screen and I've never actually seen a difference between that and the speedometer. I also find these agree with the roadside speed monitors - at least within the tolerance of an eye traverse.

However I've only done a few thousand miles so there will be minimal tyre wear.

Speedometer's reading high were necessary when the mechanical mechanism tolerances were high - no need for that with transducer based sensors because tyre wear means the speedometer will over read - ie never underread as long as you don't increase the tyre diameter.

As Todor said check the tyres! ( Does your GPS agree with the map screen GPS by the way? )

 

[peterca]

As Todor said check the tyres! ( Does your GPS agree with the map screen GPS by the way? )

My map screen shows exactly the same speed as the speedo - both are approximately 3mph fast.

 

[prawlin]

The map screen is not GPS speed. It’s fed from the same doctored system as the main Speedo.
You can fiddle with the tyre pressures but you won’t correct the built in over read. Peter.

 

[prawlin]

Feels like something odd - I have a soul, which has the same electrics/mechanics as the niro - I've got the GPS speed showing on the map screen and I've never actually seen a difference between that and the speedometer. I also find these agree with the roadside speed monitors - at least within the tolerance of an eye traverse.

However I've only done a few thousand miles so there will be minimal tyre wear.

Speedometer's reading high were necessary when the mechanical mechanism tolerances were high - no need for that with transducer based sensors because tyre wear means the speedometer will over read - ie never underread as long as you don't increase the tyre diameter.

As Todor said check the tyres! ( Does your GPS agree with the map screen GPS by the way? )

I’m sorry but you are wrong on both counts. Run a GPS Speedo app on your phone. You will see the car reads over.
Note. For GPS speed to read accurately you must be going in a dead straight line and at a steady speed.
Peter

 

[Sean Nugent]

Given that the car gets its speed from the ABS system - and there is 4 of them - more than one of which may contribute to the binnacle speed - I am going to need to find a way to bodge the speed reading into the ABS ECU. Possibly from all 4 ABS Sensors (to maintain a consistent signal). Hmm strikes me as rapidly getting into the "beyond the sensible" territory.

 

[idiotzoo]

I’m sorry but you are wrong on both counts. Run a GPS Speedo app on your phone. You will see the car reads over.
Note. For GPS speed to read accurately you must be going in a dead straight line and at a steady speed.
Peter

Also not changing altitude which can make quite a difference to the accuracy of GPS vs actual ground speed.

 

[John Page]

OK, so my inner OCD is bugging me.
My speedo reads about 10% high. I am doing a GPS 45 and the car reads 50mph or thereabouts. I don't mind this except that all the speed camera warnings are based off the car reading and not a GPS reading. So I am doing actual 48 in a 50 and the car is bleeping at me.

So - how can I change the in car speed to read a more accurate number?
I went to Kia today and was told the reading comes from the ABS sensors, into the ABS ECU and from there to the cluster but that they have no mechanism to recalibrate the speedo.

Any ideas?

Yes, turn off the speed camera warnings. You are clearly aware of the speed limits and your own speed so you don't need them.

 

[Sean Nugent]

What I do like is the symbol on the screen of what the speed limit is. Its hasn't been wrong yet that I have seen. Turning the speedcams of turns that off as well

 

[David M]

A couple of software updates back, the Satnav speed actually showed the GPS reading but for some reason they switched it to the same incorrect speed as the Speedometer. Ah well, that's progress for you?!!

 

[Sean Nugent]

In some ways I can understand that as the GPS speed lags behind whereas the ABS sensor speed doesn't lag.
I'd still like to be able to change the speedo to be more accurate

 

[davidtm]

I'm not sure, but I think US cars don’t suffer this nonsense and they read correctly. Maybe someone can confirm/deny?
AFAIK there's nowt you can do about it.
Peter.

My US 2019 Niro EV EX Premium speedometer is accurate, especially below about 60 mph. Above that, it can be 0.5-1.0 mph above GPS speed.

Sent from my P027 using Tapatalk

 

[Sean Nugent]

If mine was that close I would be fairly happy

 

[Nick Heenan]

OK, so my inner OCD is bugging me.
My speedo reads about 10% high. I am doing a GPS 45 and the car reads 50mph or thereabouts. I don't mind this except that all the speed camera warnings are based off the car reading and not a GPS reading. So I am doing actual 48 in a 50 and the car is bleeping at me.

So - how can I change the in car speed to read a more accurate number?
I went to Kia today and was told the reading comes from the ABS sensors, into the ABS ECU and from there to the cluster but that they have no mechanism to recalibrate the speedo.

Any ideas?

My Kia also over-reads, but the error is different for each "limit" of 20, 30, 40, 50, 60 and 70 mph (or higher kph limits on the continent)
Here are 3 suggestions I follow myself.
1. Turn-off that **** annoying bleep permanently. (Its one of the few driver aids that you CAN permanently disable).
2. Only use your GPS speedo, preferably one running on your phone or a Road Angel. (the latter will give you accurate overspeed warnings if you really need to listen to reminder beeps !
3. Set your cruise control at the speed limit by using the GPS speedo, not by the car's internal speedo. Cameras are accurately calibrated, but also seem to incorporate a safety margin of 1-2 percent to avoid flagging-up cars that are NOT breaking the limit.

 

[Richard Wood]

The speedo over read is deliberate on most if not all EU compliant cars. The car will know the correct speed but it adds a bit on in the software.

The reason is the type approval rules specify that a Speedo can over read by some silly amount (8%??) but cannot under read by any amount whatsoever. So due to manufacturing tolerances of wheels, tyres and sensors etc (and tyre wear so rolling circumference changes) it is impossible to calibrate the plus/minus tolerance at the correct actual speed (with variations some will read over and some under which is unacceptable to the specification)

I'm not sure, but I think US cars don’t suffer this nonsense and they read correctly. Maybe someone can confirm/deny?
AFAIK there's nowt you can do about it.
Peter.

I think the problem is made worse by the fact that the 'safety margin' is added in km/h and the conversion and rounding up to mph exaggerates the offset. It seems to vary by 3 or 4mph. Indicated 75 gives true 70/71mph. And, yes, it's a pain with the speed limit warnings.