Technical Speedo Overreading

[PaulStep]

Greetings all,
First time here - I'm in Germany but find English forums easier.
I have a 2015 Ducato (180ps) which when I bought it had 16" wheels, unfortunately 16" wheels are not an approved fitment for this model (L3H2), so I had to drop down to 15"s.

Now the speedo overreads by approx. 20%.

Is there a coding option to state what size wheel/tyre combination?

 

[the green vanper]

Hello,

I've just checked in MES, I can't see such an option for the x250 nor the x290. Which model do you have?

 

[PaulStep]

To be honest - I've no idea - are you talking about the van model or the ecu?

 

[PaulStep]

Okay, I've done a bit Wikipedia searching and I'm still no clearer.
It's a 2015 model (first registered 2016), it has the 180 PS 3L motor.

 

[the green vanper]

To be honest - I've no idea - are you talking about the van model or the ecu?

That's the x250:

That's the x290:

Both of them have the VIN number starting with ZFA250 You can thank FIAT
The body is generally the same since 2006 until now, but FIAT made several modifications in the electrics/electronics, engines, suspension + brakes and the external look.

They changed the model in May 2014, so in theory if 2015 would be the year of the first registration you could have both models... Thanks for clarifying in the next post it's the 2015 registered in 2016, we can be pretty sure it's the x290.

There were several body versions available, with different chassis (light/heavy), payload etc, some of them on the 16" rims. You cannot say that generally the L3H2 had only 15" rims.

Try checking in the forum ePER (link on the bottom of the forum banner, search window top left of the screen) if the VIN of your vehicle can be recognized (normally the database is limited to 2014, but I know it works for some of the early x290 models, too). If so, you should be able to see the technical details of your van, including the wheel size.

If not, check this leaflet, there's a possibility you'll find an information which wheel size should be on the van ex-factory:

Fiat Ducato x290 Goods Technical Specifications Sheet November 2014 (ENG)

Fiat Ducato x290 Goods Technical Specifications Sheet November 2014 (ENG)

www.fiatforum.com

You should be able to find some helpful information to determine which exact version do you have on the VIN plate under the bonnet.

 

[PaulStep]

That's the x250:
View attachment 468015

That's the x290:
View attachment 468016
Both of them have the VIN number starting with ZFA250 You can thank FIAT
The body is generally the same since 2006 until now, but FIAT made several modifications in the electrics/electronics, engines, suspension + brakes and the external look.

They changed the model in May 2014, so in theory if 2015 would be the year of the first registration you could have both models... Thanks for clarifying in the next post it's the 2015 registered in 2016, we can be pretty sure it's the x290.

There were several body versions available, with different chassis (light/heavy), payload etc, some of them on the 16" rims. You cannot say that generally the L3H2 had only 15" rims.

Try checking in the forum ePER (link on the bottom of the forum banner, search window top left of the screen) if the VIN of your vehicle can be recognized (normally the database is limited to 2014, but I know it works for some of the early x290 models, too). If so, you should be able to see the technical details of your van, including the wheel size.

If not, check this leaflet, there's a possibility you'll find an information which wheel size should be on the van ex-factory:

Fiat Ducato x290 Goods Technical Specifications Sheet November 2014 (ENG)

Fiat Ducato x290 Goods Technical Specifications Sheet November 2014 (ENG)

www.fiatforum.com

You should be able to find some helpful information to determine which exact version do you have on the VIN plate under the bonnet.

Okay thanks for that info, I have the x290.
In Germany the only models that are allowed to have 16" wheels (from Fiat) are the Heavyline. My registration document tells me that the only 215/70R15C wheel/tyre combinations are permitted.

At the time of purchase it had Fiat 16" wheels and the speedo was accurate. Unfortunately it failed it's next 2 yearly inspection (MoT) because of incorrect wheel fitment. I then fitted standard 15"s and now have a speedo that overreads.
I suspect that the guys who converted the van did some coding to change the wheel size. It wouldn't come from Fiat with a speedo that overreads by 20%, nor would it meet the German requirements.

 

[rayc]

I checked with Fiat if there were any changes to hardware or software if 15" or 16" wheels were fitted on my 2017 X290. They assured me there were not. Mine could be provided with 15" steel or 16" alloys. On all the three 15" ones I have had with 215/70 R15CP tyres the speedo has over read the actual speed by 10%. The two with 16" 225/75R16CP tyres the speedo has been spot on. I also had one with a heavy chassis fitted with 16" wheels as standard and the speedo was spot on.
I motorhome regularly in Germany and can assure you that there are many German motorhomes on the Fiat CamperCar Special [CCS] light chassis that are supplied as new with 16" 5x118 wheels. The 16" wheels were an option to15" wheels after about 2014. Up market ones usually have 16" alloys as standard.

 

[the green vanper]

Okay thanks for that info, I have the x290.
In Germany the only models that are allowed to have 16" wheels (from Fiat) are the Heavyline. My registration document tells me that the only 215/70R15C wheel/tyre combinations are permitted.

At the time of purchase it had Fiat 16" wheels and the speedo was accurate. Unfortunately it failed it's next 2 yearly inspection (MoT) because of incorrect wheel fitment. I then fitted standard 15"s and now have a speedo that overreads.
I suspect that the guys who converted the van did some coding to change the wheel size. It wouldn't come from Fiat with a speedo that overreads by 20%, nor would it meet the German requirements.

Knowing how the HU (MOT) looks in Germany, I'm surprised that it passed the previous checks. I assume the 9 year old vehicle neeeded at least two of them prior the one that failed. And I understand that the brief says it should be on 15" wheels.

Having 205 tkm on the clock I assume it's not a camper, but I might be mistaken. Has it been converted at some point by a company to a special version? Camper? Workshop? Ambulance? Disabled people transporter?

Such modifications usually require a secondary homologation and might require the wheel diameter change. However a change in the Brief should follow.

I will go through MES once again in the evening, checking thoroughly the x290 menu to be sure there's no place you could change the wheel diameter or circumference.

 

[RS3100]

My 2016 X290 6.0 metre light chassis van was fitted with 15 inch wheels from the factory, and the speedo over-read from new by around 8%. In the last few years, new vans sold in the UK are offered by Fiat with 16 inch wheels as an option, and the converter of my motorhome now fits them as standard. My understanding (which appears to be the case from the newer owner's handbooks) is that 215/75R16 tyres are offered or permitted on the light chassis vans, with 225/75R16 tyres for the heavy chassis variants. I believe the narrower cross section tyres are used on the light chassis variants because they don't have the moulded wheelarch extensions, and the 225 cross section tyres might extend beyond the arch and therefore be illegal.

In any event, before a trip to Norway last year I changed to 16 inch wheels with 215/75R16 all season tyres, and the speedo on my van is now about as accurate as it could get.

I'm pretty certain that there is no facility to reprogram the tyre circumference anywhere on the Ducato though.

 

[the green vanper]

Went once again through the x290 MES menu and have not found anything that might be clearly related to wheel size / circumference.

 

[AsdaPricey]

Hello @PaulStep

If it cannot be programmed out what about recalibration ? There’s a few companies in the UK such as this one that provide such a service - do you have anything like this in Germany ?

 

[NavNie]

Hello Paul,

Is there a coding option to state what size wheel/tyre combination?

yes, you have to use the Tiresize option in Car configuration Change in AlfaObd. Here an example from Tiresize 215/70R15: 2080 mm circumfence to 225/75R16: 2295mm:

to Confirm:

Proxydata Values:

Using Hex Calculator: 2080 = 0820, 2295 = 08F7

you can Change the Values in the hidden Hexdump Menu in Mes, now knowing the Position of the Data and the necessary Values.
Or edit the Stored Proxy Values an then read the Values from the edited File.

regards Klaus