[Guide] [T6_modified] T6 Speedo Adjustment with VCDS

[NC35]

Hi Everyone.
For my sins I have followed the heard and bought some 20" wheels and tyres.
My17 T6 Highline 17" Devonports to 20" Venoms. Standard suspension.
The % change is 5.18%
I have changed the K value from 4 to 2.
Happy with the speedo over reading, ~ 2mph over reading, 70mph is 68mph on Waze.
The problem I have is with the "suggested" gear I should be in. Suggesting I should be in a gear higher than I personally think is appropriate.
More worryingly it reads 5th as 6th (and 6th as 6th)
Any way to correct this???
Tomorrow I am going to try K=3. Kinda nervous that the displayed and actual speeds won't have any tolerance, which I am used to.
Any help with this much appreciated.
BTW using OBDeleven not VCDS

 

[@KC1]

Hi Everyone.
For my sins I have followed the heard and bought some 20" wheels and tyres.
My17 T6 Highline 17" Devonports to 20" Venoms. Standard suspension.
The % change is 5.18%
I have changed the K value from 4 to 2.
Happy with the speedo over reading, ~ 2mph over reading, 70mph is 68mph on Waze.
The problem I have is with the "suggested" gear I should be in. Suggesting I should be in a gear higher than I personally think is appropriate.
More worryingly it reads 5th as 6th (and 6th as 6th)
Any way to correct this???
Tomorrow I am going to try K=3. Kinda nervous that the displayed and actual speeds won't have any tolerance, which I am used to.
Any help with this much appreciated.
BTW using OBDeleven not VCDS

Hi @NC35 - you just have to land on the appropriate k number and the gear indicator will display as expected. I posted about this somewhere further up the thread .

 

[Rosski]

Hi everyone

6 years ago I adjusted the speedo on my T6 4 motion DSG after fitting 20" wheels, worked great.

Today I've refitted the original 17" wheels and need to revert back to factory default. VCDS told me I needed an update so it's now on V25.3.1

I'm guessing a lot has changed in 6 years because I cant find the K-Numbers. Does anyone have a step through guide for VCDS 25.3.1

Cheers

**All sorted. I had to set the coding to Polo (4)** The setting for Transporter didn't work.

 

[Bagshot]

Just a post to say thank you to the op for the information and add the information from my van in case it helps someone.

Vans a 2010 T5.1 140 6 speed Kombi.
I've fitted 235/65/17 Wildpeaks which made the speedo under read by about 5% which in these times of enthusiastly enforced 20mph zones concerned me, the odometer also under read by nearly 2 miles on my usual 18 mile journey.
So I've adjusted mine to No 3 setting (6 was original setting) this made the speedo over read by about 5% which is pretty much standard for most vehicles, the odometer also now reads the correct mileage.
I tried setting 4 but the speedo and odometer was still under reading, could have done with a setting 3.5 ideally as the difference between 3 and 4 was quite large.

Settings from my van are

7 k=23464
Wc=2046

6 k=23232 (Standard)
Wc= 2066

5 k=23000
Wc= 2087

4 k=22768
Wc= 2108

3 k=21312
Wc= 2252

2 k=21100
Wc=2275

1 k=20888
Wc=2298

On setting 3 my vans dash also fails to display 5th gear, instead showing it as 6th but its a minor annoyance as the next best setting (4) was too far out, although it did read the gears correctly.

 

[Paynewright]

I need to put my big boy pants on and do mine! I have VCDS but plugging it in is always a journey of adventure!

 

[b-quan]

Hi All,
Anybody noticed after changing the wheel circumference option via VCDS on a T6 (to suit 17's with 235/65/17 tyres) that the MFD display, gear indicator, now shows that the van is in 6th gear when actually in 5th and also shows 6 when in 6th. 1 through 4 gears, are showing as normal values.
Haven't had a chance to test cruise control in 5/6th yet.
I made this change a while ago but it is possible I never noticed this till now so I'm wondering is it a symptom of the above or something different.
UPDATE: cruise control works fine but… the +/- buttons seem to be increasing/ decreasing by 10kmh. Reading elsewhere it seems short press changes the speed by 5mph so maybe it’s just that, a bit strange though, all other vehicles cruise controls increase / decrease by 2kmh usually.

UPDATE : --------------------------------------------------------------------
Original Factory K-Number = 5 | Byte0 = 15 - Factory wheel/tyre = 205/65/16
Wheels changed to 235/65/17
First Change - K-Number = 2 | IDE00842 = 21100 | IDE80045 = wheel circ 2275mm | Byte0 = 12
With the above the Speedo was overreading by 3Kmh(100kmh GPS = 103kmh Speedo), I was fine with this as a buffer but the above problem of the current gear indicator on MFD display was showing as 6 when running in gear 5 or 6
First Change - K-Number = 3 | IDE00842 = 21868 | IDE80045 = wheel circ 2195mm | Byte0 = ? 13(from memory)
With the above the Speedo and GPS are in parity, < than 1kmh apart and now MFD current gear indicator is showing as expected, displaying 5 when in fifth gear and 6 in sixth with the proper prompt to change from 5 to 6 so all working as it should.

Hope this helps somebody out in the future.

Thank you for sharing, good to see someone else has experienced the same as me and shared the solution.

For reference....

Van = T6 T28 Highline 2019 Manual
Factory Settings:
K Number (IE00842) = 23232
Wheel Circumference (IE00845) = 2066mm
Factory Tyres = 205/65 R16
GPS 70mph = Speedo 73mph

I then fitted my new wheels and changed the settings as follows using ODB11.

New Tyres = 235/65 R17
Changed to K Factor #2 (in Module 17 under long coding using ODBEleven)
K Number (IE00842) = 21100
Wheel Circumference (IE00845) = 2275mm
GPS 70mph = Speedo 73mph

I found the gear indicator was doing exactly as you described. Showing 6 when I was in 5th.

So I changed to K factor #3
K number - 21868
Wheel circumference - 2195mm

Now the speedometer and GPS are accurate and the gear indicator reads correctly.

Before i fitted them, i used willtheyfit.com to calculate the difference and it showed the new tyre circumference as 2314mm i then measured one rotation of the wheel on a flat carpark and measured exactly 2275mm (Conveniently what is shown in the table in the first post of this thread for #2)

Could anyone help recalibrate my speedo around the Essex area? Just had 245/65/17 fitted today and speedo reading 70mph but gps saying 74/75mph! Don’t mind the discrepancy being the other way around but I’ll likely end up with speeding tickets if I keep it like this .
Happy to travel and pay.
Cheers!

I know 3 years have passed, so assume you have solved this by now but im in Essex (Near Southend) and have an OBD11 Pro subscription until around Feb 2027 if you needed help.