Larger Tyre options with ACC

[tomdavy]

@tomdavy What wheel size was originally fitted to your van?
@Samro What wheel size was originally fitted to yours?
Speculating, but on T6.1, I wonder, could it be down to the original wheel circumference variant programmed from the factory?
From my research (currently looking at tyre options on 18” and irreversibly reprogramming theT6.1 wheel circumference), 17” vans are programmed with wheel variant 3 and 16” vans are programmed with wheel variant 1.
With variant 3 being closer to the larger rolling diameter of the 255/55r18, could it be that it’s within the tolerance of whatever the van is doing for ACC to work, but that variant 1 is just outside of the tolerance?

A good thought! The original wheel size on my van as supplied was 16". If it turns out it was originally programmed with wheel variant 1, a change to 3 wouldn't be too drastic and I could see if that fixes the ACC fault. All I need now is to find someone, preferably in the Edinburgh area, to do it ...

 

[EAN]

A good thought! The original wheel size on my van as supplied was 16". If it turns out it was originally programmed with wheel variant 1, a change to 3 wouldn't be too drastic and I could see if that fixes the ACC fault. All I need now is to find someone, preferably in the Edinburgh area, to do it ...

It’s only a theory and remember it can’t be changed back on a T6.1.
See what @Samro says regarding his original wheel size

Edit:
Have a read through this thread, as when others with a T6.1 have changed the wheel variant, their ACC errors went away

Thread 'T6.1 Speedo Adjustment for larger wheels'
T6.1 Speedo Adjustment for larger wheels

 

[Samro]

@tomdavy What wheel size was originally fitted to your van?
@Samro What wheel size was originally fitted to yours?
Speculating, but on T6.1, I wonder, could it be down to the original wheel circumference variant programmed from the factory?
From my research (currently looking at tyre options on 18” and irreversibly reprogramming theT6.1 wheel circumference), 17” vans are programmed with wheel variant 3 and 16” vans are programmed with wheel variant 1.
With variant 3 being closer to the larger rolling diameter of the 255/55r18, could it be that it’s within the tolerance of whatever the van is doing for ACC to work, but that variant 1 is just outside of the tolerance?

Both my vans originally were fitted with 17" Devonports on 215/60r17's

I originally fitted Canteras with 255/45r19 for summer, and chunky BFG KO2 tyres on 17" wheels (225/65r17) as a winter setup on my camper.

On my work vehicle, I got really bored of punctures this winter, and I bought some 18" smoothies from another forum member which had Falken 255/55r18 fitted. I am amazed that they just fitted with no problems and have nothing like the road noise of the 17" wheels with the BFG tyres.

None of these options have given me any problems at all and I really rate the chosen 18" option for grip and comfort.

My Speedo seems pretty much spot on with GPS for all of the options which I've tried. (With next to no error between GPS speed and Speedo.) having said this, the speedo under was by about 5% with the factory wheel/tyre setup but I'm yet to come across a setup which causes issues with ACC.

Here is the original setup info from the door pillar:

 

[Samro]

From factory setup to 255/55r18 you get 6.49% difference in rotation:


The question is whether or. It this is enough to throw an error? It isn't in my case.

 

[EAN]

@Samro Thanks, you were originally on 17”, so wheel circumference variant 3.
I reckon there is something in this.
On the T6.1 Speedo adjustment thread I linked to above, another member that was on 16” had ACC problems until they changed the wheel circumference variant.

 

[tomdavy]

Thanks, @Samro and @EAN. Looks as if it’s worth my trying variant 3 to see if that’s close enough to fix the ACC problem. Even though it’s unreversible, it’s not that radical a change in case I later swap for a smaller wheel/tyres

 

[Samro]

Thanks, @Samro and @EAN. Looks as if it’s worth my trying variant 3 to see if that’s close enough to fix the ACC problem. Even though it’s unreversible, it’s not that radical a change in case I later swap for a smaller wheel/tyres

It is way above my pay grade to offer advice on this subject. I don't fully understand what is involved with changing your settings or the effect of the changes.
All I know is what wheels I started with and what wheels I have fitted and I can confirm I don't have issues!

 

[SMHinthewild]

Interested in this... I've got a T6 (2018) with oversized tyres. I don't get an error message but my speedo is out by +8% so when speedo says 60 I'm doing about 64.5 according to sat nav... I've spoken to VW engineers and there's no way to reprogram the vehicle to inform it you've got bigger tyres. Other manufacturers allow this via ODB2 etc... Will have a play with the winter tyre setting and see if that makes a difference.... thanks for the suggestion @temporarysecretary

Hi there Mark - did you find any quick answers to speedo correction ? - We have a T6 Cali Ocean running on 17 inch alloys (215/60/17) and those awful Conti tyres. I am looking for something a bit better for wet grass (not a 4Motion) but don't want to upset the speedo. - we live in wales and the police are zero tolerance.

 

[EAN]

@SMHinthewild
There’s a link with all the info in post 11 of this thread for adjusting the T6 speedo and a link in post 22 of this thread for adjusting the T6.1 speedo (which can’t be undone).