T6.1 Speedo Adjustment for larger wheels

lolope96 said:
Hi loz, just about to make the move to new tyres... im on T6 DSG 150hp (remaped to 190..) will this sice afect to my gearing a lot? and how? are you manual?...
Im with 235 55 17... my first option was 235 60 but i love the look of 235 65, and there is more tyres opcions as well...
Click to expand...
For what it’s worth. I went 235/65 on mine (T6.1 DSG 4motion) the gearing was awful, acc was not working most of the time and speedo was underreading by approx 7%.
But when I corrected the speedo, the gearing issue disappeared and the acc has been faultless ever since.
 
Desmoben said:
For what it’s worth. I went 235/65 on mine (T6.1 DSG 4motion) the gearing was awful, acc was not working most of the time and speedo was underreading by approx 7%.
But when I corrected the speedo, the gearing issue disappeared and the acc has been faultless ever since.
Click to expand...
Thank you, i will give it a think one more time... See who can make me the speedo here in spain...etc
if not i will go straight to 235 60 and i mybe don´t need to adjust nothing
 
Desmoben said:
For what it’s worth. I went 235/65 on mine (T6.1 DSG 4motion) the gearing was awful, acc was not working most of the time and speedo was underreading by approx 7%.
But when I corrected the speedo, the gearing issue disappeared and the acc has been faultless ever since.
Click to expand...
How did you correct the speedo?
I have 245/65R17 AT tyres, and keep getting Front Assist Not Available errors constantly (as well as Speedo not reading correctly). Did you DIY or take it somewhere - if so, what was the cost?
 
Loz said:
Yes, you can change the adaptions on the instrument module to cater for this. I did it recently for another member. Do you have access to VCDS.
Where are you located?
Click to expand...
My T6.1 came from the campervan converters with 245/65R17 KO2s and I only just now discovered (two weeks later) that my Speedo is out. I am in need of a recalibration. Suggestions?
 
Markopolo said:
How did you correct the speedo?
I have 245/65R17 AT tyres, and keep getting Front Assist Not Available errors constantly (as well as Speedo not reading correctly). Did you DIY or take it somewhere - if so, what was the cost?
Click to expand...
Hi,
You either need one of these (or a friend with one of these) and about 8 hours uninterrupted time on this or the VCDS/Ross tech forum to figure it out. There are a number of people here on the T6 forum that are far more knowledgable than I.
Me, I just felt my way through it asking questions of other forum member who were very generous with their time (thanks lads).
You can ask here for members with the unit and knowledge in your area or …alternatively, if you get onto Leighton vans or Transporter hq they may be able to put you in touch with someone with the knowledge and hardware close to you.
Read through my posts and the connected answers from other forum members and it explains most- if not all of the procedure. Best of luck.

A3C61263-DF3C-4C1B-A598-862721B43E6B.jpeg
 
Desmoben said:
For what it’s worth. I went 235/65 on mine (T6.1 DSG 4motion) the gearing was awful, acc was not working most of the time and speedo was underreading by approx 7%.
But when I corrected the speedo, the gearing issue disappeared and the acc has been faultless ever since.
Click to expand...
Just changed from 235/55/17 to 225/65/17… speedo and gearing are Ok but…
My fuel consumption is reading like crazy… from 7,8l/km up to 15l/km aprox…
I understand this is a problem cause the van is making all the reading with the old circurference and this must be changed to get it right
 
lolope96 said:
Just changed from 235/55/17 to 225/65/17… speedo and gearing are Ok but…
My fuel consumption is reading like crazy… from 7,8l/km up to 15l/km aprox…
I understand this is a problem cause the van is making all the reading with the old circurference and this must be changed to get it right
Click to expand...
tiresize.com

Tire Size Comparison

Tire size comparison the easy way. Use our tire size comparison calculator to compare diameter, width, sidewall, circumference and revolutions per mile.
tiresize.com tiresize.com

The circumference variation between your 2 tyre sizes is approx 4.5 to 5% … that is not what’s throwing your fuel consumption out. The speedo with the OE tyre size is about 5% optimistic. So all that’s happened is that your new tyre size has corrected that more or less.

A1926EAB-B8A3-4D22-98A4-77D788AEEEED.jpeg
 
Is there anyway of changing the speedo to read correct if you have 275/40's on 20' rims?

According to all the online calcs i can find, it currently makes it read 5.5% slow (true 31.7mph @ indicated 30).

Not a massive issue if i'm honest. More concerned the wife wont remember and get a ticket
 
G13FRS said:
Is there anyway of changing the speedo to read correct if you have 275/40's on 20' rims?

According to all the online calcs i can find, it currently makes it read 5.5% slow (true 31.7mph @ indicated 30).

Not a massive issue if i'm honest. More concerned the wife wont remember and get a ticket
Click to expand...

Take a look at this thread.
 
I have a 2023 SWB T6.1 Transporter in Australia which came with 205/65R16 tyres that have been changed to 235/65R17. The speedo is under reading by 5% - Speedo = 100km/h, GPS = 105km/h. I need to have the wheel circumference changed. So I’m very thankful for all the postings and work @JimmyAK and others have done. Thanks guys, I now understand what has to be done and the risks.

I found it helpful to summarise the T6.1 wheel circumference settings in this and other threads in two tables and I think it may be helpful for others too.

T6.1 Transporter IDE00845 Wheel circumference values
Wheel circumference VariantIDE00845-MAS03213 Wheel circumference-Average circumference for trip distanceIDE00845-MAS03213 Wheel circumference-Maximum circumference for speed
1
2066​
2149​
2Coding rejected Error 31: Request out of range
3
2111​
2195​
4Coding rejected Error 31: Request out of range
5Coding rejected Error 31: Request out of range
6
2195​
2293​
7Unknown
8
2355​
2449​

T6.1 Transporters and matching wheel circumference variants
VanWheelsTyresWheel Circumference (mm)Matching Wheel circumference VariantResult Reported
Factory 16"16x6.5205/65R16
2114​
1​
Factory 17"17x7215/60R17
2166​
3​
@JimmyAK20x8.5 275/40R20
2287.1​
6​
@ascotvan17x8235/65R17
2316.3​
?​
my van, wheel circumference variant not yet changed
BFGoodrich17x8225/65R17
2275.5​
6​
@Bluephantom16x8235/70/16
2310.3​
6​
Speedo = 100km/h, GPS = 98km/h
@ldm82245/65R17
2357.1​
8​
@Desmoben 245/65R17
2357.1​
8​
Speedo is now about 4% on the optimistic side but still better than the other way round

From these tables I draw the conclusion that the Matching/correct wheel circumference variant for a van, is the one which the Wheel circumference is between the Average circumference for trip distance and Maximum circumference for speed values. Factory 17" for example, has a wheel circumference of 2166 mm which in between the 2111 mm and 2195 mm values of variant 3.

However, Bluephantom is an exception. It is set to variant 6 and reported as being calibrated, even though its 2310.3 mm wheel circumference does not fall between the 2195 mm and 2293 mm values of this variant.

There is a range gap between the values for variants 6 and 8 - a circumference between 2294 mm and 2354 mm has no corresponding variant.
This makes me think that perhaps variant 7 is valid. However, I have not found it reported anywhere.

Which brings me to a question, has anyone set a T6.1 to variant 7?
Sharing the result, either Coding rejected Error 31: Request out of range, or IDE00845 Average circumference for trip distance and Maximum circumference for speed values for variant 7 would be appreciated.
 
Does anyone understand the difference between and the possible usage of:
  • wheel circumference variant - Byte 3, bit 0-2 - options 1 to 8 available; and
  • wheel circumferance2 variant - Byte19, bit 0-4 options 1 to 32 available?
 
ascotvan said:
I have a 2023 SWB T6.1 Transporter in Australia which came with 205/65R16 tyres that have been changed to 235/65R17. The speedo is under reading by 5% - Speedo = 100km/h, GPS = 105km/h. I need to have the wheel circumference changed. So I’m very thankful for all the postings and work @JimmyAK and others have done. Thanks guys, I now understand what has to be done and the risks.

I found it helpful to summarise the T6.1 wheel circumference settings in this and other threads in two tables and I think it may be helpful for others too.

T6.1 Transporter IDE00845 Wheel circumference values
Wheel circumference VariantIDE00845-MAS03213 Wheel circumference-Average circumference for trip distanceIDE00845-MAS03213 Wheel circumference-Maximum circumference for speed
1
2066​
2149​
2Coding rejected Error 31: Request out of range
3
2111​
2195​
4Coding rejected Error 31: Request out of range
5Coding rejected Error 31: Request out of range
6
2195​
2293​
7Unknown
8
2355​
2449​

T6.1 Transporters and matching wheel circumference variants
VanWheelsTyresWheel Circumference (mm)Matching Wheel circumference VariantResult Reported
Factory 16"16x6.5205/65R16
2114​
1​
Factory 17"17x7215/60R17
2166​
3​
@JimmyAK20x8.5275/40R20
2287.1​
6​
@ascotvan17x8235/65R17
2316.3​
?​
my van, wheel circumference variant not yet changed
BFGoodrich17x8225/65R17
2275.5​
6​
@Bluephantom16x8235/70/16
2310.3​
6​
Speedo = 100km/h, GPS = 98km/h
@ldm82245/65R17
2357.1​
8​
@Desmoben245/65R17
2357.1​
8​
Speedo is now about 4% on the optimistic side but still better than the other way round

From these tables I draw the conclusion that the Matching/correct wheel circumference variant for a van, is the one which the Wheel circumference is between the Average circumference for trip distance and Maximum circumference for speed values. Factory 17" for example, has a wheel circumference of 2166 mm which in between the 2111 mm and 2195 mm values of variant 3.

However, Bluephantom is an exception. It is set to variant 6 and reported as being calibrated, even though its 2310.3 mm wheel circumference does not fall between the 2195 mm and 2293 mm values of this variant.

There is a range gap between the values for variants 6 and 8 - a circumference between 2294 mm and 2354 mm has no corresponding variant.
This makes me think that perhaps variant 7 is valid. However, I have not found it reported anywhere.

Which brings me to a question, has anyone set a T6.1 to variant 7?
Sharing the result, either Coding rejected Error 31: Request out of range, or IDE00845 Average circumference for trip distance and Maximum circumference for speed values for variant 7 would be appreciated.
Click to expand...
On my van with 235/65R17 tyres, I have now changed the Wheel circumference Variant to 6 (0x5).
The result on my initial testing is my speedo now reads 2% over (speedo = 50km/h, GPS = 49km/h) and my odometer reads 2% under (odometer = 10km, GPS = 10.2km).
I have only tested on a short city drive, but it looks pretty good.

For reference, before changing Wheel circumference Variant it was 1 (0x0) and my speedo was reading 5% under (speedo = 100km/h, GPS = 105km/h) and the odometer was reading 9% under (odometer = 10km, GPS = 10.9km).

As a test, I attempted to change Wheel circumference Variant to a value for smaller wheels/tyres (I tested changing from 3 to 1). This resulted in Coding rejected Error 22: Conditions not correct or request sequence error. It could not be set to a smaller wheel circumference on my 2023 T6.1 VW Transporter.

Changing Wheel circumference Variant Byte 3, bit 0-2 had no effect on Wheel circumference2 Variant Byte19, bit 0-4 - it did not change. I didn't test changing Wheel circumference2 Variant directly.

After changing the Wheel circumference Variant, the first time the engine was started a Front Assist not available fault occurred. This was displayed in the instruments messages and the yellow warning light was on. However, stopping the engine and restarting it cleared the fault and the Front Assist functioned correctly after that.
 
@Loz, @Ads_Essex .Whilst I realise I’m reigniting this thread and I’m cognisant this is a T6 forum - is there any way of changing the VCDS tyre parameters for a T5.1?

I’m currently looking into some AT tyres on 17 inch rims but am hesitant due to the speedo inaccuracy. I’m currently running 235 55 17 - perhaps just stick to the 225 65 option? I’d love to know if anybody is n the Essex area has been successful for the larger tyre sizes.

TIA
 
Alexander4699 said:
@Loz, @Ads_Essex .Whilst I realise I’m reigniting this thread and I’m cognisant this is a T6 forum - is there any way of changing the VCDS tyre parameters for a T5.1?
Click to expand...
I would expect the principles of the T6 adjustments would help - see below
www.t6forum.com

[Guide] [T6_modified] T6 Speedo Adjustment with VCDS

Module 17 – Instruments carries also the coding to select a few scaling factors for speedometer. Byte 0, bits 0..3 have mysterious value “K-number”. It turned out changing this coding adjusts measuring values IDE00842 (K-number) and IDE00845 (Wheel circ. mm) of module 17 - Instruments, and...
www.t6forum.com www.t6forum.com

And specifically for T5.1

Speedometer Calibration

BTW: Don't calculate based on the analog gauges, if in doubt use the digital display as reference. Both the analog and digital speedometers read incorrectly. If I use anything for a reference, it would be my GPS of which I have three. Another thing I can do to confirm is to drive 10 kilometers...
forums.ross-tech.com forums.ross-tech.com
 
Alexander4699 said:
@Loz, @Ads_Essex .Whilst I realise I’m reigniting this thread and I’m cognisant this is a T6 forum - is there any way of changing the VCDS tyre parameters for a T5.1?

I’m currently looking into some AT tyres on 17 inch rims but am hesitant due to the speedo inaccuracy. I’m currently running 235 55 17 - perhaps just stick to the 225 65 option? I’d love to know if anybody is n the Essex area has been successful for the larger tyre sizes.

TIA
Click to expand...
As mentioned earlier in this thread, the 235/65/17 actually corrects the oem speedo error on the T6 (and I assume T6.1) so that it matches GPS exactly.
It may not be necessary to do anything on the T5.1 either and that size is chunky looking enough to suit many of the AT tyres available.
1000004848.jpg
 
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