T6.1 Speedo Adjustment for larger wheels

Loz

California 204 DSG 4Motion MY17
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I run that size and there is no need to recalibrate as the speedo will become GPS correct.
You only need to do this like I did yesterday for another member if you went up to 245/65/17 when the speedo would read under.
 

Loz

California 204 DSG 4Motion MY17
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So... Forgive my ignorance, I have never GPS checked my speedo. Are you saying that from the factory the speedo reads over, but with this tyre size it reads closer to the speed on a GPS?
Yes, exactly that.
 

MrEds

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I’ve just ordered some fuel zephyrs with the Goodrich 245/65/17. Changing from standard 16 inch Clayton alloys and standard everything else. My Speedo is currently running over - speedo 30 gps 28 - Speedo 60 gps 57. Checking on “will they fit” it says minus 8.5% I was assuming it would take the gps readings further down say 25 actual gps when at 30 Speedo and so on. Am I going the wrong way? Also, what was the issue with running the 245’s? Error messages or just that the Speedo was out by some? I can live with the Speedo being out for now, just don’t want errors popping up all the time. Would a local garage be able to recalibrate. I have a T6.1 btw.
 

Loz

California 204 DSG 4Motion MY17
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I’ve just ordered some fuel zephyrs with the Goodrich 245/65/17. Changing from standard 16 inch Clayton alloys and standard everything else. My Speedo is currently running over - speedo 30 gps 28 - Speedo 60 gps 57. Checking on “will they fit” it says minus 8.5% I was assuming it would take the gps readings further down say 25 actual gps when at 30 Speedo and so on. Am I going the wrong way? Also, what was the issue with running the 245’s? Error messages or just that the Speedo was out by some? I can live with the Speedo being out for now, just don’t want errors popping up all the time. Would a local garage be able to recalibrate. I have a T6.1 btw.
no, the other way, with 245/65/17 you will be doing 34 when reading 30. That was the change we did to correct it so it read 30 at 30.
 

MrEds

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Thanks Loz, so even with it reading under now it’s still going to read over by some! Gotcha!
im guessing this is way above and beyond correcting via carista and my capabilities. I’ve managed to change my dials to sweep on start up so far:) anyone in Cheshire area upto this job should I need to sort it, or garage recommendations. Thanks again!
 
My Zephyrs running Pirelli Scorpion All Terrain Plus 235/65/17 (Exact Wheel/Tyre combo can be seen HERE) are being fitted on Monday. I'll post some pics and report back on the GPS vs speedo readings.

To answer your question about 245s @MrEds , If the suspension has any droop or the van is really loaded, they can rub on full lock if you hit a pothole or bumps, hence my choice of 235s, but most of the time you'l probably be fine.
 

MrEds

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Those Pirelli’s are real nice!! I was going with the 245’s based on recommendation on the website for the wheel tyre combo. Upon reflection and based on useful info here and across the web - also the calculation I worked out, it would be to close to the inner arch moulding for me to feel comfortable with. With the 245’s I calculated and physically measured the gap between the arch and moulding I would only have approx 5mm if that. Also the Speedo would be - 10.5% error according to “will they fit” moving from 205. I don’t know if the gap is so tight because of the pop top, bed, furniture etc, but I would assume this is so. Anyways getting the same wheels with bfg 225’s now. I’ll post up a pic when they are on.
 

Walshy690

New Member
I currently have fuel zephyrs on my T6 and when we connected VCDS we noticed there was wheel related "faults" Apparently you can provide it a value of how many wheel revolutions are required to travel 1KM and this is supposed to adjust the speedo.....Does this sound about right?

We haven't done that yet but I know I nee to adjust my speed because at 70MPH on the dash I'm travelling at about 74/75 MPH so any help would be much appreciated.

I went from the standard 16inch claytons to 17 inch zephyrs with 245/55/17 Falken Wildpeaks AT tires and the difference in wheel size is quite big
 

Loz

California 204 DSG 4Motion MY17
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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?
 

Finter22

New Member
I run that size and there is no need to recalibrate as the speedo will become GPS correct.
You only need to do this like I did yesterday for another member if you went up to 245/65/17 when the speedo would read under.
Hi Loz, I have a t6.1 factory fitted with 215/60R17 alloys and going with the fuel zephyrs at 235/65R17. Is there anything I will need to change and is this change something I can do easily or do I need a VCDS? Thanks in advance for any advice?
 

Loz

California 204 DSG 4Motion MY17
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Hi Loz, I have a t6.1 factory fitted with 215/60R17 alloys and going with the fuel zephyrs at 235/65R17. Is there anything I will need to change and is this change something I can do easily or do I need a VCDS? Thanks in advance for any advice?
No change from a technical point of view.
 

Finter22

New Member
OK thanks, does the van automatically recalculate the 7% difference then based on wheel rpm/gps somehow. I wasn't sure if it had the brains to do this?
 

Loz

California 204 DSG 4Motion MY17
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OK thanks, does the van automatically recalculate the 7% difference then based on wheel rpm/gps somehow. I wasn't sure if it had the brains to do this?
no, the tyre size you were using meant the speedo read 2mph faster than true and the new size will make the vehicle travel 2mph after than is was so the speedo will now read the real speed.
 

Finter22

New Member
no, the tyre size you were using meant the speedo read 2mph faster than true and the new size will make the vehicle travel 2mph after than is was so the speedo will now read the real speed.
perfect thank you. I hadn't realised they were wrong from the get go. Thanks for your help
 

Desmoben

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T6 Pro
Hi folks,
I’ve a T6.1 with bfg 245/65 R17’s and my Speedo is out by about 7% vs GPS.
Plugged in my newly acquired Ross tech dongle to learn that the T6.1 coding differs a bit from that of the T6.
Also read here on the forum of a chap who tried coding it (as he had done with a t6) only to lose ACC altogether and not being allowed to revert the coding to original… eek!

I noticed that the mysterious K value is not to be found and that wheel circumference is in byte3, bit 0-2 and that wheel circumference2 (ya what?) is in byte 19, bit 0-4 …???
Also, my current wheel circumference on the system is stated at a value of variant1 and that the drop down menu goes up to a value of variant8 (or maybe variant 10)

I’ve virtual dash ..but understand that it’s the same for the t6.1 with regular clocks/dash.

Any help would be greatly appreciated.

Thanks,
B.
 
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Desmoben

Member
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T6 Pro
Hi folks,
I’ve a T6.1 with bfg 245/65 R17’s and my Speedo is out by about 7% vs GPS.
Plugged in my newly acquired Ross tech dongle to learn that the T6.1 coding differs a bit from that of the T6.
Also read here on the forum of a chap who tried coding it (as he had done with a t6) only to lose ACC altogether and not being allowed to revert the coding to original… eek!

I noticed that the mysterious K value is not to be found and that wheel circumference is in byte3, bit 0-2 and that wheel circumference2 (ya what?) is in byte 19, bit 0-4 …???
Also, my current wheel circumference on the system is stated at a value of variant1 and that the drop down menu goes up to a value of variant8 (or maybe variant 10)

I’ve virtual dash ..but understand that it’s the same for the t6.1 with regular clocks/dash.

Any help would be greatly appreciated.

Thanks,
B.
Oh yeah… also, when searching ide0084
only 3 lines show up:
00843 starting impulse
00845 wheel circumference average
00845(again) wheel circumference maximum
 

ldm82

Member
VIP Member
Hi, I changed the variant to sort the speedo out on my 6.1 when I put 245/65 r17 BFG A/T's on, I ended up on variant 8 before the speedo was correct.
However...... I have since changed to Cooper Discoverer ATT 225/65 R17 (found the BFG's too heavy and braking wasn't great when fully loaded) and can't change the variant back so stuck with a speedo reading a bit over. Seems a few people have seen this to proceed with caution.....

 
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