Speedo Adjustment For Bigger Tyres

[Glenn Board]

Hi, I was going to have the Seikel raised suspension kit fitted to my van which includes
235/65R17 108H tyres being fitted to my standard wheels, they tell me that if they do s speedo adjustment to match these tyres that there is a possibility that the cruise control will stop functioning completely! this I don't want to happen to the extent that I will not have the conversion, however I cannot understand why this will happen, and wonder why I cant do myself with VCDS or use the snow tyres option, what do members of the forum think, it does seam odd to me?

 

[Loz]

The winter tyres option does not adjust the speedo, it just adds a warning if you exceed the speed you set.

The oversize tyres might correct your speedo to exact instead of reading over. You can't adjust it in vcds as far as I know.
There will be no issue with cruise..

 

[Glenn Board]

Ok, so what they propose is a sort of bodge which might backfire and knock out the cruise control, i am surprised no option in VCDS as done some models come with 18inch wheels, so i would have thought some option, but that a guess.

 

[mmi]

As @Loz above, seems that for T6 there is no easy way to adjust the speedo. The lengthy method described in Speedometer Calibration - Page 3 (including referenced links) for T5 doesn't work for T6 . Looks like the correction table (last post) is filled with a constant value in T6 .

Edit: There is a way to adjust the speedo somewhat. Details in Speedo Adjustment With Vcds

 

[Loz]

Ok, so what they propose is a sort of bodge which might backfire and knock out the cruise control, i am surprised no option in VCDS as done some models come with 18inch wheels, so i would have thought some option, but that a guess.

As long as you have the same size (overall dimater) all round the cruise and abs and tpms will all be fine.

 

[Glenn Board]

I was going to fit 235/65R17 108H so this will increase the overhaul diamater a bit, so apart from changing the speedo reading, will it cause problems with the cruise and ABS, and if so how will it know?

 

[Loz]

I was going to fit 235/65R17 108H so this will increase the overhaul diamater a bit, so apart from changing the speedo reading, will it cause problems with the cruise and ABS, and if so how will it know?

you are talking 7% larger. So no problems with Cruise TPMS or ABS, however your speedo may read low and your braking efficiency will decrease, but if you are happy with that, it's your choice.

 

[Glenn Board]

Thanks, so maybe the speedo will read the correct speed and not over read? I am fitting the tyres with a Seikel suspension raise kit as I fly hot air balloons and need to go off road a bit, I just want to keep the van as good on the road as possible too.

 

[Loz]

Thanks, so maybe the speedo will read the correct speed and not over read? I am fitting the tyres with a Seikel suspension raise kit as I fly hot air balloons and need to go off road a bit, I just want to keep the van as good on the road as possible too.

I have the seikel kit fitted but with standard size tyres , with all terrain Michelin Latitude Cross Tyres.

I used to do balloon recovery... stressful

 

[Glenn Board]

Seikel recommend 235/65R17 108H Yokohama Geolandar A/T (G015) so I am taking their advice, have a look at my ballon loading system, so much easier:

 

[Glenn Board]

how do you find the Seikel kit on the road, any different to the standard van?

 

[Loz]

how do you find the Seikel kit on the road, any different to the standard van?

Nice tyre, not too noisy, had a set on my Touareg for a while.
The seikel is great on the road. The California is loaded up all the time but you wouldn't know it.

 

[Glenn Board]

Nice to know, was a bit concerned, having the conversion done at Seikel beginning of May, thanks for all of your advice.

 

[Glenn Board]

Hi, still debating to go ahead with the Seikel conversion, im a bit worried that the handling on normal roads will change too much for me, do you remember if the van rolls more, and what are your overhaul impressions of the van after conversion with regard to the handling of it please?

 

[Loz]

I would say it actually rolls less due to the better shocks. Where about's are you located? you are welcome to come a try mine..

 

[Glenn Board]

Thanks, i'm in Maidstone kent

 

[Loz]

Thanks, i'm in Maidstone kent

That's 3 1/2 hours away but the offer still stands.

 

[Glenn Board]

im only in UK for a few days, and unfortunately up to my neck in it, but thank you for the offer.

 

[xpfloyd]

Use www.willtheyfit.com and it will tell you the % your speedo will be out. I have 20’s and chose tyres that give me under 5% error and now I don’t think about it. I’ve tested with a GPS and it seems the van is now bang on whereas before it would always be saying 2-3mph below the actual speed being done. I got speed gunned in a 50 zone and I was doing 51mph on my digital display on the T6 dash and no issues

 

[Glenn Board]

Hi, just to let you know that I have now had the Seikel conversion done and I could not be more happier with it, the van actually rides and handles better and now is much smoother over bumps, it looks great too, plus you were right re speedo, the bigger tyres corrected the inaccuracies of the speedo and it now reads exactly as it should.

Photo enclosed.