Changing wheel size with dynamic chassis control

[mike roberts]

They have to be flexible to allow for mandatory winter wheel/tyre rules.

The coding is interesting though, presumably that sets the car for the combo it was supplied with and is only for the speedo. It can't be for the adaptation of the DCC, as that'd be more interested in unsprung weight.

[pixelcellar]

There’s no problem, it’s a very common change a lot of owners make. Just look at www.willtheyfit.com and put in the sizes. If going for 19’s then you just go to a 35 profile and it keeps the circumference almost the same. My speedo is out by less than 0.2 mph for every 30mph, so it’s negligible at legal speeds

Cheers, thought that was ok and they were the size profile I was going for anyway based on what the wheels usually come with when ordered directly via VW.

[Imteyaz]

Is the coding needed for accurate speed display? Its not needed for DCC is it?

Nothing needed for DCC, the coding is only to correct the speedo reading I imagine (although it's inherently over-reading anyway). I didn't code the 18's for almost a year and it all worked fine.

[mcmaddy]

The coding isn't even needed! Do you think you get different coding on a car that comes from the factory with 19s on as an option rather than standard 18s? The answer is no so what's been done is absolutely pointless.

[SRGTD]

The coding isn't even needed! Do you think you get different coding on a car that comes from the factory with 19s on as an option rather than standard 18s? The answer is no so what's been done is absolutely pointless.

And to develop this a stage further, if coding was needed, presumably it would need to be done periodically throughout the life of the tyres as they wear down. Tyres that are getting towards the end of their life would have smaller rolling radius (and circumference) compared to new tyres; maybe as much as 6-7mm difference depending on how worn the old tyres are, which would have a small impact on speedo reading. Is coding done to compensate for this? No, I don’t think so......

[mike roberts]

The easiest way to prove this would be to get a sample of DCC cars that had different factory fit options and see if they differ. You can't just dismiss it without first looking.

[mcmaddy]

The easiest way to prove this would be to get a sample of DCC cars that had different factory fit options and see if they differ. You can't just dismiss it without first looking.

why would you even do that? The rolling circumference of the 18 and 19 VW wheels is near enough the same and not enough to cause the speedo to be out. Coding something that doesn't need coding is just pointless.

[mike roberts]

I'm not suggesting you would bother, I wouldn't.

However, there's various settings you can code, they're there for a reason. If you're going to make a sweeping statement such as "Do you think you get different coding on a car that comes from the factory with 19s on as an option rather than standard 18s? The answer is no..." then I simply suggested a way you can actually prove your theory.

[mcmaddy]

Doesn't even warrant proving to be honest. This is probably the first post in the history of the mk7 golf that has even raised the question 

[fredgroves]

It is curious as to why the setting is in there.

I'll bet that any car leaving the factory has it accurately set for the wheel size.

Why is almost certainly for speedo accuracy... you know... Germans...