Weird WLTP emission results - bigger wheels = lower Co2!

[Jim_mk7.5]

Surely VW wouldn't try and fiddle the test results...............again 

[fredgroves]

Surely VW wouldn't try and fiddle the test results...............again 

Everyone in everything games the rules.

Tax avoidance
F1
GDPR

The rules are there, you can do anything not prohibited by the rules.

The out and out cheating with the "test detection" was not fair game, everything else is.

[kmpowell]

It seems there might be an element of truth to all this.

Here's the sticker on my car:



41psi all round for a normal load...

[fredgroves]

Don't be surprised if:

1) when you replace your tyres you find that the centre has worn much more than the outside, possibly even getting your tyre fitter to tell you that your tyres are over inflated

2) That you actually have less grip - not having the full width of the tyre in contact with the road will do that... especially in the wet or snow...

I'd doubt if VW have changed the tyres to give a different recommended pressure, these are the same tyres as fitted right from the start of the Mk7.

I'm fairly sure its been inching up already - that my 2014 GTD ran at 33 and the 2017 GTD I have now (same tyres, same car effectively) is 36...

[kmpowell]

2) That you actually have less grip - not having the full width of the tyre in contact with the road will do that... especially in the wet or snow...

I'm going to be totally honest here. I've been very surprised at how easily the front wheels have been spinning up in these damp/cold conditions. I've owned powerful cars (various TVR, M, RS products etc), so I like to think I'm fairly versed at how to get the power down on FWD/RWD/AWD cars, each needing their own driving style, but i've been surprised at how easy the Golf has been losing traction.

Back in 2010 I owned a R56 Factory John Cooper Works Mini, and that never struggled like the Golf does.

I'm going to take a few PSI out of my tyres to see how that effects things.

[fredgroves]

It could be pressures, worth a try.

On the other hand, the OEM tyres VW use on the Mk7 performance models are notoriously bad.... probably give excellent CO2 figures but not suited to cold UK winters. Might be OK in Germany, because you don't run summer tyres in the winter...(by law)

Swapping to PS4's makes a hell of a difference.

[Watts]

Pressures for 19s hasn't changed since my 2015 car:



and I've not had any uneven wear or grip issues. It does appear to have gone up a bit for 18s though.