Cornish Camper

[DXX]

I would have thought that by careful selection of tyre profile in order to retain the original rolling circumference, the gearing (and therefore speedo readings) would remain pretty much the same? I made a point of choosing my wheel/tyre combo on this basis. Or am I missing something?

You are correct in trying to match the tyre circumference as you mentioned.
I haven’t experienced it myself as I’m running stock wheels and tyres, just mentioning that there have been reports on the forum.
With standard wheels and tyres the speedo will register more than the true speed over ground with GPS on straight flat roads. My van speedo shows 74MPH at a true 70.

Check this thread;

Morning all.
I've upgraded my wheels from the standard 215/50/17 Devonports to 275/40/20 on Super Metals.
Two immediate things stand out, apart from the improved looks

My MPG has decreased and the speedo reads pretty much exactly what the GPS shows. For me this is an increase in speed vs the speedo reading.

Now, according to 'will it fit', the speedo will be -5.25% and original vs new 20" speedo readings;
60mph is 56.85mph on the new 'bigger' wheels.
View attachment 72543

I clearly don't understand this correctly as I know my van is going faster at any indicated speed than it was on the original wheels.
Also, my mpg reading is lower - so I assume this is also set to the original wheels.
If the circumference of the wheel is bigger, then for every one revolution I will travel further????

I'm planning to get a VCDS cable and software as I need to program for a tow bar and clear my airbag error message. VW fit these wheels on some of their new vans, so assume they must make configurational changes to the ECU?

 

[ThreeBridgeT6]

You are correct in trying to match the tyre circumference as you mentioned.
I haven’t experienced it myself as I’m running stock wheels and tyres, just mentioning that there have been reports on the forum.
With standard wheels and tyres the speedo will register more than the true speed over ground with GPS on straight flat roads. My van speedo shows 74MPH at a true 70.

Check this thread;

I've just put Ollie's wheel/tyre sizes into 'willtheyfit' and it tells me his speedo will be 11.15% out rather than 5.25%? That would obviously have an identical impact on his indicative fuel consumption even before you factor in the additional rolling resistance of the wider rubber. However, if the wheel/tyre settings are updated in the MFD (must confess I've never tried this myself) then that would correct the speedo and therefore distance readings.

All I really know is that if I'm daft enough to leave my MFD on the instant consumption read-out, I can hear my bank balance drain as fast as my fuel tank!!

 

[webbywebsta]

 

[webbywebsta]

 

[webbywebsta]

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