Which tyres for 7.5J 18’s

[The Bear78]

Looking at how the 235/55/18 compares in circumference to standard transporter sizes, I'm surprised that this would under read at all?
Hopefully the speedo hasn't already been adjusted.

 

[PaulR83]

Looking at how the 235/55/18 compares in circumference to standard transporter sizes, I'm surprised that this would under read at all?
Hopefully the speedo hasn't already been adjusted.

Agreed. Mines bang on now to GPS but came with 17s standard so the variant type is different in the adaptations to that of a 16inch wheel standard.

@EAN What pressures are you running out of curiosity?

 

[EAN]

@The Bear78 The 235/55/18 are larger in circumference by quite a bit compared to the original 205/65/16s that were on my van from new, so for every revolution of the wheel a greater distance is now being travelled and therefore a higher speed attained.
At 70mph on the Speedo my GPS is saying 73mph, so it’s definitely under reporting.
My understanding is my van will have been set to wheel circumference variant 1 from the factory as it had the smallest wheels a transporter comes with. I’ve had it from new so it’s not been adjusted (yet). Variant 3 should improve the error and may make it bang on.

@PaulR83 I’m running 44psi front and rear

 

[The Bear78]

There are often threads about 17 inch AT tyres and how they compare to normal sizes. I admit I forgot quite how small the 16's are compared to these which I wrongly based my comment on.
Typically the 17 inch setting is 3 or 4 mph optimistic which means going even bigger than your 235/55/18 still reads true on GPS.

The 16" setting must be closer to reality than the others.

 

[EAN]

I have finally had my wheel variant changed from wheel circumference variant 1 to wheel circumference variant 3 on my T6.1 and can confirm that the Speedo is now bang on with 235/55/18’s against GPS.