But if they're too small, with smaller circumference wont the speedo read optimistic.... I thought it was only illegal if pessimistic ?

Possibly, but I thought it had to be within 10% either way anyway. Could be wrong.
Most overread anyway, so that will show a much higher speed than reality.

will try and get the right tyres. the wheels were on a passat

From a Passat, definitely the wrong size.

Ye the boy got them from a audi and changed the tyres to fit his passat

I've 19 inch rims on my S8. I was running 255/40 but last week I fitted 255/35. I couldn't get the tyres I wanted in 40 series. The difference I've noted is the acceleration is better due to the smaller rolling radius. The top speed will be down but that's not an issue as I never see it. The speedo will be out, reading 70 but actual speed 67. The odometer will be out as well. This difference is not too much of an issue but I am trying to see if I can recalibrate the speedo using VCDS to take into account the new tyre size.

I'm running 255/40/19 (I think :o) on the same wheels. I'll check when I get the car back +++
Looks like this:


http://forum.a8parts.co.uk/attachmen...1&d=1393181832

You bought the right wheels. Nothing better +++

I do like the blue. is that original?

Nogaro (or "Noggy") Blue is even better in the flesh than in that photo, although it is looking mighty shiny there Steve! By the way, I've re-found that other Noggy Blue one I saw in Swindon a while ago - it's owned by a garage owner but has had a few gearbox issues, I will try and get him onto the forum and see if we can help him resolve them, oh and get some pics of it! +++

Nice+++. So that's 2 of the 3 'noggies' we know about then. Look forward to seeing the pics. :D