Pinging at idle

[Corey_R]

From a tyre size calculator (so keep in mind that there can still be slight variations between different makes and models or tyres).

225/45 R17
Rolling Radius 317.15mm
Circumference 1992.71mm
Diameter 634.3mm

223/35 R19
Rolling Radius 323.55mm
Circumference 2032.92mm
Diameter 647.1mm

Differences between Wheel/Tyre 1 & 2
Rolling Radius 6.4mm
Circumference 40.21mm
Diameter 12.8mm
When your speedo reads 100km/hr you're actually at 101.98 km/hr

So there you go - the change from the 17" GTI wheel to the 19" R wheel (or aftermarket wheel) is only 12.8mm, and within the 15mm requirement of the ADR. So if a wheel really was 15mm then it would give an inaccuracy in excess of 2% hence making Topend's request illegal under Australia Design Rules.

Thanks for the info pologti18t. Good detective work.