« Reply #62 on: 23 January 2021, 16:49 »
Yea, I think those markings are to do with the studs, the 19 might be the amount of millimetres the bolt thread needs to pass through before it screws into the hub/disc (bore length)?
There are quite a few markings on wheels, from Max weight load through bead profile, type of hump etc as well as the usual physical measurements and safety accreditation.
I’ve seen wheels with the actual alloy used in code too.

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‘23 8R, ‘20 8CS, ‘19 135iX, ‘19 TCR, ‘17 Ed40, ‘17 GTD, ‘15 7R, ‘13 GTI PP, ‘11 GTI, ‘09 GTI, ‘98 Ibiza Cupra, ‘05 GTI, ‘06 Polo GTI, ‘04 GT TDI, ‘05 Fabia vRS, ‘02 GTI T, ‘03 Ibiza TDI 130, ‘01 Leon 180, ‘89 mk2 16v, ‘99 Ibiza TDI, ‘96 VR6, ‘98 Ibiza TDI, ‘92 VR6, ‘88 mk2 8v, ‘92 Polo G40, ‘91 mk2 8v, ‘89 mk2 8v, 205 GTI 1.9, ‘83 mk1 GTI, ‘80 Scirocco GTI, plus some others I’ve forgotten