The LDraw nomenclature "width_(mm) / profile_as_%age_of_width x rim_diameter_(mm) [optional qualifier]" was defined to try and match the ISO standard, which is what is used by TLG for the imprints on some tyres.
The "width" should be the maximum outer width. The rim diameter should be measured where the rim meets the tyre - so that (in theory) the dimension for the "rim diameter" of the tyre should match that dimension in the wheel rim nomenclature "width_(mm) x rim_diameter_(mm) [optional qualifier]".
The 32998.dat on the Parts Tracker has not been updated to match this nomenclature, but should be updated before becoming official. As with any eveolving standard, there are some legacy files in the official library that need recycling through the tracker to bring their names into line. Any help with that is, of course, welcome.
The "width" should be the maximum outer width. The rim diameter should be measured where the rim meets the tyre - so that (in theory) the dimension for the "rim diameter" of the tyre should match that dimension in the wheel rim nomenclature "width_(mm) x rim_diameter_(mm) [optional qualifier]".
The 32998.dat on the Parts Tracker has not been updated to match this nomenclature, but should be updated before becoming official. As with any eveolving standard, there are some legacy files in the official library that need recycling through the tracker to bring their names into line. Any help with that is, of course, welcome.
Chris (LDraw Parts Library Admin)