I did a search of all '.meta', '.dat' & '.xml' files in the game but never found anything I could use to define a new wheel category
I did discover that lowrider wheels appear to have 3 categories:
VWT_SUPERMOD1--- Benny's originals or bespoke (not sure which is which)
VWT_SUPERMOD2 --- Benny's originals or bespoke
So in total there are 10 different wheel categories in the game:
Although I'm not sure if 'VWT_SUPERMOD1' & 'VWT_SUPERMOD2' can be used in 'vehicles.meta' '<wheelType>' line & spawn on ambient cars on the streets? I think they might be mod shop only.
I also happened to notice that modded add-on/replace vehicles always spawn with the default wheels defined in their '.yft' so I actually think the easiest way to do this might be to break out ZModeler3 & use that to set a specific wheel in the '.yft'. I also think the wheel that's in the '.yft' overrides any wheel category set in 'vehicles.meta' so if you want to do this with a modded add-on/replace vehicle ZModeler might be a good way to get it done.
Note: The vehiclemodelsets way outlined above will work no matter what. It overrides 'vehicles.meta' '<wheelType>' & the default wheel in the '.yft'