you can do anything you want with wheels in gp4 but keep in mind that theres some fixed issues.
the original gp4 wheels has 2 mesh levels (or layer) so ZM cannot read it entirely and shown only the level 2,so the wheel appear without tread.
you can design an entirely new wheel in zm, any size you want, the ony thing is that it must be rounded and centered in the axis. you can design a 3d rim or a flat one and map it on a texture
just look at some wheels maked by viper (for 3drims) or caelen (2drims) for some inspiration on the constuction
the fixed issues are that the tyre tread must be mapped on the michelin_tread_0_right_0.tex and the tyre spokes must be mapped on wheel_michelin_0.tex
gp4 uses these textures names as reference and it is changed on the fly when it runs
with the textures names needed by the car (i.e. for ferrari it changes both names michelin with bridgestone then read the tex)
the wheels has 4 lod levels from 0 to 3 and must be named car_wheel_front_lod_X.gp4 for the front and car_wheel_rear_lod_X.gp4 for rear
if you design a 3drim you need to scale it for other lods or there is a big performance issue.
if you use 3drim you must change in your f1graphics.cfg the following line
0 rotate wheels via textures
bye