Tyre for GP4 need 3 tyre shapes: car_wheel_front_cockpit (the base) and car_wheel_front_lod_0 are the same (front wheels base, the same than wheel_front_cockpit) and car_wheel_rear_lod_0 is the rear wheel shape.
Each tyre shape for GP4 have got the same number of objects and the same names. The 3 shapes contain these objects:
F_wheel_R_InnerRim
F_wheel_R_OuterRim
F_wheel_R_SideRim
F_wheel_R_Spoke
F_Wheel_R_Tread
F_Wheel_R_TreadI (inner tread)
F_Wheel_R_TreadO (outer tread)
Each tyre is assigned with these 2 textures: wheel_michelin_0.tga and michelin_tread_0_right_0.tga
For Lee's version like mine, we have a third texture named: rimbolt.tga (Hega's tyre doesn't need a rimbolt texture..The rimbolt is already included to the rim into the wheel_ texture because on the shape, rimbolt and rim are attached.
Starting from this, yes it is possible to have tyre type specific sidewalls and sidewalls in the tread texture. this is just a matter of how you decide to map your objects, either on the first or the second texture. This is what Hega did: tread+sidewall and rim.
But be careful, if you want , for example to use Hega's tyre shape and to make tyres+ rims and treads specific liveries, it means that the mapping and textures need to be different (probably also to modify the SideRim and Spoke objects)
Let me explain a little further: Spoke object for the tyre (rim for me) needs an alpha layer in order to see the rim in game.
On Hega's shape, the spoke object is hidden because it don't need specific rim as the rim for him is an object and not an alpha ( the InnerRim object).
Excuse-me, it is a bit technic for me to explain in english....
Maybe Hega, Vesuvius or someone else could explain better... IMO, you should use Hega's tyre and textures as they are, as a base to make your feature. My shape and rim with this alpha method is a bit old, now... Or remap Hega's tyre in order to get sidewalls and rims on a texture and only tread on another...
About the rimscolours, I don't know why there are 4 colours... while GP4Tweak use 1 colour per rim/car.
CAR01=#4B4B4B,#4B4B4B,#4B4B4B,#4B4B4B
CAR02=#4B4B4B,#4B4B4B,#4B4B4B,#4B4B4B
CAR03=#FFFFFF,#FFFFFF,#FFFFFF,#FFFFFF
CAR04=#FFFFFF,#FFFFFF,#FFFFFF,#FFFFFF
CAR05=#4B4B4B,#4B4B4B,#4B4B4B,#4B4B4B
CAR06=#4B4B4B,#4B4B4B,#4B4B4B,#4B4B4B
CAR07=#4B4B4B,#4B4B4B,#00D2D2,#4B4B4B
CAR08=#4B4B4B,#4B4B4B,#00D2D2,#4B4B4B
CAR09=#7B6129,#7B6129,#7B6129,#7B6129
CAR10=#7B6129,#7B6129,#7B6129,#7B6129
CAR11=#4B4B4B,#4B4B4B,#4B4B4B,#4B4B4B
CAR12=#4B4B4B,#4B4B4B,#4B4B4B,#4B4B4B
CAR13=#0A0A0A,#0A0A0A,#0A0A0A,#0A0A0A
CAR14=#0A0A0A,#0A0A0A,#0A0A0A,#0A0A0A
CAR15=#00001A,#00001A,#7B6129,#00001A
CAR16=#00001A,#00001A,#7B6129,#00001A
CAR17=#4B4B4B,#4B4B4B,#4B4B4B,#4B4B4B
CAR18=#4B4B4B,#4B4B4B,#4B4B4B,#4B4B4B
CAR19=#001A00,#D2A800,#4B4B4B,#001A00
CAR20=#001A00,#D2A800,#4B4B4B,#001A00
CAR21=#7B6129,#7B6129,#7B6129,#7B6129
CAR22=#7B6129,#7B6129,#7B6129,#7B6129
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