To make a mod for a wheel you need a version 0.7.371 or above.
You do everything as usual but you need to add a new parameter called “collider” and set it’s value to “wheel”.
Here is an example mod:
Place your 3d model at the center of a world and it should be horizontal as in this picture:
There is a folder called “Sources”, it can be deleted but you can use .psd file from it to make your own texture for this 3d model.