SCS Software will be bringing more in-depth wheel customisation options to both American Truck Simulator and Euro Truck Simulator 2 in upcoming updates. Update 1.2 in ATS’ case, and update 1.23 for ETS 2.
I’m not even going to pretend I fully understand all the terminology used here, but the wheel customisation will be as follows: “This will be new customization tool for truck wheels separated to multiple components: Tire and Disk separation which was introduced recently. In addition we now added sub-components of the disk: Hubs, Hub Covers and Nuts.”
In case a visual aide is more useful, SCS have put together a video too.