The Grave Digger Tank has rubber treads. If they break then the tank will no longer work. You can 3D print a replacement with this model.
Print in TPU with standard settings.
https://cad.onshape.com/documents/ba4158077b227d58e665e90f/w/d45d261a12366cbbf90aa5b9/e/cf392fa9cb78d8cd83be3f10
The author marked this model as their own original creation.