I had meant to ask, are the tires just penetrating the ground, or did you distort them so it looks like they press against the ground?I've made tire rigs in the past which can squish when they touch the ground with a lattice deformer.
I Distorted them a little bit to give it some bulge but then I shoved it through the ground. I need to learn some rigging.
Awesome Job! I think I like the red better but the blue is still cool! Great job on the modeling