My 3yo Son has a battery car he cruses around our property on, however the wheels that come with it have no grip in mud, rock or any incline. I designed some mud terrain wheels with a spiderman hub cap to hide the bridging when you print. They work really well in PLA however I think PETG might be better in the long term as the Aussie sun will melt the PLA eventually, especially when he ditches it outside all the time. Each wheel is around 650g filament, 230mm in diameter & 90mm wide. Axel diameter is 10mm and I've attached the step file so you can mod it to suite other car designs.
The author hasn't provided the model origin yet.