DrRonny on Thingiverse made a great improvement to the STEMFIE car: extra tires you can 3D-print using flexible TPU filament and place on the car's wheels.
Check out these tires and download the files from Thingiverse. Note that DrRonny also adapted the wheels to fit metal ballbearings!
This toy is not suitable for children under three years due to the choking hazard! 
