The inner wheel is made from PLA (3 perimeters and 30% infill), and the tire was printed with a flexible filament (5 perimeters and 5% infill). Yes, you need a high number of perimeters for the tire to be rubber-like.
The hex size is 17mm, make sure it will fit your car before printing. Once the parts has been printed, slide the wheel and tire together with a few drops of super glue.
EDIT: I have now added a 12mm hex version of the PLA wheel, make sure you pick the correct size!
I printed the inner PLA wheel on the Creality CR-10 and the flexible tires on the Tristarbot M1.