The wheels are 2mm larger than the standard size at 54mm in diameter, and the tires are HDPE, low aspect ratio, and 1mm larger than the standard size at 62mm in diameter.
We aimed for a size that looks like a 20-inch wheel with an aspect ratio of 30 when made into an actual car.
The offset is 7mm.
The letters on the tires are recessed, so you can easily color them with Posca etc.