A tyre rim to suit Tamiya buggy tyres. Has a flattened 5mm shaft hole for stepper motor connection - I have mine fitted to cheap and cheerful 28BYJ-48 motors.
Approx 45 minute print at these settings. Change as you see fit for your application
After printing I manually adjusted the stepper shaft hole using my soldering iron at a low heat (about 250 degrees C), and then held the iron to the shaft of the motor as I pressed the rim on, allowing the heat on the shaft to melt the PLA to fit.
Designed in FreeCAD using basic cylinder parts in union and cut. Took about 25 minutes to design the part.