Hello BuggyFan21,

I made my own wheels as well. Mine is for 1/8th OffRoad application. As far as I do research that the Industry mostly use Polyamide or Nylon. To get certain stiffness You could pick Nylon with Glass Fiber filling, or even Carbon filling. Carbon Fillied will get the most stiffness but will be very expensive and Injector Screw might have less life due to abrasive nature of the material.

Cheers..