Here's our attempt at cast urethane tread a couple of seasons ago. The mold was 3D printed in ABS (in 4 pieces). The resultant "flashing" was minor and easily removed with a razor blade. We used a 2-part 50A durometer urethane from Eager Polymers (Part # EP-1150). The surface finish was adequate, but you can improve it with a little sanding and acetone.
