Haha, I didn't print them. These are cast. Truth is, my workbench is such a mess I didn't want to use it as a backdrop for the pic. My 3D printer was the best choice
John, I just temporarily slid one on to test fit so I'll flip it around. Good eye, though!
Regarding heat for urethane, a post cure at elevated temps will help with physical properties. Production wheels are actually processed at high heat already and then further baked, but using room-temperature curing two-part urethanes will also benefit from heat too. Having said that, not all urethanes are equal when it comes to formulation so luckily we have several systems with very high physical properties that are performing well for these wheels. I explained in more detail further back in the thread about casting wheels from urethane.