[dtxscott]

Not to add fuel to the fire...... But adding an extra half inch in radius to the wheel may have contributed to its failure. The wheel was probably originally designed as a system of wheel/tire based on a 16in diameter. When you remove flexible material and add rigid material a longer moment arm is created and more lateral torque is transferred to the wheel center.

I'm sure for street applications the modified 16" wheels are fine. For track applications I would be skeptical as your results show show the physics may hold true.