Thanks for that tip - I'll watch with my guys and their wheels. I use the same that you have pictured and I've not had any chewing of the wheels (they're too busy spinning each other out of the wheel to have time to chew - quite cute with five crammed on one wheel and some go flying out the sides when they get going! LOL)
Knock on wood, no chipped/chewed paint and no rust on any of my wheels - been using them since April.