I blew up a rear tire once... ONCE. Holy hell it was loud and left a welt on my leg. Then I grabbed the wheel to change the tire and burned my hands. I'll never forget again.

I've heard people in the alps say they've seen steam coming from hot rims... so that's 100C... maybe a little less because altitude.

Brake on, brake off. The rims generally cool pretty fast if you give them a chance, but if you drag the whole time, you're asking for trouble.