Originally Posted by
cyccommute
It would be possible to get the rim hot but you’d also have to get the tire that hot as well. Rubber doesn’t conduct heat all that well
I've seen steam coming out of spoke holes after running through a ford before climbing and then descending a steep, twisty road. Considering the braking sidewall would have to generate the heat that was conducted down to the rim tape? Let's just say I wasn't going to measure sidewall temperature with my finger! But I suspect the sidewall in contact with the tube was well over 212F.
To Pete's question, I doubt you'd need to worry about 1-3 mile grades of 12-15% with hairpin turns in Florida. But I'd be happy to have butyl tubes in my wheels when I encountered them elsewhere.