I ride a Specialized Roubaix pro with Roval aluminum wheels and wonder if anyone has thoughts on how well aluminum dissipates the heat caused when braking. Is there risk of the heat building to such a point it may cause the air to expand in the tube and cause a blowout of the tube and/or tire? I normally don't worry about it much, but was just riding and climbing a hill yesterday and wondered about this as it was a VERY steep hill and required heavy braking to control my speed. Several factors worried me. It was very warm (warm for me anyway in CO), the stretch had a couple of miles of fresh (black) pavement radiating lots of heat, and the descent was extremely steep. (Don't know me for being ignorant. I'm not completely new to cycling, just am not all that knowledgeable of the mechanics and physics of things.)

aluminum dissipates heat very well. that's why it's used for cpu heat sinks and radiators. I wouldn't worry at all.
carbon fiber insulates heat and is a concern, especially with carbon clinchers.

https://www.novemberbicycles.com/blog...r-blowups.html

On extended mountain descents, you do need to pay attention to heating your rims. But don't sweat it on anything that could reasonably be called a hill. On steep hills, your rims can get hot enough to burn you, but that's not a problem if it's just for a short time.

If your running carbon clinchers then you have a chance of that happening if the descent is long enough and if you ride the brakes a lot. With aluminum brake tracks i wouldn't worry about it. And warm for you in CO is how hot?

I'm pretty sure you'd glaze your brake pads long before the pressure would go up enough to pop, so worry about that first.

A guy popped a front tire on alloy clinchers, and took himself down hard on a descent on a group ride last year. It looked pretty nasty, bent his front wheel up too. I was in front of him of course, but I heard he was riding the brakes like an old lady. I've found on descents it's better to go faster on the edge of control, then to ride brakes, and potentially kill yourself. It was also like a 100deg day when that happened as well.

On steep twisty descents on a tandem this can be an issue. You can actually hear and smell the brake pads off gassing. When this starts to happen, it's time to let them cool.

I know a rider that crashed after riding the brakes down a long hill. The pads started to melt and the braking power was lost.

I think it's better to alternate braking heavily, then let off the brakes, instead of riding them. Or switch between front and back brakes.

That won't help as much as just going faster and letting the air provide the braking.

No.

Thank you for the article and the response. They were very informative.

Umm, hot for me (and I would argue for most of us in CO) is anything over 95, but this is as reported by news stations. Since heat emanating off of road surfaces can be much higher. I guess on my particular ride that I mentioned the ride data from my Garmin only reported around 91 degrees during that particular climb, but it feel particularly warm due to the fresh black pavement (the difference felt noticeable when I got off the new pavement to older pavement that had faded). An article posted by "rdubbz" did mention rider size/weight as being a contributing factor. The hill was pretty steep, at least steeper than what I typically see because I don't usually enjoy climbing, but that's a different subject altogether. I'm 230lbs and was having a hard time keeping my speed at a comfortable spot. I didn't want to push it. (the mentioned article did advise that one could still blow a tube due to heat building up.)

Heated rims from braking on a descent can absolutely cause the tube to pop if the rider comes to a complete stop at the bottom after using the brakes a lot. I went riding with a friend to an unfamiliar mountain area that he trains on all the time. He dropped me on the descent of course since he knew it and I didn't. When I caught up to him at the bottom, he was waiting for me sitting still, and suddenly his rear tube popped like a gunshot. His rims were super hot.

We changed the tube, and then I paid him back for dropping me on the descent by leaving him behind on the climb.

This is where disk brakes would be beneficial if they weren't so damn heavy. Modolo used to make these sintered composite brake pads way back which didn't heat up................................they also didn't stop you.

In my experience, the heat damage mostlly affects the valve stem, causing a leak, not a blow out. Yes, blowouts do happen (for other reasons), but the heat caused by heavy breaking on a steep down hill is more likely to cause a fairlly strong leak, not a blowout.

Yep, I've seen that happen too. I think with a stopped bike, the heat buildup is much quicker than one in motion - the latter more likely to suffer a leak around the valve stem. I presume this is because of the metal in the valve stem coming in contact with a hot rim.