TPU tubes, rim-brakes, a 4500ft descent -- and a near epic self-own.. #facepalm

[marciero]

Originally Posted by dddd

I think robt57 hit on a good point, about the sizing.

A TPU tube that tenses enough upon inflation to feel firm inside of the still loose-feeling tire may have enough tension to pull itself apart at the seam when the rim side gets hot and starts yielding in tension (so that the balance of the tube's minor perimeter can "relax" some of it's high tension).

But, if the tube size is closer to the actual inside diameter of the tire's cross-section, then it might be orders of magnitude more resistant to heat-induced failure of the more-heated inner "side" of the tube.

This sounds plausible but I am not so sure. When a TPU tube stretches it becomes tensioned to a point but then does it not permanently deform? The last bit of expansion will probably be tensioned, but without that-for example if you oversize the tube- you are risking a wrinkle, which would be worse. So I am guessing that the amount of tension is about same whether the tube is slightly undersize or a bit more undersize, and the only way to guarantee no tension would be to oversize. Keep in mind that the tire also expands, so a tube larger than the inflated tire would have to be more significantly larger than the uninflated.

[Lionel]

For me rim brakes = tubular. Period.