Originally Posted by smontanaro

I have a pair of 27mm Challenge Elite tubular tires. I stretched them on some rims, hung them from a hook, then promptly forgot about them for a couple months. This morning, moving stuff around, I needed to reclaim the hook for something else. The tires seem (using an educated thumb) to probably still be holding about 80psi. What are the tubes in those puppies made of? I have no normal butyl tubes which would hold air pressure that long.