Originally Posted by
diabloridr
Modulus is stress divided by elastic strain.
Figure 2.8 show that the kevlar bead will inherently stretch and become looser as temperature increases.
Again, in post 11, you mentioned tensile strength, not modulus.
Elsewhere in the link, they discuss the coefficient of thermal expansion in the longitudinal direction and compare it to other materials. The coefficient has a negative value…i.e. it shrinks with temperature. Steel has a positive coefficient of expansion of slightly larger magnitude in the positive direction. In other words, heat steel and it expands slightly. Heat Kevlar and it shrinks slightly.
Out where the rubber meets the road, Kevlar bead tires have been around for decades without issues. They have been used in high speed, high friction rim brake applications thousands, even millions, of times. They aren’t any more prone to blow off than a steel bead is. It’s a nonissue even if the Kevlar were to do what you say it does, probably because the tire never gets all that hot to begin with. Tires blowing off the rim because of braking is one of those things that is far less common than people think it is. The heat that builds up just doesn’t have the effect that people think nor does the pressure increase as much as people think.