Measures the expansion of the rim bead when under pressure from an inflated tire.
Three separate steps:
Security test: Measure the rim with an inflated tire (145psi) at three points, and let sit for 24 hours. Deflate the tire and measure again: measurements should be the same.
2. Deformation test: Measure the rim width at the spoke holes. Inflate the tire to 130psi. After 10 minutes check the rim width again at the same points. At least three points should have less than .05mm of deformation.
3. Blowout: Inflate a tire to 102psi, then pause 60 seconds and listen for noise. Inflate by 7.5psi more and repeat. There should be no noise until 170 psi. Noise is ok until 170 psi but no blowout or breakage is acceptable.
This test ensures that rim beads can handle well above the maximum inflation levels for road tires.