Originally Posted by
alcjphil
80 psi is very high pressure if the bike in question has 27 x 1 1/4" tires and rims without hook beads. 60 - 70 psi for a setup like that would be closer to the realistic maximum
45 years ago, I was running wire bead 27x1-1/8 tires at 100psi on unhooked rims (Ukai rims that were original to my '75 Fuji) with no problems at all. My second set of rims were hooked and had no issues, but were then replaced with another unhooked set after taco-ing that set while on tour in ~1980... 15 years later, I noticed a trend of replacement 27x1-1/8 tires blowing off even at lower pressures - unless I was very careful to make sure they were seated absolutely concentric on the rims.
I have since upgraded to hooked rims and fixed that....