Originally Posted by
cudak888
As a general rule when working with 27X1-1/4" tires:
Anything over 75 PSI on a smooth-bead 27" rim is usually inviting trouble. Aluminum straight-side might take 80 PSI, but doing so would be dicey.
Going back 30+ years and until fairly recently
IRC produced 27x1-1/4 95psi rated tires designed for straight side rims. These were full sized tires, and extremely reliable.
The issue isn't that you can't make a straight side tire that will hold high pressure on a straight side rim. The issue is that
most of today's tires are designed for hook edged rims, and require the hook for proper resistance to blow off.