Originally Posted by MattTheHat

Nope, I definitely made a mistake on the sidewall pressure rating. The 115 PSI number was for the Continental GP4000SII 28mm tire which I put on the bike after the Roubaix Pros. The pressure on the sidewall matched the pressure shown on the Specialized page I quoted earlier: 75:95 PSI. I examined the tire very carefully. I found no damage on the tire at all, not on the top part of the tire, not on the sidewall, not on the bead area, nothing.

So, yes, the tire was run slightly over pressure. But when left over night, the tire was not over pressure. I'm not sure what it would take to blow the tire off the rim, but my gut feel would be something like 150% of the max pressure specification. I'm surprised the tire blew off the rim at all, having not been inflated over 101.5 PSI. I'm definitely surprised it blew off at 90 PSI. And I'm surprised that it blew off just sitting there at a lower pressure than while being ridden under load at the higher inflation. Lots of surprises for me.

I'll retire these Roubaix Pros out of caution. I'll eventually give tubeless another shot when I find some other tire that I want to try.

-Matt