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I did once destroy a new rim by inflating a 50 mm wide tyre to about 80 PSI. My idea was to use overpressure to properly seat the tyre beads on the rim. Doing that also destroyed the inner tube, but the tyre survived. ...
Thorn recommendations for maximum pressure in a rim have changed over time. Last time I saw some numbers, I thought that the recommendations were a bit too conservative, but rims can be weaker than tires, especially if the rim has had brake wear and if the rims are corroded.
I wish all rims came with labels on them with that data. My (now twenty plus years old) Mavic A719 rims did, photo attached.
I think I have put up to 60 psi in a 50mm tire, but not more than that. I might have put 80 psi into a 40mm wide tire on the rear wheel of a touring bike with a heavy load, that was a really solid rim that was designed for touring, the now discontinued Salsa Gordo rim that I have on my Sherpa.
I think I have put 50 psi into a 57mm wide rear tire with a heavy load, that would have been the Andra 30.
I did a quick google search, found this:
https://thorncyclesforum.co.uk/index.php?topic=13100.0And I posted this a decade ago:
https://thorncyclesforum.co.uk/index.php?topic=11833.0