I’ve run a 2.2” tyre on a rim that’s 38mm external (so must be 34-36mm internal) and has no issues.
I did worry that the sidewalk might be more vulnerable being that it doesn’t pull in to a narrow rim but it never actually seemed to be an issue and that was with a Conti RaceKing so quite a lightweight tyre.
a rim that’s 38mm external (so must be 34-36mm internal)
If you haven't actually measured, assume internal is external minus at least 5mm for a hooked aluminium rim, so that 38mm rim is no more than 33mm internal.
I’ve run a 2.2” tyre on a rim that’s 38mm external (so must be 34-36mm internal) and has no issues.
I did worry that the sidewalk might be more vulnerable being that it doesn’t pull in to a narrow rim but it never actually seemed to be an issue and that was with a Conti RaceKing so quite a lightweight tyre.