My trailer tires are labelled only with the following:
Carlisle made in USA
That's it - there is no max PSI, # of plies, load rating, or any other information at all that I can see.
The actual pressure is ~33 PSI and ~35 PSI and they both seem to hold air fine. (I don't know if these values are meaningful, the last person to inflate them might have guessed.)
The rims are in two halves (inside & outside) which are bolted together. I think therefore this means the tires have inner tubes, if that makes any difference. I don't know if it has any bearing on inflation pressure.
Is there any way to determine what a proper & safe operating pressure would be?
Given the lack of markings, could these not be meant for road use? Or just really old? (Their condition seems OK, FWIW).
Edit: Photo of tread pattern, in case that helps with identification.