I've had 3 Coleman/Fleetwood pups since 1992 and each either had a sticker outside or inside a cabinet with the recommended tire pressure. Fact of the matter is, all of them were at the max tire pressure. Go by what the sticker says first. Should the tire sticker be missing, inflate them to the max tire pressure on the sidewall. Unlike autos, pup manufacturers seem to put the minimum tire designed to carry the weight. There is very little extra capacity beyond the pups Gross Weight. How many of you have weighed your pup to find out how close it is loaded to the gross weight? I'll bet not too many have. Trailers light weights are notoriously wrong (being much too light). In the absence of a recommendation for tire pressure from the pup manufacturer, I'd run them at the max pressure on the sidewall. Make sure that if the tires had been replaced, that they are of the same size and load rating. There are too many instances here on the portal of people with blowouts from tires lacking extra capacity or substandard tires. The last thing I would do is underinflate them. BTW, putting the ST tire at the maximum pressure is not overinflating them. That is the pressure ST tires are designed to run on.