But if you inflate to the max when cold, you'll exceed that value when you hit the highway and they warm up. The correct tire pressure is related to the trailer and its weight, not the markings on the tire. If you over inflate them you'll reduce your contact patch which will affect towing behavior, tire wear, and especially stopping grip. Every trailer is different (dual axl, single axl, etc) and the tires were meant to support varying loads. You need the right pressure for your load, not some arbitrary max pressure listed on the tire.