How do I know what is the ideal tire pressure for the tires on my boat trailer?  The outside of the tire says "max 50 psi" but I can't imagine that's the ideal pressure.  On one of the cross members of the trailer frame, there is a label that also says "max cold tire pressure 50 psi" but again, there is nothing about what the tire is supposed to be at, ideally.  The recommended psi for the tires on my truck are listed on a similar-looking sticker on the inside of the door but this number differs than the max psi.

Yup, 50psi Sound about right. You want the tires inflated properly so they can hold up to the rigors or hauling a boat all over the place. 

Max on trailer tires is ideal