Ok, I replaced my 4.80-12 Load Range C (990 # max at 90 psi) trailer tires. I totalled the weights of my 16' hull, 27 LT motor, trailer, battery and extras to around 1100 #. This is well below the max weight rating (990x2= 1980). Should I inflate the tires to the max pressure of 90 psi? I am sure I underinflated my last pair the last three years at 55 psi, and maybe that's why now I am replacing them. I do keep them on cement slabs, protect them from the Florida sun, and I never go faster than 60 mph when trailering the boat. I'm thinking that if I inflate them at 90 psi with the heat down here that might not be good either. Any suggestions? I bought the C load range thinking because of the higher weight capacity that might be better even if I don't trailer that much. It just seems too high to fill them at 90 psi even though that is the max rating.

I would say 55-60 lbs but if that wore the last set out to fast i need to change mine there at 50lbs.Sorry no help

inflating to 90 will not hurt them. go 85 if your worried about it.

Trailer tires are bias ply and are designed to run at the max inflation. If you under inflate them it will cause irregular wear, and eventually cause a blow out.

10-4! Thanks all. I will fill them to 80 psi so I can sleep at night. The learning curve takes decades for some of us.

^^ on the note. If the trailer starts bouncin too much lower em.

Air 'em up, under inflated tires will heat up fast and come apart on you.

My hunting trips are 700 + miles one way, don't bother asking me how I know.

If you are running a light rig then running max pressure will make them wear in the middle. what kind of wear is happening on the tires? My tires were rated 60 psi and i was going thru a set a year. I started running at 30 psi and i am on season two on the same set. take a drive and see what the tires look like. if you are running on the middle then drop it 5psi at a time. BTW when i owned a carolina skiff and was running with full live well 3 deep cycle batteries and 12 gallons of gas 60 psi was correct.

All of the answers above are correct on many applications. Too much air will wear in the middle, too little air will build heat and blow out. With a tire with a higher weight rating than the load, you may run slightly less than the max. Example to the extreme- It's like running 38" tires on a Toyota, you may only have 15 psi that will hold the truck fine versus the max 65 psi that will actually baloon the tire out and make it ride on the middle of the tread.

Pay attention to where the shoulder of the tire sets. Like garjacker said, you can fill them up to max and let the pressure out until they are riding square. Get down and look at the outer edges of the tread while on concrete, if it is not touching, let more air out until it does and you should be good.

Or just get some good radial trailer tires like Goodyear Marathons and be done with all of that bullshit. They will probably start dry rotting because of old age before the tread is gone. Although I can't imagine someone putting enough miles on them to wear them out, I guess anything is possible. I can tell you that it sure as hell beats having to deal with those crappy Carlisle bias ply's that come on most trailers. They are the worst tire ever made in my opinion.