Tire Pressure Recommendation for 5th Wheel

[Craig and Linda]

How much psi should I put in the 4 tires of my 5th wheel.  I check the pressure in the am when cold.
The pressure printed on the side of the ST235/80R16/E tire is 80psi.  The tire guy at Big O said to keep it lower (70psi) because they expand when warmed up.
He didn't sound very confident.  I've been keeping them at 80psi when cold.
Any recommendations?
Craig

 

[Back2PA]

The tire guy is wrong, fill to the sidewall pressure as you have been. The manufacturer takes into account the expansion

 

[xrated]

Actually, the tire guy and Back2PA are both wrong!  The trailer has a sticker on it that tells you the tire size and the tire pressure required for the tires to be able to provide the required load capacity for your trailer.  Having said that, many times the tire sidewall number will be the same number as on the trailer sticker....but not always. 

And another tidbit of info.  The number on the side of the tire is the psi needed for that tire to be able to supply the load capacity that the Tire is rated for....not maximum pressure.  Yes, that is the maximum amount of air pressure that you should ever inflate it to (Cold pressure), but the tire pressure will certainly be higher than that when it is being used.  The good news is that the tire manufacturers design and build the tire for safely operating at that increased air pressure when the tire is in use.

 

[Utclmjmpr]

Only one way to be right on,, stop the guess work and weigh the TT loaded and ready to roll,, then consult the TIRE MANUFACTERERS load tables.( found on the internet) and do the math per tire.. ( make a sticky label for each hub with the pressure printed on it for future use)>>>Dan

 

[Craig and Linda]

Thanks everyone, that helps a lot. 
Craig

 

[Gary RV_Wizard]

As a practical matter, you won't go too far wrong if you inflate a trailer tire to the max load psi shown on the side wall. No recreational trailer has oversized tires for the load and most are in fact running very close to their max capability.

The guy at the Big O tire shop was wrong, and dangerously so.  Sadly, bad info at tire shops is all too common. Few tire shop employees know anything at all about correct tire inflation or care. They are trained to sell or install tires according to some standardized formulas that are simple and will avoid lawsuits.  In this case, the tire guy didn't even do that right and I'm confident the Big O management would be horrified.