Correct inflation of trailer tires

Inflate to max inflation as shown on the sidewall.

You will get two answers. As you stated max psi stated on the tire or the trailer placard which is more then likely max psi on the tire sidewall for the oem tires.

The other answer is weigh the rig and set the psi per the tire manufacturers load inflation table for that tire. which may or may not be the max psi on the tire sidewall that will depend on the weight they are carrying.

Personally (and I have upgraded the tires on my trailer to a higher load rated tire than came oem) I go by the load inflation tables based on the weight of the axles and I add extra for an additional safety margin.

My trailer came with Ranier 225/75/16 load range d tires with a max load of 2540 at 65psi, my new tires well at the time new were load range e with a max load of 3420. Even at 65 psi (same psi as the max on the oem tires and trailer placard) have a load rating of 3000lbs substantially higher load at the same psi rating. My trailer axles weigh in around 7900lbs for both axles for how I load the trailer so for easy rounding lets say 2000lbs per tire and according to Goodyear's table I can run that at 35psi for a load of 2020lbs. Which is not enough margin for me so I run them at 55 to 60psi which is 2730-2870 worth of load well above the oem tires load of 2540 at 65psi. I get a better ride at the lower psi and still a larger load margin so win win for me in my mind. I am sure someone will tell me I'm an idiot for not running the max 80psi on my (new) tires. However I trust the tire manufacturers knowledge of their tires much more than the trailer manufacturer who does not make or engineer tires.

For ST tires running them at or very close to max psi supposedly increases their ability to perform as designed, inflated to low causes them to heat up which eventually leads to bubbles and tread separation. We always run our ST tires very near to or at max psi and have had no blowouts or even a flat over the last dozen years, although we dutifully replace our ST tires after 4 years of use. LT tires are typically filled to a psi that matches the load they are carrying, we keep our LT tires filled to the psi stated on the door placard of our Silverado HD truck.

To be clear, I'm asking about the trailer tires. I keep my 2017 SRW 3500 in the sixties when empty, at 80 when towing.

rvshrinker wrote:
Everything I read says tires should be inflated to Max psi. Is there general agreement on that? I plan to do whatever is safest and as of last evening, my tires are at 60 and Max is 80, so I have some filling to do.

I called my tire dealer (Les Schwab) with the same question. The general agreement is to fill the tires to the max. capacity of your tire. To run your tires at 60 psi could lead to tire damage/blow outs/damage to your trailer and accidents. When I am not towing my 5th wheel trailer I run my tires at about 60 to 65 to make the ride more comfortable.

rvshrinker wrote:
Everything I read says tires should be inflated to Max psi. Is there general agreement on that?

General agreement, yes - total agreement, no. ;) Forum pundits who will claim to be experts on the subject would insist you load the trailer as it would normally be for a camping trip, take it to a weigh station, and measure not just the gross weight of the trailer but also the weight bearing down on each side of the trailer, then adjust your tire inflation to match. The reality is almost no one does this, simply inflating to the maximum imprinted on the tires' sidewall.