frjeff

clarkbre

The following opinion will be correct until the next poster says I'm wrong. Take it for what it's worth:

If they are stock tires and the door says 38 psi, run 38 psi. Ford (and all other manufacturers) calculate the needed PSI for maximum traction, braking, fuel efficiency and comfort based on the vehicle's GVWR. While the tires may have a max of 51 psi, they will safely carry the GVWR of the truck at 38 psi.

Ford doesn't calculate the PSI needed for an empty truck and a different PSI for a loaded truck. If you're going to get a load of dirt, do you drive it with 38 psi empty then right before they our the yard of soil in fill up to 51 psi? No.

Here's a quick read on TIRE TECH: TIRE SPECS EXPLAINED: MAXIMUM LOAD

Surely, there will be other posters on here that know way more than the experts at Tirerack.com

77Ranger460

If you have P metric tires, I would run max sidewall pressure in the rear when towing....Matter of fact, I do....With some trial and error, I found my TT towed better that way.

I would also weigh the tongue of that AS. With propane, water in the tanks and loaded, I bet your tongue weight is over 800 lbs.

TerryD64

you have to figure this out for your self based on how it rides when towing your trailer.
Minimum is 38 (based on door frame) max is 51 based on tire side wall.

Assuming your WD hitch is adjusted properly if that is what you're using.
start at 38, hitch your trailer and find a bumpy road.
If it bounces around add 5 pounds to stiffen.
Wash rinse repeat
inflating and/or deflating until you find a pressure you're happy with.

My tires are at 45 either way. I hate adjusting tires when I hook up.

smokeywren

In your case, I would probably tow with 38 PSI in the rear tires and 26 in the front tires.

I tend to ignore the PSI indicated by the vehicle manufacturer and rely on the TRA Load/Inflation tables. The Load/Inflation table for your tire is:
PSI. Load
26 . 2260
29 . 2381
32 . 2502
35 . 2601 (max weight capacity for standard load tires with 114 load rating )
36 to 45. 2601 max PSI for tires with 114 load rating
36 to 51. 2673 max PSI for tires with 116 load rating which your tires have.

Note that increasing PSI over 35 PSI for tires with 114 load rating or 36 PSI for tires with 116 load rating does not increase tire weight capacity.

So you need to load the truck with everybody and everything that will be in it when towing, including the wet and loaded trailer with spring bars adjusted for travel, then weigh the rig on a CAT scale. The CAT scale will give you the weights on the front, rear and trailer axles. If you didn't overload your rear axle, then Ford's recommended 38 PSI is just fine for the tires on your rear axle, because the rGAWR on your F-150 is a lot less than the 5,346 pounds tire weight capacity that 38 PSI will give you. You could also use the 38 PSI in the front tires, but I would prefer closer to the PSI indicated by the load/inflation table to increase life of the tire while being plenty of weight capacity for the load on the tire. The minimum PSI in your tires is 2,260, which gives you a front axle capacity of 4,520. Your front GAWR is probably less than 4520, so 26 PSI is plenty for your front tires if you don't overload your F-150.

Most tire manufacturers no longer recommend PSI other than the max on the sidewall because of the legal liability. They just refer you to the vehicle manufacturer's recommended PSI. But the vehicle manufacturer dodges that liability by overstating the PSI required by TRA because application of the TRA load/inflation tables is too complicated for Average Joe to apply. As a result of all that legal wrangling, you have a requirement for enough PSI in your tires to far exceed the GAWR capacity of your tow vehicle. If you run 38 PSI all the time as your sticker indicates, then the center of your tires will wear out faster. But you won't have any problem with overheated tires caused by under-inflation.

Blackbuzzard

I've been thinking about using one of these to see how tire temp varies at diff psi when loaded heavy.
r

Run-n-gun

This is 100% correct although I like the feel better (when towing at max gross) at 45 lbs myself. Less porpoising for sure and less sway I think.

I carry and use one on every trip. Very handy for monitoring tire, hub, and brake temps.

Maury82

I have LT load range C on my 2018 HDPP with a door PSI of 48. The truck isn't a daily driver, so I run 42 PSI when not towing, and 48 PSI while towing.

I keep a two gallon air compressor in the bed so I can air up my tires back up from my non towing pressure.

NC F150

I concur. My 23 AS tongue weight is 900lbs.

8100hd