Hello, I have a 2019 King Ranch F150 SCrew 3.5V6EcoB with the Tow Package. I haul a gooseneck horse trailer that adds a substantial amount of payload to the bed of the trailer. Sometimes short trips, sometimes long trips with dirt/gravel roads to reach our destination. My Engine handles all of this just fine, however, my tires weren’t and I got two flats and felt the tires were too “squatted”. I recently switched from the Original Tires on my truck 275/55R20 specs for 35psi cold on the door sticker, to LT275/55R20 that have an 80PSI on the sidewall. The tire shop wanted to set the psi at 35psi per my door sticker, but these are LT’s and the originals weren’t. Shouldn’t they be set to the Max PSI spec’s on the side of the tire? Especially towing that amount of weight? Thanks!

 

they should not be set to max. Psi is determined by tire (including construction) and load…the stock tires that came on your truck at the recommended psi will meet the max payload of your truck.

you can now bump your tires up a little if you want, but not 80.

LT tires usually need a few more psi compared to the same size P tire to achieve the same load rating.

heres a calculator that lets you type in the stock and the new and it will give you a recommended minimum psi to run that matches your stock ratings.

https://tiresize.com/pressure-calculator/

 

The 80 PSI is needed if you're driving a 1 ton truck with over 10,000 lbs GVW.. Even guys who drive 3/4 and 1 ton trucks only put 50-60 PSI in their tires unless they are loaded very heavy. and those trucks are around 7000 lbs empty.

I've always run 35 PSI in a 1/2 ton truck with E rated tires but it sounds like you're going to be putting more weight on your truck than I do. You need to experiment with different PSI. I wouldn't go over 45 PSI and you may find 35 works just fine. I find ride quality in a 1/2 ton with E rated tires acceptable at 35 PSI. Never had an issue, tires last a long time, wear evenly and IME do a better job of handling weight than P series.

 

Listen to the Moose. LT tires have load capacities that vary greatly depending on inflation pressures. 35 psi is probably not enough for your load.

 

For what it’s worth, the 2013 F-150 I had prior to my current one rolled off the assembly line with E range LT all terrain tires. The payload door sticker had the tire pressure spec at 55 front, 60 rear. The TPMS in the truck was also set to these pressures from the factory.

If it were me, I’d use that as a starting point and adjust from there.

 

I'd run 65 psi in them. That's what I used to do in my Suburban when it had that type of tire. Gives you a nice ride whilst ensuring a decent load-carrying ability.

 

There have been some posts on this forum from guys with OEM LT C rated tires and their door sticker called for 48PSI front and rear. That's what I set my LT E rated at when towing. I drop them to 44/40 when empty since trips are typically 3-4 weeks apart.

 

I'd be at at least 45psi.

You need to look at the load rating on the tire and go from there. The load rating is at 80 psi, less pressure lowers the rating.

People think just because its an LT E range its a tougher tire and can handle the loads at lower pressure, but the reality is they generally need to be inflated much higher than a normal SL tire for the same carrying capacity. And SL might handle 2500 lbs at 30 or 35 psi but an LT E range would need to be closer to 45psi or more for the same rating.

 

"LT-Metric" tires is more than a name, it is an industry standard. Go to https://www.toyotires.com/tires-101/...lation-tables/ and open https://www.toyotires.com/media/pxcj...s_20200723.pdf. Go to page 28 and look for your tire geometry to see the load limit at various PSI. There is nothing Toyo-specific about these numbers, they apply to all "LT-Metric" tire brands +/- a few percent at most. It really comes down to the volume of air stored in your tire. Less volume = more PSI, more volume = less PSI for a given load rating.

Generally speaking your half-tonne truck doesn't have the GVWR and GAWR to ever "require" above 50 psi. You can still go above 50 but you will simply cause uneven tread wear and harsher bumps. I'd recommend 50 in the rear with the gooseneck, 35-40 unladen. In the front just a constant 40 or so. If you take your truck and gooseneck to the scales you can more precisely calculate the ideal pressure for your loaded and unloaded scenarios.

 

Great advice on going to the scales. I can take it to our local dump and get them weighed.