I have f350 with the 7.3L godzilla with the short bed and 3:73 gears, and the stock 18in wheels and tires. . I am towing an 11000lb fifth wheel. The tires on the truck (from the dealer). Are just under 60 in the front, and around 70 in the rear. If i go more PSI then when I am running around town after I disconnect the trailer the ride is more rough. Should I inflate the tires more to tow, then have to let air out when I get to the campsite , or roll as is? What does everyone else do?

 

I run them higher when towing. If it's just running around a little leave them high. I also bring my Milwaukee M18 inflator if I decide I want to air down and then pump them up.

 

While I do carry a 12V inflator, I simply go by what the manufacturer recommends. It's inside the driver's door jamb. Call me a rebel, I guess. 🤷‍♂️

 

I run 60F / 55R when not carrying weight.
I run 60F / 80R when loaded heavy.
Best thing would be to hit a scale to know your exact weights. Then check load versus psi chart from your tire manufacturer.

 

I have an onboard compressor with 2.5 gal air tank. I don't air them down when unhitched at a campsite.

 

Yep, this. When using the load chart, allow a bit extra (15 - 20% is what I use) to account for load variations and differences in individual tire weights. In the meantime, I think I'd go 70 front and 80 rear on a SRW truck towing an 11,000 lb fifth wheel. Pin weight is likely around 2,200 lbs.

Dave

 

Knowing actual axle weights and adjusting tire pressures in accordance with the tire manufacturer's load charts is the correct answer. The PSIs listed on the door jam are for the potential max load and cover everything down to the bare truck as a lowest common denominator value to give an end user.

I would not personally bother airing up and down during a camping trip - just live with the slightly harsher ride with tires appropriately aired for the load.

 

Dont bother. 11,000# 5'er junk, pulled by an SRW truck.

Go straight to 80 in the rears. I go 10% over as per the engineers advice, so 88psi. Run over a board to set the fronts to your liking, or follow the method above. But max out the rears.

 

Same here. Maybe if I was parking the trailer for an extended stay, I would air down. But for a week or two, I just accept the rougher ride... and it ain't that bad anyway.

 

Go to a CAT scale, weigh your truck with trailer hooked up then look up load inflation tables for the tires based on weights.
That is the correct way to do it.

 

this
Absolutely

 

What is your psi and loaded weight?

 

Good advice. It all depends on the actual axle weight, everything else we could say are just pure speculation.

Here is a guide Toyo published that I found handy. On page 27 it lists LT275 70R18 size tire pressure and weight each tire can support

https://www.toyotires.com/media/pxcj...s_20200723.pdf

Here is a chart from Falken

https://www.falkentire.com/load-inflation

Both are saying saying around 60psi the tire can handle about 3000lbs each, 2840lbs at 55psi. So that seems to be a consistent range that's relevant to the discussion here. Depending on the pin weight, what's in the bed, people and cargo in the cab, etc, OP could adjust if he can weigh the truck with all load attached and onboard and go from there.

 

The 2,840 pounds at 55 psi is for a D rated 275 70 18 tire. I would not run my E rated tires at that with a load. The chart shows 70 psi for the lower weight. On highway 70 psi would be my minimum, on sand or beach or equivalent I would lower to 25 or 30 psi not driving over 20 mph.

I would go as low as 65 psi empty with mine on the pavement.

Tire shops sometimes will put on C or D rated tires on a truck so you should check right before they install them. I think all Super Duty trucks should have the E rated tires but you do not have to, if you are going to work the truck you should.

Know what tires you have and use them at their rated capacities.

 

I think you are mixing a few things up. Read this first especially the charts at the bottom and compare them to why (D) is called out where they are in the inflation pressure charts

https://www.tirerack.com/upgrade-gar...es-ply-ratings