44 vs 51 psi tires on 2016 Ram 1500 SLT

[sevarg]

I've towed a 7,000 travel trailer over 45,000 miles with the original Goodyear 265/70R17 load 113 (2nd set), Florida to Oregon, all over USA. I use the Equalizer hitch setup, which apparently NOBODY (!!) knows how to properly adjust, and adjusted it myself such that both the truck and the trailer are perfectly level going down the road. No airbags, no sway, almost forget the trailer is back there.

So .... I am thinking of replacing the fast-wearing Goodyear Wranglers with 51 psi max, load 115, insofar as when not towing run them at the placard recommended 40 psi, and still get good gas mileage; but when towing, I could jack the rear tires up to 48 psi. Is that a good plan? Safe? Or should I stick with 44 psi tires? {I am not considering going to E rated 80 psi tires: more $$, less mpg, exceed axle weight rating}

These are what I am looking at, all are 51 psi 115:
Nokian one ht
Falken Wildpeak H/T HT02
Goodyear Wrangler Fortitude HT

 

[bm02tj]

If I was doing a lot of towing I would run the LT's
The air pressure will be about the same but side wall is stiffer with less side flex

 

[sevarg]

I only will consider either a 44 or 51 max psi tire.

1. What is the comparison in mpg running either at placard 40 psi?
2. How do I determine the load capacity of either running at 40 psi?

 

[crash68]

I have the factory LT265/70/17 Load E tires on my Outdoorsman, the door says to run them at 43 psi, I usually run the rears at 40 psi. When I'm towing the rears will usually be inflated to 50 psi. The tires have a Max PSI of 80, no way would I ever run that much unless I want to truck to ride like crap.
It's the tire size and actual load that determines the inflation pressure, the max psi doesn't really factor into the running inflation pressure.

 

[sevarg]

The Outdoorsman is a 2500 4WD, much heftier than my 1500 2WD. With the 8 speed, 5.7 v8 I get nearly 25 mpg by turning off 4 cylinders. From what I've researched so far, the E rated tires are heavier, reduce mpg, and exceed the axle rating in their ability to transport load. So supposedly overkill for my vehicle. And, they cost another $50/tire. However, your post resolves one of my issues, namely that the placard on your truck for the LT tires says 43, and when towing you pump them up to 50. So it seems I am getting closer to figuring out what to purchase, probably the Nokian HT ONE 115T, which I can run at the placard stated 40 psi, and crank up to 50 when towing, without affecting my mpg. Thanks (I hope).

 

[pacofortacos]

Ok, the 51 psi tires have the same exact rating as your old tires at the old tires rated pressure which is 35 psi.
To get the higher load rating, the XL tires must be inflated to at least 41 psi - which is the pressure that the load rating is made at and no higher than 51 psi @ 68 deg F.

So standard load @ 35 psi = tire side wall load
XL load @ 35 psi = Standard load tire
XL load @ 41 psi = XL load on tire sidewall.

So run the tires at 41 psi @68 deg F for maximum load capacity that the tire is rated for.
If it is warmer when you check the pressure go a couple of psi high, colder lower.

 

[pacofortacos]

His Outdoorsman is a 1500 not a 2500.

I run my XL tires in the 39-46 range, slightly better mpg at 46

 

[crash68]

The Outdoorsman is a 2500 4WD, much heftier than my 1500 2WD..

The Outdoorsman is a trim package that was available before the Rebel came out, it was available in both 1500 and HD platforms. It was a more off road capable truck but we'll equiped like the BigHorn.
Mine is a 1500 CC w/6.4' bed 4X4 EcoDiesel
Increasing the tire pressure won't hurt your fuel economy. Too much pressure can cause handling issues along with burning the center of the tread out faster.
When I inflate the rear tires to 50 psi, it's for stability reasons as I usually have 8k or so behind me.

 

[sevarg]

As I drive myself nuts with this ... according to the Toyo load ratings table, the P265/70R17 at 35 psi LCC is 2535 lbs, while a LT265/70R17 at 35 lbs is only 2075 lbs. The LT LCC doesn't surpass the P's LCC (still at 35 psi) until you inflate the LT to 50 psi. Note that the load ratings table does not specify a psi greater than 35 for a P265/70R17, which makes me wonder why the placard says 40 psi. RAM's recmd pressure for the LT265/70R17 is 43 psi.

Quote from TruckTrend, "When comparing tires that are the same size/same internal static air volume but have different load ranges, one with a higher load range at higher air pressures actually may have a lower LCC. For example, a P275/65R18 can have a 2,500-pound maximum LCC at 35 psi, whereas an LT275/65R18/C (six-ply rated) might only have a 1,948-pound capacity at its maximum 50 psi. The difference: P versus LT."

Too much pressure can reduce the footprint and adversely effect braking, so somewhere in all of this is the SweetSpot.

Another seeming useful tip from TruckTrend: "rear-tire psi can be fine-tuned for towing/hauling. The time-honored tape-measure method: With the vehicle on level ground, measure the front from the top of a rim to the ground. Adjust rear pressure until a rear rim-to-ground measurement is 3⁄16 inch higher than the front distance. This ensures control and stability of the load."
Hmmm.

I'm going to go to the local RAM dealer and peep around at what tires are on what, and what the placards say.