New LT tires on f150, what PSI

E rated are too much for a standard 150. for a standard 150 "C" rated tires are all that is necessary. running "E" tires underinflated for extended periods of time while under a load will heat them up considerably. you want to at least run them at 55-65psi to get the best use of them!

Very simple, use the weight charts based on what the weight on your tires are, loaded or unloaded.

I convinced a friend to do the "E" Michelins on his Chevy 1/2 ton figured out what psi he should run. He had well over 100k on the tires when he sold it with tread left.

Great mod it will give a much more solid towing experience.

CapriRacer wrote:

rhagfo wrote:
.....The pressure on the sidewall is max pressure for max load!....

Please note: That is only true for LT and ST type tires. It is NOT true for P type tires.

I found that difficult to believe, so I went out and looked at the tires on the PT Cruiser, the only P rated tires on the place.
Sure enough:
Tire size 205/55R16 91V M+S
Sidewall 1 ply
Tread 1 ply polyester+2 steel belts+1 ply nylon
"MAX load 1356 lbs at 51 PSI MAX Pressure" (of course, the Metric equivalents are there, too, but I ignore them)

There is no way I would ever inflate those tires to 51 PSI!

As I previously stated, the Jeep Rubicon came from the factory with LR E tires. LT245/75R16E to be exact. The data sticker states to inflate to 33 PSI.
It now has LT285/75R16D tires, and I still inflate to 33 PSI.
It works.

The OP and anyone considering changing the class of tire should know
that it is re-engineering of that vehicles suspension system

The tire is only one component of the suspension system.

The tire's duties are:

• to hold up or carry weight, just like the
  springs
• accelerate by transmitting the axle torque to pavement
• brake
• steer
• more than steering, but holding it on a curve, a slalom, etc

Most folks only see and talk/address the 'carry weight' aspect as an
absolute (meaning that is all a tire does). Also the only thing between
the vehicle and pavement

With the abuse and misconceptions with tires, it is astounding to me
that they hold up. A testament to design margins dialed in by the
tire engineers...but...there is a limit or point where they will fail
Some instantly...others over a short time period

So much is taken out of context and as an absolute.

Confusion abounds with the different class of tires. From the above
and that they 'look' the same between classes (not all, but some)

Take a class 'P' and a class 'LT' from the same OEM, same model,
same tread design, same size, etc. One will weigh more and also
cost more. Why? Maybe the 'Z' rated 'P' class will cost more, but
that is a specialty tire vs a truck tire (LT)...or that most 'LT'
class tires are speed rated for 100MPH (most, not all) because pickups/SUVs
are not designed to run over 100MPH, generally

Then that confusion rolls over to their PSI vs weight carry rating.
That confusion is not just from those asking, but from so many advisers

PSI is NOT just for carry capacity (it is only ONE attribute) but
mainly for the tire to be able to keep it's shape between wheel rim
and pavement.

On that shape, note the the main or the greatest enemy of a tire is heat
Generally heat self generated by flexing with some ambient contribution. Oh, yes...the rim width also very important and tough
one to get folks to see/understand how that contributes to how
a tire flexes

Speed is the main 'flexing' issue for 'that' load

Then the specifications (published, door label, glove box manual,
tire sidewall, etc) taken as absolutes and out of context from one
class tire to the other class tire

Or the various ratings tossed in an absolute manner. Like a 'C' or 'E'
is thought to be it...but it is only a suffix or prefix modifier for
a tire size. A 'E' for one tire size has a different weight rating than
an 'E' for another tire size. There is a move to the 'P' class weight
rating with numeric identifiers and those are absolute. Meaning a 120
load rating for any size tire or class tire will have the same weight
rating.

There is a bunch more, but not now...no time as shopping and getting
ready for the 4th BBQ party...will come back to this later

I put "d" rated LT tires on my 1500 Ram. The tire store inflated them to 40# as per the door sticker. Manager told me that they could not inflate to a higher pressure,(whether law or store policy I don't know). He then pointed me to their outside air hose and told me to do what I needed. I added 10#.
The Post Office runs all their 14" P rated tires on the LLV's at 50#. I drove the same truck for 15 years and never had any unusual wear.

When I had Mich MS/2 E's on my 10 F150 (275/65/18) Discount tire said 45psi was all that was needed to carry the trucks RAWR.

FWIW i run the same size tire on my 2010 Supercrew and i have them inflated to 44psi. I used the tables mentioned above to see what pis would cover my axles and 44psi does that. 10,000 miles on the tires now and no signs of irregular wear and 3,000 miles of that was pulling my trailer.

I have compared my table results to 2-3 other load tables and each time my values have come up a little higher than the other load tables. I have read where many feel that you should run your tires at max pressure regardless.

If you have a load table in mind Id be glad to compare again.



ON EDIT:
I found this Michelin table - although it does not cover the mentioned tire ratings it shows how the values compare:

Based on the Michelin table
5250/2=2625
2625# requires 65PSI for this load


Based on my formula
2625/3024=86% load
80*.86=68.8 PSI


Based on the Michelin table
1700 should have 35 PSI for this load


Based on my forumula
1700/3024=56% load
80*.56=44.8 PSI for this load


The following information will not format correctly but you can count columns for the proper values:

Based on these values:

PSI 35 40 45 50 55 60 65 70 75 80
Single 3400 3730 4060 4410 4670 4960 5250 5530 5800 6084

The table:
http://www.michelintruck.com/michelintruck/tires-retreads/load-inflation-tables.jsp

This is just my opinion.

rhagfo wrote:
.....The pressure on the sidewall is max pressure for max load!....

Please note: That is only true for LT and ST type tires. It is NOT true for P type tires.

wittmeba wrote:
....I would scale the tire pressure to your load using FN's chart posted above. Here is how it works.....

I omitted the image - as it is wrong.

You have to use the load tables. The formula is much more complicated and it isn't proportional to the inflation pressure.

DO NOT USE THAT FORMULA. You will be underinflating your tires.