All I know is I set my pressures using the chalk line method until it wears evenly at operating temperature. I'm not plunking down $2500 on tires just to wear them suckers out prematurely by following a sticker.

A lot of good knowledge and information has been posted, as well as occasionally crammed down throats. Just goes to show that there's a wide expanse of knowledge and information here, as well as a ton of opinions and counter-opinions - as is the case with pretty much anything automotive related ever

 

I've always gone by load-inflation tables when going above the specified GAWR. The only time I've ever been at 80 PSI was when the tires were loaded close to the max with almost 3,000 lbs additional weight on the rear axle. The fronts were at 45.

I've attached a table with most common sizes.

 

I got it Stewart, HECK, I really get it, I prefer paddles over tows BUT the PSI preference had gone a little overboard IMHO. I wasn't trying to be a moderator, I'm just saying there is no point in beating a dead horse to death

PS: The above statements are not directed at you Michael

 

Good catch

I posted that last night at 1am. I was thinking load range D but typed load range E

here is my certification

I will try and answer your questions in coming post

 

Actually I am more of a " get it correct" type but when it comes to dispensing advise I try and stick to facts that I can back up with a fairly high degree of certainty.

when it comes to tire pressure while piloting a 5 ton vehicle at 60 mph "see how it Feels and then tinker with it until you like it" is far to subjective of a guideline for me to accept. think about it for a minute, what if somebody took the advise and lost control and crashed ? what would I ask , So how did that feel ?

so lets dig into a more engineering approach to the question of tire pressure.

first of all i don't proclaim to be a tire expert nor an engineer, but I have been fortunate enough to have worked with several tire engineers from the major manufactures and have logged enough hours testing their products in an official capacity to respect their knowledge and recommendations.

A tires Load Carrying Capacity is dictated by heat and heat is controlled by the tires construction and air pressure.

the LCC or Load Carrying Capacity is a industry standard and all tires with the same LCC number will have the same maximum load carrying capacity. The LCC is a number between 0-150 and corresponds to a published weight

The Load Range is is sort of a carry over back from the day of bia ply tires but all tires of the same size and load range will also have the same LCC

example, all 265/75/16 E rated tires will have a maximum weight rating of 3415 pounds and a LCC of 123 @80psi (3420# )

Now, 3415 x 4 = 13,660 pounds however in the case of the excursion the GVWR is 10,000 so there is no need to use 80 psi if this is the tire you are running. can you ? YES. will it damage the tire ? No
will it negatively affect the way the vehicle handles ? YES


now I will interject with my subjective opinion. A common handling or mishandling characteristic of Higher then required air pressure is being squirrelly or wandering ( a familiar complaint amongst Excursion owners no ? )
this is caused by a reduction in the contact patch between the tire and the road. if the vehicle were heavier then the 10,000 GCVRW of the excursion it would squish the tire more and require more air pressure. a vehicle that weighs less then the tires max load will not squish the tire as much and require less air pressure to obtain the desired contact patch.

ok, that was longer then i wanted but i am trying to be as through as I can and still make this a brief summary.

more to follow

 

lets move on ( feel free ask specific question and I will do my best to answer them or get the answer from a qualified source )


lets take 2 tires that you could run on an Excursion of a similar overall diameter but have a different construction

255/80/17 E 121 3195@80 psi
285/70/17 D 121 3195@65 PSI

just as a refresher my 2001 7.3 4x4 Excursion calls for the factor 265/75/16 D

3195 x 4 = 12,780

Lets apply this to the 10,000 GVWR

what pressure should we run ? 80 ? 65 ? or the 50/55 on the door certificate ?

 

I have a mathematical formula given to me on one of my many factor tire test sessions that can answer the question however I am reluctant to share it publicly.
I call the source of the formula today to find its origins and if it is the manufactures actual method or just an easy guideline that he shared with me.

So rather then possible lead people astray I went to Americas Tire today and asked some questions. it turns out the guy I spoke with doesn't have any idea what the formula is he just punches the numbers in the computer program and it spits out the sticker. But he did let me try out a few diffrent scenarios and I was able to confirm my equation ( at least on the samples I entered ) and he even printed out a new door psi sticker for my Excursion based on the vehicles GVRW and the tires LCC

My tires are a 37x12.5x17 D 123 and here is the PSI recommended
( it confers with my equation as well )

 

So lets compare how you answered the question vs how the the computer program at Americas tire answered the question

the 255/80/17/E @ 50 front and 60 rear
the 285/70/17 D @ 50 front and 60 rear

So what if you are not operation at the GCWR of 10,000 pounds ?

The Americas Tire computer sez..... 50 front 55 rear

Since I just got home and have not had time to crunch any numbers I have not yet figured out what weight their non full loaded recommendation is based on but my HUNCH is curb weight.

 

My Apologies to Country Mouse for the lengthy reply to her " Quick Question "

My QUICK ANSWER is, stop by a Tire Shop ask them to calculate the needed PSI for you.

*Disclaimer
I have no affiliation with Americas Tire nor have I used them before. they were just the Shop I stopped in to get some answers.

 

I keep mine set at 75 frt and 80 rear. Seems to be the best setting.

 

Wow, I didn't know this was so controversial!

I appreciate everyone's opinions. I was away for the weekend so it was hard to read through all of these responses. I will have to re-read the whole thread. I called BF Goodrich and they looked up the exact tire I have. Door jamb sticker says 45 front 55 rear for normal use since I have stock size tires. The E rating apparently doesn't change that.

They gave me a little chart. I would need to go to a scale to figure my exact weights on each axle so for now will just need to guess it. If I went by the RAWR in the rear of 5250# (5250/2= 2625 exactly) then that would equal no more than 55# in the rear tires which is what the sticker says. So I would have to be over that rating to justify adding more air. I understand many go over that rating anyways or swap out for heavier springs in order to meet the actual axle rating of 7K something.

Cold PSI weight rating per tire:

45= 2280#
50= 2470#
55= 2625#
60= 2790#
65= 3000#
70= 3105#
75= 3260#
80= 3415#

 

Those aren't manufacturer specific. Look towards the bottom of page A9 of the document I posted and you'll find the same information. Load-inflation tables are an industry standard.

 

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An empty gallery.

PC show us some pics of your rig(s) towing with your Excursion in various conditions. Different trailers, WDH, whatever, show us your rig.

Hopefully you have some CAT scale weights to enlighten us. Or maybe not.

Pirate Camo scoffs (okay, scoff might be harsh "irresponsible" was the terminology) all who tow with more than 35 PSI...because he "knows better" and we are unsafe (allegedly).

In all of his "experience" drivers never asked for more 'traction'...'power'... etc. ?

 

I tried to make it clear that the 35psi I listed applied to MY tire size and weight.
My "irresponsible" comment was referring to posting " I run xx psi " as a response to somebody asking what pressure they should run when the correct pressure for that persons setup will be dependent on their tire and weight and not what you run as you may have a completely different setup.

In all of my experience more traction and power is a common request.

 

Even unloaded I wouldn't think of running 35psi in a D rated tire on an X! the X with a driver weighs 7500lbs (probably a few hundred more for a diesel). You got your info from a tire dealer that, and you said it yourself, he has no idea, just punches numbers in! for the best ride and from a safety standpoint those tires should be run at 55 psi (max for a "D" rated tire). just like the door sticker states.