Proper tire inflation of F-150 pulling Cougar 22 MLS

[flybouy]

I have not seen ANY subject that generates more "experts", "engineers", and "gurus & mystics" as tire discussions do. Typically these discussions drift off into the realm of "insider tire engineering ", to outright BS. My point being (other that some laughter and some frustration) is why? Why do some folks jump right into the rabbit hole and type paragraphs of postulation without any refrence as to why someone should follow these "star charts" of tire inflation.

I would suggest that this subject is often overthought IMO. I can't see the average trailer towing person finding and then visiting a facility capable of weighing each individual tire on a trailer much less doing this at the start of every trip. I'm a firm deliver of the old saying "know your audience " when writing. The audience in most of these tire questions are novices that have little to no experience with changing tire ratings. That's why they are here asking for help. IMO, throwing a bunch of inflation charts and equations at someone will just confuse and alienate them. I would suggest keeping the responses to as SIMPLE, and FACTUAL as possible so that the intended reader isn't overwhelmed with useless, irrelevant, and often confusing information.

I apologize for the long rant but I'm most concerned with the OPs attempt at getting useful and factual information that they can use. This seems like a fairly simple and straightforward issue that should be fairly easy to advise upon. I don't see the need to trying to impress folks with your "knowledge" when a simpler, less confusing, real-world and practical answers will suffice. I will say that many of these posts are amusing and remind me of another old saying, "If you can't impress them with your knowledge them dazzle them with your BS."

 

[Rhagfo]

The bolded part is to laws of nature not right.
For lighttrucks sometimes people change from standard load P-tires to E-load LT.
Then about 15 psi higher pressure needed to carry the same load.

In official lists in US the loadcapacity's are calculated for the pressures for one loadrange, and the other loadranges belonging referencepressures , the maxload of those loadranges replace the calculated values.
This gives strange yumps up or down , if you would make graphics of it.

In Europe, for every loadrange of same size tire, a seperate pressure/ loadcapacity- list is made.
If then graphics made of those list, it gives a fluid line .

If you would calculate maxload/ AT pressure, from for instance C- and E- load of same size LT or ST tire, the E-load has lesser lbs/psi then the C-load.

Example ST225/75R15
C-load 2150 lbs /50 psi = 43 lbs/ 1 psi.
D- load 2540 lbs/ 65 psi = 39.07 lbs/ 1 psi.
E-load 2830 lbs/ 80 psi = 35.38 lbs/ 1 psi.

It is pretty simple that if you put LT E rated tires on a F150 you don't want to run them at 80 psi! This is truly where one refers to the inflation table to inflate to a max to cover your axle rating.
This is why the rear axle tires on our Ram DRW with a 9,750# axle rating shows a an inflation of 65 psi for max load on tire with a max inflation of 80 psi. I am not that heavy, so run at 55 psi.

 

[jadatis]

Answer to post # 42 above here.

But you also dont want the probably recomended pressure 35 psi for the OEM P-tires.
Can be that 65 psi is still not to much( so comfort and gripp gets unaceptable ) for your real lower weights,and that would give reserve for things like:

unequall weight R/L.
Misyudged weight on axle.
Inacurate reading of pressure.
Pressureloss in time.
And so on.

@post 41 from flybouy

I began simple in my first reaction post #19.
With giving a better calculated list , with build in reserve. And mentioned that determining the axleloads in your use is the most tricky part, and your responcibility.
All to make it simple for topicstarter, so he ( or she , or genderneutral) does not have to do pre- and/or after-calculations.

And next was reaction to same pressure all around on 4wh drive .

Then some daubted the correctnes of my given info, and needed further explanation.

All that tech info , you can yust read until you understand , then forget it .

 

[Rhagfo]

Answer to post # 42 above here.

But you also dont want the probably recomended pressure 35 psi for the OEM P-tires.
Can be that 65 psi is still not to much( so comfort and gripp gets unaceptable ) for your real lower weights,and that would give reserve for things like:

unequall weight R/L.
Misyudged weight on axle.
Inacurate reading of pressure.
Pressureloss in time.
And so on.

@post 41 from flybouy

I began simple in my first reaction post #19.
With giving a better calculated list , with build in reserve. And mentioned that determining the axleloads in your use is the most tricky part, and your responcibility.
All to make it simple for topicstarter, so he ( or she , or genderneutral) does not have to do pre- and/or after-calculations.

And next was reaction to same pressure all around on 4wh drive .

Then some daubted the correctnes of my given info, and needed further explanation.

All that tech info , you can yust read until you understand , then forget it .

Well at 65 psi my tires are responsible to carry 2,437.5#, max weight is 3,042# at 80 psi.
So two tires at 65 psi would support a 4,875# axle. This is where an inflation table comes into play.
Some 18” and 20” truck tires have high weight rating, so could be lower than 65 psi.

 

[wiredgeorge]

I have not seen ANY subject that generates more "experts", "engineers", and "gurus & mystics" as tire discussions do. Typically these discussions drift off into the realm of "insider tire engineering ", to outright BS. My point being (other that some laughter and some frustration) is why? Why do some folks jump right into the rabbit hole and type paragraphs of postulation without any refrence as to why someone should follow these "star charts" of tire inflation.

I would suggest that this subject is often overthought IMO. I can't see the average trailer towing person finding and then visiting a facility capable of weighing each individual tire on a trailer much less doing this at the start of every trip. I'm a firm deliver of the old saying "know your audience " when writing. The audience in most of these tire questions are novices that have little to no experience with changing tire ratings. That's why they are here asking for help. IMO, throwing a bunch of inflation charts and equations at someone will just confuse and alienate them. I would suggest keeping the responses to as SIMPLE, and FACTUAL as possible so that the intended reader isn't overwhelmed with useless, irrelevant, and often confusing information.

I apologize for the long rant but I'm most concerned with the OPs attempt at getting useful and factual information that they can use. This seems like a fairly simple and straightforward issue that should be fairly easy to advise upon. I don't see the need to trying to impress folks with your "knowledge" when a simpler, less confusing, real-world and practical answers will suffice. I will say that many of these posts are amusing and remind me of another old saying, "If you can't impress them with your knowledge them dazzle them with your BS."

The positive take-away when having the "experts" bloviate in tire threads is that they don't seem to haunt any other type thread and it gets them all in one basket to ignore. I believe we have all seen the way tire threads go many times.

 

[jadatis]

Well at 65 psi my tires are responsible to carry 2,437.5#, max weight is 3,042# at 80 psi.
So two tires at 65 psi would support a 4,875# axle. This is where an inflation table comes into play.
Some 18” and 20” truck tires have high weight rating, so could be lower than 65 psi.

Then I calculated back, that you first added 5% for reserve, but correct me if wrong.

When I make my lists, I standard give 90% of calculated axleloadcapacity for the cold pressure for max 160 kmph/ 99 mph.
This is the same as first adding 11.1% to the carefully determined axleloads, and then calculate pressure for that.

I once determined by reactions about comfort, that if less then 85% of calculated axleloadcapacity for the pressure, that then no discomford of that tire, and acceptable gripp..
So if then weightdifference on the axle, so one side using 85% and the other 95%, so average 90% , still no discomfort and the other side still some reserve.

So if your 2437.5 lbs per tire,do 2437.5/ 0.9=2708 lbs to search back pressure for in official list, and still acceptable comfort and gripp.
Did you look in the dualload list? Gives lower maxload then for singleload list.

 

[Notanlines]

Marshall, I believe I have been dazzled! (What is this stuck to my shoe?)

 

[Rhagfo]

Then I calculated back, that you first added 5% for reserve, but correct me if wrong.

When I make my lists, I standard give 90% of calculated axleloadcapacity for the cold pressure for max 160 kmph/ 99 mph.
This is the same as first adding 11.1% to the carefully determined axleloads, and then calculate pressure for that.

I once determined by reactions about comfort, that if less then 85% of calculated axleloadcapacity for the pressure, that then no discomford of that tire, and acceptable gripp..
So if then weightdifference on the axle, so one side using 85% and the other 95%, so average 90% , still no discomfort and the other side still some reserve.

So if your 2437.5 lbs per tire,do 2437.5/ 0.9=2708 lbs to search back pressure for in official list, and still acceptable comfort and gripp.
Did you look in the dualload list? Gives lower maxload then for singleload list.

I don't understand any of your gobbledygook, but 65 psi on my DRW is what is needed to carry 9,750# on the rear axle, from the payload sticker.
The 2,437.5 is what each tire is supporting at that pressure.
Yes, I am aware that in DRW applications, I loose a bit of max weight due to heat, BUT the OP is a SRW.

 

[jadatis]

If you would weigh per axle-end, you would see that one side on the axle has more weight then the other.
For instance your average 2x2437.5= 4875 lbs per axle-end
Then right 5100 lbs and left 4650 lbs
Then pressure is needed for the 5100 lbs.
Preferably even with some reserve for possible misreading and inacuracy of gauge.
My used system then 4875/ 0.9= 5416 lbs covered, and still comfort and gripp acceptable.

Can you give specifications of tires? Then I can check list for it?

I assume DRW is dualload rear wheel and SRW is single rear wheel, but again correct me if wrong.
I reacted to your given data, so for DWR.

 

[chuckster57]

I have watched this thread and I have come to the conclusion that VERY FEW people will actually weigh each tire/side and adjust the pressures in the tires. TOO MUCH trouble and if your really that OCD about it, your tire pressures will change every time you hook the trailer up due to waste/fresh water in which tank. Food eaten/bought and stored.

I dare say if your that worried about it you should pass on buying a trailer and instead stay at a hotel,motel or air BnB. I worry about the “normal” stuff. Like running out of beverages and food.

JMO, YMMV.

 

[Notanlines]

I simply cannot agree more!!

 

[Wis Dan]

I started this thread and I gotta say, I created a monster...!!
Thanks for all the responses! Bottom line, I gather running my E-rated tires on my F-150 at 80psi, would be too high, somewhere around 65-ish would probably be a good start. I haven't picked it up from the dealer yet - probably week after next. So...getting excited to get this going. Thx again!

 

[NH_Bulldog]

All this "science" aside (while entertaining, the whole topic quickly became a monster). Having been there, done that, and experienced your exact situation (how many of those "scientific" posts actually have an F150 with upgraded LRE tires, and are towing a large travel trailer)? I stand confidently behind what I said in post #4:

When I had my F150 towing my Passport 240BH, I upgraded the tires to Load Range E (LRE) and ran them at 70 PSI. With road heat, they typically increased to 75 PSI while towing. Because of the weight distribution, I kept both the front and rear the same pressure.

 

[Wis Dan]

Thanks Bulldog! I appreciate you passing along this info (and your experience) to me/us all.
Btw, when I said I'll start at 65 psi, I meant that's what I'll do when I pick up the trailer in a couple weeks - since it'll be unloaded, dry, etc.. I will take your recommendation to run at 70 when fully loaded and hitting the road!

 

[jadatis]

Mayby the seller has a braketesting bank.
Those often can also weigh the axles or seprate wheels.
Then you have a basis for the weight and weightsivision to work with.

 

[chuckster57]

Mayby the seller has a braketesting bank.
Those often can also weigh the axles or seprate wheels.
Then you have a basis for the weight and weightsivision to work with.

Haven’t seen any RV dealers with anything like that, I have personal tongue scales in my tool box, and I can attest to the statement of tongue weight in any sales brochure is not accurate, some not even close.

 

[JRTJH]

In addition to what Chuck says about the tongue weight being heavier than the brochure and in many cases being "hundreds of pounds heavier", keep in mind that the brochure "shipping weight" is not the dry weight of any "specific trailer. It is the shipping weight with no propane, no battery, no optional equipment for a trailer model number. It's the "as shipped with no optional equipment" weight.... Add a second air conditioner, change from a SolarFlex220 to a 440i, add optional batteries, dual pane windows, change from a dinette to a table/chairs or change the "goucho" for theater seating and you're going to have a SIGNIFICANT difference in "trailer weight"... NO brochure can account for each optional piece of equipment you add to the build, so brochures are a reflection of fantasy rather than anything resembling reality....

Also, there remains an "unanswered question" that I've asked Keystone repeatedly for 10 years and I've never got a "straight answer" yet... The question: Keystone offers many trailer lines with "mandatory optional packages"... Does the shipping weight reflect those options or does the shipping weight not include the "mandatory options" along with not including "optional options" ???? They either can't or won't answer that, so look at the equipment included in "your trailer model" on the Keystone website and you'll find things like the leveling system (several hundred pounds) listed as a "mandatory option" as well as many other items that are included in "mandatory optional packages".... So, sometimes the trailer weight listed in a brochure may be 1000 pounds or greater with all the "optional equipment" ....

Why does Keystone do that ???? I can't say for certain, but if they keep the "shipping weight low" they can place "light weight/ultra-lite" trailer models in a category competitive with other manufacturer's models in similar length/number of slides trailers.... It's all, for the most part, smoke and mirrors to manipulate empty trailer weight and "weight per foot" statistics... They don't list those in a brochure, but many/most shoppers pull out their cell phone and just divide shipping weight by length to get the weight per foot numbers and compare those with the competition... So it benefits a manufacturer to have "low shipping weights" with "big cargo capacity numbers" and not include those "mandatory options" in the mix.....