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Proper tire pressure for load range E 10 ply tires

jefffoxsr
Explorer
Explorer
I bought some new tires today.
Load Range E (10 ply). Cooper Discoverer AT3.

I will not tow with this 2015 Ford F150 but the 35 x 12.50 x 20 tire size only comes in a load range E.

I requested to put the tires at 35# since I am not towing.

The owner of the tire business said that although I am not towing that load range E tires absolutely MUST be run at no less than 50 psi. He said the reason was that the tire will not function correctly, the truck will not ride correctly, the side wall of the tire will break down, and the there will be cupping of the tire.

If this is generally true from a technical standpoint and design standpoint then I will run them at 50 psi. If I can safely run them at 35 psi and have the tire function correctly and ride properly then please let me know.

Thank you very much for your technical assistance and your experience. Take care. 🙂
Jeff Fox
40 REPLIES 40

Dennispel
Explorer
Explorer
One way to find proper inflation is to find a level parking lot, draw an inch wide chalk line across the tread, drive in a straight line and adjust tire pressure up or down until the chalk is wore even across the tread. You can do this loaded and unloaded.
2005 Frontier Explorer 32' bunk house
2006 Ford F250 V10 6 speed stick 430 gears 5Star Tune
Me, Wife, 3 kids and a great dane lab mix

Grit_dog
Navigator
Navigator
As this topic was beat dead pages ago......for anyone reading and wanting an easy straightforward answer. Find a tire loading chart for your size tire, similar model/capacity and put in a little more air than you think you have load.
2016 Ram 2500, MotorOps.ca EFIlive tuned, 5” turbo back, 6" lift on 37s
2017 Heartland Torque T29 - Sold.
Couple of Arctic Fox TCs - Sold

djgodden
Explorer
Explorer
schlep1967 wrote:
On my Dodge Ram 2500 the "Light Load" pressure is 45 lbs in the rear. Those are E rated tires and the door panels recommended pressure. The dealer is telling you what he thinks. Not what he knows.


x2
2012 Ram 2500 4x4 Lariat Longhorn 6.7 CTD HO, Edge Evo CTS, Extreme Tow/Haul brakes, aFePower Diff cover, LL 5000 bags, 285/70R17, Reese Q20 w/slider. 2005 Montana 2955RL w/400w solar, Renogy MPPT, 4 x 6v @ 12VDC (450AH), 3000w Inverter, King VQ4100.

mkirsch
Nomad II
Nomad II
Your 12 Ram WHAT? 1500? 2500? 3500?

The door sticker for a 1500 is meaningless when it comes to an LT-E tire. That door sticker is for the stock P-rated tires as stated explicitly on the door sticker itself.

If 2500 or 3500, it is irrelevant to this conversation.

Putting 10-ply tires on half ton trucks since aught-four.

goducks10
Explorer
Explorer
I've been running 45 PSI in my rear E's on my 12 Ram for 5 years. It's whats on the door placard. I'm not sure where all this internet guessing is coming from. E's have been run under 50 PSI for many years. Tires are aired up to the psi thats necessary for the load.

jadatis
Explorer
Explorer
An E-load tire needs higher pressure for the same load then a Standard load P-tire.
Its because the E-load is stiffer so the overgoing curve from unloaded radius of tire to flat on the ground is larger.
This gives a smaller surface on the ground at the same deflection.
To compensate that the pressure must be higher.

But this does not mean the E-load cant go low in pressure, if the load on tire is low enaugh.
Extra reason why you need even higher pressure if your tires a Offroad or ofroad-looking with large profile blocks that cover a part of the sidewall, so lesser sidewall is left to flex.
Here a picture about it, wich I made.


but I am able to present you a pressure/loadcapacity list for your tire, made with my extra save formula , so it would sertainly not give to low pressures.

You need to give me , 1. maximum load or loadindex, 2. Loadkind already given but search if you find AT 80 psi( general for E-load) on sidewall, sometimes its for instance 77 psi for some sises, and 3. Speedcode of tire, but this can not always be found, so if not given , no problem , we will have to do without that.

But then we have a list, But determining the real weights on tires is another most difficult thing.
The car maker uses the GAWR's( gross axle weight ratings, what to law is maximum weight on the axle) to determine the advice pressures, and as long as you did not weigh, we can use that , and can mostly be found on the same plate as the pressure-advices.
If you have determined real weights, even add 10% to that for reserve, and shifted load R/L.

If you find speedcode of tires , then also the maximum speed you use and wont go over for even a minute , I would like to know.
Pressure advice is also different for other speed.

Here is a link to a map on my public map of One-drive, that belongs to my hotmail.com-adress with same username as in this forum ( so jadatis) , with in the USA map the pressure loadcapacity lists in lbs and psi, that go pretty low ( 25psi for a E-load), and made with my determined extra save calculation .

Extra save P/LC lists


also a picture in wich I try to explaine why a stiffer tire has lesser surface on the ground.

tinner12002
Explorer
Explorer
I would have to agree with the dealer for using a minimum tire pressure to prevent uneven or premature tire wear, you do what you want but if you'd like the best wear and performance from your tires, do what the dealer says. Tires these days aren't cheap so most of us like to get the most wear possible out of them, but I'm sure some will want to argue that. Can you run 25lbs of air in your tires...sure but will you get good wear and performance from them, probably not but again its your money. I doubt any of those charts are concerned with tire wear.
2015 Ram 3500/DRW/Aisin/auto/Max tow/4.10s,Cummins, stock Laramie Limited--Silver
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jefffoxsr
Explorer
Explorer
There are some other web sites that have the table on there and they credit TWA by saying something like table courtesy of the tire and wheel association. I don't remember which site.
Jeff Fox

riven1950
Explorer
Explorer
http://www.michelintruck.com/reference-materials/manuals-bulletins-and-warranties/load-and-inflation...

Do you have a link to this table? Their website looks like you have to pay for any info obtained.


Here is one example for Michelin. Mine are 18" so I ended up either chatting online with them or calling, can't remember.

Perrysburg_Dodg
Explorer
Explorer
CapriRacer wrote:
Don,

3 thoughts:

1) Included on my web page is an analysis of the pressure spec. Short version: The vehicle's tire pressure spec did not result in an overloaded tire.
This is from Dr. Govindjee report on page 34. Seems to contradict you statement as to the affect of pressure and heat on a tire.
5.3 Thermal demands
The climate related degradation of properties that was seen in the return
tire survey points to the importance temperature plays in material behavior.
Likewise, aging studies on ideal laboratory specimens show a measurable
effect of thermal and oxidative aging. There are two major contributors to
the temperature of the tire: (1) is the ambient temperature and (2) is the
heat generation from within the tire.
1. Low inflation pressure, highway speeds, and heavy cargo loads all play
a negative role in terms of contributing to thermal aging. When all
three factors are present, the temperature rise in the belt region of the
tire can be as high as 50C over the ambient temperature.
2. When carrying heavy loads and at high speeds, decreased inflation
pressure can substantially increase tire temperature.


2) Firestone's own consultant (Dr. Govindjee) identified the problem in the tire.

I could not find where he said the tire was defective however there were higher failure rates between Firestone's two factories.
5 Conclusions
This study has found no single causative agent for the tire failures. It has
found a number of comparative differences in tire models that are likely
related to the tire failures and these are summarized below. The primary
issue that impedes additional progress is the lack of established criteria for
different types of tire failures. Development of such criteria is only today
becoming scientifically and technologically possible.

The other main point is why were no other vehicles seeing the same failure rates using the same tires that Ford was having with the Explorers? These tires were also being used on the Ford Ranger without any issues. The other thing pointing to low tire pressure and heat is that the vast majority of the tire failures were happen in hot climates.


3) The tire was recalled, but the vehicle wasn't. If the Feds didn't think the tire was the sole problem, why didn't they recall the vehicle?

The vehicles were recalled Ford had to replace those tires not Firestone. The vehicle manufacture is responsible ALL parts installed on their vehicles not the supplier. The total cost to Ford for the recall was over 3 billion dollars.

Barry
2015 Ram 1500 Laramie Crew Cab SWB 4X4 Ecodiesel GDE Tune.

TurnThePage
Explorer
Explorer
jefffoxsr wrote:
I called the tire manufacturer for my new tires. They said absolutely you can run under 50 psi in load range E tires. They said to refer to the tire and rim association load and inflation tables which also show load rates for inflation pressures as low as 25 psi for load range E 10 ply tires. I have this table and found it again on the internet to confirm it.

Some tire manufacturers publish documents showing what they determined to be the proper air pressure for their particular tires to meet OEM standards. They use the tire and rim association table as a starting point to make their determination for their specific tires. These are interesting to look at.

Anyway. I am satisfied, based on the above information, that I can safely run lower than 50 psi on my new tires.
Do you have a link to this table? Their website looks like you have to pay for any info obtained.
2015 Ram 1500
2022 Grand Design Imagine XLS 22RBE

Grit_dog
Navigator
Navigator
May I add, none of this has schitt to do with what tire pressure to run in any given tire today on any truck......

And does anyone care about the Ford Exploder/Firecrap tire debacle from 25 years ago?
2016 Ram 2500, MotorOps.ca EFIlive tuned, 5” turbo back, 6" lift on 37s
2017 Heartland Torque T29 - Sold.
Couple of Arctic Fox TCs - Sold

CapriRacer
Explorer II
Explorer II
Don,

3 thoughts:

1) Included on my web page is an analysis of the pressure spec. Short version: The vehicle's tire pressure spec did not result in an overloaded tire.

2) Firestone's own consultant (Dr. Govindjee) identified the problem in the tire.

3) The tire was recalled, but the vehicle wasn't. If the Feds didn't think the tire was the sole problem, why didn't they recall the vehicle?

Barry
********************************************************************

CapriRacer

Visit my web site: www.BarrysTireTech.com

Perrysburg_Dodg
Explorer
Explorer
CapriRacer wrote:
Perhaps it is time I stepped into this:

First, read my webpage on the Ford / Firestone situation a few years back.

Barry's Tire Tech - The Ford / Firestone Controversy

Summary: The problem was the tire, not Ford's inflation pressure specification.

Second, the pressure listed on the sidewall of a tire is a MAXIMUM - not a recommendation. The tire manufacturer does not know what vehicle a tire is going to go on, so they can not make a universal recommendation that could be printed on the sidewall.

Further, if you ask any tire manufacturer what they recommend for inflation pressure, they will point to the vehicle manufacturer's spec - the one on the doorframe.


Read this. At best Ford and Firestone shared the blame. Most of the tire failures were happening in hot areas.

Here is the smoking gun that puts the blame squarely on Ford.
From the link wrote:
Ford insists that Explorers fitted with Goodyear tires have experienced far fewer tread problems than those equipped with Firestones. Firestone retorts that the same tire that shreds on an Explorer holds up just fine on a Ford Ranger. General Motors last week described the safety of the Wilderness AT tires it puts on pickups as "excellent"—although the No. 1 automaker said it was planning to switch to the Bridgestone brand for some of its vehicles this summer. (Bridgestone owns Firestone.)
The number one cause of tire blow outs is the tire being run at low pressure causing the tire to over heat and blow out.

BTW Copper Tire will tell you what pressure they recommend running their tires at. I know I called them.

Don
2015 Ram 1500 Laramie Crew Cab SWB 4X4 Ecodiesel GDE Tune.