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 > E load tire pressures for daily use and how I came to it.

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TNrob

East Tennessee

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Posted: 06/02/16 05:18pm Link  |  Quote  |  Print  |  Notify Moderator

I used Google to find a Firestone commercial tire loading and pressure pamphlet.

This is the PDF page that I found.

According to it the minimum tire pressure required to set both front and rear axles to 5360 pounds for a LT275/70R18 (my Ram 2500) is 50 psi.

I went through weigh tickets from my existing TT and my old 1500 and found that the most the TRUCK ONLY rear weight above daily use on any trip was 620. The most the TT tongue weight ever scaled with fresh tank full and a load of baggage and food was 700 pounds. So I add 700 heavy tongue to bed full of firewood and come up with 1320. I round to 2000 with heavy duty new truck because I can.

New truck scales at 3000 rear and 3960 front, full of fuel and all sorts of truck stuff like tow straps, tie downs, jumper cables, etc., and my emergency bug in backpack full of too much stuff to recount--but no she or me.

I arbitrarily took new truck rear and added a rounded up 1000 pounds each for both excessive cargo plus excessive tongue weight and came to 5000 pounds rear axle. I looked at the table and found that 50 psi in the rear tires would readily accommodate 5360. That's 10 psi below factory recommended 60 psi for the front axle--whether loaded heavy or light--though not quite enough to carry the factory front axle rating of 5500 pounds.

Front axle is only 4000 pounds, and even heavily loaded (for my purposes) with 2000 pounds of tongue and other cargo, with even half of that distributed to the front axle rather than the rear; front axle will never carry more that 5000 pounds.

Again consulting the Firestone pamphlet, I determine that 50 psi in all four tires will more than cover anything I throw at my truck tires whether running light to work and back, hauling a big load of home improvement from a box store, or pulling my current camper loaded even to its GVWR of 6800 pounds. It's overkill, even.

TPMS system be danged. I will deflate my tires to 50 psi all around before I leave for work in the morning. At 50 psi it will be safe to do all I ever ask of the truck or the tires, and after I scale it a time or two with camping cargo loaded and hooked up I'll adjust it from there if I decide it might be lowered. If I ever find the perfect 5er I'll up it to 80 in the rear and 60 in the front for towing.

FCA will get a nasty-gram this week on the hazards of over inflated tires and the willful negligence required to put millions of such vehicles on the road in an effort to avoid a few extra paragraphs in the owners manual designed to educate owners on the proper management of tire pressure.

If anyone finds a flaw in my above inflation logic, please let me know so that I can better adjust both my understanding and my tire pressures.

And before I make an *** of myself in my nasty-gram to Ram.

Cheers from East Tennessee.

* This post was edited 06/02/16 05:33pm by TNrob *

spoon059

Just north of D.C.

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Posted: 06/02/16 06:19pm Link  |  Quote  |  Print  |  Notify Moderator

Sounds like you are spot on. I always wondered why Ram demanded 80 PSI for the TPMS on the 2500. At 80 PSI those tires are rated for 7000 lbs I think... WELL over the axle rating and WELL over the derated 10K GVWR.

I think the older Rams had a switch for loaded vs unloaded driving. It sounds foolish to me. I would LOVE to hear their logic for this...


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2015 Jayco 29QBS

blt2ski

Kirkland, Wa

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Posted: 06/02/16 07:21pm Link  |  Quote  |  Print  |  Notify Moderator

Hmmmmmmm..... been there doing this for close to 30 years with 25/35 series pickumups. This is new? My current regarding cab 2500 weighs all of 5600 with me and a full tank of gas. Take me out, remove pipe rack, down below 5000 lbs empty. I could get away.with lr d tires most of.the time. UNTIL I come out of a rock quarry three weeks ago with 5600 lbs of rock in the bed, 10800 gvw!

Marty


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00 Chev C2500, V5700, 4L80E, 4.10, base truck, no options!
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mrgrim007

CO

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Posted: 06/02/16 09:25pm Link  |  Quote  |  Print  |  Notify Moderator

I just got finished setting up my new TPMS on my Suburban tonight. Door jam says 50 PSI front, 80 rear. So that's what I put them at. Did some Googling and some people go with the door jam, others don't. We're headed to Wyoming next week on a trip (not towing anything) and I plan on keeping the PSI where it's at...mostly because that's what the door jam says.

But now after reading this I'm reconsidering...


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mowermech

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Posted: 06/03/16 05:29am Link  |  Quote  |  Print  |  Notify Moderator

IMO, one should always consider the tread wear patterns when determining the correct tire pressure.
If the tread is wearing mostly in the center, reduce the pressure.
If the tread is wearing mostly on the edges, increase the pressure.
If the tread is wearing evenly, the pressure is just right.
What is important is the "contact patch", the size of the patch where the rubber meets the road. That patch should always be as large as possible, to ensure safety. That can only be achieved with the correct tire pressure for the existing load!
Tire pressures shown on the door jamb sticker (at least the ones I have seen) show the pressures needed for maximum GVW or GAW. If the rig isn't loaded that heavy, you do not need that pressure!


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Hondavalk

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Posted: 06/03/16 05:45am Link  |  Quote  |  Print  |  Notify Moderator

X2 with mowermech. A primitive but workable way to check is to pour some water in front on a tire and observe the the tread pattern it lays down on dry pavement.





TNrob

East Tennessee

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Posted: 06/03/16 06:59am Link  |  Quote  |  Print  |  Notify Moderator

Now that they're adjusted I'll continue to watch tire wear and see how it's working. At factory setting both front and rear, especially rear, were wearing in the center. Almost an inch of the outside tread on the rear hadn't ever touched asphalt in over 1400 miles.

TNrob

East Tennessee

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Posted: 06/03/16 10:10am Link  |  Quote  |  Print  |  Notify Moderator

This is the letter I sent to Ram. I'm sure it will result in nothing.

The recommended pressure for front axle tires is 60 psi, with axle load rating of 5500 pounds. The recommended pressure for rear axle tires is 80 psi with axle rating of 6500 pounds. According to Firestone, the manufacturer of the factory installed tires, the pressure required for even rear axle max load weight rating is 70 psi. For normal load of 3000 to even 5000 pounds on the rear axle, 50 psi is more than adequate according to Firestone. At 50 psi a load range E tire can carry 2680 pounds, giving an axle capacity of 5360--well over the daily weight for most non-commercial drivers.
Ram has previously recommended two tire pressures for the 2500 series, with a light load pressure and a heavy load pressure. On previous models Ram even provided owners a switch to toggle between loads according to their present needs. This switched the TPMS from one warning point to another so that owners benefited from the low pressure warning system whether lightly or fully loaded, and allowed for proper inflation rather than over inflation during light duty operation.

In subsequent years the toggle was removed, but owners could still have their servicing dealership adjust the computer set points to a proper daily pressure below the factory set points. I attempted to have this done at my dealership and their effort was unsuccessful. It appears that Ram has locked the computer and disabled any reprogramming of the low tire pressure set point.

Over inflated tires not only wear poorly, they are dangerous. Over inflation greatly reduces the tread patch that contacts the road surface, causes excessive and unnecessary bouncing, increases the risk of tire damage from pot holes, and basically provides for an unsatisfactory driving experience. I'm certain the engineers at Ram are aware of these facts because in previous years they provided for BOTH light and heavy service inflation. It is utterly unacceptable and grossly negligent for Ram to recommend, and basically require, that owners operate their 7000 pound vehicles on tires inflated to carry over 13000 pounds. Ram is causing possibly millions, certainly hundreds of thousands of truck owners, to unwittingly endanger themselves and others on highways around the country with these dangerous tire inflation recommendations.

I can think of no reason beyond laziness and penny pinching that might induce a manufacturer to so grossly endanger the lives of their customers and their families—not to mention everyone else that shares the roadways with them. Ram MUST immediately notify their customers of the unsafe driving conditions they have been knowingly subjected to by their trucks’ manufacturer. Ram MUST alert dealerships and issue a “flash” for them to install on trucks that have been delivered to customers in this unsafe condition.

I await a response.

wanderingbob

monticeeo, fla

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Posted: 06/03/16 04:17pm Link  |  Quote  |  Print  |  Notify Moderator

I believe on my Ram 2500 , 2014 , that the TPMS system will learn the pressure that I am satisfied with and adapt the dash to my satisfaction . When I make a radical change in tire pressure the display will flash until I have stopped and started a few times . I think that I could just turn key off and on several times and do the same . I like it to flash as it bothers my wife !

Grit dog

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Posted: 06/03/16 04:28pm Link  |  Quote  |  Print  |  Notify Moderator

mrgrim007 wrote:

I just got finished setting up my new TPMS on my Suburban tonight. Door jam says 50 PSI front, 80 rear. So that's what I put them at. Did some Googling and some people go with the door jam, others don't. We're headed to Wyoming next week on a trip (not towing anything) and I plan on keeping the PSI where it's at...mostly because that's what the door jam says.

But now after reading this I'm reconsidering...


Reconsider, unless you want a rough ride and potentially unnecessary center tire wear.
the 50/80 is for max axle loading or gvw or something more than empty.
Seriously.


"Yes Sir, Oct 10 1888, Those poor school children froze to death in their tracks. They did not even find them until Spring. Especially hard hit were the ones who had to trek uphill to school both ways, with no shoes." -Bert A.

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