Tire pressures vs chart

[tarnold]

On CAT scales, my e350 loaded is 10,380. 3280 front, 7100 rear. Door sticker says 65f/55r. Duals on rear. Per Michelin chart a 225/75/16 s/b 55 rear as is door sticker for my weight. BUT the chart for single axel, 2 tires is 40 psi. For my front weight of 3280. That can’t be right. What am I miss reading?

[Grit_dog]

Cummins12V98 wrote:
I run 10 over on my front tires based on the fact turning removes some tread on outer edges.

This^. Tailor your pressures and rotations to load and wear, not some chart or tire monkey that says you need ___psi and an X rotation. You’ll get a better ride and better tire wear.

[Grit_dog]

Atlee wrote:
The Ford placard on the door of my F150 indicates 55# front, and 60# rear. So, that's what I keep in my truck. Have 68k miles on the OEM 17" LRE BFG tires, half of which is towing.

They have always worn evenly across the tread. I've also rotated them every oil change (5k) or every other oil change (10k).

That’s because those are Rugged Trails or whatever they’re called. Those tires are hard as a rock and wear like iron.
However when not towing, you could run 30-35psi all around and still get good tire wear and not feel like you’re in a F250.

[Atlee]

The Ford placard on the door of my F150 indicates 55# front, and 60# rear. So, that's what I keep in my truck. Have 68k miles on the OEM 17" LRE BFG tires, half of which is towing.

They have always worn evenly across the tread. I've also rotated them every oil change (5k) or every other oil change (10k).

[Cummins12V98]

I run 10 over on my front tires based on the fact turning removes some tread on outer edges.

[wilber1]

CapriRacer wrote:
I want to emphasize again: The tire load charts are MINIMUMS, not recommendations. Even the OEM's specify more pressure, because that is just good engineering practice.

X2

That’s why the charts say they are “load limits”

[CapriRacer]

Cummins12V98 wrote:

CapriRacer wrote:
I want to emphasize again: The tire load charts are MINIMUMS, not recommendations. Even the OEM's specify more pressure, because that is just good engineering practice.

GY Tech says to add 5psi to what the chart says based on ACTUAL tire load.

I prefer 15% more load carrying capacity. That's usually about 10 psi.

[Cummins12V98]

CapriRacer wrote:
I want to emphasize again: The tire load charts are MINIMUMS, not recommendations. Even the OEM's specify more pressure, because that is just good engineering practice.

GY Tech says to add 5psi to what the chart says based on ACTUAL tire load.

[Cummins12V98]

"What would be some of your specific reasons? "

Since "YOU ASKED" I will give my reasons for what i do.

First know your actual axle weights, truck and RV loaded and not. EVERY tire size and load range has a "load/inflation" chart.

For trailer tires. MOST RV's base their weights on the carrying capacity of the tires. So based on that the full "MAX PSI" is required. "SOME" of the RV's do NOT need to be aired to their MAX, example a DRV triple axle with 17,000# axle weight will only have 2,833# on each tire. The chart for that tire lowest pressure is 90 and will carry 3,695#. I would run that trailer tire at 90# for better ride braking and tire wear.

When going from "E" tires that were at their max weight capacity to "G" the pressure requirement was the same at 80 but i ran 85 per GY Technical Support. Had the tires in for many thousands of miles with perfect tread wear across the tire.

I have basically done the same on my truck tires. I would run 45 in the rear and 72 front on my 2500 4x4 RAM/Cummins unloaded and only raise the rears to 80 when towing. Perfect tread wear, fetter ride and stopping power. YES for a FACT I made 120K on a set of Michelins and 100k on BFG's. 45 was more than I needed empty but enough for the loads I carried for Construction.

On my DRW I run 35 empty rear and 80 front always. Rear loaded to RAWR I run 65.

These tires had about 38K. Third pic BGF with at least 100k. Bought the tires and wheels off a 2010 RAM with 40k. Put on my 98 2wd Cummins/RAM. Added at a minimum 60k at time of pic.

[CapriRacer]

I want to emphasize again: The tire load charts are MINIMUMS, not recommendations. Even the OEM's specify more pressure, because that is just good engineering practice.

[tarnold]

Op again. To the last question, yes more things aft. Water tank centered between axels, gen over rear axel, bath behind axel. This is a Chinook, all one piece fiberglass shell.
Will try 60lbs in front and stick to 57 in rear. Just looking at deflection sitting on pavement, can tell tire store have them all over inflated. Rode hard coming home.

[Grit_dog]

You're not missing anything. 3200 lbs on the front axle is around 1/2 of what 2 load range e little tires like you have are rated for. Hence the 40 psi MINIMUM pressure for 16xx lbs per tire. (Rvnet number crunchers, I did not look this up, so don't not pick the fine print. I'm talking rough numbers)
As said, the door sticker is a "safe" all around pressure.
Nothing to worry about, however, I'd run 10 psi above the minimum calculated pressure to help with cornering/handling.

Don't worry though, the peanut gallery will try to help confuse the issue.

My casual observation is (assuming this is a class C camper) that the front end seems pretty light. Is there a bunch of weight aft, taking some weight off the front axle?

[mountainkowboy]

Cummins12V98 wrote:
I use the charts and add 5psi for rears and 10psi for fonts.

Same as you but reversed....my TC only adds 100lbs to the front axle. Empty I run 45psi.

[wilber1]

Tire manufacture's charts are the maximum load for that pressure, not recommended pressures because they don't know what vehicle they will be mounted on. Vehicle manufacture settings are a compromise and take in account load, ride, handling and braking for that vehicle.

I like to have some extra load capacity in my pocket as well.

[time2roll]

Cummins12V98 wrote:
I use the charts and add 5psi for rears and 10psi for fonts.

+1 unless there is a reason to run the absolute minimum.