Front tire pressure?

[Ramblin__Ralph]

Rig: 2006 GMC 2500HD with 2001 Lance 845 camper. Tires are Michelin LT265/75R16.

My door jam plate says:
Front 53 psi
Rear 80 psi

I have been airing up to:
Front 60 psi
Rear 80 psi

My axle weights with camper and loaded for long term travel are:
Front 3350 lb
Rear 5800 lb

That's just under my GVWR of 9200 lb.

Last summer I had my tires rotated when traveling and the shop said I had wear on the front (cupping IIRC) indicating not enough pressure. So they boosted the front to 70 psi (or more).

I'm getting ready to hit the road again for several months. What is the consensus on proper front tire pressure?

Thanks,

[stevenal]

https://www.michelintruck.com/reference-materials/manuals-bulletins-and-warranties/load-and-inflatio...

[JIMNLIN]

My old '01 2500 Dodge/Cummins came with LT265/75-16 E. The silly tire placard said 50 psi in the front and 80 in the rears.
As I drove the new truck home (165 miles) I noticed the front tire plowed around corners. The back of the truck rode like a hay wagon. This truck had 4080 lb on the front axle and 2780 on the rear with no load.
I ran a chalk test on the fronts and found 65 psi worked best (2280 lb pin weight in the bed) along with no more plowing around corners.

No more weight than the 6.0 weighs IMO 70 lbs in the front may be a bit much. At 3350 lb front axle load = about 1700 lbs per tire. 60 psi sounds about right.

Agree with others on tire cupping issues.

[jadatis]

Your cupping is not from low pressure, though that can make it worse.
Alignment, bad shockbrakers( already mentioned) and someting loose are the real cources. Even going to wider tires and not compensating that in the alignment, has influence. Even the weightdivision here can havevits influence. Higher pressure then gives less cupping , but your fillings come out if your teeth.

[jadatis]

Answer to above
What you give is lineair calculation, and is not bad .
Official European calc is
( A/B) ^ 1.25 x 80 = psi.
The ^1.25is to the power, like square is ^2, and root is ^0.5.

But you dont add 10% first . Wich is for R/L unbalance, but also for pressureloss in time or misreading or inacuracy of pressure device.
Then it would give lineair 3190/3420 x 80 = 74,61 psi , so lineair calc comes to about the same as my extra safe calc is 75 psi.

Must have missed something , where did you get the 3472 maxload from?

[towpro]

here is the formula.
(A/B)x80=PSI
A is true weight on Each tire
B is max load on tire (marked on sidewall)
C is max PSI (marked on sidewall)
Hear is your rear calculation.
(2900/3472) x 80 = 66.82 so I would run 70

/ means divide by

But what your saying your front weighs appears to be a little low to me, or maybe its just me from years of driving Cummins.

[jadatis]

Filled in in my made motorhome-calculator, it comes to F 41 psi , R 75 psi.

Googled your sise tire to be loadindex 123 for single load is maxload 3420 lbs, E- load AT 80 psi.

Front that low??!! Yes , search the GAWR's, and you probably discover that rear is already overloaded, and front still have a comfortable reserve.
The vehicle-maker calculates for GAWR's ,and for that it probably needs 60 psi.

Are these the original sises and loadrange ( E- load / LRE AT 80 PSI) . If the weights are right, and tirespecifications I found too, especially the low front gives better comfort and gripp, but you yust gotten used to the kidney-belt:B

My calculator adds 10 % to the given loads( so yoy weighed ? !), and then calculates the pressure with a formula that gives higher pressure then the official European, wich America uses too but only for P-tires since 2006.
So my calculation is certainly not to low.

Determining the real weights is the most tricky part, in this all, but you weighed fully loaded, so also all the persons? , wich gives you already bonuspoints.

[S_Davis]

You have your axle weights why not go with the inflation table for your tires?

[Grit_dog]

60psi should be plenty of pressure for your setup. Check a load inflation chart but probably good for at least 2500lbs per tire
Many causes of cupping, feathering of tire tread and not all of them indicate anything is wrong.
Infrequent rotation
Curvy roads
Too low of pressure, maybe for the sway with a camper or in general
Bad shocks
Bad ball joints
Too much too little camber
Bad alignment
Not tailoring the rotation to how the tires are wearing.

If the truck is in good alignment and good condition then it could be just wear.

[MORSNOW]

BradW wrote:
When we hauled our Lance on our SRW trucks, I had less sway when we ran the front tires at 80 psi. Tires are part of the suspension and when the rear rocks side to side, the front does also. So anything you do to stiffen the front suspension helps, even though 90% of the added load is on the rear tires.

I honestly never thought about the front tire pressure and sway before due to almost all of the weight is added to the rear. Hmmm

[BradW]

Ramblin' Ralph wrote:
What is the consensus on proper front tire pressure?

Thanks,

Consensus on the TC Forum? 🙂 🙂 🙂

When we hauled our Lance on our SRW trucks, I had less sway when we ran the front tires at 80 psi. Tires are part of the suspension and when the rear rocks side to side, the front does also. So anything you do to stiffen the front suspension helps, even though 90% of the added load is on the rear tires.

bradw

[Lwiddis]

“Tires rotated every 5K with essentially similar wear.“

That’s the key you are doing right, sbryan, IMO.

[d3500ram]

The truck's placard should have tire PSI recommendations for loaded and unloaded conditions.

When I was fully loaded, I set the front to the truck mfgr laden recommendations while the rear was at the tire maximum. Under no conditions should the tire mfgr PSI be exceeded.

If your tires are "cupping" then it is generally due to bad shock absorbers.

[sbryan]

My F350 says for a fully loaded truck 65 front and 80 rear. It has worked well for me for the last 35,000 miles with the camper on board. Tires rotated every 5K with essentially similar wear.