Tire pressure

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I pull a 30. 5 fifth wheel with my eth shortbed, I was wondering what air pressure I should have in my front and back tires? I know what the placard says in the door, but that amount seems a little excessive. My hitch weight empty is 1600#. What do you all run in your tires?

 

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Pulling my 30ft fifth with 2 slides its
60lbs front and 80lbs rear

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01 Ram 2500 QC LWB ETC
Dark Garnet/Driftwood
All options except heated leather seats added Smittybilt SS Side Bars and EGR Bug Guard,ARMA Coating Bedliner
And I Love it!

 

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The listed pressures not only seemed excessive, but when inflated to 65 psi, empty truck bounced all over rough asphalt roads.

My tire size does not match the plate info.

I called Michelin Customer Service. They asked about load I was carrying (30' 5th wheel) and suggested 50-55 psi. I'm running 55 psi. Michelin LT 265R75-16.

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"Red Rage" - 2001 2500 SLT 4x4 QC Lowered Rear End 2. 5" 5spd, 4. 10 K&N Stock Replacement - 7800 miles and counting! 30' 5th Wheel

 

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Go to the web site or call customer service for whoever made your tires and get the load/tire pressure chart for the exact tires you have. No one can give you accurate advice without knowing exactly what tire (Brand, type, Load Range, size) and exactly what the weight is that the tire will carry!

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1995 2500 SLT Club 4x4, auto, 3. 54, 3300 pound Elkhorn slide in camper, AirLift air springs, Ricka dual wheel adapters, K&N, DC tow hooks, Rancho RS9000, Hellwig rear sway bar.
97,000 miles and counting.

 

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Here is some good info on tire pressure. Someone else posted it some where, I don't remember where I got it.

Find a truck scales and get your truck weighed, The scales should tell you your front, rear & combined weights. then look at the rating on your tires. (Should be something like 3042 @ 80 psi for singles and different # for duals)
Take your axle weight and divide it by the # of tires you have; then divide the per tire weight by the rating and multiply that by the max tire pressure (80 psi).
For example, my 2500's rear axle weighs 3,300 lbs and my tires are each rated at 3042 lbs @ 80 psi. To calc the tire pressure; (1650/3042) x 80 psi = 43. 4 psi. The front axle weighs 4,300 lbs, so the tire press is (2150/3042) x 80 psi = 56. 5 psi.

Barry Horner
Lake Forest
Orange County, Ca

2001, SLT+, ETH, 6 speed, White quad cab, short bed, Sport, 2wd , 3:54 anti spin, Camper Special with trailer tow, 16x8 Forged Aluminum with 265x75 tires, Fog lights, Audio controls steering wheel mounted, AM/FM cassette with CD, Travel Convenience group, Keyless entry with remote, Leather agate heated seats. Line-X bed liner. ARE LS 2 taunau cover. Pillar mount boost and EGT.

 

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I've found that for the best ride my fronts need to be 15 psi higher than my rears,that goes right along with Barry's formula above.

 

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The math in Barry's post makes sense. I agree that the formula applies to figuring the true pressures for actual loads.

But how does the variation from load rating pressures relate to tire wear? Another way . . Is 45psi in the rear tires of an unloaded 2500 . . max rated for 80psi . . under inflating the tire? Doesn't an under inflated tire wear prematurely?

How long will a tire ran at max pressure last compared to one air'd up based on the above formula?

I have the Michelin LTX A/S 245 75r 16's on a long bed quadcab 2500 2wd

Michael

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00 Driftwood 2500 ST QC ISB LB 5spd 3:54 LSD Tow & Camper Groups

my photos

 

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Michael

Don't confuse Max pressure as a must run pressure. Truck tires are designed to have tire pressure adjusted for the load. A auto tire is designed among other things for confort. The load on a passenger tire is relatively constant and the tire pressure range narrower. If you run max in the rear empty, I assure you that the tire life will be half of what it would be properly adjusted for load. Under inflation will also increase tire wear. I would guess under 30lbs. Use the formula and you will do well.

Barry Horner
Lake Forest
Orange County, Ca

2001, SLT+, ETH, 6 speed, White quad cab, short bed, Sport, 2wd , 3:54 anti spin, Camper Special with trailer tow, 16x8 Forged Aluminum with 265x75 tires, Fog lights, Audio controls steering wheel mounted, AM/FM cassette with CD, Travel Convenience group, Keyless entry with remote, Leather agate heated seats. Line-X bed liner. ARE LS 2 taunau cover. Pillar mount boost and EGT.

 

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Thanks Barry . . this is very intesting stuff.

When the truck was delivered it had 32lbs of air in them. Im sure this was for the ride factor.

Since I am new to heavy duty trucks . . I air'd them up per the sidewall data . . 80lbs all the way around. Obviously . . a noticable difference in ride and control. rear a little bouncy

I've lowered to 60 this afternoon . . all the way around. Although not the 55 front/45 rear as calculated . . its an improvement in control.

I'll lower the rears to 50 and give that a try . . Thanks again!

Michael

 

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Michael

I am running 60 front and 40 rear unloaded. This seems to work out well for me. My tires are the 265x75 Michelin's supplied as new on 8 inch wheels.

Barry Horner
Lake Forest
Orange County, Ca

2001, SLT+, ETH, 6 speed, White quad cab, short bed, Sport, 2wd , 3:54 anti spin, Camper Special with trailer tow, 16x8 Forged Aluminum with 265x75 tires, Fog lights, Audio controls steering wheel mounted, AM/FM cassette with CD, Travel Convenience group, Keyless entry with remote, Leather agate heated seats. Line-X bed liner. ARE LS 2 taunau cover. Pillar mount boost and EGT.

 

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And don't forget to read the tire manual that came with the truck. It suggests that you add 10 PSI if you are going to be running over 65 MPH for any 'extended' period of time. The extra pressure helps ensure that the tires will be running cool enough.

Proper inflation should ensure that the tread makes full, even contact with the road (assuming normal, on-road driving habits #ad
). It also helps ensure that the tire remains reasonably cool.

If your tires are underinflated, the tread may not contact the road properly and the tires will become hotter; excessive heat is known to cause catastrophic tire failure. If your tires are overinflated, they will run cooler, but will not contact the road properly. Improper tread contact results in lowered traction. (Hmmm. Might this be part of HVAC's hookup problem in 4th? #ad
)

Use the formula previously posted. And add 5-10 PSI if you'll 'normally' be running 65 MPH or over. But I don't think you should exceed the tire's max rated pressure.

Fest3er

 

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Although under gross underinflating is bad for a tire (heat), running the tires at the max pressure will wear them out faster. Take a passenger car to a tire shop and watch them inflte the tires to 35lbs. (max press on most pass. tires). Why? They will wear out quicker at max pressure, as opposed to the pressure for the load. Too low of a pressure will also cause premature tire wear, but overinflation is much more common and detrimental. Experiment with them. I once owned a 91 F-250 ( I know that is a 4 letter word) and I kept the tires inflated to 80 psi. The tire man suggested that I air them down to 50-55 psi. I did and the comfort of the ride increased 100%. I wouldn't go below 50 psi on stock size tires; however, once you get into 285's or larger you can comfortably go to 30 psi or so. And reme,ber, all these figures are for empty weight, don't overload your sidewalls.
The best solution is to call the tire manuf. and tell them your tire size and curb (or gross) weight and go with their reccomendations.