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mhbell's avatar
mhbell
Explorer
Jul 19, 2015

Tire Load and Inflation Table Questions

? Here is my Problem. I purchased 6 Samson GL283A 245/70R19.5 steel belted Radial Tires for my Motor home. The front axle is 7000 Lbs and the rear duals is 11000 Lbs total GVWR is 18000 Lbs I weighed My Motor Home axles on a Cat scale. Front 5520 Lbs Rear duals 10420 Lbs GW 1590 Lbs There is no Load Inflation table for this tire. The max PSI is 119 Lbs The Max load is single 4940 at 119 Lbs, Max load Dual at 119 Lbs is 4675 Lbs. The Manufacturer of the Motor Home states on the tire placard 80 Lbs psi on all tires. The tires are really overkill for the weight of the motor home. Without a Load Inflation table I have put 85 Lbs in the fronts and 85 Lbs in the rear. I made a Load inflation table which May not be accurate or valid. Here is what I did.

I divided 119 Lbs in to the max load for the single tire 4940 Lbs =41.51 Lbs per pound of load so if my formula is correct at the motor homes tire placard of 80 lbs X 41.51 = 3320 X 2 = 6641Lbs for the front axle So I went to 85 PSI which gave me 3520 X 2 = 7056 Lbs.

I did the same with the rear Duals at 39.3 Lbs per pound of load 80 lbs x 39.3 = 3144 X 4 = 12576
I went with 85Lbs in the rear duals = 13362Lbs Which is more than enough for the 11000 Lb rear axle.

Here are my concerns. Not enough tire pressure will ruin the tire. These Tire are 16 ply H rated. To much pressure will wear the center of the tire and give a harsh ride and possible handling problems. I contacted Samson Tire headquarters in Akron Ohio They said not to go below 80 PSI. I just want to know that I am safe with the pressures I have choose to use, and won't damage the tires.
Any Help in regards this matter is appreciated.
M H Bell
:@

13 Replies

  • Follow this chart

    http://www.rvtirepressure.com/assets/images/extrapages/Michelin_Rv_Load_Inflation.pdf

    Heat is the killer...

    I would do 100 psi fronts and 80 psi rears..

    Watch wear and ride and take from there..

    Being a worry wort as I am I would probably do the rears 90 psi..

    Possibly if the ride is fine I may even do 100 psi all around to make it easy... If it were my ride I would feel more comfortable at 100 psi all around.. After a trip I would probably do laser temp tests on the tires to see how hot they get...

    Stay below 80 mph please....

    Id rather have center wear and a cool running tire then risk under inflation and a blowout from heat at 80 MPH.. ( Front)

    Not to scare you but this happens often due to under inflation..... I probably would not of chosen those tires, although I dont have a class A..

    Just stating what I know about tires...

    See how the right front tire blows out abruptly!!!!!! Driver could not react fast enough..

    I always run max inflation when towing... But thats me...

    Class A blow out
  • if your tire company states that 80 lbs is the lowest you can go then work from there. My tire company states the same for me and I run 85. No issues for the past 20,000 miles. All depends on your load.
  • Ivylog's avatar
    Ivylog
    Explorer III
    Tire inflation tables are not linear so your math does not work. I think you will find the table for a Toyo 24570/19.5 H tire will come closer than what you've done.
    80 psi for the fronts and 80 for the rear is already 5 over what's needed.