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Alfred622's avatar
Alfred622
Explorer
Aug 11, 2018

TPMS - Newbie worried about what it shows.... is it OK?

I just added a TPMS to the motorhome. I've inflated front tires to 85# and rear to 95# which is 5# over recommended inflation based on weight they carry.

TPMS reads them cold as:
Front: 84 84
Rear: 94 95 95 94

Temperatures of all tires were close to 73 degrees (ambient)

Then I went driving for 30 miles and I see for PSI:
Front: 94 94
Rear: 105 108 109 105

and for temperatures
Front: 99 97
Rear 100 91 95 102

I'm concerned about the rear tires....

Right rear tire gained 14 PSI and outer 11.
Left rear tires gained 13 PSI and outer 11.


Outer tires ran hotter than the inners

To those with more TPMS experience than me, do these numbers look reasonable to you? If yes, what type of pressure or temperature change would you find significant?

I very much appreciate any advice those much wiser than I could offer.
  • wolfe10 wrote:
    The sidewall information tell you how much air is required to carry XX pounds (the load capacity of the tire).
    Max capacity. But folks on here put more air in ??
  • 2oldman wrote:
    wolfe10 wrote:
    The sidewall information tell you how much air is required to carry XX pounds (the load capacity of the tire).
    Max capacity. But folks on here put more air in ??


    No I don't think so. The pressure on the side of the tire is the max to carry the rated load capacity of the tire. Most folks end up with lower than that number. You shouldn't exceed the sidewall number cold.
  • William B wrote:
    2oldman wrote:
    wolfe10 wrote:
    The sidewall information tell you how much air is required to carry XX pounds (the load capacity of the tire).
    Max capacity. But folks on here put more air in ??


    No I don't think so. The pressure on the side of the tire is the max to carry the rated load capacity of the tire. Most folks end up with lower than that number. You shouldn't exceed the sidewall number cold.


    Correct.

    Only reason to consider (improperly) doing this is that the actual weight exceeds tire capacity. If that is the case more air is NOT the answer. Selecting a tire with a higher load range IS the answer.
  • William B wrote:
    2oldman wrote:
    wolfe10 wrote:
    The sidewall information tell you how much air is required to carry XX pounds (the load capacity of the tire).
    Max capacity. But folks on here put more air in ??


    No I don't think so. The pressure on the side of the tire is the max to carry the rated load capacity of the tire. Most folks end up with lower than that number. You shouldn't exceed the sidewall number cold.

    Partially correct.
    The number on the side of the tire is the MAXIMUM load that the tire can carry and the air pressure is the MINIMUM needed to carry that max load. In other words, if you put in less than the printed air pressure, the load capacity of the tire will go down.
    Also if you have to carry the maximum allowable weight on a tire, and you inflate it to the Minimum tire pressure as printed on the sidewall, the tire pressure will increase as you drive and the tire heats up. This is all well within the design parameters for the tire.
    One other things is that if you go to a higher load rated tire like from an F to a G rated tire, and you plan on carrying the SAME load that is within the specs of the F rated tire, the tire pressure will be the SAME with the G rated tire.
  • And don’t forget to find out max inflation rating for the wheels. I ran into that on my old F53 chassis. Went to Gs but rims were rated for 80 psi. I cheated and went to 90.
  • And, for both tire and wheel, the PSI is cold.

    Cold is defined as at ambient temperature before driving, tire not in sun, etc.

    Both tire and wheel manufacturers KNOW and take into consideration the PSI increase with temperature increase. After all the Ideal Gas Law has been known for a very long time and most tire/wheel engineers knew about it from high school chemistry/physics.