Trailer Tire and Rim Pressure Capacities and Correct Inflation

Question:

Bought a 5th wheel equipped with 14 ply load range G tires max cold PSI 110. Rims also have a 110 PSI rating. Question, the person I bought the camper from said they put 90 PSI in tires so when they warm up the increased PSI will not go above 110PSI. Is this correct? Or should I fill tires to recommended cold 110 PSI? Will the rims handle the increased pressure as they get warmed up? My camper fully loaded weights 15,000 lbs.

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Helpful Expert Reply:

In a trailer tire the limiting factor for PSI pressure is usually the valve stem. Different valve stems handle different pressures. Some rubber stems like # AM20903 are good to 65-psi while others like # AM20904 are good to 80-psi or to 100-psi as with # AM20907. Metal stem # AM20906 can handle pressure up to 200-psi. Usually a rim itself will handle any pressure required by the tire sizes that fit it.

Any trailer tire will be able to meet its maximum weight load rating only when inflated to its specified maximum psi pressure. With very few exceptions trailer tires should always be inflated to the maximum psi pressure that is noted on the tire sidewall. One exception is Goodyear, which for its Endurance Special Trailer tires does actually test load capacity at various inflation pressures. The linked chart shows how the weight capacity for various sizes of this tire changes with inflation pressure. Unless the maker of your tires provides documentation like this you should ALWAYS inflate to the maximum pressure shown on the tire sidewall.

It is normal for a tire's temperature and pressure to vary. Ambient temperature, driving speed and the weight load on the tires all factor into how warm it will get in use. Even if a tire is just sitting still, an outside temperature change of 10 degrees F will result in about 1-lb pressure change.

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Adam R

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