How Does Temperature And PSI Level Affect Trailer Tires

Question:

I have a 5th wheel 13k lbs running 14 ply radials I monitor them with a TMPS, on a 95° day doing 65mph my tire pressure increases about 18-20 psi, temp about 120°. I inflate my tires to 90psi so they max out at recommended 110psi. Ive had blowouts in the past with 10plys inflating starting out at cold max psi. My question is running 20psi over max cold psi a problem??

asked by: Steve

Expert Reply:

For every 10 degrees the temperature for the tires rise the psi will increase by 1psi. The typical tire should run about 158 degrees Fahrenheit when going down the road, but this can vary greatly depending on the weight of the trailer, how fast you're traveling, etc. You should always inflate the tires to the max cold psi otherwise you're in a gray area when it comes to capacity.

The capacity of tires, like the # AM10501 you were looking at, are set for the cold psi maximum with the knowledge that the tire's temp will rise and increase the psi. The actual psi maximum for the tire will be much higher but isn't listed by the manufacturer. Going under the cold psi maximum rating will reduce the load capacity of the tire and can cause it to wear unevenly and or blowout, depending on the load.

If you had a tire blowout in the past because the psi got too high I'd say you were underrated in load range and would need to switch to tires with a higher range while still keeping the psi at the cold max psi rating. I would also check your TPMS system since you'd have to have the tires raise 200 degrees from the temperature they were at cold to increase 20 psi. Most tires have a maximum temperature of 198 degrees, so I'd double check that the psi rating your seeing isn't actually the temperature.

expert reply by: Kevin C