Correct Tire Pressure for ST235/80R16 Trailer Tires

Question:

I am running a ST235/80R16 trailer tire. Filling it to 80 psi cold. I have a tire pressure monitoring system to watch the tire pressure. What is too high/dangerous for pressure readings?

asked by: Jim C

Helpful Expert Reply:

Special trailer tires should always be inflated to the maximum psi pressure figure shown right on the tire sidewall.

Always check pressure and inflate as needed with the tires cold, such as first thing in the morning. As you drive and as the daytime temperature increases the pressure within the tire will then increase from the cold starting pressure but this is normal and does not require you to compensate for it. Each 10 degrees of Fahrenheit ambient temperature change equates to about 1-lb of pressure change.

Not all ST235/80R16 trailer tires require the same inflation pressure. For instance, the Westlake Load Range E tire # LHWL401 require a cold psi pressure of 80-psi while the Load Range G tire # PRG80235 requires a cold pressure of 110-psi. The more weight a tire is rated to handle generally the more pressure it will require.

Trailer tires of any given size also vary in their rated maximum operating speed. Tires have a letter code rating for speed too, just like they do for weight capacity. Speed rating J means 65-mph maximum; speed rating L means up to 75-mph and speed rating M means the tire is safe for operation up to 81-mph.

Tire selection should me made so that you have a safety margin in both the weight and speed ratings. Too much weight or driving too fast both cause excess heat build-up in a trailer tire and that heats is what tends to cause failures. You should not have to worry about the readings from your TPMS so long as you observe correct cold psi pressure and observe weight load and driving speed limits for your specific tires.

expert reply by: Adam R