Inflation Pressure and Speed Rating for ST205/57D15 Special Trailer Tires
Question:
Sir, I just installed 2 new ST205/57 D15 tires on my open 5X8 Utility Trailer. I plan on making a 1400 mile trip shortly from Texas to Michigan. My trailer load will be about 600 lbs. or less. My question is : Should I inflate both tires to the Max. of 50 PSI before I start my trip? Most of my trip will be on Interstate Hwy. What should I maintain as my Max. speed limit for these tires? Thank You for your assistance.
asked by: Dan V
Helpful Expert Reply:
You ask a very important question. Trailer tires should always be inflated to the maximum psi pressure rating that is noted on the tire sidewall. Any trailer tire can deliver its rated weight carrying capacity only when fully inflated to its maximum pressure.
It is never appropriate to under- or over-inflate a trailer tire. Doing so increases the risk of heat build-up and tire failure. As with your vehicle's tires, always check and inflate trailer tires when they are cold.
Trailer tires carry a speed rating that uses a letter designation. For example, a K rating means a maximum speed of 68-mph while am M rating means a maximum speed of 81-mph. Be sure not to exceed the speed rating of your trailer tires. Their speed rating code should appear on their sidewall.
The linked series of articles concerning trailer tires may be of interest to you.
