Determining Proper PSI of Trailer Tires and Troubleshooting Inside Tread Wear

Question:

I bought a new trailer that went through a set of tires in one summer 2 times a week going about 80 miles round trip. I bought 2 more tires and read about tire inflation so I set the tires to 15PSI. I have a small boat on it totally loaded which weighs about 200 lbs. The trailer is good for 2000 Lbs. So I set the PSI to 15. Now the new tires are wearing better than before but I have inside wear. Camber is off or what? Never hit anything with the axel. I looked at the Axel and it is bowed upward. Tires are ST175 80 R13. I was thinking of going to a 14inch rim and tire but is that a good idea?

asked by: Richard L

Expert Reply:

Most trailer tires are designed in a way that they should always be inflated to the max psi as listed on the tire's sidewall, regardless of the trailer's weight. This is different from standard passenger vehicle tires, as trailer tires are constructed with stiffer sidewalls capable of handling heavier weights.

I highly recommend checking the sidewall of your trailer tires for this number. The exact max psi for your ST175/80R13 tires will differ depending on its load capacity but it's definitely higher than the 15 psi you have been setting them at. Just as an example, the lowest rated ST175/80D13 tire we have available, the Load Range B Kenda # AM1ST74, has a maximum load of 1,100 pounds at 35 psi.

Inner tread wear on a tire is also an indication of the axle/tires being overloaded. This falls in line with the tires being under-inflated as filling them to below the max psi essentially reduces their capacity to an unknown number.

As long as you have the fender and trailer frame clearance to account for a larger tire, you could certainly move up to a larger 14 inch combo but I'm not sure it's the solution to the issues you have been having. The main cause for tire failure is excessive heat, which can be caused by under-inflated tires, overloading their capacity, or traveling faster than their speed limit.

I have attached a couple articles on trailer tires that you might also find helpful.

expert reply by: Chris R