Uneven trailer tire wear

I have a tandem axle 1991 Titan stock trailer (2 horse size). I bought it used and had the original tires on for at least 5 years (I haul less than 5K miles/year). They were actually not in bad shape tread-wise when I got a replacement set of cheap foreign tires. Within months, I noticed the center tread on all the tires wearing badly. Since this part of the tread seemed to stick out more than the rest of the tire, I went back to the tire place (my local farmer’s co-op), which tried to tell me my trailer axles must be bent. Less than a year ago, I decided just to get new tires (another foreign set, but not the cheapest, and trailer-rated), and already the center tread on the front tires is almost gone, although the wear is not quite even around the entire tire circumference. The outside tread still seems ok on both sides, and the rear axle tires are fine. I don’t THINK I overinflate. I test pressure cold, trailer empty, and inflate to the trailer mfg suggested pressure of 60 psi. The trailer appears to ride level on the hitch; it does not slant forward. Do I need to test pressure with the trailer loaded instead? Could something wrong with my trailer be causing this? Surely even cheap tires should last longer than 5K miles. Why is this happening now, when the original tires lasted FOREVER?

Are your current tires meant to hold that much air pressure? Check the sidewall to make sure you are not way over the maximum inflation pressure. Many trailers come originally equipped with bias ply tires (which seem to last forever anyway), and if you installed radial tires and have them inflated to 60 psi, they may be grossly overinflated for the design of the tires. This would definitely cause them to wear out very rapidly in the middle. If you are running radial tires with a maximum inflation pressure of, say, 44 psi, try 30 or 35 psi and see how they wear.

If your trailer tires need 60 lb. of pressure you need commercial grade tires made for the pressure and load). The load rating of the tires should exceed the GVW of the trailer (including load. And tandem axle trailers are balanced to keep a positive tongue weight on the tow vehicle so the front axle will carry more of the weight than the rear.
Loar up the trailer with the heaviest load you carry and go to a truck scale and weigh just the trailer and then just one axle to see what your load is on each tire.

Start by posting the entire number on the tire.

One often overlooked item on trailers is the bearings. I admit I don’t check and the ones on my trailer as often as I should, but I have a utility trailer I use for taking my motorcycles to the shop, so I don’t put a lot of weight on it. When is the last time someone checked, lubricated, or replaced the bearings on this trailer?

I inflate the tires on my trailer to 60 PSI, and I don’t think tire pressure is the issue. If you were over-inflating your tires, there would be excessive wear on the middle of the tread, and if you were under-inflating them, there would be excessive wear on the outer edges of the tread (both sides). Based on the symptoms you have, I think you either have a bent axle, or the axle is straight while the trailer is empty, but it is (or they are) bending when the trailer is loaded. On a car, the symptoms you have would be the sign you need an alignment. I would look under the trailer for signs of wear and/or damage to one of both of the axles and all the hardware attached to them. Perhaps one of the bolt-on clamps, that holds the axle straight against the trailer has broken off?

What kind of brakes does your trailer have? Are they surge brakes, or do you have a brake control unit inside your truck? When is the last time you checked the settings on your brake control unit, or the trailer brakes themselves?

One other possibility - are the tires the size specified by the trailer maker?