Im not sure what is causing your unusual wear. I had a similar problem when my trailer was new. It was wearing tires on the inside really quickly. After the third set of tires, I took it to a buddy's shop who builds trailers. He informed me that most boat trailer's axles are too light. I had a half ton axle under my trailer. He told me to replace it with at least a 3/4 ton axle. I did and it fixed the wear problems!!! I hope this helps.