Over the years I've had two different boat trailers to wear out the tires on the inside like the picture above. I had a man at the machine shop teach me how to check to see if you have a bad axle. Take axel out from under trailer , remove the tires, take axel out in yard step on both hubs push them down in the ground where hubs will not move. Take your foot & roll the shaft with hubs not moving. If one of the hubs wobbles while you roll the shaft you have a bad axel needs to be replaced!! On both my trailers that the hub wobbled I replaced the axel & I had no more tire trouble. This tip works try it!!