They just scrub. I bet there was more than 50k miles on the original tires, so if there is increased wear because of it, is not apparent. I swapped them out last year and the trailer had been to Florida at least seven times, plus all the trips everywhere else it's been. It's been an awesome trailer. I've never touched the bearings or seals. There is a grease zerk at the end of the spindle, I just pop the dust cap, and pump grease in until new stuff comes out.