To start with, the actual model # below the seat is what is needed to order parts. Many times it starts w/ 917. If you are consistently wearing bushings, it is quite likely that the wheel spindle has been damaged by the bushing being worn out and the wheel is hogged out the same way. So if this is the case, a roller bearing would be of no help. It would be necessary to replace the wheel and spindle. There are roller bearings that can be used in place of the bushings if the wheel will hold and the shaft of the spindle is not worn. More commonly, the alignment is off from a bent crosslink after a front tire hits something. Axles can crack where the spindle is supported, spindles can bend too etc.