What was found
(CAN) DURING TAXI OUT THE FLIGHT CREW REPORTED THE ACFT SUDDENLY SHUTTERED AND CAME TO A STOP. AS A WHEEL OR BRAKE FAILURE WAS SUSPECTED THE FLIGHT CREW DECIDED TO HOLD THEIR CURRENT POSITION AND WAIT FOR MAINTENANCE. FAILURE OF THE NR 4 MAIN WHEEL INNER HUB WAS CONFIRMED REQUIRING THE FOLLOWING MAINTENANCE ACTIONS TO BE COMPLETED. INSPECTION OF NR 4 MAIN WHEEL ASSY AND BRAKE COMPLETE AND FOUND NR 4 MAIN WHEEL ASSY INNER BEARING HUB DAMAGED. NR 4 MLG AXLE INSPECTED FOR DAMAGE IAW AMM 32-45-11. NR 4 MAIN WHEEL ASSY REPLACED IAW 32-45-11. PIECES OF NR 4 MAIN WHEEL ASSY FOUND IN NR 4 BRAKE. NR 4 MAIN BRAKE REPLACED IAW AMM 32-41-41. NR 3 MAIN WHEEL REPLACED AS A PRECAUTION FOR OVER LOADING IAW AMM 32-45-11. ACFT RETURNED TO SERVICE.