Park the mower on level ground and remove the key from the ignition.Place the jack at the rear of the mower. Make sure the jack is under the frame and not the transmission. Raise the mower and place jack stands under frame behind the rear wheels. Lower the jack so that the tractor rests on the jack stands.Pull the cap off the rear right tire, exposing the axle rod and "E" clip.Remove the "E" clip using the flathead screw driver. The tire will slide off, and the brake disc will be exposed.Tighten the nut in the center of the plate connected to the brake disc one half turn, using a 13mm socket.Place the gear shifter on the right side of the fender to neutral. Make sure the emergency brake -- located on the left side of the mower on the deck -- is off. With your left hand spin the exposed axle. With your right hand slowly depress the brake pedal.If the axle stops rotating the brake is adjusted. If it keeps turning, re-adjust the brake disc nut half a turn and keep adjusting it until the axle stops rotating while the brake pedal is depressed.Reinstall tire, the "E" clip and the tire cap. Lower the mower back to the ground.