The Shimano PD-M505 off-road sport pedal is a double-sided pedal with an SPD mechanism on both sides. It features a compact and lightweight body which spins on sealed ball bearings and a large axle. These pedals are ideal for mountain bikers who need a double-sided, compact pedal for trail riding. Most of the parts can be replaced, including the bearings, the races, the axle and the body plate. Rebuilding a pair of these pedals can help breathe new life into an old component that takes a lot of abuse on the trail.
Unscrew the pedal from the bicycle's crank arm using the pedal key. Point the threaded end of the pedal down so the pedal looks like a lollipop. Pry the plastic seal cap off the top of the pedal with your awl. Set your pedal into the pan.
Remove the first nut that you find under the cap using the smaller Shimano key. This is the locknut. Use the larger wrench to remove the nut below that. This is the bearing race. Ball bearings, 62 in all, will be released as you remove the bearing race and pull the pedal body away from the axle. These bearings should fall into your pan.
Check the rubber seal that sits closest the larger end of the axle and replace it if needed. Clean and inspect the axle, the outer bearing race and the ball bearings for any signs of excessive wear, like galling or pitting. Replace any or all parts depending on their condition and your budget for the rebuild.
Point the large threads down again. Lightly grease the axle and stack the seal and 31 of the 62 bearings into place. Pack grease in around the bearings and then slide the pedal body into place to capture them. Place the other 31 bearings into the open side of the pedal body and pack them with grease. Thread the outer bearing race down until it is snug enough to prevent play but not so tight that the pedal binds up when you spin it. Thread the locknut loosely over that.
Hold the bearing race with the larger Shimano wrench and put the smaller wrench inside the larger one so it grabs the locknut. Keep the race in the correct position with the large wrench as you tighten the locknut firmly into place with the smaller one. Pop the plastic cap back on the end.
Clean and inspect the two body plates, which are attached to the pedal body on either side. Each of these plates is attached with two Phillips screws and creates the platform that the cleat slides into. Use your screwdriver to remove and replace them if they show excessive wear.
Reinstall the pedals using the pedal wrench.
The spring and adjustment mechanisms are not user serviceable. Do not try to unscrew the adjuster screws or remove the springs, as this will destroy the pedal.