Check pedal bearings by holding the pedal body and twisting it sideways. The pedal should feel firm on the axle and should not knock from side to side. Spin each pedal on its axle. It should turn silently and keep spinning freely.
If the pedals are knocking or binding, it‘s new bearing time. They‘re an unusual size: 3/32 inch. If your bike shop doesn‘t have them, try a bearing shop. If the bearing surfaces or cones are pitted or otherwise damaged, replace the whole axle. Take care not to swap the plastic sleeves between pedals – it’s best to do one pedal at a time to avoid confusion. Remove both pedals from the bike, remembering that the left-hand pedal has a reverse thread and comes off clockwise. Follow the instructions below to replace the bearings. The final readjustment of the bearings can be a bit tricky – you have to reassemble the pedal and refit it to the cranks before you can be sure that your adjustment is correct. Sometimes it takes a couple of goes – adjusting the pedal bearings, reassembling the pedal and checking the adjustment – before you‘re satisfied.
Refitting the pedals
Step 1: To strip the pedal, you need the Shimano grey plastic pedal tool, that you can order through your bike shop. Clamp the tool in a vice and turn the pedal in the direction of the arrow printed on the tool. Wrap a cloth around the pedal for extra grip if necessary. The threads are plastic and strip if forced backwards, so check the direction carefully.
Step 2: Pull the pedal right off the axle. Take the axle out of the vice, remove the plastic tool and clamp the pedal axle back in the vice, narrow end upwards. You see the top row of bearings (A) trapped under the cone. The second set is between the steel tube and the washer below it.
Step 3: The top of the pedal has two spanner flats, 7mm and 10mm. Shimano has a neat coneadjusting tool, which makes the job easier, but you can use ordinary spanners. The 10mm must be narrow to fit in the space. First remove the locknut, then the cone; the lower one is the cone and takes a narrow 10mm spanner, the upper one is the locknut and needs a 7mm spanner.
Step 4: Remove the lock nut and cone. Pick off all the bearings, then pull off the steel tube. Pull the rubber spacer off the axle, then lift off the lower washer complete with bearings. Pull off the plastic sleeve and the rubber seal. Clean all parts carefully and check for pitted bearing surfaces. If they‘re worn out, replace the axle. (B) Rubber sleeve; (C) Lower washer; (D) Locknut; (E) Cone; (F) Steel washers.
Step 5: Refit rubber seal and plastic sleeve. Dry the curved washer so that the grease sticks, and grease it. Place 12 3/32 inch bearings carefully on the washer, then slide it gently over the axle to rest on top of the plastic sleeve. Refit the rubber spacer. Grease the bearing surface in one end of the metal tube, then pack another 12 bearings onto it. Slide it carefully over the axle.
Step 6: Tighten the cone, curved side down, onto the axle by hand. Make sure it traps all bearings. Refit the locknut loosely. The cone must be tightened onto the bearings, so there is no play between the axle and the metal tube but so the tube can still turn freely. Holding the cone still, tighten the locknut onto it. This is fiddly: you may have to repeat the action several times to get it right. Refit the axle assembly into the pedal body, then use the grey tool to tighten firmly.
Source : BIKE MAINTENANCE TIPS, TRICKS & TECHNIQUES
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