Your shock is held in place by pivot bolts at either end. These need to move smoothly, so that the shock can rotate with the rear end of the bike as the shock moves through its travel. If the pivots become stiff, the shaft of the shock is forced to slide in and out of the shock body at an angle, wearing the seals and the shaft. Loose, sloppy pivots make your bike feel uncertain, since the back end hesitates before following the front end around tight turns.
Checking pivots for slop
- Check the pivots for slop by holding the main frame still and rocking the back end of the bike. There should be no lateral movement, and definitely no knocking or clunking noises. If the pivots are worn, order fresh ones before you start, so you can refit them as you go along. It makes sense to replace the bushings at the same time as the reducers, while everything is open. This takes a little more work, but it is worth the effort.
- Undo the bolts at either end of the shock using either an Allen key and socket, or two Allen keys.
- Release the spring : For air shocks. Make a note of the pressure in the shocks so you can reset it at the end. Then release all air pressure. For coil shocks, back off the preload nut, so that the spring is baggy.
- Check the orientation of the shock so you can refit it correctly later. Remove the shock from the bike. The bike folds up when you take out the shock – support it so that no hoses or cables are stretched or kinked, and that your vulnerable paintwork is protected.
- Pull the reducers from either side of each eyelet. The bushing is the part that lines the inside of the eyelet. You need to use the new one to push the old one out, installing itself in the process. It’s a tight fit, so you need a vice for controlled force. I’ve seen this done with a hammer, but it wasn’t pleasant.
- Support the far side of the eyelet with something hollow for the old bushing to push out into. A socket is ideal. Choose one where the hole is slightly bigger than the bushing, so the bushing does not touch as it pushes out.
- Look closely at the eyelet. The bushing is slightly shorter than the width of the eyelet, maybe 0.5mm (1⁄50 inch). This creates a shoulder to rest the new bushing on, aligning it precisely. Sit one of the old reducers in the new bushing for protection.
- Set up the shock in the vice, with all the parts in order: socket lined up with shock eyelet, shock, new bushing, old reducer.
- Carefully close the jaws of the vice. This pushes the new bushing in through the eyelet, forcing out the old bushing in the process so it ends up inside the socket. Leave the new bushing exactly flush on one side with a shallow shoulder left on the other side, so you can repeat the process next time.
- Refit or replace the reducers. Grease the part in contact with the bushing.
- Refit the shock to the bike, checking direction and orientation. Refit the bolts, using Loctite on the threads. Reset the sag by preloading the spring or by refilling with air.
Check for play by rocking the back end of the bike sideways
The performance of the rear suspension depends utterly on the free movement of the pivots that join the struts and swingarms to the frame. All the hard work that went into designing and building the frame and shock is completely wasted unless you keep the pivots clean and lubricated. There are as many designs as designers, but they have one common enemy – the jet-wash. Never directly jet-wash at the side of your bike – you blow any lubrication out of the bearings.
Check the pivots twice a year by hanging the back of the bike up, taking off the back wheel, removing the rear shock completely and moving the back of the bike through its travel. Don’t kink or bend hoses or cables. Rock the back end of the bike sideways. There should be no movement. If there’s pivot slop, or if the rear end of the bike doesn’t swivel freely, it’s time for pivot maintenance. Details depend on your frame, so check the owner’s manual. Usually pivot maintenance is not at all difficult.
Undo the bolts through the pivots and disassemble carefully. Make a note of the position and orientation of any washers. Remove and inspect bushings or bearings. Bushings have to be ordered from your frame manufacturer, but sealed bearings are almost always common sizes so your bike shop or an auto supply shop can supply fresh ones. You can also service bearings; use a sharp knife to peel off the plastic seals on both sides of the bearing, degrease, rinse, dry and repack with fresh grease. Refit the seals, pressing them gently into place with both thumbs. Hold the central part of the bearing and rotate the outer part to check they run smoothly. Refit into the frame. Use Loctite on the bolt threads to stop them rattling free. Retighten the bolts firmly. Once you’ve refitted the bearings, and before you refit the shock, move the rear end of the bike through its travel again to check you’ve cured the problem. Check the fixing bolts are still snug after your first ride.
Replace worn reducers
Source : BIKE MAINTENANCE TIPS, TRICKS & TECHNIQUES
See also bike maintenance tips, tricks and techniques “Fitting and adjusting a Fox Float Air”