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Shock Servicing
THROWING OUT YET ANOTHER SET OF SHOCKS? MICHAEL HAYES OUTLINES A BASIC DIY THAT WILL MAKE YOUR PERFORMANCE SHOCKS LAST!
Most of us now have bitten the bullet and got some performance shocks whether they are smoothies or remote reservoir they all are basically the same inside.
But after a year or two instead of just throwing them away like a basic twin tube, a quick refresh or tune up just before you head off on the next big trip may be all that's needed. This is really one of those things that anyone can do with the right instruction and a bit of patience.
So here is a quick breakdown on the basics of rebuilding a Superior Engineering shock. Ideally get the full instructions that relate to your brand of shock.
Tools REQUIRED
Safety glasses, latex gloves, assembly lube / lithium based grease, Loctite ™ #271, gas or propane torch, pin spanner wrench (profender combination tool), 2.5mm hex key ("Allen wrench"), scribe or seal pick, flat blade screwdriver, pin punch, 14 & 17mm socket, circlip pliers - small external, oil stone, rubber mallet, nitrogen tank w/ regulator, cleaning solvent, vice w/ soft jaws, tape measure. shock oil (5 to 10wt).
1. Read
through all of these instructions first to familiarise yourself with the rebuild procedure.
2. Make sure
you have a clean work area, and all of the necessary tools are available. Always use proper safety equipment when working on shock absorbers.
3. Clean
the entire shock assembly with soapy water, cleanliness is critical! Before you even think about pulling anything apart, it is important to release all the nitrogen out of the reservoir. CAUTION: pressures range from 100-300psi.
4. Once the nitrogen is safely removed
you can simply push the schrader cap in with your fingers, about 30mm - enough to get to the wire spring clip. Using a pick / screwdriver remove the clip and pull the cap out gently with pliers (on the cap) or an air-valve tool. Once you have that removed, look inside the reservoir tube, there should be almost no oil in here. If you see more than a few drops then you need to replace the seal.
5. Now that's apart
it's time to pull the shock itself down. Hold the base / mount of the shock in a vice, NOT the body! Be sure to use soft jaws and do not over tighten. Use soft jaws and a rag / towel as it's easier on the shock base and will catch some of the oil that may spill when you pull out the piston.
6. With the shock held securely
undo the small locking grub screw from the dust cap. Then using a pin-spanner unwind the cap and slide up the shaft. The neckbush assembly should now be visible. Push it down a little and remove the wire clip just like you did in the reservoir. Next, slowly pull the shaft and piston vertically out of the shock body. You may spill a little oil, but keeping everything vertical and taking your time will reduce the amount lost.
7. The main shaft assembly
can now be inspected and taken apart to allow changing of the seals in the neckbush assembly and the dust-cap assembly, at the same time it is also easy to do any tuning or valving changes. This is all done by holding the shaft in a vice by the rod-end or pin-end, NEVER clamp the shaft! Inspect the shaft for any dents or damage, high points that cut seals can be gently buffed out with the use of a fine oil stone. Remove the piston nut (heat may be required) and lift off the piston, keeping the shims and washers in correct order. The neckbush and dustcap assemblies can now slide off.
8. Using a pick remove and replace any seals
lubricate with oil and re-assemble onto the shaft. CAUTION! Do not scratch the surface of the seal groove as this will cause the new seal to leak or fail. If you need to tune the shocks now is the time to change any shims in the stacks, easy to do but this is where the tuning gets technical so we will leave that for another article. Install the piston shim assembly and do up the nut, add Loctite as per manufacturers specs. Install back into the shock gently and slowly keeping an eye on the seals as well as allowing the air to escape.
Add any oil that may have been lost - don't overfill! With the neckbush nearly seated on the seal, slowly push the shaft into the body until oil touches the neckbush and all the air is out of the shock. Seat the seal and push the neckbush home. Finish putting the shock together, making sure all the ring clips are well seated. Extend and compress fully to test for air pockets. Clean off excess oil and be sure to pressure test once you are happy with the re-assembly.
