One of the best features of high performance off-road racing shocks is that they can be easily serviced, repaired, rebuilt, and revalved. While this may seem like a complicated process, you have to remember that they are specifically designed to be easy to work on so that race teams can make repairs quickly, even when they are out in the middle of the desert. If this is your first time rebuilding a shock, take your time and follow these steps carefully. After a few times, you'll be able to complete the process in about 10 minutes.
Step 1: Clean The Shock
Clean the shock completely using paper towels or a shop rag to remove any and all dust and dirt. Do not bleed the nitrogen pressure from the shock just yet.
Step 2: Loosen Set Screw
With the shock shaft fully extended, use an allen wrench to loosen the set screw in the lower wiper cap. Make sure the allen wrench is a good fit so as not to strip the screw. Unscrew it just a few turns.
Step 3: Loosen the Wiper Cap
Set the spanner wrench securely into the two indented holes on the wiper cap and using a medium amount of force turn the wiper cap counter-clockwise.
A small tap with a dead blow hammer usually does the trick.
Do not remove the wiper cap in this step, only loosen a few turns.
Note: Nothing in this rebuild process should require more than a small to medium amount of force and everything should come apart smoothly.
Step 4: Bleed the Nitrogen Pressure
Bleed the pressure from the reservoir or shock body on an emulsion shock through the Schrader valve using a small screwdriver or allen wrench.
Note: The pressure is kept inside the shock through this step because it keeps the internal seal cap pressed against the snap ring to keep it from spinning freely while the wiper cap is loosened.
Step 5: Unscrew the Wiper Cap
Finish unscrewing the wiper cap and slide it up to the end of the shock shaft.
Step 6: Lower the Seal Cap
Press down firmly on the internal seal cap to push it down below the snap ring.
Tip: If you move the shaft up and down a few times forcefully and then bleed the pressure in the reservoir again it will create a vacuum and suck the seal cap down on its own. This may take a few tries.
Step 7: Remove the Snap Ring
With a small screwdriver or dentist pick, remove the snap ring and set it aside.
Step 8: Remove the Shock Shaft
Carefully pull on the shock shaft to remove it from the shock body.
Tip: If you plan to reuse the shock oil, be extra careful because it is easy to lose a lot of oil in this step.
It may also be helpful to bleed the reservoir again to release the vacuum pressure created by pulling out the shaft.
Step 9: Drain the Oil
Drain the oil from the shock into a clean container.
Bypass Shocks: Make sure the bypass valves are open so the oil can drain from the bypass tubes.
Remote Reservoirs: Lift the reservoir up to drain the oil from inside the reservoir and reservoir hose.
Piggyback Reservoirs: Lean the shock body such that the oil can drain from the piggyback reservoir into the shock cylinder. Then turn the shock over and let the oil drain out.
Tip: At this stage it is a good idea to inspect the oil for unusual debris or metal shavings and inspect the shock shaft and cylinder walls for scratches and damage.
Step 10: Remove the Piston Retaining Nut
Secure the lower rod end (bearing side) of the shaft assembly in a vice and protect it with a towel or rubber pad, then remove the piston retaining nut.
Note: The wear band on the piston is normally good for the life of the shock and only rarely needs to be replaced.
Tip: Never clamp the shock shaft in a vice without the proper shock shaft clamps.
Step 11: Remove the Piston and Shims
Carefully remove the shock piston, shims, and spacers and lay them out in order.
If you are revalving your shocks, then this is the time to replace the existing shims with the new ones. Remember that compression shims go on the bottom and rebound shims go on the top, towards the nut.
For help choosing new shims, see Shock Tuning.
If you are not replacing any seals, then the seal cap and wiper cap should stay on the shock shaft.
Step 12: Replace Cap Seals (Optional)
If you are performing a shock rebuild, remove the seal cap, spacer, and wiper cap from the shock shaft.
Remove the existing seals and o-ring carefully using a small screwdriver and/or small pliers.
The new seals are a tight fit but will push in by hand without needing much force. Take your time to make sure they are fully seated correctly.
Step 19: Cap and Flip the Shock Cylinder
Using your hand or any clean flat block (a hockey puck works well), cover the open end of the cylinder and turn it upside down and back a few times to release any trapped air bubbles.
Add shock oil as needed to bring the oil level back to around one inch below the snap ring groove.
Step 20: Slowly Insert the Shock Shaft
Carefully place the shock shaft assembly into the shock cylinder until the entire piston is submerged. Move the shaft up and down slightly and let any remaining air bubbles work their way out.
Step 21: Set the Seal Cap
Slide the seal cap down to the top of the cylinder and settle it down so that it is sitting on top of the shock oil.
Push down on the seal cap with moderate force to move it down to just below the snap ring groove. Try and do this in one continuous push because this is how oil is forced into the reservoir.
Insert the snap ring into the groove.
Note: It is normal to lose a little shock oil here.