Maintaining the Fox Float X2 Trunnion [paid link] rear shock is essential for ensuring peak [paid link] performance and longevity of your mountain bike. A critical aspect of this maintenance is the oil change, which helps keep the shock working smoothly by reducing friction, heat, and wear. This step-by-step guide will walk you through the process of changing the oil in your Fox Float X2 Trunnion [paid link] shock, ensuring it operates at its best.

Tools Required

• 8mm socket wrench
• 10mm socket wrench
• Torque wrench [paid link]
• T25 Torx driver
• Shock oil (Fox Float Fluid or equivalent)
• Clean rags
• Shock pump
• 4mm Allen wrench [paid link]
• Fox Float X2 service kit (includes seals, o-rings, and oil)
• Drain pan or container
• Plastic syringe for oil filling
• Small brushes for cleaning

Preparation

Before you begin the oil change, it’s important to ensure you have a clean and organized workspace. This helps prevent dirt and debris from entering the shock during disassembly and reassembly. Make sure the shock is cool to the touch and the bike is securely positioned.

Step 1: Remove the Shock from the Frame

To perform the oil change, you need to remove the shock from the bike. Here are the steps for removal:

1. Use an 8mm wrench to remove the bolts securing the shock to the frame.
2. Carefully slide the shock out, ensuring the trunnion mount is not damaged in the process. Place the shock on a clean, stable surface.

Step 2: Clean the Shock

Before you begin disassembling the shock, clean it thoroughly. Dirt and debris can affect the internal components when the shock is opened. Use a clean rag to wipe down the entire shock body, especially around the trunnion mount, air sleeve, and damping circuits.

Disassembling the Shock

Step 3: Remove the Air Sleeve

The air sleeve houses the shock’s air chamber and is connected to the damper. Here’s how to remove it:

1. Use a T25 Torx driver to remove the screws securing the air sleeve to the shock body.
2. Slide the air sleeve off carefully, exposing the internals of the shock.

Step 4: Drain the Old Oil

Once the air sleeve is removed, you will see the damper shaft and oil inside the shock body. To drain the old oil:

1. Position the shock with the damper side down over a drain pan.
2. Use the syringe or a small brush to remove any remaining oil, ensuring the shock is fully drained.

Step 5: Remove the Damper Cartridge

Now that the shock is drained of oil, the next step is to remove the damper cartridge. Here’s how to do it:

1. Use a 10mm socket wrench to unscrew the damper cartridge from the shock body.
2. Gently pull the damper cartridge out. Be careful not to damage any seals during this process.

Step 6: Remove and Replace Seals

After removing the damper cartridge, it’s essential to replace the seals to ensure the shock operates without leaks:

1. Using a 4mm Allen wrench [paid link], remove the old seals from the damper body and air sleeve.
2. Install the new seals from the Fox Float X2 service kit, ensuring they are properly seated and lubricated with fresh shock oil.

Cleaning and Reassembling the Shock

Step 7: Clean Internal Components

With the damper cartridge and seals removed, clean all internal components thoroughly. Use a small brush to clean the damper shaft, piston, and internal walls of the shock. Avoid using harsh chemicals; water and a mild cleaner are sufficient. Dry all parts with a clean rag before reassembling.

Step 8: Reassemble the Damper Cartridge

1. Place the damper cartridge back into the shock body.
2. Tighten the damper cartridge using a 10mm socket wrench, ensuring it is secure but not over-tightened. Refer to the torque specifications in the service manual for proper tightening torque.

Step 9: Refill the Shock with New Oil

Once the damper is securely in place, it’s time to refill the shock with fresh oil. Here’s how:

1. Use a plastic syringe to carefully inject the recommended amount of shock oil (Fox Float Fluid or equivalent) into the shock body. Be sure to fill the oil chamber to the correct level as per Fox’s specifications.
2. Work the damper shaft in and out a few times to allow the oil to fully distribute through the internal components. This ensures all the internals are properly lubricated.

Step 10: Reinstall the Air Sleeve

Once the shock is filled with oil, it’s time to reinstall the air sleeve:

1. Slide the air sleeve back onto the shock body.
2. Tighten the screws with a T25 Torx driver, ensuring the air sleeve is securely attached.

Final Steps and Testing

Step 11: Reinstall the Shock on the Frame

Now that the oil change is complete, reinstall the shock onto the frame of the bike. Ensure that the trunnion mount and mounting bolts are tightened correctly using an 8mm wrench.

Step 12: Set the Air Pressure

Before testing the shock, use a shock pump to set the recommended air pressure based on your rider weight and riding style. Refer to the shock’s user manual for specific air pressure recommendations.

Step 13: Test the Shock

With the shock installed and the air pressure set, conduct a quick test to ensure the shock is functioning properly:

1. Cycle through the shock’s travel a few times to ensure smooth movement.
2. Check for any air or oil leaks around the seals and connections.
3. Test the damping adjustments (compression and rebound) to ensure they are functioning correctly.

Troubleshooting Common Issues

Air Leaks

If you notice air escaping from the shock, it may be due to a damaged or improperly seated seal. Inspect the seals carefully, and if necessary, replace them with new ones from the service kit.

Excessive Rebound or Compression

If the shock feels overly bouncy or doesn’t return to its original position properly, the oil level may be incorrect or the damper may need to be serviced. Recheck the oil volume and ensure the damper is working smoothly.

No Compression or Rebound Adjustment

If the compression or rebound settings do not adjust properly, the damper cartridge might be faulty. In this case, a complete overhaul or replacement of the damper may be necessary.

Conclusion

Performing an oil change on your Fox Float X2 Trunnion rear shock is a key maintenance task that ensures consistent performance and prolongs the life of your shock. By following the steps outlined in this guide, you can ensure that your shock is always in optimal condition, ready to handle even the toughest terrain.