The Fenix AIR [paid link] rear shock from Fast Suspension is a high-performance suspension system designed for road cyclists who demand precision and comfort. Over time, the internal oil in your shock can degrade, which affects its performance and ride quality. Regular oil changes are essential to maintain optimal performance and extend the lifespan of the shock. This guide will walk you through the process of changing the oil in your Fenix AIR [paid link] rear shock.
Tools Required
- 3mm, 5mm, and 8mm Allen wrenches [paid link]
- T25 Torx wrench [paid link]
- 17mm and 22mm socket wrenches
- Shock oil (Fast Suspension recommended type)
- New seals and O-rings
- Shock pump (for recharging air pressure)
- Oil draining pan
- Clean rags
- Small plastic funnel
- Torque wrench [paid link]
- Suspension grease
- Thread locker (optional)
Preparation for the Oil Change
Before you begin, ensure that you have a clean, well-lit workspace. This will help you avoid any contamination of the shock and ensure you can see any parts that may need replacing. Be sure to gather all the required tools and components before starting. Always consult your Fenix AIR’s user manual for any model-specific requirements or warnings.
- Remove the Rear Shock from the Frame
To start, you’ll need to remove the Fenix AIR rear shock from your bike frame. Use the appropriate size Allen wrenches [paid link] to loosen and remove the bolts securing the shock to the frame. Be careful not to strip the bolts, and keep them in a safe place for reinstallation. - Secure the Shock
Once removed, place the shock on a clean, stable surface where it won’t be disturbed. It’s crucial that you keep the shock in a position that will prevent any dirt or debris from entering the internals while you work.
Disassembling the Fenix AIR Rear Shock
- Remove the Air Canister
The first step in disassembling the shock is to remove the air canister. To do this, use the T25 Torx wrench [paid link] to unscrew the bolts holding the canister in place. After removing the bolts, carefully pull the canister away from the shock body. Be prepared for some residual air pressure to release, so use caution. - Drain the Oil
With the air canister removed, it’s time to drain the old oil. Hold the shock over the oil pan and carefully remove the shock’s damper shaft or oil port cover using the appropriate wrench. Allow the oil to drain completely into the pan. Be patient, as it may take several minutes for all of the old oil to exit.
Cleaning and Inspection
- Clean the Shock Internals
Once the oil has drained, use clean rags to wipe down the shock’s internals. This includes the damper shaft, air sleeve, and any other accessible parts. Ensure that there is no dirt or debris remaining inside. Contaminants could negatively impact the performance of the shock. - Inspect Seals and O-Rings
Inspect all seals and O-rings for wear and damage. If any seals appear cracked, worn, or deformed, replace them with new ones. It’s essential to maintain a good seal to prevent air and oil leakage during operation.
Reassembly and Oil Refill
- Lubricate the Shock Components
Before reassembling the shock, apply a thin layer of suspension grease to the damper shaft and the air sleeve to ensure smooth movement and reduce friction. Be careful not to over-grease as excess grease can attract dirt. - Refill with Fresh Shock Oil
Fill the shock with the recommended shock oil. Use a funnel to pour the oil into the shock body carefully. Make sure that the oil level matches the specifications provided in the Fenix AIR user manual. Avoid overfilling as this could affect performance. You may need to compress the shock slightly to allow air bubbles to escape [paid link] and ensure the oil settles at the correct level. - Reattach the Air Canister
Once the shock is filled with oil, reattach the air canister to the shock body. Tighten the bolts with a torque wrench [paid link] to the manufacturer’s specified torque setting. This ensures that the canister is securely in place and prevents any air leakage.
Final Adjustments
- Reinstall the Shock on the Bike
Carefully reinstall the shock onto the frame of your bike. Ensure that the shock is positioned correctly and the bolts are torqued to the specified settings. If necessary, apply thread locker to prevent the bolts from loosening over time. - Recharge Air Pressure
Using a shock pump, carefully recharge the shock to the appropriate air pressure as indicated in the Fenix AIR user manual. This step is crucial for ensuring proper suspension performance. If you’re unsure of the correct air pressure, it’s recommended to consult the manufacturer’s guide based on your weight and riding style. - Test the Shock for Leaks
Before going for a ride, check for any air or oil leaks. Compress the shock to ensure it moves smoothly and that the seals are intact. If there are any leaks, you’ll need to disassemble the shock again and address the issue.
Troubleshooting Common Issues
- Shock Not Holding Air Pressure
If the shock isn’t holding air pressure after the oil change, it could be due to a worn or damaged seal. Inspect the seals again and replace them if necessary. Another common issue is improper reassembly of the air canister. - Poor Suspension Performance
If you experience a reduction in suspension performance after the oil change, it could be due to incorrect oil type or volume. Ensure you’ve used the correct shock oil and filled it to the proper level. - Leaks After Reassembly
Leaks can occur if the shock was not reassembled correctly. Ensure that all bolts are tightened to the specified torque and that the seals are in good condition.
Conclusion
Changing the oil in your Fenix AIR rear shock is a critical maintenance task that will help you maintain the shock’s performance and extend its lifespan. By following this step-by-step guide, you’ll ensure that the shock operates at its best, providing smooth and responsive suspension for your rides. Regular oil changes, coupled with careful inspection and reassembly, will keep your Fenix AIR performing optimally for years to come.