Step-by-Step Rear Shock Oil Change for Tune Shock SK18

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The Tune Shock SK18 [paid link], designed by Trunnion, is a high-performance rear shock known for its smooth performance and durability. Over time, the shock oil inside can degrade due to usage and environmental factors, impacting the shock’s performance. Regular oil changes are essential to maintain optimal performance and extend the lifespan of your rear shock. This guide will provide detailed instructions on how to perform a rear shock oil change for the Tune Shock SK18 [paid link].

Tools Required

  • Shock pump
  • 5mm and 2.5mm Allen wrenches [paid link]
  • Torque wrench [paid link]
  • Small flathead screwdriver
  • 10mm spanner wrench
  • Clean cloth
  • Oil drain pan
  • Rags or paper towels
  • Suitable shock oil (recommended by the manufacturer)
  • Replacement seals (if necessary)
  • Syringe for oil transfer
  • Gloves

Preparing for the Oil Change

Before beginning, ensure you have a clean work environment to avoid contamination during the oil change. Lay out all necessary tools and components to make the process as efficient as possible.

Step 1: Remove the Shock from the Frame

  • Use the 5mm Allen wrench [paid link] to remove the bolts holding the shock to the frame.
  • Carefully detach the shock from the linkage, ensuring it remains upright to avoid spilling any residual oil.
  • Place the shock on a clean surface, preferably on a soft cloth to avoid any damage to the body.

Step 2: Depressurize the Shock

  • Use the shock pump to release all air pressure from the shock. This is crucial to avoid any mishaps while disassembling the shock.
  • Verify that the shock is completely depressurized by pressing gently on the body.

Step 3: Remove the Air Can

  • Use the 10mm spanner wrench to unscrew the air can from the shock body.
  • Place the air can and other components aside carefully, ensuring they are placed on a clean surface.
  • Check for any visible damage or wear on the air can seals. If necessary, replace the seals before reassembling the shock.

Step 4: Drain the Old Oil

  • Carefully tip the shock to drain any residual oil into an oil drain pan. Hold the shock upright to ensure all oil drains out.
  • Use a clean rag or paper towel to wipe any excess oil from the shock body. This step is vital to avoid cross-contamination during the oil change process.

Step 5: Disassemble the Shock

  • Once the shock is drained, use the 2.5mm Allen wrench [paid link] to remove the rebound and compression damping adjusters from the shock body.
  • Gently pry off the damping adjuster components with a small flathead screwdriver. Be cautious not to damage the threads or seals.

Rebuilding the Shock with New Oil

Step 6: Clean All Components

  • Thoroughly clean all parts of the shock, including the air can, shock body, damping adjusters, and seals.
  • Use a clean rag or paper towel to wipe off any dirt, debris, or old oil. Ensure all parts are free from contaminants before reassembling.

Step 7: Add Fresh Shock Oil

  • Prepare the shock oil according to the manufacturer’s specifications. Use a syringe to fill the shock body with the appropriate amount of oil.
  • The amount of oil will depend on the model and the specific type of oil recommended by Trunnion. Ensure you use the correct oil type for optimal performance.
  • Fill the shock slowly to avoid air bubbles. If necessary, gently tap the shock on a soft surface to release any trapped air.

Step 8: Reassemble the Shock

  • Once the shock body is filled with fresh oil, reattach the damping components (compression and rebound adjusters).
  • Tighten the adjusters securely but avoid overtightening, as this could damage the threads.
  • Inspect the seals and replace them if needed. Ensure the seals are installed properly to prevent leakage.

Step 9: Reattach the Air Can

  • Reinstall the air can onto the shock body. Tighten it securely with the 10mm spanner wrench, making sure the seal is properly seated to avoid any air leakage.
  • Double-check that all components are properly reinstalled and tightened to the recommended torque specifications.

Step 10: Reinstall the Shock on the Frame

  • Mount the shock back onto the frame using the original mounting bolts.
  • Tighten the bolts to the recommended torque using the torque wrench [paid link] and 5mm Allen wrench. Ensure the shock is aligned correctly and securely fixed to the frame.

Final Checks and Testing

Step 11: Inflate the Shock to the Desired Pressure

  • Using the shock pump, inflate the shock to the desired pressure based on your weight, riding style, and preferences.
  • Carefully check the air pressure and adjust if necessary to achieve the desired suspension performance.

Step 12: Test the Shock

  • Before heading out on a ride, manually compress and rebound the shock to ensure it is functioning properly.
  • Check for any leaks around the seals, air can, and damping components.
  • Take the bike for a short test ride to verify the shock’s performance and ensure everything is working smoothly.

Troubleshooting Common Issues

Low Rebound Performance

  • If the shock is slow to rebound, it could be due to insufficient oil or air pressure. Ensure the shock is filled to the recommended oil level and properly inflated.
  • Check for any damage or wear on the rebound damping components, as these may need replacement.

Sag or Air Leakage

  • If the shock feels saggy or there is air leakage, inspect the air can seals. Replace any worn-out seals to restore the shock’s performance.
  • Ensure the air can is properly threaded onto the shock body and tightened to the recommended torque.

Customization and Optimization

To enhance the performance of the Tune Shock SK18, riders can adjust the oil volume and air pressure to match their specific riding style. Lighter riders may benefit from slightly less oil and lower air pressure for a plush, responsive feel. Heavier riders might prefer a stiffer setup with more oil and higher air pressure to prevent bottoming out.

Experiment with the compression and rebound settings to fine-tune the shock for different trail conditions, ensuring maximum comfort and performance.

Conclusion

Performing a rear shock oil change on the Tune Shock SK18 is a straightforward process that can significantly improve your bike’s suspension performance. By following these detailed steps, you ensure the shock operates smoothly and consistently, offering optimal control and comfort. Regular maintenance, including oil changes, will keep your shock in peak [paid link] condition and extend its lifespan, ensuring you enjoy a reliable and high-performing ride.