How to Rebuild Your Bomber CR Trunnion Rear Shock at Home

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Rebuilding your Bomber CR Trunnion [paid link] rear shock at home can save you time and money while ensuring that your shock is in top working condition. With proper tools, knowledge, and care, you can successfully service and maintain your shock, keeping it performing optimally. This guide will walk you through the essential steps to rebuild the Marzocchi Bomber CR Trunnion [paid link] rear shock, from disassembly to reassembly, ensuring smooth performance on your next ride.

Tools Required

  • 5mm, 6mm, and 8mm Allen wrenches [paid link]
  • Torque wrench [paid link]
  • Shock pump
  • Soft mallet
  • Suspension oil (specific to Marzocchi Bomber CR)
  • Rebuilding kit (seals, o-rings, bushings)
  • Clean cloth or towel
  • Isopropyl alcohol for cleaning
  • Seal grease
  • Snap ring pliers
  • Small plastic container for parts

Disassembly of the Bomber CR Trunnion Rear Shock

Before starting the disassembly, ensure that the shock is completely unloaded of air. Use a shock pump to release all pressure from the shock’s air chamber. This is crucial for safety during the rebuild process.

Step 1: Remove the Shock from the Frame

  • Unscrew the mounting bolts that secure the shock to the bike frame. Keep track of the orientation and the hardware for reassembly. You may need a 5mm or 6mm Allen wrench [paid link] for this task.

Step 2: Clean the Shock

  • Using a clean cloth and isopropyl alcohol, wipe down the shock to remove any dirt, grime, or old grease. This prevents contaminants from entering the shock during the rebuild process.

Step 3: Remove the Trunnion Mount

  • Use the appropriate size Allen wrench [paid link] (usually 8mm) to remove the bolts securing the trunnion mount. Take care not to damage the threads.

Step 4: Disassemble the Shock Body

  • Carefully remove the shock’s body from the trunnion mount. You may need to use a soft mallet to gently tap the body free if it’s stuck due to old grease or debris.
  • Once the body is free, inspect the piston and damper assembly for any signs of wear or damage.

Inspection and Cleaning

After disassembly, the components should be thoroughly inspected for wear and cleaned before reassembly.

Step 1: Inspect the Seals and Bushings

  • Examine the seals for any cracks, wear, or degradation. If damaged, replace them with new seals from the rebuilding kit.
  • Check the bushings for smooth movement. If they are worn, it is best to replace them as well.

Step 2: Clean the Internals

  • Use isopropyl alcohol to clean the shock’s internal components, such as the damper rod and piston. Be sure to remove all dirt and old oil from the internal chambers.
  • Wipe all parts down with a clean cloth to remove excess moisture.

Rebuilding the Bomber CR Trunnion Rear Shock

Rebuilding your shock requires careful attention to detail, particularly when it comes to applying the right amount of lubrication and sealing components.

Step 1: Lubricate the Seals and O-rings

  • Apply a thin layer of suspension oil to the new seals and o-rings to ensure smooth movement and a proper seal. This reduces friction and helps prevent leaks.
  • Use the seal grease on the shock shaft and bushings to help protect against wear.

Step 2: Install the New Seals

  • Install the new seals and o-rings into their respective grooves. Ensure they are seated properly and evenly to prevent any leakage during operation.
  • For the trunnion mount, make sure the seals are properly lubricated before installation.

Step 3: Reassemble the Shock

  • Begin by reassembling the piston and damper assembly into the shock body. Carefully slide the damper rod into place, ensuring it is properly aligned with the shock body.
  • Reinstall the trunnion mount onto the shock body and torque the bolts to the manufacturer’s specified settings.
  • Install any internal components, such as the rebound or compression adjusters, making sure they are fully seated and functional.

Adding Oil and Charging the Shock

With the shock body fully reassembled, it’s time to add fresh suspension oil and air pressure.

Step 1: Add Suspension Oil

  • Pour the recommended suspension oil into the shock body, filling it to the manufacturer’s specified level. This ensures proper damping performance.
  • Be sure to use the correct oil type and viscosity as recommended by Marzocchi for the Bomber CR Trunnion model.

Step 2: Reinstall the Air Sleeve

  • Carefully install the air sleeve back into place, ensuring a tight seal with the internal o-rings. This step is crucial for maintaining proper air pressure within the shock.
  • Once the air sleeve is installed, check for any air leaks.

Step 3: Charge the Shock with Air

  • Attach a shock pump to the valve and add air to the shock, following the manufacturer’s pressure specifications. This will vary depending on your weight, riding style, and preferred shock setup.
  • Check for any air leakage and ensure the shock is holding air properly.

Reinstallation and Final Adjustments

Once the shock is fully rebuilt, it’s time to reinstall it on your bike and make final adjustments to ensure optimal performance.

Step 1: Reinstall the Shock on the Bike

  • Reinstall the shock onto the frame, securing the bolts properly with the correct torque settings. Be sure that the shock is positioned in the correct orientation.

Step 2: Set Rebound and Compression Damping

  • Adjust the rebound and compression damping settings based on your personal preference and riding conditions. The Bomber CR Trunnion features easy-to-use knobs for these adjustments, so fine-tune to your liking.
  • Make sure to test the shock by pushing down on it and observing the rebound speed and compression. Make any necessary adjustments based on your riding style.

Troubleshooting Common Set-Up Issues

If your shock does not perform as expected after rebuilding, here are a few common issues and how to address them.

Problem 1: Air Leaks

  • If the shock is losing air, check the seals and o-rings to ensure they are seated properly. Damaged or worn seals should be replaced.
  • Inspect the air sleeve and valve for any damage.

Problem 2: Poor Damping Performance

  • If the shock is not performing well, verify that the correct type and amount of oil have been used. Low oil levels can affect damping performance.
  • Double-check that all internal components, such as the rebound and compression adjustments, are functioning correctly.

Problem 3: No Rebound or Slow Rebound

  • If the rebound adjustment is not functioning or is too slow, check the rebound valve for proper installation. Also, verify that the shock oil is not too thick and is at the correct level.

Customization and Optimization for Better Performance

Optimizing the Bomber CR Trunnion rear shock can enhance your riding experience. Here are some tips for customization:

  • Adjust Air Pressure: Fine-tune the air pressure for your weight and riding style. Lower air pressure provides more plushness, while higher pressure increases firmness.
  • Rebound and Compression Settings: Experiment with different rebound and compression settings to match your riding terrain. Softer settings are great for downhill riding, while firmer settings work better for cross-country.
  • Upgrade Seals: Consider using high-quality seals for longer-lasting performance and better performance in wet conditions.

Compatibility with Other Drivetrain Components

The Bomber CR Trunnion rear shock is designed to work with various mountain bike frames, but it’s essential to confirm compatibility with your specific bike’s geometry and rear suspension design. Ensure that the shock’s eye-to-eye length and stroke length match the frame’s specifications. Using the wrong size shock can result in poor suspension performance and could even damage the frame or shock.

Rebuilding and maintaining your Bomber CR Trunnion rear shock at home not only saves you money but also helps you ensure optimal performance on your rides. With regular maintenance, your shock can provide excellent suspension performance for years to come.