Step-by-Step: Rebuilding Your Bomber 58 Suspension Fork

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The Bomber 58 suspension fork by Marzocchi is a durable and high-performance fork designed for aggressive mountain biking. Over time, regular use can lead to wear and tear, necessitating a rebuild to ensure that it continues to perform at its peak. This guide will walk you through the process of rebuilding your Bomber 58 suspension fork, covering everything from disassembly to reassembly, and providing tips for optimizing its performance.

Tools Required

  • 5mm Allen wrench [paid link]
  • 6mm Allen wrench [paid link]
  • 10mm socket wrench
  • 8mm Allen wrench
  • Fork seal driver
  • Suspension oil (viscosity as per manufacturer specifications)
  • T30 Torx driver
  • Small flathead screwdriver
  • Large, clean workbench or surface
  • Clean rags and towels
  • Torque wrench [paid link]
  • Pliers
  • Marzocchi suspension grease
  • Fork seals (new seals if required)
  • Snap ring pliers

Disassembly Process

Before you begin, make sure that you have a clean, spacious work area and all the necessary tools at hand. The first step in rebuilding the Bomber 58 is disassembling the fork to access the internal components.

1. Remove the Fork from the Bike

  • Begin by loosening the stem bolts with a 5mm Allen wrench. Slide the fork out of the frame and set it on your workbench.
  • Remove the front wheel by loosening the quick-release skewer or through-axle, depending on your setup.

2. Remove the Fork Guards

  • Use a 5mm Allen wrench to unscrew the bolts securing the fork guards on the stanchions.
  • Carefully slide the guards off to expose the fork internals.

3. Detach the Compression and Rebound Dials

  • Using a T30 Torx driver, remove the screws securing the compression and rebound dials on the fork crown.
  • Keep these components safe as you will need them during reassembly.

4. Loosen the Lower Leg Bolts

  • Using a 6mm Allen wrench, unscrew the lower leg bolts at the bottom of the fork.
  • If the fork has a thru-axle or any other attachments at the lower leg, make sure to remove them as well.

5. Slide the Lowers Off

  • Carefully slide the lowers off the stanchions. If there is any resistance, gently tap the lowers with a rubber mallet to release them.

6. Remove the Dampers and Spring

  • The Bomber 58 has both a spring and a damper cartridge. Use a 10mm socket wrench to remove the spring from the fork leg.
  • Next, carefully unscrew and remove the damper cartridge. Be sure to keep track of any washers or components attached to the damper for later reassembly.

7. Extract the Fork Seals

  • Use a fork seal driver or a flathead screwdriver to carefully pry out the fork seals from the stanchions. Replace them if they appear damaged or worn.

Cleaning and Inspection

Once disassembled, thoroughly clean all components with a clean rag to remove any dirt, grease, or old suspension oil. Pay particular attention to the fork seals and the internals of the fork legs. Inspect all components for wear and tear, particularly the stanchions, seals, and damper. If any components are damaged, it’s important to replace them with new parts to ensure proper functionality.

Rebuilding Process

1. Install the New Fork Seals

  • Apply a thin layer of suspension grease to the new fork seals and carefully slide them into place on the stanchions.
  • Use the seal driver to ensure the seals are seated correctly, avoiding damage to the stanchions.

2. Reinstall the Damper Cartridge

  • Apply suspension oil to the damper cartridge before inserting it back into the fork leg.
  • Secure the damper cartridge by tightening it to the manufacturer’s torque specifications.

3. Reinstall the Spring

  • Place the spring back into the fork leg. Ensure it is correctly oriented and seated in its proper position.

4. Reassemble the Fork Lowers

  • Carefully slide the fork lowers back onto the stanchions, making sure that the internal components align properly.
  • Secure the lowers by tightening the lower leg bolts with a 6mm Allen wrench. Use a torque wrench [paid link] to ensure the bolts are torqued to the proper specifications.

5. Reattach the Compression and Rebound Dials

  • Once the fork lowers are securely in place, reattach the compression and rebound dials using the T30 Torx driver.
  • Ensure that the dials are functioning correctly and adjust them to your desired settings.

Fork Oil and Lubrication

  • Once the fork is fully reassembled, it’s time to add fresh suspension oil. The Bomber 58 requires specific oil viscosities for the best performance. Follow the manufacturer’s guidelines to ensure you use the correct oil type and volume for both the damper and the fork legs.
  • Pour the suspension oil into the appropriate areas, ensuring that each leg is evenly filled with oil.

Final Adjustments and Reinstallation

1. Install the Fork Guards

  • Slide the fork guards back onto the stanchions and secure them with the bolts you removed earlier.

2. Reinstall the Fork on the Bike

  • Slide the fork back into the head tube of your bike and tighten the stem bolts.
  • Reinstall the front wheel, ensuring it is correctly aligned and the axle is properly tightened.

3. Test the Suspension

  • Before heading out for a ride, test the suspension by compressing it a few times to ensure everything is functioning correctly. Check for any unusual noises or resistance.

Troubleshooting Common Issues

  • Fork is too stiff or too soft: This could be due to incorrect oil levels or an improperly set spring preload. Double-check the oil levels and ensure the spring is correctly installed.
  • Leakage from the seals: If you notice oil leaking from the seals after reassembly, the seals may not be seated properly or could be damaged. Replace the seals and reassemble the fork.
  • Uneven performance between the two legs: This might indicate a problem with the damper or the oil levels in one of the fork legs. Check the internals and ensure both legs are functioning symmetrically.

Conclusion

Rebuilding your Marzocchi Bomber 58 suspension fork can significantly improve its performance and lifespan. By following these detailed steps, you can ensure that your fork operates smoothly and efficiently. Regular maintenance and timely rebuilds will allow you to get the most out of your Bomber 58, ensuring a smooth and controlled ride on even the roughest trails.