How to Replace or Service the Bearings in Your Shimano FH-M8000 Hub

Posted on
in No category

The Shimano FH-M8000 [paid link] hub, part of Shimano’s Deore XT M8000 series, is a high-performance rear hub found in many serious road and mountain bikes. Over time, the bearings within the hub may wear down due to usage, weather exposure, or lack of maintenance. This article provides a comprehensive guide on how to replace or service the bearings in your Shimano FH-M8000 [paid link] hub, ensuring optimal performance and longevity.

Tools Required

  • Shimano FH-M8000 [paid link] hub service tool kit
  • 17mm and 19mm open-end wrenches
  • 8mm Allen wrench [paid link]
  • Bearing press [paid link] (or equivalent tool)
  • Grease (high-quality bicycle bearing grease)
  • T25 Torx driver
  • Plastic mallet
  • Clean rags
  • Isopropyl alcohol
  • Torque wrench [paid link]
  • Replacement bearings (check compatibility with Shimano FH-M8000 model)

Disassembling the Hub

Before beginning the bearing replacement process, ensure that the wheel is removed from the bike and placed on a stable work surface.

Step-by-step disassembly:

  1. Remove the wheel: Use a 15mm or 17mm wrench to remove the rear wheel from the bike. If necessary, remove the quick-release skewer or thru-axle.
  2. Remove the cassette: Using a cassette lockring tool [paid link] and a 5mm Allen wrench [paid link], remove the cassette from the freehub body.
  3. Take off the hub body: Use an 8mm Allen wrench [paid link] to loosen the hub body locknut. You may need a 19mm or 20mm wrench for the locknut, depending on the specific model. Once the locknut is off, remove the freehub body from the hub shell.
  4. Access the bearings: With the freehub body removed, you will have access to the inner bearings inside the hub shell.

Removing and Inspecting the Bearings

Step-by-step bearing removal:

  1. Remove the old bearings: Use a bearing puller or a similar tool to carefully pull the old bearings out of their seated position in the hub shell. Be sure to support the hub shell adequately during this step to avoid any damage.
  2. Inspect the bearings: Examine the old bearings for any signs of damage such as pitting, discoloration, or rust. If the bearings are damaged, they must be replaced. If they appear to be in good condition, a thorough cleaning may be all that is needed.

Cleaning the Hub Shell

After removing the bearings, it’s important to clean the hub shell and other components thoroughly.

  1. Clean the hub shell: Use a clean rag and isopropyl alcohol to wipe down the hub shell, removing any old grease, dirt, or debris.
  2. Clean the freehub body: Similarly, clean the freehub body and the freehub ratchets with alcohol and a rag. Inspect the freehub for any signs of damage, dirt, or wear.

Installing New Bearings

Step-by-step bearing installation:

  1. Apply grease: Before installing the new bearings, apply a small amount of high-quality bicycle bearing grease to the bearing seats in the hub shell. This will help ensure smooth bearing rotation and reduce wear.
  2. Install the bearings: Using a bearing press [paid link], press the new bearings into their designated places in the hub shell. Be careful to keep the bearings aligned properly. If you don’t have a bearing press [paid link], use a small piece of wood or a similar flat tool to gently tap the bearings into place using a mallet. Ensure that the bearings are flush with the hub shell.
  3. Check for smooth movement: After the bearings are installed, manually rotate the hub shell to ensure the bearings move freely and smoothly. There should be no rough spots or resistance.

Reassembling the Hub

Once the new bearings are in place, you can begin reassembling the hub.

  1. Reinstall the freehub body: Slide the freehub body back onto the hub shell, ensuring it is securely seated. Tighten it into place with the 8mm Allen wrench and torque it to the manufacturer’s specifications.
  2. Reinstall the cassette: Place the cassette back onto the freehub body. Use the cassette lockring tool [paid link] and torque wrench [paid link] to tighten the lockring securely.
  3. Reinstall the locknut: Using your 19mm or 20mm wrench, reinstall and tighten the hub body locknut, ensuring it is securely torqued.

Final Check and Adjustment

  1. Check the hub for smoothness: Spin the wheel by hand and check the hub’s smoothness. It should spin freely without any rough spots or resistance. If there is any issue, the bearings may need further adjustment or lubrication.
  2. Reinstall the wheel: Place the wheel back on the bike and secure it properly. If your bike uses a quick release skewer or thru-axle, make sure it is tightened correctly.
  3. Test the performance: Finally, take your bike for a short ride to check the hub’s engagement and performance. Ensure there are no unusual noises or rough spots during the ride.

Conclusion

Replacing or servicing the bearings in your Shimano FH-M8000 hub is a straightforward process that can significantly improve your bike’s performance and prolong the lifespan of the hub. By following these steps carefully and maintaining your hub regularly, you ensure smooth, reliable operation for many rides to come. Remember to use the correct tools and follow manufacturer guidelines to achieve the best results. Regular bearing maintenance is essential for maintaining the high performance that the Shimano FH-M8000 is known for.