Shimano FH-RS400 Hub Bearing Service: How to Get It Just Right

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The Shimano FH-RS400 [paid link] hub is a reliable and efficient rear hub commonly found on road bikes, offering smooth rolling and excellent engagement. However, like any high-performance bicycle component, the bearings in the FH-RS400 [paid link] hub require regular service to maintain optimal performance. In this article, we’ll walk you through how to properly service the bearings in your Shimano FH-RS400 [paid link] hub, ensuring it continues to provide a smooth and reliable ride.

Why Regular Bearing Service Is Important

The bearings in your Shimano FH-RS400 hub are responsible for reducing friction as the wheel spins. Over time, they can accumulate dirt, grime, and moisture, which can lead to rough spinning, increased drag, and even premature wear. Regular servicing of the bearings helps keep the hub running smoothly, extends its lifespan, and maintains the overall performance of your bike.

Tools Required

  • 10mm wrench
  • 17mm wrench
  • Flathead screwdriver
  • Bearing grease (high-quality bike-specific grease)
  • Cleaning solvent or degreaser
  • Rags
  • Bearing press [paid link] (optional)
  • Small needle or pick for bearing removal
  • Torque wrench [paid link]

Step-by-Step Guide to Servicing Bearings in the Shimano FH-RS400 Hub

1. Remove the Rear Wheel and Disassemble the Hub

Start by removing the rear wheel from your bike. Once the wheel is off, you’ll need to carefully disassemble the hub to access the bearings. This involves removing the quick-release skewer (if applicable), followed by the axle nuts and any end caps that are part of the FH-RS400 hub assembly.

  • Use a 10mm wrench to remove the axle nuts from the hub.
  • Once the nuts are off, gently slide the axle out from the hub body.

2. Clean the Hub and Remove the Bearings

Before inspecting and replacing the bearings, it’s essential to clean the interior of the hub. Use a cleaning solvent or degreaser to remove any old grease, dirt, or debris from the bearing areas.

  • Carefully use a flathead screwdriver or needle to remove any seals around the bearings. The Shimano FH-RS400 typically has rubber seals to protect the bearings from dirt and moisture, so be cautious not to damage them.
  • Once the seals are removed, you’ll see the bearings inside the hub. Gently pick out the old bearings using your needle or pick.

3. Inspect the Bearings

Take a moment to inspect the bearings for any signs of wear or damage. Healthy bearings should be smooth and free of pits or cracks. If you notice any issues, it’s best to replace them. You can find the appropriate replacement bearings for the FH-RS400 hub either through Shimano or a reputable bike parts supplier.

  • Run your fingers over the bearings to ensure they are free from rough spots or noticeable damage.
  • Check the bearing races (the grooves in which the bearings sit) for any scoring or excessive wear.

4. Clean the Bearing Area and Re-Grease

Once the bearings are removed, clean the bearing race area inside the hub thoroughly. This will ensure that no dirt or debris is left inside when you install the new bearings.

  • Use cleaning solvent or degreaser to wipe down the inside of the hub.
  • After the area is clean, apply a generous amount of bearing grease to the bearing race and around the new bearings. Be careful not to over-grease, as excess grease can attract dirt.

5. Install New Bearings

Carefully insert the new bearings into the hub’s bearing race. Ensure that the bearings are properly seated and spaced evenly around the race. Shimano FH-RS400 hubs typically use loose ball bearings, so it’s important to install them in the correct number and arrangement.

  • Start by installing one bearing at a time, ensuring it sits snugly within the race.
  • If you’re using a bearing press [paid link], gently press the bearings into place to avoid damage.

6. Reassemble the Hub

Once all the bearings are in place, it’s time to reassemble the hub. Start by replacing the rubber seals that you removed earlier. These seals prevent dirt and moisture from entering the bearing area, so it’s essential to reinstall them correctly.

  • Carefully slide the axle back through the hub.
  • Reattach the end caps and secure them using the appropriate tools.

7. Test the Hub

After reassembling the hub, it’s crucial to test it for smoothness and function. Spin the wheel by hand and check for any resistance or rough spots in the movement. If everything is functioning correctly, the wheel should spin smoothly without any noticeable drag or noise from the hub.

  • If you hear any grinding or if the hub feels rough, you may need to re-check the bearing installation or clean and regrease the components again.

8. Reinstall the Wheel on the Bike

Once you’re satisfied with the performance of the hub, reinstall the rear wheel onto the bike. Tighten the axle nuts securely and ensure that the wheel is properly aligned and spinning freely. Double-check the quick-release skewer or axle nut torque to avoid any movement or loosening while riding.

Common Issues and How to Fix Them

Even with regular maintenance, there are some common issues that can arise with the Shimano FH-RS400 hub bearings:

  • Grinding or rough movement: This usually indicates that the bearings have been contaminated by dirt or moisture. Regular cleaning and lubrication should prevent this.
  • Loose bearings: If the bearings are not installed correctly or have become loose over time, they can cause instability in the hub. Always ensure that the bearings are securely seated and that the seals are in place.
  • Excessive drag: This can occur if the hub is over-greased or the bearings are too tightly installed. Check the tightness of the bearings and ensure that there is no excessive resistance when spinning the wheel.

Conclusion

Regular bearing maintenance is vital for keeping your Shimano FH-RS400 hub in top condition. By following these steps to clean, inspect, and replace the bearings, you can extend the lifespan of your hub and maintain smooth, efficient performance on every ride. Always use high-quality bearings and grease, and take your time to ensure everything is installed correctly. With proper care, your FH-RS400 hub will continue to perform like new for many miles to come.