SB20 - Flywheel Bearing Service

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Can You Service Sealed Bearings?

Sealed bearings, like those in the SB20 flywheel, can be serviced to extend their lifespan.  


✅ Bearings with plastic dust seals are serviceable. You can remove the seal, add grease and then replace the seal in a few minutes. The Axle and Cog Bearings have plastic dust seals. This post shows you how to service them.

⚠️ The Flywheel Bearings have metal dust seals that are not easily removed. I will offer a partial servicing option in my next blog post. 

  

What about Clicking Sounds?

"Clicking sounds" are a common issue with the SB20 flywheel. This happens with the outer ring of a bearing moves side-to-side.

🔬 Stages has issued a service bulletin to address the issue: Flywheel Bearing PTFE Application.  It tells you to spray lubricant into one bearing on each side of the flywheel. 

I must admit, I am not a fan of this method. Spraying light lubricant is a half-measure. PTFE spray can dilute the grease inside bearings. While it can temporarily reduce clicking noises, PTFE spray can negatively affect bearing durability.

Greasing and re-seating the Axle and Cog Bearings, as shown here, is often a better alternative.

Video

Here's the video that shows the procedure.



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Who Should Do this Service?


1. Anyone who wants to extend their flywheel life. Sealed bearings can last a lifetime without servicing - but they can also fail after a few years. One way to maximize lifespan is to add grease once or twice a decade.

2. If you have grinding, clicking and thudding sounds that indicate bearing failure. All SB20 flywheel bearings are inexpensive. None costs more than $5. The service procedure shown can also be used to replace bearings.

3. You read the Stages service bulletin on quieting clicking flywheel noises, and want to do a better job.


Difficulty Level

Servicing the Axle and Cog bearings, require moderate DIY skills. I rate the difficulty to be 7 out of 10.




For context: Belt tensioning and alignment is a 5 out of 10.  Servicing the flywheel bearings (the subject of future blog post) is a 9 out of 10.  

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Servicing Details

Here are the main flywheel components:




Bearing Service Steps

Servicing Axle and Cog Bearings requires the following steps:

  1. Remove plastic covers, lower PCB and brake stay. 
  2. Remove bolts, drive belt and tensioners. 
  3. Slide out flywheel.
  4. Disassemble axle and cogs, add grease to bearings, re-assemble axle and cogs.
  5. Slide in flywheel.
  6. Replace tensioners, brake stay and lower PCB
  7. Replace belt. Check tension and alignment. Tighten bolts
  8. Replace plastic covers. 


Remove Plastic Covers




  • Start on the non-drive side.  Remove both flywheel covers. All use 3 mm hex bolts.
  • Move to the drive side. Remove the front and side covers. Once again, 3 mm hex bolts.
  • Side cover tip: Position cranks at 7 o'clock. Pull the cover down and to the left, to remove.
  • 🎬 vid for more details.

Remove Belt and Flywheel Fasteners

  • ⚠️ Loosen the Vertical 6mm Bolt behind the non-drive Axle Bolt. 
  • Loosen both 14 mm non-drive Axle Bolts.
  • Remove Tensioners.


Slide Out Flywheel


  • Remove connectors from Lower PCB.
  • Remove Lower PCB.
  • Remove Flywheel Brake Stay.
  • Position support under Flywheel and slide out. 

Remove Drive Cogs





Summary:

The Drive Cog is removed by unscrewing the Flange and Lock Nuts followed by the Retainer Clip.

You can then push out the axle from the other side after removing the Cap Nut.









  • Remove Flange and Lock Nuts.
  • Remove Retainer Clip.
  • Lift Cog assembly to remove. 

Service Drive Cog Bearings


  • Service outer Cog Bearing first. Lift dust seal with utility knife
  • Add NLGI 2 bearing grease.
  • Replace dust seal.
  • Repeat these steps on inner Cog Bearing.  

Remove Axle and Axle Bearings






Summary:

The Axle is removed by unscrewing the Flange Nuts followed by the Cap Nut.  

The Axle and Axle Bearing on this side can then be pushed out from the drive side.  

You can then use the Axle and Lock Nut to push out the drive side Axle Bearing.  








  • (non-drive-side) Insert Freewheel Tool (Park FR-1) and unscrew splined Cap Nut.
  • Tap drive-side Axle from to extract.
  • Use Axle and Lock Nut to push out drive-side Axle Bearing.


Service Axle Bearings


  • Lift dust seal on drive-side Axle Bearing with utility knife
  • Add NLGI 2 bearing grease.
  • Replace dust seal.
  • Repeat these steps on non-drive-side Axle Bearing (while still attached to axle).

  • Stages suggests adding Loctite to prevent clicking and squeaking. You should clean the outer ring of both bearings with isopropyl alcohol, apply Loctite adhesive and then wait 24 hours prior to use. I consider this step optional since bikes are shipped without adhesive and only a small percentage develop clicking/squeaking issues.

    I will offer an alternative adhesive-free assembly method in my next video/blog post.   

Re-Assemble Flywheel



  • Replace drive-side Axle Bearing.
  • Insert Axle from non-drive side
  • Replace and tighten non-drive-side Flange and Lock Nuts
  • Replace and tighten Cap Nut
  • Replace Retainer Clip
  • Replace and tighten drive-side Flange and Lock Nuts




  • Tighten 14 mm Axle Bolts.
  • Tighten the vertical 6mm bolt behind the non-drive Axle Bolt. 

Replace the Covers 


    • Non-drive-side: Replace both flywheel covers.
    • Drive-side: Replace drive-side main and front covers.  

    Cleaning Up

    Use isopropyl alcohol for cleanup. It will not affect bearings if you splash them.  Solvent properties also disappear after the alcohol evaporates in a few minutes. 



    References

    For drive belt tensioning and alignment, see my blog post: 

    The 6000 2RS bearings on the flywheel axle have plastic dust seals that are easily removed and replaced.  They are serviceable and can be greased. The same goes for thr 6807 2RS bearing in the flywheel cogs.  

    The 6910Z bearings in the rotating flywheel have permanent metal dust seals that are not easily removed.  I will cover how to do partial servicing in an upcoming blog post.

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    🔺 If you need to replace the flywheel shell bearings, see Stages Service Bulletin:

         TSB-02202025 – SB20 Flywheel Repair Kit

    These instructions are complete - just a bit complex 😀.

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    Replacement Bearing Numbers

    6000 2RS bearing

    6910Z bearing

    6807 2RS bearing


    Stages Service Documents

    Stages SB20 Service Bulletins 

    TSB-02202025 – SB20 Flywheel Repair Kit














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