SB20 - Replacing the Bottom Bracket

-

Let's see how to replace an SB20 smart bike bottom bracket.

When to Replace

Bad bottom brackets are pretty easy to identify. They will exhibit one or more of the following behaviours:

  • Grinding that feels like sand in the bearing when rotated slowly.
  • Excessive play when pushing the cranks in and out.
  • Wobbling when riding - especially when pushing hard.

What is NOT bottom bracket failure

  • Clicking noises. Instead: Check pedals and look for loose crank bolts.
  • Rubbing noises. Instead: Look for problems around plastic covers.
  • Noises that get loader as you pedal faster. Instead: Check the flywheel.  

Tools Needed

Car mechanics can rejoice. You have most of the required tools.


Tool Summary:

  • Heat gun for loosening red Loctite that holds drive side bottom bracket fastener (alternative: hair dryer).
  • NLGI #2 automotive bearing grease (alternative: bike bearing grease).
  • 18" or longer torque wrench for tightening bottom bracket when reassembling (Alternative:12" wrench - it's short enough that you probably can't over tighten).
  • 24" breaker bar to remove bottom bracket  (alternative: big wrench and a little luck).
  • 8mm ratchet or wrench for removing cranks (alternative: none).
  • 12mm bolt (two possible options shown) and washer to hold bottom bracket tool in place when loosening and tightening bottom bracket (alternative: none).
  • 8 tooth ISIS bottom bracket tool (Alternative: none).
  • 3mm hex wrench (Alternative: none).

Summary of Work

Parts to remove:

  1. Front cover.
  2. Right (drive-side) cover and crank.
  3. Left (non-drive-side) crank and cover.
  4. Bottom bracket.

You can then re-lube or replace the BB cartridge.

Reassembly is just doing the previous steps in reverse.

---------------------

Steps

Remove drive side covers and cranks



Remove:

a. 2 x front bolts and front cover. 
b. 7 x side bolts and side cover.
c. Crank with 8mm wrench
    (counter clockwise to remove).




Remove non drive side crank and cover



Remove:

a. Crank with 8mm wrench
    (counter clockwise to remove).
b. 3 x side bolts and side cover.




Using Botton Bracket Tool




a. Tool fits notches in BB 
b. 12mm fine thread bolt
c.  Bolt holds tool in place





Removing Bottom Bracket



a. Heat the bottom bracket for about one minute to soften Loctite on frame threads.
b. Use a breaker bar to loosen and remove the bottom bracket (clockwise to remove!)





Repair and reassembly notes

You can now re-lube with #2 automotive bearing grease or replace the original BB cartridge.  

I use blue Loctite so that heating is not needed from removal next time. 

I tighten the BB to about 55 Nm (40 ft-lbs). It's counter-clockwise to tighten.

If you want to remove the non-drive-side fastener, you can use the same procedure. Removal is in the traditional counter clockwise direction.


Watch the Video

Watch my video to see the complete removal and reassembly procedure.



========

Questions

Where can I get the bottom bracket removal tool?

Try this one: 8 Notch Bottom Bracket Tool on Amazon.


-----------------

Where to get a new bottom bracket?

Getting a replacement from Stages is your best option.

Edit (July 2024): Getting replacements from Stages may be difficult after the Stages US shut down in April 2024.  

July 25, 2024: This vendor has SB20 BBs in stock: Stages Bottom Bracket - Part No. 000-3758. Get 'em while they last 😁.


-----------------


Can the OEM cartridge be disassembled and repaired? 



-----------------

When did my BB fail?

It didn't.  My 3 4 year old bottom bracket is doing just fine.

I made this blog post and video for a few reasons:
  1. I wanted give DIY riders some hope that they can replace fix their BB if and when they need to.
  2. Check the wear on my bottom bracket. Conclusion: Still looking good with no excessive play.   
FWIW: The OEM bottom bracket cartridge is well made. The 1 7/8" (47mm) diameter allows large, standard sized bearings to be used. Good for longevity.


----------

What type of Loctite adhesive should I use?



If you plan to remove the cartridge for future inspection or maintenance, use blue Loctite. If you expect the re-installation to be permanent, use the original factory applied red Loctite.

I often choose the blue pill. You need heat - plus some cursing and swearing - to loosen a stuck/seized red Loctite part. I like to avoid the cursing and swearing 🙂.

Here's a good summary of Loctite blue versus red. 


===========

Final Thoughts

It's a good idea to keep moisture and sweat away from the axle and BB. Here's what I did: Let's Talk About Sweat.


Comments

Post a Comment

Popular posts from this blog

Stages SB20 - Drive Belt Adjustments

-
Image
 STAGES SB20 DRIVE BELT ADJUSTMENT  Stages includes belt adjustment tips in their support note on fixing SB20 noises:   Flywheel Making Noise . Several people have mentioned these instructions are incomplete. I’ll try to help . I wish this process was easier. Good news: With practice, you can complete all adjustments in less than 30 minutes. TWO GOALS Adjusting the drive belt accomplishes two things: Align the belt to ride as much as possible in the centre of the drive cogs. This reduces friction and positions the front axle perpendicular to the drive belt. Don’t be too worried about this step. The SB20 manufacturing tolerances aren’t perfect. Getting the front drive wheel roughly aligned and generally perpendicular is about all we can expect to achieve. Get belt tension right. Optimal tension means quieter running and no slipping during hard efforts. For most of us, this is a trial-and-error process.You want tight but not too tight. For me, this is measured as a 1 cm deflection when p
Click to Read

Stages SB20 - What's Inside?

-
Image
The Stages SB20  indoor smart bike was released in 2020. Let's take a look at the electronics that enable it  on platforms like Zwift.com and TrainerDay.com. An external power supply routes power to different bike components through a series of printed circuit boards (PCBs). The bike also includes two battery powered crank-based power meters. Here's an overview the basic functions: USB Board - Wedged vertically under the phone tray. It powers 3 USB ports. Upper Board - Fastened horizontally under the phone support rail. This System On a Chip (SoC) handles wireless communication and controls the bike itself. Switch Board - This wire distribution board sits inside the aluminum handlebar stem. It routes connections for the brake level controls  and under handlebar tape "blip" shifter buttons.  Lower Board - This mainly analog circuit board is attached to the flywheel / electronic brake unit. It controls bike resistance and sends power to other PCBs. Power Meters - A
Click to Read

Indoor Bike Improvement #10 - SB20 Rocker Plate

-
Image
10 of 10 - Leaning one way and another Rocker plates make indoor riding more realistic. I'm not entirely convinced. Indoor bikes struggle to recreate outdoor resistance, road conditions, pedalling dynamics and acceleration. I'm not sure that side-to-side movement helps with realism. My personal take is more conservative. Two years of rocker plate riding has improved my overall comfort and helped with out-of-saddle sprints.   My Journey I began experimenting with different rocker plate designs in 2021, starting with the following requirements: ✓ Progressive side-to-side movement that offers stronger resistance as you move from the upright or vertical position. ✓ Forward-and-back movement. Many riders claim this is a critical element in real-world riding simulations. ✓ Small footprint. Commercial products are often quite large to accommodate a wide range of bikes. A custom design for my particular bike should be smaller. ✓ It should remain easy to get on and off the bike.  
Click to Read

Stages SB20 - Measuring Torque Against Factory Specifications

-
Image
Torque Measurement I previously documented how to compare SB20 power meters with a set of calibrated pedals. It gives you a good indication of how your power meters compare in actual riding scenarios.   This test  statically measures  torque with a pair of fixed weights. It tells you if your power meters meet factory specifications . This test does not provide the full calibration that you can perform with Garmin or Favero pedals. You can't change  offset  or slope parameters to get the Stages PM measure correctly in the future. Basic Testing Procedure The basic method involves two ( big ) steps: 1. P osition the cranks horizontally to get raw measurements produced by hanging 25 lb weights from each crank. 2. Use a spreadsheet to process raw measurements and get an average reading for both cranks. Compare these readings against expected values  (t he list of expected values is shown later in this post ). The test setup looks like this: With equal weights on each side, cranks can
Click to Read

Smart Bikes, Zwift and Bike Computers are all WRONG

-
Image
My SB20 smart bike comes with an app that shows power, distance, cadence, L:R balance and current virtual gear. You can also use a bike computer like a Garmin 540/840/1040  to show similar data. When you use either at the same time as  Zwift, you see different numbers.  Who is correct? Answer: They are ALL CORRECT and ALL WRONG!  How can that be?   Let's find out. Before getting started,   it's a good idea to agree on basic parameters. Note: In this discussion, I use the term  Indoor bike  for smart bikes and smart trainers along with their related apps. RESISTANCE AND POWER 1. RESISTANCE - An indoor bike creates resistance that makes it harder or easier to pedal.  2. POWER - The harder you push against the indoor bike's resistance (measured in newton metres) multiplied by how fast you pedal (RPM) defines the POWER you are producing (specified in watts per second or just watts). POWER is a measured number and is EXACTLY the same if you are riding with Zwift, using your
Click to Read

What is Erg Mode and Why Can it Suck?

-
Image
Free Riding is Easy Let's start with the relationship between resistance , cadence and power (watts) when doing an indoor free ride (sometimes called sim mode ). Free riding follows a simple formula:  Power in watts  =   How hard you push   ⨉   How fast you pedal   Your indoor bike offers constant resistance when you stay in the same physical or virtual gear. Pedal at a constant RPM and you get a consistent number of watts. If you then pedal 10% faster, you produce 10% more watts.  Pedal 10% slower, you produce 10% fewer watts. 📣 Free Riding Summary: When simulated riding conditions stay the same, pedalling faster produces more watts. Pedalling slower produces fewer watts. And don't forget: There is one way to go faster in Zwift.  Produce more watts 💪.    If only indoor riding was always this simple... Erg Mode When doing structured workouts, Erg mode is popular. It allows you to produce a desired number of watts whether you pedal fast or slow. It's very useful fo
Click to Read