SB20 - Improving Shifter Buttons

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The stock SB20 shifters are OK-ish on a good day, and borderline awful on a bad day.


If you have considered rebuilding the SB20 membrane switches and have optimized your remote buttons by wrapping your handlebars with new tape, improving the physical shifter buttons will take your shifting to a new level.

From Worst to First?

Some people complain that their SB20 shifters are the worst they have used.  The modifications described in this post will make the stock shifters among the best anywhere. 

Tools Needed



You will also need an X-Acto knife if you choose to cut brake hoods for better button performance.

Difficulty

Building better buttons requires working with epoxy glue plus doing filing and sanding.




I rate difficulty to be about 5 out of 10.

What Can You Fix?

Minor design deficiencies can cause the SB20 shifter buttons behave erratically as they age. Small changes have a significant impact on performance.

1. Shape of the Brake Lever Buttons

The Brake Lever Buttons have a small dent on the bottom. It can become misaligned, causing button presses to be missed.


My solution is to add epoxy to the base. This makes the button bottom flatter and moves it closer to the switch membrane. 


A flat base extension eliminates most false and missed button presses. It also reduces the amount of free play when the button is idle.

Epoxy Base Extension

Follow the removal steps in SB20 Fixing Broken Shifters to remove the brake levers.




Open the Shift Lever. Remove the Button Frame and and unscrew the Button PCB.




Remove the buttons from the Button Frame. 

Add a dab of mixed epoxy to the base of each button.

Try to achieve a flat bottom profile.  If not, you can just sand or file each button after it dries in about 6 hours.

Ensure that the modified buttons move freely in the Button Frame.  File the base and shaft as required.
 

2. Brake Lever Buttons + Cut Out

Brake Lever Buttons sit under the Brake Hood.  This thick rubber cover can make buttons hard to locate by feel. It also reduces tactile feedback. 




My solution is to add epoxy to the button shaft and cut a hole in the brake hood.  This makes the buttons easy to locate by feel.  It also significantly improves tactile feedback.

🔬 Cutting the hood is optional.  Cutting open the brake hoods does not make the buttons susceptible to moisture.  The flange at the bottom of the button keeps moisture out.  Following SB20 Fixing Broken Shifters makes the membrane switches themselves moisture proof. 

Extend Button Shafts

Wrap button shafts with masking tape to create an 'extension tube'.

Pour mixed epoxy in each masking tape 'extension tube'.  Allow to dry for 8 hours.

🔬 I used a wood block with 5/16" holes to hold each button vertical.





When dry, remove the tape. Don't worry. The tape does not stick to the epoxy.

File and sand to get an extension of about 5 mm (~3/16"). 



🔬 I extended my top two buttons by 5 mm.  I extended my bottom buttons by 2 mm since I don't expect to every use them very often. I also marked each button with a different colour paint stick.  

☑ Use 2 mm extensions if you will not be cutting the brake hoods.
 

3. Remote Buttons

Each pair of remote buttons are surrounded by a rubber cover that sits under the handlebar tape. It has a tiny 1 mm plastic insert that is intended to press the switch membrane. It often becomes misaligned, causing presses to be less accurate.


My solution to replace this insert with a large dab of epoxy.  This makes membrane presses more reliable.  It also improves tactile feedback.

Extend Remote Button Inserts

Clamp the rubber Remote Button Cover inside out.




Pour epoxy into each inverted button.  Allow to dry for 6 hours.

Completed buttons should have an epoxy insert of approximately 3 mm in diameter.

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Cut holes in Brake Hoods

You can consider cutting holes in the brake hoods to improve responsiveness. Extended buttons up to 2 mm work with unmodified hoods.  Longer buttons work better with cutouts.  Your choice.


Trim around the raised buttons marks on the hoods

🔬 I cut a single hole for the upper two buttons.

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Testing the Results

Use GearView or the Stages Cycling app to test button accuracy and speed. When combined with switch membrane improvements, my shifting is nothing short of spectacular 🏆.  My bike can now reliably detect up to five presses a second.  No double presses.  No missed presses.  

Was it Worth the Effort?

Upgrading my shifters took a couple of days. Some of the work was a bit tedious. Aligning each switch membrane took time to get just right. In the end, I am thrilled with results 🚀. 


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