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The Stages SB20  indoor smart bike was released in 2020. Let's take a look its electronics and drivetrain components. Updated in February 2026 🎉 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.  Key internal drivetrain components include a bottom bracket and electronic flywheel brake.  Here's an overview of the basic components: USB Board - Wedged vertically under the phone tray. It powers 3 USB ports. Upper PCB - 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 PCB  - This mainly analog circuit board is attached to the flywheel / e...

 STAGES SB20 DRIVE BELT ADJUSTMENT (2025 Update) I adjust my SB20 drive belt once a year to keep things running smoothly.  I wish this process was easier. With practice, you can complete all adjustments in less than 30 minutes. UPDATED: December 2025 - New video and pictures. Simpler procedures. 📐 These instructions augment the Stages support documents:  Belt Tension Adjustment (SB20) Flywheel Making Noises . TWO GOALS Adjusting the drive belt accomplishes a couple of things: Gets belt tension right. Optimal tension means quieter running and no slipping during hard efforts. Aligns the belt to ride as much as possible in the centre of the flywheel cogs. This reduces friction and positions the front axle perpendicular to the drive belt.  🎬 VIDEO Here's a new four minute video showing how to adjust tension and align the drive belt. The Details Part Names Here are part names related to drive belt adjustment. BELT ADJUSTMENT SUMMARY “ It’s all about the tensioners ”....

The SB20 smart bike uses both Bluetooth Low Energy (BLE) and ANT+ to wirelessly communicate with apps like Zwift.  You can get communication dropouts and glitches.  Here's how to fix them. BUT FIRST, make sure your wireless environment is optimized: Better Wireless Communication  👈👈👈 Background ANT+ was the dominant fitness protocol prior to 2020. While there is nothing wrong with ANT+, most wireless development and testing in the past 5 years has focused on the Bluetooth Low Energy (BLE) protocol. Stages wrote the firmware for the SB20. It preforms 3 primary wireless functions: a) Controls bike resistance - usually as requested by an app like Zwift. ? b) Gets power and cadence readings from the power meter cranks. c) Sends updates to apps like Zwift. Includes power and / or cadence depending on how you configure the app. Stages did not write the firmware components for doing wireless BLE or ANT+ communication. It was written by Nordic Semiconductor who manufactu...

Breaking a Drive Belt Tensioner Adjusting SB20 drive belt tension is something your should consider performing every couple of years. Here's how: Stages SB20 - Drive Belt Adjustments The good news: A properly adjusted belt is quieter and extends the life of the drivetrain. The bad news:  The belt tensioners ( one on each axle ) can break if you over tighten them. The tensioner bolt will typically snap next to the washer assembly 😖.   DIY Fix Getting SB20 replacement parts is challenging these days. Here's how to fix a broken tensioner. 1. Drill out the broken bolt that is welded to the tensioner ring.  2. Find replacement bolts. I recommend M5 x 1 with thread length of 30 mm. Use stainless steel if possible. If you have a hex cap bolt, you can use it directly.  If you have a round head, you will need to file one edge.  You will also need matching lock nuts. You can also use SAE bolts.  A 10-24 or 10-32 bolt with 1-1/4" thread length works well. Here's a ...

The SB20 smart bike has dual power meters. They work together to give you accurate left:right power measurements. Here's a  dual power meter example with Zwift: Right Crank measures power and sends it to the Left Crank . The Left Crank adds its measurements and sends a single message with consolidated L:R data to any connected apps ( Zwift in this example ). Apps like Zwift support a  Power Source  connection to: The Stages Bike or Directly to the left crank. When both power meters are working correctly, both  Power Source connection methods provide similar performance. For more information, see  How to Pick a Zwift Power Source . What if One Crank Fails? Some SB20 owners have abandoned their bikes when a single power meter has failed. These bikes could have been saved by simply reconfiguring it to use a single power meter. Single-sided power measurement is still very accurate. You simply lose left:right pedal metrics. If one cranks fails, the other crank can...

Are my Power Meters Accurate? One of the most common complaints on cycling social media is: "My power meters are inaccurate." Reasons include: 1. Riders perform better in different environments. Whether it's outdoor or indoor, many cyclists see higher power in specific scenarios. 2. You’ve done a dual meter comparison using something like ZwiftPower ( Comparing Power Meters with ZwiftPower ). 3. The power meters are actually bad ( opinions vary so please keep reading )   Here's the problem:   Comparisons can be misleading. Indoor and outdoor riding environments differ significantly . The resistance and acceleration vary greatly, causing many power meters to struggle with accuracy in one environment versus the other. Riding style is also a factor; smooth riders often see different average power measurements compared to those who vary their cadence and acceleration. With dual power meter comparisons  it is impossible to know which power meter is correct when only two a...

-- UPDATE May 2026 -- Stages Cycling  went bankrupt in June 2024. Giant subsidiary  SPIA Cycling , bought selected Stages assets in late 2024. There has been some encouraging news in 2025/26.   It's just not all good. The good news: You can  buy replacement parts on the Stages US web site .  Stages is providing limited support. They will ship some parts under warranty. Your can send email to support@stagescycling.com  or use the  US Support Site  to open a support ticket. SPIA Cycling indicated that they will be continuing the critical online services needed to keep the Stage Cycling App active for at least one more year.  (May 2026) Firmware v1.8.5 update provided for Stages power meters.This update is targeted at road bike and SC2/SC3 studio bike power meters. I would not consider it an essential update for SB20 users until its stability has been confirmed.   The not so good news: No in-home service is offered . It is D...

SB20 owners occasionally report that their bike is producing resistance  that is too high or low. Here's how to verify that your bike's resistance is correct. What is resistance and what causes it to change? Resistance is the pedal tension that you push against to generate power. The faster you pedal against a given amount of resistance, the more power you produce.  Note:  Erg mode  behaviour is different. Here's a description if you are interested:  What is Erg Mode?    This discussion focuses on  free ride/race/sim mode  resistance. What about Power Meters? Power meters  measure  how hard you are pushing against the bike's resistance. Pedalling faster against this resistance, increases power (watts).  Pedalling slower, decreases power. Power meters do NOT affect resistance. They only reflect increased resistance if you choose to pedal harder against it 💪. Example: Zwift Resistance Here's how resistance is set in a ...