PedalSmart.blog

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...

Two bikes with Different Resistance Consider these common scenarios. You have: Bought a new indoor smart bike / trainer.   Two bikes / trainers of the same brand and model. Moved a trainer from one bike to another Something is wrong . The same physical or virtual gear does not feel the same as your other bike. If you take a single set of power meter pedals and measure the power produced by each bike at a given cadence for the same virtual gear, you can easily confirm different power readings. Why is Resistance Different? Imagine for a moment, all the indoor trainers and bikes available on the market. When doing a race or free ride, each bike/trainer is controlled by an app like Zwift in the same way. Zwift will say to the bike: "Produce the appropriate resistance to simulate a 70 kg rider going up a 5% incline on an asphalt road surface" where 70 kg is the rider weight set in Zwift, and incline and road conditions are determined by Zwift according to the riding conditions i...

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 y...

In my last post, I described why Erg mode is not always optimal:   What is Erg Mode and Why Can it Suck?   In this post, I describe how the Erg mode works on a Stages SB20 Smart Bike .  SB20 Erg Mode The  Stages SB20  bike is different than other smart bikes or a trainer. It uses crank-based power meters and  not flywheel speed  ⨉  resistance  to determine power levels. This simplifies the power calculations but adds some Erg mode wrinkles. A simple  SB20 Erg mode  flowchart looks like this: The SB20 is measures cadence and power at the cranks rather than calculating power based on flywheel resistance and RPM.   On paper, this method should provide a very responsive erg mode. The reality is: it is one of the slowest erg modes to stabilize after cadence and target power changes.   Why so Slow? The Stages power meter cranks send readings to the SB20 processor once a second. Due to limited processing capability in the cranks,...

SB20 Dream Dream provides equally spaced virtual gears across the SB20's Resistance Range .  Define a configuration with 10 gears and you get 10 equally spaced virtual gears. Create 25 gears, and you get 25 equally spaced gears.  How does this compare to traditional 2X gearing with its 2 front chainrings and rear cassette?   Let's find out. What are Virtual Gears? First, let's understand  virtual gears .  How do they differ from an indoor trainer and why are virtual gears often considered better? Smart bikes and trainers expect apps like Zwift to control electronic brake resistance.  This allows the indoor bike to simulate riding conditions like flat or hilly terrain along with different riding surfaces like dirt or asphalt.  Trainers use the attached bike's physical gears to add the resistance that represents the effort needed to move a bike over the simulated terrain.  Smart bikes accomplish the same by simply increasing the ele...

December 20, 2025 Update: This bug is still present in Zwift Release 1.104.3 Bug Summary: Stages Bike is not listed as Resistance controller when Stages Power Meter is selected for both Power Source and Cadence . History For almost two four years, the  Stages SB20 bike has had an issue connecting to Zwift.   On seemingly random occasions, the  Stages Bike  is not shown as a  Resistance  option on the Paired Devices page. This bug is easy to reproduce on iOS devices (iPads and iPhones) using Bluetooth.  Stages Bike Resistance Bug Before starting, do some pedalling to wake up the Stages Power Meter cranks .   Open the Paired Devices screen. Click Power Source to continue. Select the  Left Crank  for  Power Source . Select the  Left Crank  for  Cadence . Since Left Crank selected for both Power Source and Cadence ,  Stages Bike is not listed. Note: If Stages Bike is listed ,  exit  and...

Today's question: How does battery level affect SB20 power meter measurement? Let's do a deep dive and find out! My Overall Takeaways I recommend battery change interval to be 100-150 hours. Be careful with battery level estimates. Battery levels  do tell  when the battery is healthy (when 90-100%).  Estimates then to drop off after this . Nowadays, I use  BattView   to watch for when my PMs drop below 90%. This corresponds to around 150 hours and is a good time for me to replace my batteries.  Note: You may have different thresholds. If I had a really important indoor event, I would consider replacing batteries if I was near the 150 hour or 90% remaining threshold.  In-Depth Measurements Replaceable Batteries The Stages SB20 power meters have replaceable batteries. An advantage: No degradation of built-in batteries as the power meters age. A disadvantage: No ability to top up batteries to 100% whenever you wish. Battery Life CR2032 button cell b...

In a previous post, I showed how to record data from two power meters and analyze results in a spreadsheet: Comparing Power Meters with a Spreadsheet . Today's post shows how to do power meter comparisons using ZwiftPower - and no spreadsheets 🤓. ZwiftPower Dual Power Meter Analysis Tool The ZwiftPower.com web site has a tool for comparing power meters. It works best with a Zwift activity (race, workout, group ride or whatever) although the method described here lets you compare any FIT activity files from other sites like Rouvy.com or TrainerDay.com .  Note: Comparing power meters is only useful if one or more of the power meters has been calibrated with a torque test . Skip this test and you won't know which power meter is incorrect when differences are found . Comparing SB20 Smart Bike with Garmin Rally Pedals In this example, I use my Stages SB20 smart bike to compare power readings with a set of Garmin Rally pedals.  I do a structured workout where Zwift records pow...

Like many riders, I use the same saddle on both my indoor and outdoor bikes. I had the option to buy a cheaper and heavier version of this 3D printed saddle for indoors. That was nice. Zeus 3D Printed Saddle I bought the $50 nylon frame version for indoors and the lighter $65 full carbon version for outdoors. The outdoor saddle is 2 years old with 12,000 kms and still looks like new. The indoor saddle will likely outlast me.  For the small price difference, I recommend the carbon version. I just wanted to say I paid less for the heavier indoor saddle 🙂. This is the most comfortable saddle I have ever used. That's personal of course. The saddle is average width with wider than normal nose. I had no idea this design was good for me until I tried it. At 165 grams for the outdoor carbon version, it's also the lightest saddle I've owned. For those who care... The Ensolite-like  honeycomb padding is 3D printed.  It is bonded to a carbon fibre or nylon outer frame, depending o...

Your bike's Q-Factor is the width of your crankset or the distance from the outer edge of one crank arm to the other.   More important is the measurement of stance.  That's the distance between the centre of each pedal. Getting your stance the same across bikes can make riding more comfortable while potentially avoiding knee, hip and back problems associated with less than optimal bike fit. Most of us can agree: Overall bike fit is critical. I described my method in a previous post: Better Bike Fit .  Getting the  stance the same between bikes is a probably less critical but still worth doing . Measuring Stance Road bike stance is easy to determine since the bottom bracket centre aligns with the rear wheel. Just measure from the spoke nipple centreline to the middle of each pedal. Indoor bikes, like my Stages SB20, don't have a definitive centre line so you need to measure the distance between the centre of each pedal. No big deal.  A ruler and set square ...

My Indoor Bike has 2200 Watts. I'm good, right? Answer: Maybe. Indoor Bike Resistance Let's first understand how an indoor bike creates the resistance that makes riding more realistic. 🔔 In this post, I use the term indoor bike to refer to smart bikes and trainers . My indoor bike is the Stages SB20 smart bike . I use it in most examples. Eddy Current Brakes Modern indoor bikes use an "eddy current brake" to produce resistance. It's a near magical device. An aluminum disk spins past one or more magnets that creates resistance thanks to eddy current waves . Resistance increases when the disk spins faster or the magnetic field strength is increased. That's somewhat counter-intuitive when you consider that aluminum is not magnetic. Eddy current brakes provide the smooth and progressive resistance that makes indoor riding so much better than even a few years ago. 🔬 Faster spinning = more resistance.  Keep this in mind.   Later, we'll see how lower RPMs c...