How to Install a Cadence Sensor

Almost every set of instructions you will find for this job is written for sensors that no longer exist. Magnets on the chainstay, a second magnet on the crank, a gap measured in millimeters — none of that applies any more. Current sensors use an internal accelerometer, which means they detect their own rotation and need nothing else on the bike.

What you need

The sensor, the rubber bands it came with, and about two minutes. No tools. Do not throw the box away until you have paired it, because the mode-switch instructions for dual-purpose sensors like the Magene S3+ are printed there.

Step 1 — Work out which sensor you actually have

Many sensors sold as "speed and cadence" are one sensor that does one of the two jobs at a time. A cadence sensor goes on the crank arm. A speed sensor goes on the wheel hub. If yours is switchable, set the mode before you fit it rather than after.

On a direct-drive trainer you only want cadence, because the trainer already reports speed and power. On a wheel-on or classic trainer you may want both — cadence sensors on a stationary bike covers the gym-bike version of this question.

Step 2 — Fit it to the non-drive crank arm

The sensor goes on the inside face of the left crank arm — the face pointing at the frame — with the body of the pod sitting along the arm toward the bottom bracket. Two reasons: that face is shielded from your heel on every pedal stroke, and the pod is closer to the axis of rotation, which keeps it out of the way of a chainstay.

Stretch the first band over the sensor and around the crank, then the second in the other direction so they cross. Pull them tight enough that the sensor does not rotate when you twist it with a finger. Then check clearance: turn the cranks backwards a full revolution and watch that the pod misses the chainstay, the front derailleur and your shoe.

If the crank arm is a shape that will not take a band — a deep aero profile, a power meter already bonded to it — use the shoe-clip option some sensors provide, or move to a sensor that offers one.

Step 3 — Wake it up

Magnet-less sensors sleep to save the battery and wake on movement. Spin the cranks for five or ten seconds before you go looking for it in an app. If there is an LED, it will blink while it is awake and broadcasting — which is your confirmation that the sensor works before you start blaming your software.

New sensors usually ship with a plastic battery tab. If there is no LED and no signal, that tab is the first thing to check.

Step 4 — Pair it

In Zwift, open the pairing screen and select the Cadence box specifically. Keep pedaling while you do it. If the sensor does not appear, see the troubleshooting list in cadence sensor not working.

On a Garmin or Wahoo head unit, use Sensors → Add Sensor and pick the cadence type. On a phone or tablet, pair inside the app rather than in the operating system's Bluetooth settings — most cycling apps want an exclusive connection, and a sensor already bonded at the OS level can be invisible to them.

Where it goes on a trainer bike, specifically

Nothing about the install changes indoors, but two things about the decision do. First, most smart trainersalready broadcast cadence, so check before you buy a sensor at all — you may be solving a problem you do not have. Second, if you are on Apple TV, every sensor you add consumes one of the platform's two Bluetooth connections, which is covered in Zwift on Apple TV.

If you are not sure whether you need one at all, do you need a cadence sensor for Zwift answers that honestly, and cadence sensor vs power meter covers what each one is actually for.

The short answer

Cadence sensors that are easy to fit

#	Product	Best for	Score	Price
1	Garmin Cadence Sensor 2 The simplest sensor to fit: two rubber bands around a crank arm, and it is on the bike for a year.	Easiest to fit, and the easiest to pair	8.7★★★★☆8.7 out of 10	$64.11 · View on Amazon $69.99Save 8% #ad We may earn a commission · Price as of October 21, 2026
2	Magene S3+ The value pick, and the most flexible one to fit: two mounting options in the box and a mode switch if you change your mind.	Best value, and switchable between speed and cadence	8.5★★★★☆8.5 out of 10	$16.99 · View on Amazon #ad We may earn a commission · Price as of October 21, 2026
3	Wahoo TRACKR Speed The companion sensor: fit it to the hub if you need wheel speed on a wheel-on setup, and pair it alongside a cadence sensor rather than instead of one.	If what you actually need is speed, not cadence	8.4★★★★☆8.4 out of 10	$44.99 · View on Amazon #ad We may earn a commission · Price as of October 21, 2026
4	Coospo Cadence Sensor The budget pick, and the one with the useful escape hatch: if the crank arm will not take a band, it clips to your shoe instead.	Cheapest way to get cadence on the bike	8.0★★★★☆8.0 out of 10	$26.99 · View on Amazon $28.79Save 6% #ad We may earn a commission · Price as of October 21, 2026

Three mistakes that cause most failed installs

Fitting it to the drive side. It will work, but the pod is then alongside the chainring and the chain, which is a worse place for it and harder to keep clear.

Bands too loose. A sensor that can rotate on the arm will read intermittently, and the symptom looks exactly like a flat battery.

Pairing at the operating system level.Bonding a sensor in your phone or tablet's Bluetooth settings can make it unavailable to the app that actually needs it. Pair inside the app.

Battery, and when to change it

These run on CR2032 coin cells. Garmin claims up to about twelve months; Wahoo quotes around 200 hours for the TRACKR Speed. Keep a spare in your toolbox — the cell is the single most common cause of a sensor that has stopped appearing, and the symptom is intermittent readings before it is total silence.

When you change it, note the orientation of the old cell before you lift it out, and check the rubber gasket seats properly when you close the case. A badly seated gasket is how sweat gets in on an indoor bike, and sweat protection is a real consideration for anything mounted on a trainer bike.