Garmin Cadence Sensor 2 Review

Cadence is the most underrated number in indoor cycling. Power tells you how much work you are doing; cadence tells you howyou are doing it, and the difference between grinding 250 W at 65 rpm and spinning it at 95 is the difference between a session that builds you and one that empties your legs. It is also the single most useful thing to watch when ERG mode starts to bite.

The Garmin Cadence Sensor 2 is the default way to get that number onto a screen. It is an accelerometer in a small pod that rubber-bands to your left crank arm, senses rotation directly, and broadcasts over ANT+ and Bluetooth. There is almost nothing wrong with it. The interesting question is whether you need one at all.

Check this before you buy anything

A large share of the people shopping for a cadence sensor already have cadence and do not know it. Work through this list first.

If you have a smart trainer, it almost certainly broadcasts cadence. Direct-drive trainers derive it from the drive unit and transmit it alongside power over FE-C or FTMS. It may simply not be paired in your app — in Zwift, cadence is a separate pairing slot from power, and plenty of riders have never filled it. Check there before spending anything.

If you have a power meter, it definitely reports cadence. Every crank, spider and pedal meter measures cadence as part of calculating power, so a 4iiii Precision, an Assioma or a Quarq makes this sensor redundant.

If you have a wheel-on dumb trainer, an unconnected spin bike, or a bike with neither, this is exactly what the sensor is for. Our cadence sensor for a stationary bike guide covers that scenario in detail, including the ones where a crank-mounted sensor will not fit.

Why magnet-free matters

Older cadence sensors worked by watching a magnet on the crank pass a fixed pickup on the frame. That design produced a specific and universally hated set of problems: the gap had to be right, the magnet worked loose, the pickup rotated on its zip-tie, and the number dropped out on rough road or when someone knocked the bike.

The Cadence Sensor 2 uses an accelerometer to detect the crank arm rotating. There is no magnet, no pickup, and no alignment. It attaches with rubber bands to any crank arm of any length, works out its own orientation, and starts counting. Fitting it takes under a minute, and moving it to a different bike takes the same.

For an indoor setup, that has a practical consequence worth naming: if you keep one bike on the trainer and one for outdoors, this sensor is trivially portable between them. There is no frame-mounted half to leave behind.

Dual broadcast is the reason to pick Garmin over cheaper options

ANT+ and Bluetooth simultaneously sounds like a footnote and is the specification that decides how well this sensor fits a pain cave.

ANT+ is a broadcast protocol: the sensor shouts, and any number of devices can listen without pairing exclusively. Bluetooth is paired, and paired connections are limited. In a room with a tablet running Zwift, a head unit recording a backup, and possibly a trainer relaying sensors, a single-protocol sensor gets claimed by the first device and disappears from the second. That is a meaningful share of the questions our connection troubleshooting guide answers.

If your laptop or tablet is Bluetooth-only and you want to use the ANT+ side, a cheap ANT+ dongle unlocks it — worth knowing, because the ANT+ path is generally the more robust of the two indoors.

Living with it: the rubber bands are the weak point

The sensor pod will outlast the bike. The rubber mounting bands will not — they perish over a year or two, particularly on a trainer bike, where indoor sweat is far more concentrated and corrosive than anything outdoor riding produces. Spares are cheap and worth having before you need them; our accessories checklist covers the rest of the small-consumables problem, including why a sweat net earns its place.

Battery is a CR2032 rated for up to twelve months, changed with a coin and a quarter turn. The 1 ATM rating means rain and sweat are fine and immersion is not, which is the correct priority for a part that lives beside a drivetrain.

One pairing note: if you also have a power meter or trainer broadcasting cadence, pair only one of them as the cadence source. Two sources reporting slightly different numbers into the same session is a recipe for confusing data, and Zwift will not always pick the one you expected.

Who should buy it

Buy it if cadence is genuinely missing from your setup — a dumb trainer, an unconnected bike, a rollers session where you want the number to keep you honest. It is the most frictionless sensor of its kind and it will work on any bike you own for years.

Buy the cheaper Magene if the price of a Garmin badge for a revolution counter feels disproportionate, which is a reasonable view. Buy nothing at all if you own a smart trainer or a power meter, and instead check your app's pairing screen — the number is very likely already there. Our cadence sensor roundup covers the field, and cadence sensor vs power meter settles the bigger question about which number to spend money on first.