Do You Need a Cadence Sensor?
Yes, if: You use an indoor trainer without a power meter (cadence helps estimate effort). You want to track cadence during outdoor rides and your computer doesn’t estimate it from GPS. You’re working on cadence drills and need real-time feedback.
No, if: You have a power meter — it already reports cadence. Your GPS watch estimates cadence from wrist movement (most modern Garmin/COROS watches do this acceptably for running, but cycling cadence from a wrist sensor is unreliable).
Do You Need a Speed Sensor?
Yes, if: You ride a dumb trainer indoors (wheel-on trainers need a speed sensor to estimate power). You want accurate speed regardless of GPS conditions (tunnels, dense urban areas).
No, if: You use a smart trainer (it reports speed directly). You ride outdoors with GPS (speed from GPS is accurate enough).
Quick Comparison
| Sensor | Type | Protocol | Battery | Weight | Price |
|---|---|---|---|---|---|
| Garmin Cadence Sensor 2 | Cadence | ANT+ / BLE | CR2032, ~12 mo | 7g | $39 / €39 |
| Garmin Speed Sensor 2 | Speed | ANT+ / BLE | CR2032, ~12 mo | 10g | $39 / €39 |
| Wahoo RPM Cadence | Cadence | ANT+ / BLE | CR2032, ~12 mo | 7g | $39 / €39 |
| Magene S314 | Speed OR Cadence | ANT+ / BLE | CR2032, ~500 hr | 9g | $18 / €17 |
| CycPlus S2 | Speed AND Cadence | ANT+ / BLE | CR2032, ~300 hr | 10g | $15 / €14 |
Editor’s Picks
Best Reliable
Garmin Cadence 2
$39 · 7g
Best Value
Magene S314
$18 · 500hr battery
Best Budget
CycPlus S2
$15 · 2-in-1
Individual Reviews
Garmin Cadence Sensor 2 / Speed Sensor 2
The default choice. Mounts on the crank arm (cadence) or rear hub (speed) with rubber straps — no magnets needed. Dual-broadcast ANT+ and Bluetooth simultaneously, so it connects to your Garmin head unit and phone app at the same time. Pairs instantly with every Garmin device and most third-party apps.
Battery lasts about 12 months on a CR2032. Auto-sleep when you stop pedaling. At $39 each ($70 for the bundle), they’re the most expensive option but the most reliable. Buy these if you want zero setup issues.
Verdict: Most reliable, best ecosystem support. Worth the premium for hassle-free data.
Wahoo RPM Cadence / Speed
Identical in function to the Garmin sensors. ANT+ / BLE dual broadcast. Same CR2032 battery, same ~12 month life. The RPM cadence sensor is slightly more rounded and some riders find it sits better on thick crank arms. The speed sensor mounts to the hub with a zip-tie rather than rubber strap.
At $39 each, same price as Garmin. Choose based on your ecosystem — if you use a Wahoo head unit, buy Wahoo. If Garmin, buy Garmin. They’re functionally identical.
Verdict: Equal to Garmin. Buy whichever matches your head unit brand.
Magene S314
The value champion at $18. ANT+ / BLE dual broadcast. The S314 works as either a speed sensor OR cadence sensor (not both simultaneously — you need two if you want both). Battery life is exceptional at ~500 hours, roughly 2x the Garmin.
Accuracy is within 1 RPM of the Garmin in side-by-side testing. The mount is slightly less secure on thin crank arms but holds fine on standard cranks. Auto-sleep activates after 10 seconds of no movement.
Verdict: Best value by far. Half the price of Garmin with comparable accuracy and better battery life. The smart buy.
CycPlus S2
The cheapest option at $15. Claims to detect both speed and cadence from a single sensor mounted on the hub, but accuracy for cadence estimation from hub rotation is inconsistent — it works at steady cadence but struggles with cadence changes during intervals. Best used as a speed-only sensor at this price.
Verdict: Cheapest entry point. Good enough for indoor speed on a dumb trainer. Don’t rely on it for cadence accuracy.
What We’d Buy
Best overall: Magene S314. $18, 500-hour battery, dual broadcast. Buy two if you want both speed and cadence for $36 total — less than one Garmin sensor.
Best reliable: Garmin Cadence Sensor 2. $39 for zero-drama pairing. Worth it if troubleshooting Bluetooth issues isn’t your thing.
Skip if: You have a power meter (cadence included) and ride outdoors with GPS (speed included). Save the $18–$39 for something else.
Your sensors collect the data. We turn it into coaching.
Paincave syncs via Strava and works with any sensor, any head unit, any bike. Every ride scored, every week planned.