Torque sensor vs cadence sensor e-bikes: which to choose

The difference

Cadence sensor. It measures how fast the cranks turn. Bosch describes a separate cadence sensor that "measures crank speed." With a basic cadence-sensing system, the motor responds to pedaling and to the assist level you set. For its own system, Lectric's XP4 manual says pedal assist works only when you are pedaling, and that "the motor output always depends on your pedaling and the PAS level you have set."

Torque sensor. It measures how much force you put through the pedals. Bosch says of its Performance Line CX: "The torque sensor measures how much force is exerted on the pedals." Bosch's drive units combine that with cadence, acceleration and tilt sensors. Our bike data records the Aventon Abound SR and the Lectric XP4 as torque-sensor bikes, from their makers' pages.

Throttle is separate. A throttle lets the motor run without pedaling. Throttle bikes can be Class 2. See e-bike classes explained.

What changes on hills and in traffic

These are the editors' reading of how each method works, not ride impressions:

• Starting from a stop. A cadence system waits for the cranks to turn, while a torque system reacts to the force you apply. Lectric's manual advises pedaling when starting from a standstill.
• Hills. A torque system can raise or lower assist as your effort changes. A cadence system gives the assist your chosen level provides while you pedal. Lectric's manual says to use lower pedal-assist levels and pedal when climbing hills, to save battery.
• Traffic. Smooth, predictable assist matters when stopping and starting. Read the maker's description of start-up behaviour. Bosch's pages use words such as "direct" and "responsive," which are marketing terms rather than measurements.
• Range. Assist level affects range more than sensor type does. See how far can an e-bike go.

How to find out which sensor a bike has

1. Open the maker's spec page and look for "torque sensor," "cadence sensor," "PAS sensor" or "sensor type."
2. Check the manual. Look in the pedal-assist (PAS) section for the sensor type.
3. Check the drive-system maker. Bosch names the torque sensor on its drive-unit pages.
4. Ask the maker if the page doesn't say. A "PAS sensor" with no further detail is not enough to tell.
5. Check torque sensor claims against specs. A listed Nm figure is motor torque, not sensor type.

Which to choose

1. Tight budget, flat routes: a cadence-sensor bike can be enough. Look for adjustable assist levels.
2. Hills, loaded riding or stop-and-go routes: consider a torque-sensor bike, and look at the motor's stated torque too. See hub vs mid-drive motors.
3. First-time buyers: whichever you pick, read the maker's description of how assist starts and stops.
4. Check the maker's return policy if you can't try the bike first. Our bike pages show returns and warranty from the makers.

Spec-based, not ridden: these descriptions come from makers' documents and our reading of how the sensors work.