Torque Sensor vs Cadence Sensor: What Changes When You Pedal
In this piece:
Light goes green. You put weight on the pedal and for a beat, nothing happens. Then the motor arrives all at once and shoves the bike forward, and you're slightly behind it, adjusting.
That's a cadence sensor. Now the same light on a different bike: you push, and the bike goes exactly as hard as you pushed, immediately, like someone quietly doubled your leg strength. That's a torque sensor.
One second of riding tells you more than any spec sheet, which is inconvenient, because the spec sheet is usually all you get before you buy.
What each sensor is actually measuring
Both sensors exist to answer the same question — how much help should the motor give right now? — and they answer it with completely different information.
Cadence sensing: are the cranks turning?
A cadence sensor is typically a ring of magnets on the crank spider passing a fixed sensor on the frame. Each magnet that goes by generates a pulse. Count the pulses and you know two things: that the cranks are moving, and roughly how fast.
That's it. It has no idea whether you're standing on the pedals up a 10% grade or spinning with your feet barely resting on them. So the controller does the only thing it can: it delivers whatever power your selected assist level calls for, ramping in over a fraction of a second, and holds it until you stop pedalling or hit the speed limiter.
Cheaper systems use fewer magnets, which makes the delay before power arrives longer and more noticeable, because the controller has to wait for the next pulse to confirm you're really pedalling. Same reason there's a lag when you stop — it needs to see the absence of pulses for a moment before cutting power. That trailing push after you've stopped pedalling into a corner is a cadence-sensor signature.
Torque sensing: how hard are you pushing?
A torque sensor uses a strain gauge — a component whose electrical resistance changes very slightly when the metal it's bonded to flexes. Put one in the bottom bracket spindle, the rear axle, or the crank spider, and you can read actual rider force hundreds of times a second.
The controller then multiplies. Assist levels stop being power settings and become multipliers on your effort: low might roughly match what your legs are doing, high might triple it. Push harder, get more. Ease off, and it eases off with you, right now, with no waiting.
Most good systems combine the torque reading with cadence and wheel-speed data, because the useful quantity is your power output — force times how fast the cranks are turning — not force alone. When a manufacturer says "multi-sensor" or lists torque, cadence, and speed sensors, that's what they mean, and it's a good sign.
There's a rough correlation with motor placement
Mid-drive systems from the established suppliers are almost always torque-sensing, partly because the sensor fits naturally where the motor already lives. Hub-drive bikes go either way: budget hub bikes are usually cadence-only, while better hub bikes fit a torque sensor in the bottom bracket or the rear axle. Don't assume from motor position alone, but if a bike has a mid-drive from a major brand, torque sensing is a safe bet.
Side by side
| Situation | Cadence sensor | Torque sensor |
|---|---|---|
| Pulling away from a stop | Brief pause, then a surge you have to anticipate | Power arrives with your foot, proportional to effort |
| Soft-pedalling on the flat | Full assist for the level anyway; you coast on the motor | Almost no assist — the bike matches your input |
| Climbing at low cadence | Weakest here; slow cranks mean less assist just as you need more | Strongest here; hard pushing reads as high torque |
| Easing off into a corner | Motor keeps pushing for a moment after you stop | Cuts with your effort, predictably |
| Walking pace in a crowd | Twitchy — power tends to be on or off | Controllable, feathered by how gently you pedal |
| Energy use for the same route | Higher, because assist doesn't scale down when you relax | Lower, because you're always part of the equation |
| Cost and repairability | Cheap, simple, easy to replace | More expensive, often integrated into the drive unit |
| Feels like | A scooter with pedals attached | A bicycle with stronger legs |
The row that surprises people is the climbing one. It's easy to assume a cadence system is stronger, because it feels more forceful in normal riding — but its output is tied to crank speed, and crank speed is exactly what collapses on a steep grade. You end up in the worst arrangement available: pushing your hardest while the motor contributes least. Torque sensing does the opposite, reading that hard push as a demand for more power.
The range effect nobody mentions
Here's the counterintuitive part. A cadence-sensor bike often feels faster and more powerful than a torque-sensor bike with identical hardware, and it will usually go less far on the same battery.
The mechanism is simple once you see it. On a cadence bike at assist level 3, the motor draws roughly the same power whether you're contributing 150 watts or 20. So riders do what anyone would — they contribute 20. The motor covers the rest, and the battery pays for all of it.
On a torque bike at the same nominal level, motor output tracks rider input. Relax, and the motor relaxes too. You keep pedalling meaningfully because that's the only way the bike keeps moving briskly, and the energy comes partly from your legs instead of entirely from the pack.
So the range difference isn't really about efficiency in the motor. It's about how each system invites you to ride. Which is also why range claims from any manufacturer are close to meaningless without knowing the sensor type and the assumed rider effort.
The flip side is honest: if your goal is to arrive without working, a cadence bike delivers that better, and you'll accept the range cost or just buy a bigger battery.
When a cadence sensor is the right call
The internet has decided torque sensors are correct and cadence sensors are junk. That's too simple.
Cadence sensing genuinely suits some riders:
- Knee or hip problems. If pushing hard hurts, a system that requires hard pushing to give you power is the wrong system. Cadence sensing lets you spin gently and still move.
- Flat routes, short trips. The cadence sensor's weakness is low-cadence climbing. No hills, no weakness.
- Throttle-first riders. If you mostly ride on a throttle anyway, the pedal sensor barely matters. Note that throttles are typically paired with hub motors and cadence systems, and are restricted or prohibited in some places — check your local rules before buying one.
- Utility bikes you don't want to worry about. A cadence sensor is a magnet ring and a reed switch or hall sensor. When it fails, it's cheap and any shop can fix it. A torque sensor integrated into a proprietary drive unit is a different repair bill.
And tuning matters more than category. A well-implemented cadence system with a gentle ramp-up and several assist levels can feel perfectly civilised. A badly implemented torque sensor with coarse resolution can feel worse than a good cadence one. Category tells you what to expect; the test ride tells you what you're getting.
How to tell which one a bike has, without asking
Spec sheets hide this. Sometimes deliberately — "intelligent pedal assist system" and "smart sensor" are marketing phrases that mean nothing. If the listing doesn't say "torque sensor" explicitly, assume cadence. Brands that spent money on a torque sensor put it in the headline.
On a test ride, four tests settle it in under two minutes:
- The soft-pedal test. Set a mid assist level, get rolling, then pedal as gently as you possibly can without stopping. Cadence: the bike keeps pulling hard. Torque: it goes nearly slack.
- The dead-stop test. Stop on a slight uphill, lowest assist level, and pedal away gently. Cadence: pause, then lurch. Torque: smooth, immediate, and proportional.
- The release test. At speed, stop pedalling abruptly. Cadence: the motor pushes for a beat afterwards. Torque: it stops with your legs.
- The one-leg test. Pedal with one foot doing the work. On a torque system you can often feel assist pulse with your power stroke. On a cadence system it's a flat, constant push.
If you're buying online with no test ride available, look for owner videos of a start from a dead stop. The lurch is visible on camera.
One more thing worth knowing before you talk yourself into a cheaper bike: you generally can't upgrade to torque sensing later. Torque-sensing bottom brackets exist as standalone parts for some hub-drive setups, but the controller firmware has to understand the signal, and most budget controllers simply don't speak that protocol. Assume the sensor you buy is the sensor you keep for the life of the bike.
The buying rule
If your route has hills, if you carry cargo or a kid, if you ride in traffic where low-speed control matters, or if you want the bike to feel like cycling — pay for the torque sensor. It's the single spec that changes how the bike feels every time you touch a pedal, and it's the one most likely to be missing from a bike that otherwise looks like a bargain.
If you want the bike to do the work, your route is flat, and your budget is firm, a decent cadence system is a reasonable, unembarrassing choice. Just test the start-from-stop behaviour before you commit, because that lurch is the thing you'll live with for years.