Before buying an electric bike, you should learn the difference between a “cadence” and “torque” sensor. These sensors tell the motor of an electric bicycle how much assistance to provide while pedaling. Sensor type is one of the most important aspects of a bike’s ride quality, so unfortunately it’s this specification often overlooked when it comes to horsepower or battery size.
For some riders, the difference between a cheaper cadence sensor and a more sophisticated torque sensor is huge and can dramatically affect the quality of the ride. For others, torque transducers aren’t worth the premium.
Whichever side you fall into, it would do you good to know the difference.
Cadence sensors offer the most basic type of pedal assist technology. They measure how quickly you turn the pedals, often placing a series of magnets around the crank arms.
A typical electric bicycle may have 8 to 14 magnets arranged in a circle, which are used as “control points” for the rotation of the pedal. When motion is detected, the sensor signals the motor to start running.
While each e-bike manufacturer will set their bike’s power differently, cadence-sensing e-bikes typically send specific amounts of power to the motor based on your pedaling speed and the level of pedaling assistance you select. If your bike is tuned to a low assist level, for example, the manufacturer has likely set a hard limit on how much power the motor can deliver at a given cadence.
The net effect is that cadence sensor e-bikes tend to feel a lot like riding with a pedal-activated on / off switch.
As a rule, cheaper e-bikes are only equipped with cadence sensors. Almost anything under $ 1,500 will be cadence only.
A torque sensor, on the other hand, measures how difficult you pedal – how much force you apply to the pedals.
On the surface, it may seem that the pace is directly related to the effort, but not always. For example, when going up a hill, hauling heavy cargo, or starting from a stop, you will need more power than when cruising on a flat road. Likewise, you probably want your bike to give you less power when you get off.
Because it constantly analyzes the effort rather than just checking the rotation at a few intervals, a torque sensor is able to adjust the motor assistance more dynamically and intuitively.
Let’s say you are driving on a flat path and cross a hill. On a cadence sensor bike, you will likely get the same amount of power uphill as you would on the flat; if you are at a low level of assistance, you might find yourself increasing the level of assistance to compensate. Granted, the motor may increase a bit if your cadence drops below a certain threshold, but it does not fully respond to your efforts.
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With a torque sensor electric bicycle, the power supplied by the motor can vary more widely and dynamically. In some cases, you may not need to increase the level of assistance when tackling the hill, as the e-bike may tell you that you need more assistance.
Likewise, the cadence sensors can feel a bit choppy at high pedal assist levels. They will tend to take longer to start “ calculating ” your cadence, and if you are at a high assist level, moving your pedals a bit can result in a sharp increase in engine power.
A torque sensing electric bike can tell if you gently press the pedals. If you gently move the pedals (for example, when riding in the rain) it won’t deliver a ton of power even if you’re at a high assist level. But pedal difficult and the bike will respond proportionately.
This means that a well-implemented torque sensor will feel much closer to riding an “ acoustic ” bike – less like you’re being pushed by a motor and more like having superhuman legs.
Torque sensors also generally extend the range of the battery, as they only provide the power that is needed. On the other hand, I find myself having to brake more often on cadence systems only to regulate my speed.
The caveat is the price. Torque sensors are much more sophisticated components and therefore much more expensive to manufacture, so they are usually only offered on more expensive e-bikes.
In my experience, most torque sensor bikes cost over $ 2,000, and under $ 1,500 is extremely rare. And if a bike’s spec sheet doesn’t specify the type of sensor, it almost certainly uses a cadence sensor only, especially if it has a hub-drive motor.
Are torque transducers always better?
In my experience, yes. But there are a few nuances to be aware of.
Some cadence-sensing bikes attempt to replicate a more natural pedaling experience by using smoother power distribution curves or by using more magnets to find cadence at smaller intervals.
If you want a throttle, you’re also more likely to find one on a cadence-based electric bike. This is because many torque sensor electric bikes use mid-drive motors, and the majority of them do not support throttles. The throttle partially makes up for the difference, as it allows you to get all the power you need from the engine without having to change the levels of assistance.
Likewise, not all torque sensing systems are created equal and some are smoother than others.
There are even some people who might prefer a cadence-only system, such as some of those with sensitive joints. Torque sensors are usually (not always!) Set to take a little more effort to really start, whereas a cadence-based electric bike doesn’t care about your effort, only that you’ve turned the pedals enough. .
But are torque transducers worth the extra money?
There are a lot of variables to consider. But all things being equal, is a torque transducer worth the premium? It is something that only you can decide.
For example, you might not find the significant difference if you just want a bike for errands, commutes, and freight.
On the other hand, if you really enjoy the cycling part of e-bikes, chances are you would prefer the more natural input provided by a torque sensor. You don’t have to be a serious cyclist either; I am an occasional cyclist and still struggle to switch back to cadence-only bikes these days.
Of course, that doesn’t mean you can’t enjoy the cycling experience with a cadence-only bike; it’s just the torque sensing bonus that might not be worth it.
If possible, try to test the cadence-only and torque-only electric bikes available around you, and see if you can tell or care about the difference. It’s easier said than done in the coronavirus age, but it will give you a better idea of what to expect.
Hopefully as e-bike technology advances and components get cheaper, you won’t have to choose.
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Published March 25, 2021 – 17:59 UTC