E-bikes are electric bikes that come with a motor and a sensor to assist the rider when cycling. These bikes are growing exponentially in popularity, and it’s projected that forty million e-bikes will be sold in 2023 alone. There are two main types of sensors on e-bikes: cadence sensors and torque sensors.
An e-bike cadence sensor is a magnetic sensor that switches the motor on and off when the pedals move. A torque sensor is more automatic, and it changes the power of the motor based on the pedaling speed. A torque sensor acts automatically, whereas cadence sensors change at certain intervals.
In this article, I’ll discuss the difference between the two and if there’s a benefit to having both. When buying an e-bike, you’ll need to decide which one is best for you based on the benefits of each one.
What Is a Pedal Assist Cadence Sensor?
A pedal-assist cadence sensor is a magnetic sensor that works like a manual switch. Once you begin pedaling the bike, the cadence sensor turns on the motor, and the motor turns off when you stop pedaling. A cadence sensor is a cheap sensor that comes standard with many e-bikes.
Cadence sensors are a cheap, easy way to add pedal assistance to an e-bike, and since they come with most models, you won’t have to worry about finding and adding one.
A cadence sensor uses a magnet on a pedal crank that turns the motor on when you start pedaling. When you stop pedaling, the sensor will switch the motor off until you start pedaling again. Unfortunately, you have to manually adjust the different speed modes on a cadence sensor, which I found to be a downfall when I needed to change speed mid-ride.
Since a cadence sensor is a manual type of pedal assist, it can be difficult to use if the pedaling speed doesn’t match the sensor’s current mode or speed level. The difference in speed levels can lead to the motor trying to slow you down when you pedal faster or vice versa.
Additionally, I’ve found that the manual cadence sensor can make for a rougher ride since it can cause the bike to be bumpy or jarring. This is also confirmed by Juiced Bikes.
For a good, easy-to-install cadence sensor, I recommend that you purchase the Wahoo RPM Cycling Cadence Sensor. The sensor is easy to install on your e-bike’s arm and includes a mount. The sensor will connect to more than fifty smartphone apps that can track the bike’s speed and other metrics in real-time.
What Is a Pedal Assist Torque Sensor?
A pedal-assist torque sensor gauges an e-bike’s speed to determine how fast the motor should run to assist us when riding. Torque sensors are the most expensive type of sensor, but they’re also very precise in their speed and adjustments, making them ideal for athletes and serious cyclists.
The consensus is that torque sensors are better than cadence sensors, even though they can cost up to ten times more. Torque sensors will usually cost a couple of hundred dollars, and most e-bikes don’t come with a torque sensor, so you’ll need to buy and add one yourself.
A torque sensor will constantly track your speed and pedaling power, so the motor will change how much energy it provides to the bike. This power changes as soon as you pedal more or less, and it’s all automatic, so there’s no extra effort needed on your part.
For example, according to The Next Web, the power on the motor will adjust as I ride up or down hills, so I get more power going upward and less on the way down.
Another benefit of having a torque sensor is that the battery life is much longer. The torque sensors require you to pedal with less effort, so they use less power. Less power means we can ride for longer on an e-bike with a torque sensor instead of an e-bike with a cadence sensor.
Finally, a torque sensor can help you stop your bike fast if there’s traffic or something else suddenly in your path. The sudden change also works if you need to accelerate quickly. Since the torque sensor responds to a change in speed immediately, it’ll assist you in suddenly speeding up or slowing down.
If you’re looking to buy a torque sensor for your e-bike, I recommend the TongSheng Torque Sensor. This torque sensor kit has a 500W, 36V motor that’s easy to assemble.
Methods of Torque Sensing
Torque sensors have many different methods, including pedal force, a chain tension sensor device, or a chainring torque sensor. These are three of the most popular, but there are other methods of torque sensing if you want a different type on your bike, such as a rotation sensor.
A chainring method is the most accurate way to measure the bike’s torque. Since the chainring is where we pedal the bike, measuring from here is the best place. On bikes with a chainring torque sensor, we need to have a wireless method of reading torque, such as a smartphone app via Bluetooth or a device on the bike’s handlebars to communicate with the sensor according to an article by Ebikes.
Another popular method of torque sensing is the pedal force method. This method measures how much force we put on the pedals when we ride, and the power output by the motor adjusts accordingly. This is just like the method we discussed in the section above, where the motor power will be different when going uphill versus downhill per an article by Gazelle Bikes.
A rotation sensor is similar to a pedal force sensor, but it’s more like a cadence sensor which we discussed above. If you want to understand more about the difference between a pedal force sensor and a rotation sensor, watch this video on YouTube from Royal Dutch Gazelle:
A final popular method of torque sensing is the chain tension method. This method measures the tension on the chain when you pedal to sense how much power is needed. Some past e-bikes have come with this type of torque sensor, which uses a pulley system when in use, according to Ebikes.
Both Sensors Together
E-bikes can have both a cadence sensor and a torque sensor at the same time. While it may be more expensive to have both, the benefit is that you can have the precision of a torque sensor with the easy feel of a cadence sensor. This will give you the most accurate readings possible.
Having both sensors on one bike gives you all the benefits of each sensor, allowing them to cover anything that may be missed by one alone. The torque sensor provides you with a fast response time as you pedal and changes the motor constantly as you change speed or pedal harder or softer. The cadence sensor gives a more natural feel to the bike when you ride, according to Evelo.
On a bike with both sensors, you’ll still need to manually adjust your cadence sensors to your speed and pedal levels; however, when you need a quick adjustment to your power, the torque sensor will help.
Once you begin pedaling, the cadence sensor will activate to help you ride smoothly, and the torque sensor will activate as you change speeds like when riding up or downhill. Additionally, you can still use the torque sensor and cadence sensors separately, depending on the intensity of your bike ride.
Downsides include a high price since torque sensors are expensive alone, so adding a cadence sensor will make it cost even more. Also, since cadence sensors don’t last as long as torque sensors, you’ll have to replace them more often.
One e-bike with a torque sensor and a cadence sensor is the Smartmotion electric bike, which is a commuter-style bike. You can learn more about this in the following video from Electric Bike Report:
In conclusion
We’ve discussed the two main types of sensors used on e-bikes – pedal-assist sensors and torque sensors.
Pedal-assist sensors are the next most popular and use a motor to give you a boost when you need it, such as when you’re going up a hill.
Torque sensors are the most popular and use a motor to constantly adjust the power based on how hard you’re pedaling. These provide the most natural feel and the longest battery life.
One additional type of sensor is a Speed sensors which are the least common type, but they’re still used on some bikes. These sensors determine how fast you’re going and use a motor to assist you.
You can find all of these sensors on different types of bikes, so it’s important to choose the right bike for your needs. Consider what type of bike ride you want and what kind of sensor will work best for you.