What Is E-Bike Pedal Assist and How Does It Work

When you are browsing the parameter table of electric bicycles, you may notice a word that appears frequently: pedal assist, or PAS. They refer to the same function, that is, the electric bicycle moves forward by pedaling and the power of the motor at the same time. The motor “assists” the rider to pedal. As we know, one of the great things about electric bikes is you can choose to exercise your legs or just sit back enjoying the wind blowing through your hair, it’s all up to you. You may find the electric mode quite easy to understand, and pedal assist a little confusing. So I will tell you something about pedal assist in this article, and also include the differences between pedal assist mode and pure electric mode.

What is pedal assist mode

The pedal assist mode or pedal assist system (PAS) is a mode on electric bikes to make pedaling easier and faster. Once you activate the PAS mode, the motor will start to work and you will notice that riding the bike is suddenly being much easier, even when you are going uphill. It feels like someone is pushing you when you are riding a bike. Different PAS levels have different motor outputs. Take Ado A20+ as an example, it has 3 pedal assist levels. If you just need a little push and want to extend your battery range, choose PAS 1. You can work out without feeling sore. If you want to enjoy the speed, choose PAS 3, the motor will do its best to help you reach the top speed 25km/h.

To meet different application scenarios, most of the electric bicycles selling in BuyBestGear have three modes: pedal, pedal assist and pure electric. However, the pure electric mode is not allowed when riding on public roads in most European countries, that is, riders must pedal when electric bikes move forward.

The working principle of pedal assist mode

When you set your electric bike to pedal assist mode, normally the screen will show PAS, and the pedal assist sensor will start to work. Pedal assist sensor is an essential part of electric bicycles, there are two types of pedal sensors: cadence sensor and torque sensor.

Cadence sensor works like a switch, its function is to sense whether you are pedaling. The cadence sensor allows the motor of the electric bicycle to start as soon as the crankset is rotated. The working principle of the cadence sensor is quite simple: the sensor or probe which is the fixed part will pick up a signal sent by magnets. The magnets will then emit a signal when the user pedals, and this signal will be picked up by the probe. At last, the information will be transmitted to the motor to indicate that it must start. It is the most commonly used pedaling assist sensor in affordable electric bikes. Generally speaking, electric bicycles that do not specify the type of pedal assist sensor use cadence sensor.

Torque sensor is more advanced (and more expensive of course), it measures how hard you are pedaling. With torque sensor, the harder you pedal, the more power the motor will provide. It will provide a very nature-feeling cycling experience, and the adjustment is in real-time. Electric bikes with torque sensors include Fiido D21, Fiido M21, Himo C30S, Himo C30R and Lankeleisi XT750 plus.

There is also a speed sensor on the electric bicycle, which will sense the real-time speed of your riding. For the bicycle with speed limit function(which is necessary for electric bicycles that meet European ebike regulations), when you reach the maximum speed of your selected gear, the motor will stop working, so that you can only rely on the pedal to move forward, so as to achieve the purpose of deceleration.

The benefit of PAS mode

Electric bicycles with pedal assist mode meet the ebike regulations in Europe

It is important to know that in France and most other European countries, the bike with pedaling assist system is the only type of ebike allowed that can go on the road without registration. Pure electric without pedaling is not allowed on pedelecs(pedal electric cycle) in most European countries, and the EN 15194 standard states that the electric assistance of a bicycle must be triggered under the impulse of the pedaling produced by the cyclist. If the bike is not equipped with a pedal sensor but with a trigger-type accelerator, it will be assimilated to a moped, which implies an obligation to have insurance, registration and the wearing of a helmet. However, most of electric bikes support both pure electric mode and pedal assist mode considering different usage scenarios, so please keep your ebike in PAS mode if you are riding on public roads.

Pedal assist mode makes e-bike cycling easier and more fun

Although many cyclists shy away from pedal assistance systems, it really makes sense for users with reduced mobility, those who use the bicycle as a means of transport or even recreational cyclists. For example, many people do not travel by bicycle because they do not want to show up to work sweaty and out of breath, sometimes due to the distance or the elevation such as the hills in our region. For these people, electric bikes with pedal assist systems solve all problems perfectly. E-Bikes don't just get the cyclist from point A to point B in comfort, they also keep them in shape. The cyclist decides the level of assistance and enjoys all the fun.

Pedal assist mode vs electric mode

When you choose the pedal assist mode, you need to pedal like riding an ordinary bicycle. The motor will provide you with a certain power. The assistance reduces the effort required. The power supplied by the electrical system depends on that supplied by the cyclist. A sensor measures this force.


  • It is legal to ride 250W electric bikes in pedal mode on public roads in all countries and areas.
  • A good quality pedal assist system has a more intuitive feel compared to the throttle mode.
  • The battery can last longer in pedal assist mode, Engwe Engine pro with 16Ah battery lasts 120km in pedal assist mode, while the pure electric mode can only last 70km.


  • The pedal assist mode of some electric bikes are activated only when pedaling.
  • Pedaling on rough terrains or uphill may increase the pressure on knees.

The pure electric mode is the mode that offers full electric driving force. In other words, you can't pedal yourself, you are carried away completely by the motor. You can adjust the speed with a handle or button on the handlebar(thumb throttle or twist throttle). The force provided by the cyclist has no impact on that provided by the bike.


  • No pedaling, no sweating.
  • Greater speed and instant response.


  • The battery can not last very long, especially when the cyclist is heavy or the terrain is rough.
  • Can be difficult to master in traffic.

If you have more questions or concerns about the pedal assist mode or need some advisce & recommendations, please send emails to support@buybestgear.com or chat online with us.

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