In this article, we aim to shed light on what the PAS system is—the pedal-assist system in electric bikes—and why Delfast decided to incorporate it into our designs. Additionally, we'll explore whether this system is truly essential for e-bikes.

The electric bike represents a fascinating blend of human-powered and electric propulsion. Without the electric motor, it would simply be a conventional bicycle. Conversely, without the pedal system, it would resemble an electric scooter. Historically, the advent of motorized bicycles arose due to the limitations of early engines—motors were often weak and unreliable. As a result, the pedal system served as a backup mechanism in two primary scenarios: when the motor failed and the rider needed to reach their destination manually, and when the motor lacked sufficient power to tackle inclines or challenging terrain.

Over time, electric motors improved in both reliability and power, leading to the diminishing importance of the pedal system. This shift marked a clear evolutionary path where the two distinct drive systems began to function independently. Consequently, the pedals became redundant on powerful and heavier motorized bikes. To enhance efficiency, the bikes had to become lighter while accommodating the growing weight demands of increasingly robust motors.

As a result, bicycles with motors diverged into two distinct categories: one focused solely on electric power, and the other emphasizing the hybrid model. The integration of advanced electronics into electric bikes has transformed them into highly efficient personal vehicles. These electronics precisely control the rotational speed and torque of the electric motor, offering riders a smoother and more effortless experience. Furthermore, the PAS system allows cyclists to supplement their pedalling efforts with motor assistance, thereby extending battery life and increasing overall range.

Electric bikes typically offer multiple modes for controlling the motor's speed. While most two-wheeled electric vehicles rely on a standard accelerator handle, electric bikes often include the PAS system. This pedal-assist system responds to the cyclist's pedalling motion, activating the motor-wheel accordingly. Designed to provide gentle support during rides, the PAS system has become a mandatory feature across Europe, ensuring the seamless integration of electric bikes into traditional cycling infrastructure while maintaining safety for all users.

There are various designs of PAS systems available today. Some entry-level systems utilize a sensor that detects pedal rotation and a disk with permanent magnets. This setup works effectively but lacks precise speed control. When the system senses pedalling, it triggers the motor to engage at full power almost instantly. While this approach is simple and reliable, it can lead to sudden surges in acceleration, which may surprise riders, especially when entering turns. Additionally, the system requires continuous pedalling to maintain motor engagement; otherwise, the motor-wheel shuts off after a brief pause. To address these limitations, many modern electric bikes also include a throttle handle as a secondary control mechanism.

On the other end of the spectrum, more advanced PAS systems employ torque sensors that measure the actual force applied to the pedals. By analyzing this data, the controller adjusts the motor's output to match the rider's pedalling intensity. This results in a far more nuanced and responsive experience. Manufacturers like Bosch, Shimano STEPS, and BionX produce high-quality torque-sensing PAS systems. These systems are commonly found on premium mountain bikes, where precision assistance is paramount. Typically, these PAS units are designed to fit seamlessly into existing bike frames with minimal modifications.

Despite the growing popularity of PAS systems, debates persist among manufacturers regarding the optimal level of motor assistance. Should the motor consistently compensate for 50% of the rider's effort, or should riders have the option to toggle between full assistance and manual pedalling? Another consideration is the legal threshold defining when an electric bike transitions into a moped or motorcycle. Depending on how these questions are answered, the resulting e-bike can vary significantly in terms of performance, design, and regulatory classification.

Ultimately, the PAS system serves as a valuable asset for e-bike enthusiasts. By smoothing out the riding experience and reducing peak battery drain, it enhances both comfort and longevity. From a cost perspective, the battery remains the most expensive component of an electric bike. Thus, extending its lifespan through PAS technology makes perfect sense. At Delfast, we believe that the pedal-assist system strikes the ideal balance between human and machine collaboration, creating an experience that feels natural yet empowering.