Napęd środkowy czy silnik w piaście: który jest lepszy?

Electric bicycles (e-bikes) offer pedal assistance through two primary motor configurations: silniki piastowe I silniki środkowe. Hub motors are integrated into the wheel hub, either at the front or rear, providing direct propulsion. In contrast, mid-drive motors are centrally located at the bike’s bottom bracket, working in tandem with the bike’s gears to deliver power.

When developing an e-bike product line, selecting the right motor is a critical decision. Whether you’re designing a cargo bike that needs strong torque for heavy loads or a commuter e-bike that prioritises efficiency and weight, the motor type directly impacts performance, cost, and user experience. Mid-drive and hub motors dominate the market—but beyond the specifications, what do these choices mean for your brand’s product strategy?

In this article, we’ll break down the key differences between mid-drive and hub motors, analysing their advantages, limitations, and best use cases. Whether you’re optimising for performance, cost, or market positioning, this guide will help you make an informed decision.

What is a Mid-Drive Motor?

A silnik środkowy is an electric-assist motor positioned at the bicycle’s bottom bracket area, near the crankset. Unlike hub motors that power the wheel directly, a mid-drive motor transmits power through the bike’s chain or belt drive, working in sync with the gear system. This setup provides a more natural pedaling feel and allows for better torque distribution, making it highly efficient for various riding conditions.

Ten “mid” in mid-drive refers to its central placement on the bike frame, ensuring balanced weight distribution and improved handling. Since it delivers power through the drivetrain, it can take advantage of the bike’s gears, automatically adjusting torque and output to match different terrains. This makes mid-drive motors particularly suitable for cargo bikes, high-performance e-bikes, and applications requiring greater power efficiency.

In recent years, mid-drive technology has evolved significantly, becoming more powerful, lighter, and increasingly energy-efficient. Leading manufacturers continue to refine these motors, enhancing their performance and making them a preferred choice for premium e-bike brands focused on optimal riding experience and long-term durability.

Advantages of Mid-Drive Motors in Cargo Bikes:

1. Efficient Power Transmission: The mid-motor directly acts on the pedal system, with the energy-to-motion conversion rate generally above 80%. Compared to traditional hub motors, which have an efficiency of 70-80%, the mid-motor is more efficient.

2. Reduced Resistance: The internal clutch ratchet design of the mid-motor allows it to completely disengage from the bottom bracket ratchet when not powered, eliminating magnetic resistance. Therefore, even when the battery is depleted, the rider can still ride smoothly without any resistance.

3. Higher Torque Output: The mid-motor uses an internal gear shifting mechanism. Multiple clutch gears inside the motor casing form a shiftable ratchet, which increases torque output, providing higher power for load and climbing.

4. Reasonable Weight Distribution: With the motor located in the middle of the frame, the vehicle’s center of gravity becomes more balanced, which helps improve stability and handling during riding.

5. High Integration Design: The integrated, unified design of the mid-motor results in fewer wiring connections, fewer accessories, easier maintenance, and a cleaner appearance.

6. Enhanced Protection Performance: The mid-motor’s casing usually has very high defense capabilities, typically achieving an IP65 or higher protection level. The motor, when in operation, can fully resist the intrusion of external objects and dust, as well as low-pressure water jets from any angle.

Disadvantages of Mid-Drive Motors in Cargo Bikes:

1. Increased Drivetrain Wear: The additional stress on the chain and gears can lead to accelerated wear, necessitating more frequent maintenance.

2. Higher Cost and Complexity: Mid-drive systems are generally more expensive and involve more intricate installation and maintenance compared to hub motors.

3. Dependence on Drivetrain Integrity: If the chain breaks, the motor cannot assist, potentially leaving the rider stranded—a significant concern when carrying heavy cargo.

What is a Hub Motor?

A hub motor, often referred to as an in-wheel motor, is an electric motor integrated into the hub of a wheel, providing direct propulsion without the need for external transmission components like chains or belts. This design is prevalent in various electric vehicles, notably electric bicycles (e-bikes), due to its simplicity and efficiency.

Types of Hub Motors

Hub motors can be categorized based on several factors:

1. Motor Type: Brushed vs. Brushless

• Brushed Hub Motors: These utilize brushes to conduct electricity to the motor windings. While simpler and often less expensive, they tend to wear out faster and require more maintenance.

• Brushless Hub Motors: Commonly used in modern e-bikes, these motors employ electronic controllers to direct current to the windings, resulting in higher efficiency, reduced maintenance, and longer lifespan.

2. Placement: Front vs. Rear Hub Motors

• Front Hub Motors: Mounted on the front wheel, these motors provide a feeling of being pulled. They are generally easier to install and maintain but may offer less traction, especially on slippery surfaces.

• Rear Hub Motors: Located on the rear wheel, they deliver a sensation of being pushed. Rear hub motors typically offer better traction and are more common in e-bike designs.

3. Drive Mechanism: Direct Drive vs. Geared Hub Motors

• Direct Drive (Gearless) Hub Motors: These motors have no internal gears; the motor’s outer shell rotates to drive the wheel directly. They are larger, heavier, and provide smooth, quiet operation with minimal maintenance. Direct drive motors are particularly efficient at high speeds and are often used in Class 3 (speed pedelec) e-bikes.

• Geared Hub Motors: Featuring internal planetary gears, these motors allow the motor to spin at a higher RPM while reducing the wheel’s rotation speed, resulting in higher torque. They are typically smaller, lighter, more efficient, and better at climbing hills than direct drive motors. However, they have more moving parts, which may require maintenance over time.

Further Reading: Różnice między silnikami piasty roweru elektrycznego z napędem bezpośrednim i przekładniowym

Hub Motors in Cargo Bikes

Cargo bikes are designed to carry substantial loads, making motor assistance particularly beneficial. The choice between hub motors and mid-drive motors in cargo bikes depends on various factors, including cost, maintenance, and performance requirements.

Advantages of Hub Motors in Cargo Bikes:

• Cost-Effectiveness: Hub motors are generally more affordable than mid-drive systems, making them an attractive option for budget-conscious consumers.
• Simplicity and Low Maintenance: With fewer moving parts and a straightforward design, hub motors require less maintenance, offering a hassle-free riding experience.
• Independent Drivetrain Operation: Hub motors operate independently of the bike’s drivetrain, allowing the bike to continue functioning even if the chain or gears fail. This independence can be crucial when carrying heavy loads.
• Regenerative Braking: Some hub motors, particularly direct drive models, offer regenerative braking, which can be beneficial for controlling speed on descents and extending battery life.
• Compatibility with Belt Drives and Internal Gear Systems: Hub motors work seamlessly with belt drives and internal gear hubs, resulting in a nearly maintenance-free drivetrain.

Disadvantages of hub motors in cargo bike

1. Limited Torque and Hill-Climbing Ability: Hub motors typically provide less torque compared to mid-drive motors, making them less effective for climbing steep hills, especially when carrying heavy loads.

2. Weight Distribution and Handling: Placing the motor in the wheel hub adds unsprung weight, which can negatively affect handling and ride quality. This weight distribution can be particularly challenging in cargo bikes, where balance is crucial.

3. Maintenance Challenges: In the event of a flat tire or wheel maintenance, hub motors complicate the process, making repairs more cumbersome compared to non-motorized wheels.

4. Reduced Efficiency: Hub motors operate independently of the bike’s gears, leading to less efficient power usage, especially on varied terrains. This inefficiency can result in decreased battery life and reduced range.

5. Traction Issues: Front hub motors can suffer from reduced traction, particularly on loose or slippery surfaces, which can be problematic when starting from a stop or climbing inclines with a loaded cargo bike.

Scenario-based purchasing guide: Which one is more suitable for you?

In our upcoming article, we will delve into a scenario-based guide to help you select the most suitable motor for your electric bicycle. As one brand engineer aptly puts it, “There is no perfect motor, only precise matching.” To assist you in making an informed decision, we will introduce a quick self-assessment flowchart titled “Three Steps to Find Your Ideal Motor”

• “How to choose the right motor for your particular cargo bike“
• “Flat Urban Roads,Hilly or Mountainous Areas,Mixed Terrains: Selecting the Appropriate Motor“
• ” Any Hidden Considerations in Motor Selection?”

Lastly,

Choosing the right motor can be tricky, even with a basic understanding. If you’re developing a new cargo e-bike model and need a tailored solution, the Regen team has you covered. Simply get in touch with the Regen team. After answering a few key questions, we’ll deliver a comprehensive Customization solution and a ready-to-go product.