Torque improves acceleration and climbing, while power influences efficiency. The right balance depends on your application.
Power and torque for a better understanding of electric bike motors
Let's take a look at all those numbers and abbreviations you're presented with when browsing electric bikes and comparing motors. The bell rings. The class begins - welcome to the Electric Bike Motor Basics course.
Understanding a little about the specifications of an electric bike's motor not only enables you to anticipate its performance, but also to compare it accurately with other models. It helps you get beyond the marketing hype and focus on the essentials.
To put it simply: power is generally measured in watts (W), while torque is expressed in newton-meters (Nm). These abbreviations are ubiquitous. In this article, you'll find out what they mean and why they're important.
How do electric bike motors work?
The role of the motor on an electric bike is to provide electrical assistance when pedaling. Unlike a moped, scooter or motorcycle, which use an accelerator-type control, the motor on an electric bike only provides power when you pedal. There are, however, electric bikes with a throttle handle. There are motors with a central drive (at the bottom bracket) or motors in the rear hub.
The motor is powered by electrical energy from the battery. Depending on its specifications, it can produce different torque and power values. These two elements determine the motor's overall performance and capabilities, including maximum speed and level of pedaling assistance, whether on the road or uphill.
What is a couple?
Torque is a measure of rotational force. In a motor, it measures how hard it "turns". The more torque an electric bike motor generates, the more force it can transmit to the transmission. In short, higher torque propels the bike with more power.
All types of electric bikes benefit from higher torque. For example, higher torque improves acceleration, especially at standstill. It's also essential not to overwork the motor when climbing steep inclines, which is why an electricMTB is generally equipped with a high-torque motor.
What is power?
The motor's power indicates the maximum amount of energy it can deliver. It is calculated by multiplying torque by the speed of the motor shaft (similar to the rpm of a combustion engine). On an electric bike, this speed depends on your pedaling cadence and the gear ratio used.
The more powerful the motor, the more efficient the electric assistance, and the less effort required from the rider. This is particularly noticeable when riding uphill. Higher power also means better support for additional loads, such as a passenger or luggage.
We also need to distinguish between rated power and peak power. Rated power is the power the motor can deliver continuously, while peak power is the maximum the motor can deliver over a short period of time (e.g. a steep climb). Some low-end brands only display peak power for marketing purposes.
How torque and power influence your choice
In general, the more powerful the motor, the more energy it consumes, reducing range and battery life. If you're looking for a fast, agile electric bike, capable of easy climbing or carrying a load, you'll need a more powerful motor to ensure this performance.
If autonomy and durability are your priorities, choose a less powerful motor combined with a long-life battery. Although many factors influence range (speed, pedaling power...), a less energy-intensive motor will put less strain on the battery, and a higher capacity in Watt-hours (Wh) will enable you to ride longer.
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Key points to remember
- Torque = Acceleration & Climbing power : Measured in Newton-meters (Nm), torque determines your bike's acceleration force - particularly useful when starting off or climbing. High torque is essential for a full-suspension MTB or electric cargo bike.
- Power = Efficiency & Load Capacity: Measured in watts (W), motor power influences assistance efficiency. Higher power makes it easier to carry heavy loads and ride faster.
- Know your needs before you buy: The choice of motor specifications depends on your lifestyle. Urban or occasional cyclists will prefer autonomy with a modest motor. Adventurers or cargo bike users will be looking for high power and torque.
Your most frequently asked questions
What's more important: torque or power?
How much power do you need for a good electric bike?
250-500 W are sufficient for city use. For slopes or heavy loads, choose 500 W or more.
What does 80 Nm mean on an electric bike motor?
This indicates high torque, perfect for steep climbs, rough terrain or cargo bikes.
What's the difference between rated power and peak power?
Rated power is constant, peak power is temporary for short efforts such as a steep hill.
Does a more powerful motor consume more battery power?
Yes, more power = more consumption. You need a high-capacity battery to maintain good autonomy.