In the car and truck world, two key numbers are bandied about when referring to performance capability: Kilowatts (or horsepower for the old-timers) of power, and Newton-meters (or foot pounds) of torque. Torque is the engine’s rotational force, while power defines how quickly that work can be delivered. Power is calculated by multiplying the torque by the speed of rotation.
To understand this, think of the difference between a race car and a tractor with motors developing the same power. The race car is light and aerodynamic so does not need a lot of torque to accelerate it, but needs to reach high speeds so gearing is used to drive the back wheels at high speed with relatively lower torque. A tractor, on the other hand, may have the same amount of power, but that power is harnessed through low gearing to spin the back wheels slowly but with massive torque. The tractor can’t reach high speeds, but it can pull and push huge amounts of weight.
In the ebike world, torque (rotational force) is measured in newton-metres, while power is measured in watts. Most ebikes have around 50 or 60 newton-metres of torque, while some deliver 80 or 85 newton-metres of torque. The more newton-metres of torque your motor can produce, the less hard your legs have to work to turn the pedals on your bike.
So what about watts? There are actually two different measures of watts: continuous and peak. Most ebikes have a 250 or 300 watt motor. This defines the continuous power of the motor: What the motor can sustain on a continuous basis without overheating. Peak power is calculated by multiplying the voltage of your ebike (most are 36 volts) times the amps of your motor controller. It is very rare to see ebike brands defining the number of amps in their motor controller. As a rule of thumb though, most are going to have controllers that are in the vicinity of 15-20 amps. A 36 volt ebike with a 15 amp controller will deliver 540 watts of peak power, while a 36 volt ebike with a 20 amp controller will deliver 720 watts of peak power. Peak power can make a significant difference to your performance on steep hill climbs.
Will a motor that has more turning force plus more peak power outperform a bike with a lower turning force and peak power? Of course, the answer is yes. And it’s a key reason we at MeloYelo have chosen the MaxDrive motor from Bafang for our top-end bike models: The Ascent MD and the Traverse MD. The MaxDrive motor delivers 80 newton-metres of torque plus a highly impressive 792 watts of peak power (thanks to its 22 amp controller). So not only does the MaxDrive motor with its 80 newton-metres of torque reduce the leg effort you need to apply, it also has the ability to “get you there faster” with its 792 watts of peak power. This is why, in their review of 5 different brands of ebike motors, Consumer Reports NZ said the “Bafang MaxDrive motor delivers excellent hill-climbing torque and power.”