#### Bike_On

##### Well-Known Member

The force that accelerates the bike and enables a bike and rider to overcome gravity. It can come from the motor or your legs.

What is torque mathematically? Simply the force at the end of a lever times the distance of the lever.

ex. A typical bike crank is 7 inches. A 200 lb man standing up will create 7 x 200=1400 inch-pounds, or 1400/12 = 116.7 ft-lbs.

Many torque specs are in Newton-meters (Nm). 50 Nm = 36 ft-lbs. So the 200lb man asserts 116.7/36*50 = 162 Nm.

What about ebike motors? Many give a nominal spec and a max spec. A motor will produce a higher torque at SLOWER rmps of the motor. As a motor reaches a max speed, it's torque goes to zero. See the simulator on the ebikes.ca website.

How about comparing ebikes?

The Bosch mid drive specs it's motor at 60 Nm. The Impulse II system is 70 Nm. Neither give an rpm. The Optibike boast a 2.5x a Bosch system, so that is 150 Nm. A Bionx dd hub D-series specs 25/50 Nm, and the Falco dd hub is 40 Nm max. As you can see, the mid drives can put out a higher torque, which is usually attributed to the gearing, while the dd hubs are limited to "one" gear. In order to accommodate speeds at 20 mph+, a balance is struck for torque. More torque, less speed. More speed, less torque.

I am use to power, not torque. What gives? Well, power is directly proportional to torque which is proportional to battery current, FYI. More current> more torque > more power in general. Power is actually torque * rpm (of rotating source). Thus, when you shift down on a bike and spin faster with the same force, your power goes up, and so does your speed. For a motor, very low rotational speeds can be deadly for a motor. Torque may be high, but the wheel needs to spin to produce power. A high torque output at a low speed mean current is high in the motor and things are getting hot. A little leg power is needed to help the motor, or shift down in a mid drive system.

Optibike is doing a blog on torque on their web site, if you want more.

What is torque mathematically? Simply the force at the end of a lever times the distance of the lever.

ex. A typical bike crank is 7 inches. A 200 lb man standing up will create 7 x 200=1400 inch-pounds, or 1400/12 = 116.7 ft-lbs.

Many torque specs are in Newton-meters (Nm). 50 Nm = 36 ft-lbs. So the 200lb man asserts 116.7/36*50 = 162 Nm.

What about ebike motors? Many give a nominal spec and a max spec. A motor will produce a higher torque at SLOWER rmps of the motor. As a motor reaches a max speed, it's torque goes to zero. See the simulator on the ebikes.ca website.

How about comparing ebikes?

The Bosch mid drive specs it's motor at 60 Nm. The Impulse II system is 70 Nm. Neither give an rpm. The Optibike boast a 2.5x a Bosch system, so that is 150 Nm. A Bionx dd hub D-series specs 25/50 Nm, and the Falco dd hub is 40 Nm max. As you can see, the mid drives can put out a higher torque, which is usually attributed to the gearing, while the dd hubs are limited to "one" gear. In order to accommodate speeds at 20 mph+, a balance is struck for torque. More torque, less speed. More speed, less torque.

I am use to power, not torque. What gives? Well, power is directly proportional to torque which is proportional to battery current, FYI. More current> more torque > more power in general. Power is actually torque * rpm (of rotating source). Thus, when you shift down on a bike and spin faster with the same force, your power goes up, and so does your speed. For a motor, very low rotational speeds can be deadly for a motor. Torque may be high, but the wheel needs to spin to produce power. A high torque output at a low speed mean current is high in the motor and things are getting hot. A little leg power is needed to help the motor, or shift down in a mid drive system.

Optibike is doing a blog on torque on their web site, if you want more.

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