Torque figures

[danfoto]

When an e-bike maker quotes a torque ("power") figure, that's obviously measured under ideal circumstances e.g. a test lab. But where do they measure that value? Output sprocket, or what?

 

[Woosh]

for all motors, at the axle.
For front and rear hub motors, that's the same as 'at the wheels'.
For crank drive, that the same as 'at the chainring'.
For crank drive, you have to multiply the torque figure at the chain ring by the sprocket to ring ratio. For example, 100NM at a 44T chainring when you are on 22T sprocket at the rear = 50NM. When you are on 11T, it's 25NM.
Manufacturers ought to be more precise when quoting their torque figures, they should say 'measured at x RPM'. This is important because you can work out if the motor is suitable for your application.
50NM at 20 RPM is half of 50NM at 40 RPM.

 

[danfoto]

for all motors, at the axle.
For front and rear hub motors, that's the same as 'at the wheels'.
For crank drive, that the same as 'at the chainring'.
For crank drive, you have to multiply the torque figure at the chain ring by the sprocket to ring ratio. For example, 100NM at a 44T chainring when you are on 22T sprocket at the rear = 50NM. When you are on 11T, it's 25NM.
Manufacturers ought to be more precise when quoting their torque figures, they should say 'measured at x RPM'. This is important because you can work out if the motor is suitable for your application.
50NM at 20 RPM is half of 50NM at 40 RPM.

 

[danfoto]

Much obliged

Point noted about RPM, but isn't it the case that the spread of torque across the rev range is very different to that of an infernal combustion engine?

Whatever, I wish they'd quote torque in foot-pounds. I can't get any imagination of it until I've converted from kN ...