Watts, torque, and the sticker that does not mean range

Continuous rated power is the figure street rules use. It is what the motor can sustain, not the number a marketing line puts next to a hill. Peak is a short claim: a second or two, sometimes less, and often at a voltage and a current the pack has to be able to deliver. A 2,000 W peak on a 250 W nominal motor is not a 2,000 W road bike.

Torque is the shove

Newton-metres are the turning effort at the shaft the maker measured. On a mid-drive that shaft is the crank, so the bicycle’s gears multiply it. On a hub the figure is at the axle, and the wheel size changes how that feels at the road. A 135 Nm mid-drive and a 35 Nm hub are not on the same ruler. Compare torque inside one architecture.

What to write down before you compare

• Continuous watts, and who stated them.
• Peak watts, kept in a separate column.
• Torque, and whether it is at the crank or the hub.
• The voltage the torque was claimed at.
• Motor mass, without the pack, and system mass with the named pack.
• The speed at which assistance stops.

CYC Photon 2 is the clean example on this site: rated 250 W or 750 W, peak 2,000 W, 135 Nm, 3.5 kg, battery extra. Bafang BBSHD is 1,000 W and 160 Nm in the record we publish. Tongsheng’s TSDZ2B has a price and a torque sensor; the watt figure was not in the table, so the watt field stays empty. Empty is more useful than a borrowed number.

Range is not a watt

Watt-hours are the tank. Watts are how fast you can empty it. A 173 Wh all-in-one wheel and a 500 Wh downtube pack are different afternoons even when both motors say 250 W. Cold weather and a headwind move the result more than a 50 W argument on the sticker.