Originally Posted by CdCf

Because it takes POWER to go fast, and power is force multiplied by speed, or in this case pedal torque multiplied by rotational rate (cadence). If your torque is indeed higher throughout (which I doubt), his cadence at the lower torque level he is at, is sufficiently greater than your speed.

Let's say a sprint finish for Robbie McEwen requires him to put out 500 W. His gear is 53/11 and he's riding on 20 mm tyres. Let's also assume that the sprint is at 60 km/h. 60 km/h is 16.7 m/s, and the circumference of a wheel is 2.074 m. That means ~8 wheel revolutions per second, and the 4.82 pedal-to-wheel ratio gives us a cadence of ~100, or 1.7 revs/sec. Dividing power by "second-cadence" gives torque, and 500 W / 1.7 r/s = 294 Nm. That's his average torque. Peak torque per half pedal cycle will be higher. How much higher is hard to say.

This was just an example. His actual speed and power during a sprint may well be higher. But you still calculate it the same way.