Cranks are available in lengths of 170, 175 and 180 millimetres. 175 millimetre cranks are standard. There are two reasons for the different lengths. While everything else on the bike is adjusted to the rider's height, this rarely happens with the cranks. The wrong crank length can cause knee pain. For short people under 1.60 metres tall, 170 mm cranks are recommended. Tall people over 1.90 metres are better off using 180 mm cranks. The second reason is the torque. Professionals get more torque on the cranks thanks to the longer lever. However, the relatively small gain is only of interest to them. If a sprinter produces a maximum of 1000 newtons of force, a 175 mm crank produces 175 Nm. With a 180 mm crank, it is just 180 Nm. However, this gain in torque comes at the cost of greater strain on the muscle. The leg has to go a longer way, the muscle is stretched more.
