What part of the bike is responsible for transmitting power from the pedals to the wheels?

The component responsible for transmitting power from the pedals to the wheels is the crank arms. When a cyclist pedals, the force applied to the pedals is transferred through the crank arms. The crank arms, which connect the pedals to the bike's bottom bracket, rotate as the cyclist pushes down on the pedals. This rotational movement is essential for creating the energy that moves the bike forward, as it directly affects the chain ring attached to the crank.

While the chain, cassette, and derailleur play important roles in the overall drivetrain mechanism, they rely on the initial power transfer initiated by the crank arms. The chain connects the chainrings attached to the crank to the cassette located on the rear wheel, facilitating the movement of the bike once the crank arms have begun turning. The derailleur is responsible for shifting the chain between different gears, but again, it cannot function without the crank arms providing the initial power. Thus, the crank arms' role in transforming the cyclist's effort into forward momentum is crucial and ultimately what makes them central to the power transmission process.