What are crank arms in a bicycle?

Crank arms are fundamental components of a bicycle's drivetrain system, and they play a crucial role in transferring the rider's pedaling power to the bike's chain and ultimately to the wheels. Specifically, crank arms are the levers that connect the pedals to the bottom bracket, which is part of the bike's frame.

When a rider rotates the pedals, the crank arms also turn, causing the movement of the attached front chainring. The front chainring engages with the bike's chain, allowing the energy generated by pedaling to propel the bicycle forward. This connection is essential for efficient power transfer and optimal cycling performance.

Understanding the function of crank arms is important for cyclists, especially when considering maintenance or upgrades to the bike's drivetrain. The other options, while related to bicycles, do not accurately define the specific role of crank arms in the bike's mechanical system.