We are independent & ad-supported. We may earn a commission for purchases made through our links.
Advertiser Disclosure
Our website is an independent, advertising-supported platform. We provide our content free of charge to our readers, and to keep it that way, we rely on revenue generated through advertisements and affiliate partnerships. This means that when you click on certain links on our site and make a purchase, we may earn a commission. Learn more.
How We Make Money
We sustain our operations through affiliate commissions and advertising. If you click on an affiliate link and make a purchase, we may receive a commission from the merchant at no additional cost to you. We also display advertisements on our website, which help generate revenue to support our work and keep our content free for readers. Our editorial team operates independently of our advertising and affiliate partnerships to ensure that our content remains unbiased and focused on providing you with the best information and recommendations based on thorough research and honest evaluations. To remain transparent, we’ve provided a list of our current affiliate partners here.
Engines

Our Promise to you

Founded in 2002, our company has been a trusted resource for readers seeking informative and engaging content. Our dedication to quality remains unwavering—and will never change. We follow a strict editorial policy, ensuring that our content is authored by highly qualified professionals and edited by subject matter experts. This guarantees that everything we publish is objective, accurate, and trustworthy.

Over the years, we've refined our approach to cover a wide range of topics, providing readers with reliable and practical advice to enhance their knowledge and skills. That's why millions of readers turn to us each year. Join us in celebrating the joy of learning, guided by standards you can trust.

What is a Crank Arm?

Dan Cavallari
By
Updated: May 23, 2024
Views: 9,548
Share

What many people consider to be the pedals on a bicycle are actually a series of important parts that propel the bike forward. The pedal itself is the platform on which a cyclist's feet rest. The pedal is then attached to a crank arm that connects the pedal to the bottom bracket, which is a series of bearings inside the frame that allow the crank arms to rotate. While this sounds somewhat complicated, the system itself is quite simple and allows for a smooth pedal stroke that propels the rider forward.

The crank arm is usually made of steel, aluminum, or higher end materials such as carbon. Inexpensive bikes will have a simple steel crank arm that is very strong and much heavier than other materials, and more expensive bicycles will use lighter materials to save weight. It is important for this part to be very stiff so that pedaling power is not lost to flexing crank arms; instead, the power should transfer directly to the chain, which propels the bike forward using a series of gears.

A crank arm set contains two arms. The non-drive side crank arm, or the crank arm opposite the chain, is a simple arm that connects the pedal and the bottom bracket. The drive side crank arm, however, is a bit more complex: it holds the pedal at one end just like the non-drive crank arm, but at the other end, the arm must attach to the bottom bracket and it must attach to chainrings, or the front "gears" of a bicycle. These chainrings are one component of the drivetrain, which is the system that propels a bike forward. It includes the chainrings, the chain, and the rear cassette--or cluster of gears.

In recent years, the design of crank arms has changed considerably. The method by which the pedals attach to the crank arms has remained largely the same, but the way that the crank arms connect to the bottom bracket has gone through many design changes meant to make the system more efficient and less susceptible to power loss due to flex. The crank arms have historically attached to the bottom bracket by a square hole that attaches to a square tapered arm on the bottom bracket; the crank arms are then secured by a threaded crank arm bolt. Many varieties of fastening systems exist, from splined bottom bracket systems to through-axle systems that are lighter and stiffer.

Share
WikiMotors is dedicated to providing accurate and trustworthy information. We carefully select reputable sources and employ a rigorous fact-checking process to maintain the highest standards. To learn more about our commitment to accuracy, read our editorial process.
Dan Cavallari
By Dan Cavallari
Dan Cavallari, a talented writer, editor, and project manager, crafts high-quality, engaging, and informative content for various outlets and brands. With a degree in English and certifications in project management, he brings his passion for storytelling and project management expertise to his work, launching and growing successful media projects. His ability to understand and communicate complex topics effectively makes him a valuable asset to any content creation team.
Discussion Comments
Dan Cavallari
Dan Cavallari
Dan Cavallari, a talented writer, editor, and project manager, crafts high-quality, engaging, and informative content for various outlets and brands. With a degree in English and certifications in project management, he brings his passion for storytelling and project management expertise to his work, launching and growing successful media projects. His ability to understand and communicate complex topics effectively makes him a valuable asset to any content creation team.
Share
https://www.wikimotors.org/what-is-a-crank-arm.htm
Copy this link
WikiMotors, in your inbox

Our latest articles, guides, and more, delivered daily.

WikiMotors, in your inbox

Our latest articles, guides, and more, delivered daily.