What is Chainline? A Guide to Cycling's Invisible Spec

Choosing a new crankset can be exciting, but it can also be confusing.

Before you even think about brand or material, there's a crucial first step: understanding the basic specifications. Getting the specs right ensures that the crank arm you buy will actually fit your bike. This guide will quickly walk you through the essential measurements you need to know to become your own expert.

The Heart of the Crank: Spindle & Bottom Bracket

The spindle is the axle that connects your two crank arms, and the bottom bracket is the set of bearings that allows it to spin inside your bike's frame. This is the most important point of compatibility. Most modern bikes use a crankset with an integrated spindle, and the most common spindle sizes are Shimano's 24mm, SRAM's DUB (28.99mm), and the larger 30mm standard.

Chainring Interface: BCD vs. Direct Mount

This specification determines how your chainrings attach to your crank arm. There are two main systems on modern cranksets:

• BCD (Bolt Circle Diameter): This is the traditional standard. It's the diameter of an imaginary circle that runs through the center of the bolts that hold your chainrings to the crank's spider (the "arms" that extend from the crank). Common BCDs are 110mm for road compact cranks and 104mm for many mountain bike cranks. You must match the chainring's BCD to your crank's BCD.

  

• Direct Mount: This is a newer, simpler system where the chainring mounts directly onto the crank arm, eliminating the need for a separate spider and bolts. This setup is generally lighter, stiffer, and allows for much smaller chainring sizes, which is why it's very popular on mountain bikes with 1x drivetrains.

  

Chain line: The Invisible Spec for Smooth Shifting

Chain line is the distance from the center of your bike's frame to the center of your chainring(s). Why does this matter? For your gears to shift smoothly and quietly, the chain needs to run as straight as possible from the front chainring to the rear cassette cogs.

A crankset with the correct chain line for your frame and rear hub will result in better shifting performance, less noise, and less wear on your drivetrain components. This is especially important on mountain bikes, which have different chain line standards like "Boost" to accommodate wider tires.

Conclusion

Now that you understand the key specifications, you can see how they come together in a high-performance product. The CRODER SPIRIT Crankset is engineered to be compatible with the most common modern standards, making it a powerful and straightforward upgrade. Here are its specifications in a simple chart:

Armed with this knowledge, you are now fully equipped to choose the right components. The specifications of the CRODER SPIRIT Crankset are designed to offer a perfect blend of high performance and wide compatibility, making it an ideal choice for your next build or upgrade.