Bike chainrings
Our Stars page brings together our tips on the chainring, the part that connects the crank to the chainrings: mounting diameter and number of arms, compatibility with chainrings and cranksets, removable chainrings and direct mounting, and chainring bolts, for replacing or upgrading your transmission.
The part that connects the crank to the chainrings.
The role of the spider
The spider, or star, is the star-shaped part that connects the right crank to the chainrings. It transfers the pedalling force to the chain. On some cranksets, it is integrated with the crank; on others, it is removable, allowing you to change the chainring format, install a power meter, or replace a damaged part.
The rest of the pedalling
Pedalling components also include:
All the parts can be found on the pedalling page.
The fixing diameter
The essential criterion is the fixing diameter, or BCD, the diameter of the circle passing through the chainring screws, expressed in millimetres: one hundred ten or one hundred thirty on many road cranksets, one hundred four or sixty-four on older mountain bikes with three chainrings. The number of arms, four or five, must also match the chosen chainrings.
Without a spider
Many modern cranksets, especially on single-chainring mountain and gravel bikes, use the direct mount: the chainring is fixed directly onto the crank, without a spider, for a lighter and stiffer setup. A removable spider is still useful for installing an integrated power meter. The screws are tightened to the specified torque, with a light thread locker.
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Frequently asked questions
What function does a bike crank spider serve?
The spider, or star, connects the right crank to the chainrings and transfers the pedalling force to the chain. Its arms hold the chainring screws, which determine the format of chainrings that can be mounted.
What is meant by the BCD of a crank spider?
The BCD, or bolt circle diameter, measures in millimetres the circle that passes through the centre of the chainring screws. Along with the number of arms, it determines which chainrings can be mounted on the spider.
How can I tell if a spider is compatible with my crankset?
You need to check the fastening mode on the crank, specific to each manufacturer, the number of arms, and the fixing diameter. The chainline must also match the bottom bracket and frame.
Why choose a removable spider?
A removable spider allows you to change the chainring format, switch to a single chainring setup, install a power meter, or replace a damaged part without changing the entire crank.
What should I do if the chainring screws loosen?
You take them off, apply grease or thread locker according to the manufacturer's recommendations, then retighten them in a crisscross pattern to the specified torque. Loose screws can cause the crankset to creak and wear the threads.
