Parts of a Bike Crankset – Chainrings to Bottom Bracket

All 9 parts on the diagram

Show the list

The crank 4

Chainrings The toothed rings that pull the chain round.
Crank arm The lever between the pedal and the spindle.
Spider The arms of the right crank that carry the chainrings.
Crank bolt Holds the crank on the end of the spindle.

The bottom bracket 5

Spindle The axle of the bottom bracket. A crank fits on each end.
Bearings Rings of steel balls that let the spindle turn freely.
Bottom bracket shell The short tube of the frame that the bearings fit inside.
Fixed cup The right-hand cup, with a flange that stops against the shell.
Adjustable cup The left-hand cup, turned in or out to set the bearings.

How this list was compiled: Every name checked on 2026-10-01 and kept only where two of these use it. (1) Wikipedia, Crankset and Bottom bracket, https://en.wikipedia.org/wiki/Crankset and https://en.wikipedia.org/wiki/Bottom_bracket : crank arm, spider, chainrings, the bolt that holds a crank on the spindle, the spindle, the bearings, the bottom bracket shell, the fixed cup on the drive side and the adjustable cup. (2) A bicycle glossary, https://www.sheldonbrown.com/gloss_cn-z.html , https://www.sheldonbrown.com/gloss_bo-z.html and https://www.sheldonbrown.com/gloss_sp-ss.html : crank, crankset, spider, chainring, bottom bracket axle, cups, the fixed cup and its flange, the adjustable cup, the bottom bracket shell. (3) A tool maker's repair guide, https://www.parktool.com/en-us/blog/repair-help/crank-removal-and-installation-square-spindle-type : crank arm, crank bolt, spindle. Licence: own work

The drawing: Own drawing from plain geometry; nothing traced. Licence: own work

How it works

The crankset turns the push of your legs into the pull of the chain. One drawing shows the right crank face-on. The other takes apart the bottom bracket it turns in.

Read the full guide

The parts of a crankset

Each crank arm is a lever with a pedal at one end. On the right crank a spider of arms carries one or more chainrings, the toothed rings the chain runs on. A crank bolt holds each crank on its end of the spindle.

The parts of a bottom bracket

The spindle runs through the bottom bracket shell, the short tube at the bottom of the frame. On a cup-and-cone bottom bracket it turns on two rings of bearing balls, each held by a cup threaded into the shell: the fixed cup on the chain side and the adjustable cup on the other.

A crank arm is often just called a crank, a chainring a chainwheel, and a spindle an axle. The quiz accepts each.
Many newer bikes use sealed cartridge bearings in place of loose balls and cups. The crank, spider, chainrings and shell keep their names.

Questions and answers

What are the parts of a bike crankset?

Two crank arms, the spider on the right-hand arm, the chainrings bolted to the spider and the bolts that hold it together. In some cases the word also covers the bottom bracket spindle and its bearings.

What are the parts of a bottom bracket?

A spindle, the bearings it turns on and the cups that hold them. They sit in the frame's bottom bracket shell. On older designs the right cup is fixed and the left cup is adjustable.

What is the spider on a crankset?

The multi-armed part of the right crank that the chainrings are attached to. On most good cranks it is made in one piece with the crank arm.

What holds a crank arm on a bike?

On a three-piece crank, a crank bolt or nut on the end of the bottom bracket spindle presses the arm onto it.