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  • Writer's pictureKeith Houghton

Who knew that a bicycle could be so complex!

Want to know your bottom bracket from your head tube, well here is a simple guide to the main components of a bike.

The simplest way to get your head round what seems like a huge number of parts is to break them down into 5 main groups:

  1. Frame

  2. Wheels

  3. Drivetrain

  4. Steering

  5. Brakes


Everyone should know what the frame is but what about all the parts of the frame?

  • Top Tube – the tube which runs across the top of the frame

  • Down Tube – the tube which descends from the front of the bike towards the pedals

  • Seat Tube – rises from the bottom of the down tube towards the saddle

  • Head Tube – the short section running between the top tube and the down tube

  • Chain Stay – extends backward from the point where the down tube meets the seat tube

  • Seat Stay – drops from the rear end of the top tube to meet the back of the chainstay

  • Seat Post - extends upwards from the seat tube to hold the saddle

  • Fork - the double-ended section which the front wheel attaches to

  • Saddle - the bit your bum sits on (or hangs over)


The wheel might be simple but there are a lot of parts and an increasing number of options.

  • Rim – the circular part of the wheel to which the tire is fitted

  • Tire – the bit that touches the ground, in traditional tires it will contain an inner tube that holds the air, many tires are now tubeless and do not need an inner tube

  • Valve – pokes through a hole in the rim and is used to inflate the inner tube, valves are either the long, thin Presta valves (normally found on road bikes) or the wider Schrader valves (more common on mountain bikes)

  • Spokes – thin rods connecting the rim to the wheel’s hub

  • Hub – the central part of the wheel, containing ball-bearings that allow the wheel to spin.

  • Fastening / axle – there are several methods of fixing the wheel to the frame, before disc brakes the most common method was quick-release skewers. With disc brakes most wheels use thru-axles.


These parts are how you get your legs to make the bike move, this is where we move on to some names you may have heard but not know what they are.

  • Chain – transfers energy from the turning pedals to the rear wheel, you need to keep the chain clean and lubricated

  • Pedals – provide a contact surface for your legs to turn the chainset, there are a number of types of pedals including flat pedals where you just put your feet on them or a range of different ‘clipless’ pedals that you clip into!

  • Crank Arms and Crank – the arms that connect the pedals to the crank and the crank connects to the two crank arms together

  • Chainrings – the front set of cogs or gears. There may be between 1 and 3 chainrings with the larger on the outside and smaller on the inside

  • Chainset – the name given to the crank, crank arms and the chainrings as a unit

  • Bottom bracket - the crank passes through the frame inside the bottom bracket, the bottom bracket includes bearings that allow the crank to turn

  • Cassette – the rear set of gears and usually contains between 5 and 12 sprockets of different sizes

  • Front Derailleur - the mechanism that shifts the chain between the different chainrings at the front. The derailleur is controlled by gear / brake levers, usually found on the handlebars. There are many different options for gear levers.

  • Rear Derailleur - the mechanism which shifts the chain between the different sprockets at the rear

  • Jockey Wheel - the two small sprockets in the rear derailleur

  • Derailleur Hanger – the metal piece connecting the rear derailleur to the frame. Also known as ‘frame-savers’, they’re intentionally designed to bend under pressure as a failsafe to prevent damage to the frame, which is far more costly.


  • Handlebars - The bike’s handlebars provide control for steering as well as controls for the brakes and gears. They come in all sorts of shapes and sizes including drop handlebars, commonly found on road and gravel bikes, and flat bars usually found on mountain and hybrid bikes.

  • Brake and gear levers – the position of the brake levers depends on the style of the handlebar. On drop handlebars, the brake and gear controls are sometimes combined into a single pair of levers which are squeezed to apply the brakes or pushed to the side to change gear. Flat bars are more likely to use trigger shifters.

  • Stem – connects the handlebars to the steerer tube (which extends from the top of the fork)

  • Headset – the name for the collection of parts that allow the fork and steerer tube to rotate within the head tube


There are two common types of brakes; rim brakes and disc brakes and we will deal with these separately. Rim brakes use the rim of the wheel as the braking surface and disc brakes have a rotor at the centre of the wheel.

Rim Brakes

  • Brake Blocks – usually made of rubber, they’re pressed against the rim to slow the bike down

  • Shoes – the part which holds the brake block

  • Calliper Arms – the moving parts which press the brake blocks onto the rim

Disc brakes

  • Rotor – the metal ‘disc’ attached to the wheel hub

  • Brake Pads - these are within the callipers and are pushed against the disc to slow the bike down

  • Callipers – fitted on either side of the rotor, they hold the brake pads and push the pads against the disc to slow the bike down

And that’s it! Why not ask Howard to test your knowledge when you are next in the shop?

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