Bike Glossary

Seat post clamp

The seat post clamp is the bracket which holds the seat post in place. The seat post clamp means that when you sit on your bike the saddle doesn’t go down immediately. These days most bikes have a quick release lever so saddle height can be adjusted quickly and easily.

Seat post

The seat post attaches to the saddle via the saddle rails and is inserted into the frame’s seat tube. The post is what you use to adjust your saddle height. Seat posts usually have a a mark to show the minimum amount which you should have inserted in the frame.

Brake levers

Usually found on the handlebars, these are the levers that let you apply the brakes. The lever gives you enough mechanical advantage to stop your bike. On the brake levers there is usually an adjusting barrel which allows you to fine tune the tension of your brake cables. Also, many modern brakes allow you to adjust how far your fingers have to reach from the levers. Great for those with small hands!

Brake pads

These are the part of the brake which rubs against either the rim of the wheel itself, or a disc, in the case of disc brakes. With caliper brakes these are usually made from rubber and for disc brakes

Brake hoods

Brake hoods are found on bikes with drop handlebars. These are the plastic parts which stick out between the handlebar and the brake levers. Riders often use these as an alternative hand position to riding “in the drops” or “on the tops”. This called riding “on the hoods”.

Brake cable

Brake cables are attached to the break levels and your actual brake unit. They transmit the force from your hands to the brakes. They are usually made from stainless steel and are found inside a plastic cable housing, basically a plastic tube which protects them from the elements.


These help you stop. These days there are many different braking systems out there but the two most common are caliper and disc brakes.


A bicycle wheel consists of a central hub, with spokes radiating out to a rim. A tyre an inner tube are mounted on the outside of the rim.

Tyre valve

This is the small valve which allows you to fill your tyres with air. These run from the inner tube, through a hole in the rim. These come in two main varieties – Schrader and Presta. Schrader valves are most commonly found on mountain bikes and are wider, like the valve on a car tyre. Presta valves are thinner, and are usually found on road bicycles where the tyres are inflated to a higher pressure. These days many pumps are able to inflate both types but not all, so check when buying. If not, you can buy a cheap adapter to screw on to the end of your pump.

Top tube

The top tube runs from the head tube to the seat tube, and is also known as the crossbar. It’s really important when choosing a bike to make sure the standover height – the distance between your crotch and the top tube is sufficient.


Historically many bikes were made from steel, particularly the light and strong steel alloy chromoly. Many bicycle manufacturers began to use aluminium as it was a much lighter material. However, steel is much springier meaning that steel bikes tend to soak up more of the bumps in the road. With modern welding techniques, steel bikes can now be made with much thinner tubes, so are not that much heavier than their aluminium counterparts.


The rim of a bicycle wheel is connected to the hub in the centre by the tensioned spokes. The tension of spokes can be adjusted by turning the spoke nipples.

Spoke nipple

These small adjusters are found where the spokes meet the rim and are used to fine tune the tension of each spoke. These can be useful for realigning a buckled wheel.


The seat stays connect the top of the seat tube to the rear chainstays. Along with the chainstays, these hold the rear wheel of the bike in place.

Seat rails

The seat rails connect the saddle to the seat post. A saddle has two rails which run parallel from front to back. The seat post is clamped directly on to these rails. You can adjust the saddle back and forth by moving it along the rails. Most saddles have marks on the rails to show the safe limits of where you can move the seat.

Seat tube

The seat tube is the vertical part of the frame which connects top tube to the bottom bracket. The seat post is inserted into the seat tube and moved in and out to adjust saddle height.


Chromoly is a steel alloy popular for making bikes as it is relatively strong and light. Bikes made from chromoly, as well as other types of steel, flex more than other materials like aluminium, so they soak up more of the bumps in the road. You really notice this on long rides.

Chain ring bolt

These bolts fit the front chain rings together and attach them to the crank arms.


The chainstays are the frame tubes that run from the bottom bracket to the rear wheel.

Chain ring

These are the front cogs that you turn with the pedals. These transfer force, via the chain to the rear wheel.


The cassette is the cluster of cogs which you find on the rear hub of bikes with derailleur gears. These different sized sprockets are what allows for different gear ratios.


The chain transfers the power from the crank which you rotate with the pedals to the rear wheel. Chains come in a variety of widths depending on the type of bike you have. Single speed bikes and those with hub gears normally use a 1/18″ width chain, while bikes with derailleur gears use a 3/32″ width.

Cable housing

This is the outer tube which your gear and brake cables are pulled through. It it usually made from steel or a synthetic material to reduce friction, and is coated with plastic.

Bottle cage

This is a small frame which can be screwed on to the frame where you can store a water bottle.

Bottom bracket

The bottom bracket is where the frame is attached to the pedals and chainset. It is made of a spindle, surrounded by bearings which are housed inside the bottom bracket shell.


Aluminium is the material of choice for the majority of modern bikes, as it is relatively cheap and strong. It is also very stiff which means that aluminium bikes are highly responsive and have great acceleration. However, this also means that they soak up less of the bumps and vibration from the road, so they can get uncomfortable on long rides

Adjusting barrel

Adjusting barrels are found at the ends of both gear and brake cables and are used to make small adjustments in cable tension. These are often found on brake levers, gear shifters and deraillieurs.


This is the outer section of the wheel where the spokes attach. This is where you fit the tyres and inner tubes. Rims are usually made of aluminium these days but on some older bikes they are made of steel, and some more expensive bikes use carbon. Some braking systems work by making contact between a pair of brake pads and the rim. V-brakes and caliper brakes both work in this way.


This is where you sit! Traditionally made of leather, saddles now come in a vast range of styles and colours. Saddles attach to seat post by the saddle rails found underneath. It is possible to adjust your saddle back and forth on these rails.

Rear dropout

This is the place where the chainstays and the rear forks meet, where you attach the rear wheel.

Rear derailleur

The rear derailleur moves the chain between the different sized cogs on your back wheel. It is made up of a cage which holds two pulleys to move the chain. The rear derailleur is also spring loaded so it can take up the slack in the chain when you move to a smaller cog.

Housing stop

These are the small, often silver ends, which you find at the end of your cable housing. These keep the cable housing in place and have a smaller hole inside, which the inner cable can fit through, so it can be attached to the brake levers, gear shifters or gearing system.


This is central part of a bike wheel where the spokes radiate from. It is made from an axle, surrounded by bearings, cased in a hub shell.

Head tube

The head tube is the short section of frame which runs between the handlebars and front fork. The front fork turns inside the headtube when moved by the handlebars.

Gear shifters

The shifters are usually found on the handlebars, although sometimes on the down tube on older road bikes. These are used to select the gear you want. Shifters are attached to the gear mechanism via a cable.


The handlebars are used to steer the front wheel and are where you rest your hands. This is where you will usually find the brake levers and the gear shifters. They come in a variety of types. The most popular are drop handlebars, popular on racing bikes, and flat or riser bars which you usually see on mountain bikes and hybrids. There are many other types of handlebar such as upright bars, which are swept back towards the rider, often used on town bikes, and bullhorn bars which are seen on single speed and fixed wheel bikes.

Gear cable

These are the cables that run from the shifters on your handlebars to the front and rear derailleurs, as well as to hub gears.

Front derailleur

Usually found close to the right pedal, the front derailleur moves the chain between the front chainrings. The chain passes through a cage which is moved using the shifters located on the handlebars. Front derailleurs come in three types – top pull, bottom pull and dual pull. This refers to how the gear cable running from the handlebars is routed. Top pull models go along the seat tube, bottom pull along the head tube, and dual pull models allow for both set ups.

Front dropout

The front dropout is found at the end of your front fork. This is where the wheel is tightened on to the fork.

Fork crown

The fork crown is where the two blades join below the headset.


The front fork is the two pronged piece of the frame which holds the front wheel in place.

Fork blade

This are the two tubes which run either side of your front wheel.

Down tube

This is the tube which runs from the top of the head tube, where the handlebars are attached, down to the bottom bracket, where the pedals are located.


Derailleurs are a type of gearing system used on many modern racing and mountain bikes. The system works by shifting the chain between different combinations of varying sized cogs. Most bikes use a combination of a front derailleur and a rear derailleur to offer a wide range of ratios.

Derailleur pulley

Also know as the derailleur roller, the pulleys are the two small cogs found in the rear derailleur which help to move the chain from cog to cog.


The crankset is the collective term for the parts of your bike which allow your pedalling motion to drive the chain. These include the crank arms, the chain rings and the spider.

Crank arm

The crank arms are what the pedals are attached to – these turn the chain rings. At the other end these are attached to the bottom bracket.

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