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parts

Bike Parts Explained

For such a simple and small vehicle, the humble bicycle has a large number of parts with specific names that all cyclists should know. What follows is a run down of all the major parts of a standard bicycle, ordered alphabetically as well as a fully annotated diagram.

Adjusting barrel – a small screw on the rear mech that allows for adjustment of the gears.

Bearings (wheel) – see ‘Wheel bearings’.

Bottom bracket – the bearing assembly that the crankset spins on. Also the part of the frame that the bottom bracket bearing assembly is screwed into.

Brake cable – the brake cable is a metal cable connecting front and rear brake levers to the front and rear brake calipers. When a brake lever is pulled, tension in the brake cable increases closing the brake caliber, applying pressure to the wheel rim and reducing the speed of the wheel rotation.

Brake caliper – The most common brakes found on modern road bikes. They are metal, horseshoe shaped mechanisms that straddle the front and rear wheels enabling riders to reduce their speed by clamping each wheel, applying pressure to the wheel rim through brake pads.

Brake disc – brake disks are an alternative to calipers and are more common on mountain bikes where dirt is more likely to reduce the braking ability of a standard caliper brake. The brake disk is attached to the hub of the wheel and is about the size of a DVD disk. Braking is similar to that of a car where pressured is applied to the disk reducing the speed of the spinning wheel.

Brake hood – these are rubber coverings that protect the inside workings of the gear levers from water, dirt and other debris. They can be folded back to allow access to the cables underneath.

Brake lever - attached to the handlebars and the brake cables, these are moved by the rider to brake. In modern road bikes, the gear levers and brake levers are the same.

Brake pad – hard wearing material attached to the brake shoes. These need to be replaced often as they wear during braking when they rub against the wheel rim. Special brake pads have to be used for carbon wheels to avoid damaging the surface of the rim.

Brake shoe – two brake shoes are attached to each caliper. They hold the brake pads which touch the wheel rim during braking.

Bottle cage – available in plastic, carbon and metal these are attached to the bike frame to hold water bottles enabling easy access while riding.

Cable housing – the brake and gear cables have a plastic coating for protection. On some bikes the cables are housed within the frame and so plastic housing is not required.

Cassette – made up of a range of sprockets varying in size attached to the rear hub. On a standard road bike there are usually 9-10 sprockets in the cassette.

Chain – connects the chainring to the cassette transmitting power from the pedals to the rear wheel. Chains come in different lengths depending on the number of gears you have. Chains also vary in weight, lighter chains being more expensive. Chains should be replaced once they have ‘stretched’ beyond their limit. This can be checked very quickly by a bike mechanic. Replacing a chain after it has stretched beyond this limit may result in a damaged cassette which may then also require replacing.

Chainset – collective term for the front sprockets connected to the crankarms to which the pedals attach. Also known as ‘crankset’.

Chain stay – the part of the frame connecting the bottom bracket to the rear dropout.

Chainring – a large cog/gear attached to the crankarms. Road bikes often have either two or three chainrings. The larger the chainring the harder the gear. Riders often install small chainrings to assist with climbing and large chainrings to improve top-end time-trial speed.

Cleat – a plastic or metal attachment screwed on to the sole of a cycling shoe which allows the rider to attach their shoes to the pedals for maximum power transmission while riding. Some cleats provide some sideways movement while riding so as not to limit the movement of the knees. Professionals who have their bikes set up to match their physical dimensions, have cleats that do not move from side to side to maximise efficiency. If inexperienced, care should be taken to use cleats that allow movement to avoid the risk of injury.

Clip – see ‘cleat’.

Crankarm – the connecting bar between each pedal and the outer chainring. Crankarm lengths differ depending on the cadence and power of a rider.

Crankset – collective term for the front sprockets connected to the crankarms to which the pedals attach. Also known as ‘chainset’.

Derailleur (front) – aligns the chain with the required chainring. Attached to the gear lever by the gear cable.

Derailleur (rear) – aligns the chain with the required sprocket in the cassette. Attached to the gear lever by the gear cable.

Derailleur pulley – positioned just beneath the cassette, the pulley guides the chain away from the cassette taking up slack to ensure the chain is always taught across the sprockets and chainrings.

Down tube – the part of the frame connecting the top of the forks to the bottom bracket.

Fork – normal bike have two forks which connect the front of the frame to the front wheel.

Fork blade – the lower part of each fork, often aerodynamically shaped to reduce drag.

Fork crown – the upper part of the forks. Often connected to the front brake caliper.

Frame – the main body of the bike. Can be made out of carbon, titanium, aluminium, steel etc.

Front dropout – the slot in the front forks into which the axle of the front wheel is positioned.

Front mech – see ‘derailleur’.

Gear cable – connects the gear levers to the front mech and the rear mech enabling the rider to change gear.

Gear lever – attached to the handlebars and the gear cables, these are moved by the rider to change gears. In modern road bikes, the gear levers and brake levers are the same.

Handlebars – the front part of the bike where the rider grips the bike, changes gear and brakes using the levers.

Head tube – part of the frame connecting the headset to the fork crown.

Headset – the piece connecting the stem of the bike to the top tube. The height of the handlebars can be adjusted by changing the height of the headset.

Hood (brake) – see ‘Brake hood’.

Housing (cable) – see ‘Cable housing’.

Housing stop – small plastic attachment connected to various parts of the frame where the gear and brake cable housing stops.

Hub – the central part of the wheel that contains the wheel bearings.  A free-wheel hub allows the wheel to rotate freely when the pedals are not being turned.

Lever – see ‘Brake lever’ and ‘Gear lever’.

Nipple (spoke) – see ‘Spoke nipple’.

Pedal – attached to the end of each crank, pedals come in a range of different formats from simple flat pedals to cages which wrap around the foot, to cleated pedals which allow riders to attach their shoes to the pedal, improving efficiency.

Rails (seat) – see ‘Seat rails’.

Rear mech – the collective name for the rear dérailleur and derailleur pulley.

Rim – the outer edge of a bicycle wheel. The rim can be made of a different material to other parts of the wheel. The rims are in contact with brake pads when braking. Carbon rims therefore require different brake pads to aluminium rims to avoid damage while braking.

Saddle – the seat of the bike, where the rider sits. Saddles come in a range of shapes and weights depending on price and individual preference of the rider. Recently, holes have been introduced in the centre to reduce pressure and increase comfort for females while riding.

Seatpost – the hollow post that connects the saddle to the frame of the bicycle. Low-weight carbon seat posts are often used by professional riders and come as standard with high-performance road bikes. Some bike manufacturers integrate the seatpost where it is a permanent part of the frame. This can reduce weight and decrease drag however it often causes problems when reselling a bike (as the post is cut once to size and cannot be lengthened).  Integrated seatposts also make a bike more difficult to transport.

Seatpost clamp – the metal clamp that secures the height of the seatpost and saddle. By loosening the clamp, the height of the saddle can be adjusted as desired by the rider.

Seat rails -  metal bars located beneath the sadal. Loosening the bolts allows the rider to adjust their riding position by moving the saddle forwards or backwards.

Seat stay – the part of the frame connecting the rear drop with the top tube.

Seat tube – the part of the frame connecting the bottom bracket with the top tube.

Shifters  - see ‘Brake lever’ and ‘Gear lever’.

Spoke – spokes support the shape of a wheel, strengthening the rim. Spokes can be radial or double laced. A radial set-up required fewer spokes and so leads to a lighter wheel with slightly less drag. Spokes a connected at one end to the hub of the wheel, and at the other end to the rim using a spoke nipple. Spokes can be cylindrical in shape or bladed to provide a small reduction in drag.

Spoke nipple – a small piece of metal connecting spokes to the rim of a wheel. The nipples can be adjusted to ensu equal tension across all spokes in the wheel. If spokes have differing tensions, spokes can break resulting in a buckled (bent) wheel.

Sprocket – the cassette is comprised of a range of small cogs/gears. Each of these cogs is known as a sprocket. Different sprocket sizes are used to assist with climbing (large sprockets) or for low cadence time trialling (small sprockets).

Stem – connects the headset to the handlebars. The stem on a bike should be the correct size to allow a rider to reach comfortably to their handlebars.

Tyre (clincher) – a tyre with three sides requiring an inner tube. Clincher tyres are cheaper and easier to install than tubular tyres however there is a slight performance reduction. A clincher tyre pis required for a clincher wheel rim which has two walls for the tyre to attach to.

Tyre (tubular) – a completely enclosed tyre requiring no inner tube. Tubular tyres are attached to tubular wheels and are the most common type used by professionals due to their slightly superior performance.

Valve – the fitting on an inner tube that allows for the attachment of a pump to add air to the tyre.

Valve stem – the long metal part of a valve. Valve stems vary in length to allow for deep rims on certain wheels. If the valve cannot be accessed due to deep rims, a valve extender can be used to lengthen the stem.

Wheel bearings – small ball bearings contained within the hub of a wheel that allow a wheel to roll smoothly. Without bearings, a wheel would not rotate correctly.

Wheel rim – see ‘Rim’.

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