Bike components explained: a jargon buster for all of the key frame, wheelset and groupset parts on a bicycle
Get your head around headsets, drivetrains, derailleurs and more
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If you’re new to cycling, there is tons of bike-specific terminology to understand if you want to get to grips with how your machine works and what each bike component does. Some are pretty obvious and self-explanatory, whereas other bike parts are a bit more tricky.
Bike components such as bottom brackets and freehubs have a lot of complexity hidden away – and bike brands seem to love to come up with new and slightly different ways of doing things. Even pedals come in a bewildering number of variants.
Confused? Here’s your jargon buster on all the key bike components – and an explanation of what they do.
Want more information? We’ve got full explainers covering the key parts of a bike, so hit the links to get the lowdown on the seemingly infinite number of standards and compatibility questions.
Frame
Let’s start with the frame itself – the heart of any bike.
Bikes have been made from a variety of different frame materials over the years. Today, they’re most commonly made of either aluminium alloy or carbon fibre, although steel, titanium and magnesium alloy are also options.
Bike frames are typically a double-diamond design, with a front triangle composed of the seat tube, down tube, top tube and head tube, and a rear triangle composed of the seat tube, chainstays and seatstays. We’ll come on to each of these parts of a frame.
Full-suspension mountain bikes have a floating linkage between the front and rear triangles, with a rear-suspension system to allow controlled movement between the two.
Hardtail mountain bikes rely on a suspension fork for their bounce, combined with a rigid rear end.
Bike frame tube names explained
Down tube
The down tube is the part of the bike frame that slopes down from the head tube at the front of the bike to the bottom bracket, which houses the crankset. It’s the backbone of the bike’s strength.
Top tube
As its name suggests, the top tube runs along the top of the bike frame’s front triangle, from the top of the head tube to the top of the seat tube. Originally horizontal, it’s now more common for it to have a slope from front to back, particularly on mountain bikes.
On road bikes, the slope results in a frame designated as ‘compact’ or ‘semi-compact’, depending how much of a slope there is.
Seat tube
The seat tube runs from the bottom bracket up to the seatpost, at the rear of the bike’s front triangle. It may be straight or have a kink in it and some have a cut-out section at the rear to fit around the back wheel, allowing the chainstays to be kept shorter.
Head tube
The head tube is the short tube at the font of the frame, which supports the headset bearings that keep the fork in place.
Seatstays
The two seatstays connect to the seat tube at one end and the chainstays at the other, to support the rear wheel. They’re typically skinny, to help add comfort at the rear of the bike. If a bike has rim brakes, there’s often a bridge between the two seatstays to support the rear brake caliper.
Chainstays
The two chainstays run from the frame’s bottom bracket to the rear of the bike, where they meet up with the seatstays and support the rear wheel. On the driveside, the chainstay also supports the rear-derailleur mechanism.
Fork
Your bike’s fork consists of (usually) two legs to support your front wheel and a steerer tube that passes through the bike frame’s head tube and turns on bearings to enable you to steer.
Road bike forks are typically made of carbon fibre, but may have an alloy steerer tube, although you can also find all-alloy or steel forks, usually on cheaper bikes.
Most road cyclists will use the fork that comes with their bike or frameset, without giving it a second fork. However, tyre clearance and mounting points – for mudguards or luggage – are things to consider when it comes to the versatility of your bike.
Mountain bike forks are more complex and typically include suspension.
There are differences in how this works and how it’s damped, how the fork is attached to the frame, and also the amount of suspension travel (i.e. movement) it offers.
The amount of suspension travel will provide a guide as to the bike’s intended use, with cross-country mountain bikes offering less travel than downhill mountain bikes, due to the tamer terrain encountered.
Frameset
Frameset is used to describe the frame and fork together.
If you’re building your own bike, you will, in many cases, buy a frameset from a manufacturer, but frames and forks are also available separately.
Wheelset
Your wheelset is the pair of wheels on which your bike rolls; both the front and the back wheels.
The wheelset comprises all the bits that go to make up the wheel: hubs, spokes and rims, with the freehub that enables you to freewheel on your bike.
The wheelset doesn’t include everything else that you need to attach to your wheels to make them useful, though: tyres (although some brands such as Mavic sell their wheels complete with tyres), inner tubes, cassette and disc brake rotors.
In the case of quick-release wheels, the wheelset includes the axle and usually the quick-release skewer that attaches it to the bike. With thru-axle wheels, the axles are considered part of the bike. If you buy a thru-axle wheelset, it won’t come with them.
Bike wheel parts explained
Rims
The rim is the circular part that gives the wheel its circumference.
The rim holds the tyre in place and will be designed for use with clincher tyres (with an inner tube), tubeless tyres or tubular tyres.
Hookless rims are increasingly common on wheelsets made specifically for tubeless tyres.
Rims are typically either made from aluminium or, on more expensive wheels, carbon fibre.
Wheels for use on bikes with rim brakes – typically cheap road bikes or hybrid bikes – will have a braking track incorporated into the rim.
The rims are connected to the hub by spokes, which in turn are attached to the rims by spoke nipples.
Spokes
The spokes attach the hub to a wheel’s rim.
The number of spokes used varies between wheelsets and is often different between the front and rear wheels.
Spokes are usually made of steel, although some high-end wheels use carbon spokes to save weight. It’s common for spokes to be ‘butted’, where they’re narrower in their middle section than at their ends.
Most spokes are either straight-pull, with a hub-end flange that’s in line with the spoke blade, or J-bend, where there’s a 90-degree curve at the hub end, and the design has to match how your hubs are drilled.
They’re screwed into the rim with nipples, which may be aluminium alloy or brass.
Hub
The hub sits at the centre of a wheel, with a shell that turns on an axle, and bearings between the two to lower the friction. The hub shell will include flanges that hold the spokes, and which then lace the hub to the wheel’s rim.
If you’ve got a disc brake bike, the hub shell will also include an attachment point for the brake rotor. This can either be six bolt holes around its circumference or a serrated Centerlock ring, both on its left-hand side.
On its right-hand side, the rear hub on a modern bicycle wheel usually has a freehub, which includes a mechanism to let you freewheel, and to which you attach a cassette.
The hubs on the front and rear wheels combined are sometimes referred to as a hubset.
