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Gear & Grade

Bike Jargon Glossary

Every word a bike listing uses without explaining it, defined in one plain sentence each. Keep this open in a tab while you shop.

By Stephen V.Last updated How we pick

Bike terminology is not designed to exclude you. Most of it is old, descriptive, and made obvious sense when it was coined. The problem is that everyone using it forgot there was ever a time they did not know it.

Every term below is defined in one plain sentence, followed by why it actually matters when you are buying. Nothing here needs memorizing — keep the page open in a tab and look things up as the listings throw them at you.

Gears and drivetrain

Groupset
The gears, shifters, brakes and chain, sold as a matched set by one manufacturer.
Why it matters: The single most informative line in a bike listing. A named one means a shop can service it; an unnamed one means a routine repair becomes a problem.
Drivetrain
Everything that turns your pedaling into the back wheel going round — chain, chainrings, cassette and derailleurs.
Why it matters: It is the part that wears out, and the part a clean chain protects.
Cassette
The stack of sprockets on the rear wheel.
Why it matters: More sprockets means smaller jumps between gears. The largest sprocket decides how easy your easiest gear is.
Chainring
The toothed ring at the front, attached to the pedal cranks.
Why it matters: One or two of them, which is what 1x and 2x refer to.
Derailleur
The mechanism that physically pushes the chain sideways onto a different sprocket. One at the front, one at the rear.
Why it matters: The rear one is the part most likely to get bent in a crash or a fall, and it is the most common repair on a bike.
1x and 2x
The number of chainrings at the front. 1x (say 'one-by') has one and no front shifter; 2x has two.
Why it matters: 1x is simpler with a narrower range; 2x is wider-ranging with more to adjust. Either is fine on a first bike.
Gear range
The spread between your easiest and hardest gear.
Why it matters: Far more useful than the advertised gear count. Two bikes both saying '21 speed' can have completely different easiest gears.
Cross-chaining
Running the chain at an extreme diagonal — biggest chainring to biggest sprocket, or smallest to smallest.
Why it matters: It works, but it wears the chain fast and sounds unhappy. Avoid the extremes.

Wheels and tires

700c
The wheel diameter used on almost every road and gravel bike. A leftover from an old French sizing system, which is why the number looks arbitrary.
Why it matters: It means tires and tubes are the standard size every shop stocks.
650b
A smaller wheel diameter sometimes used on gravel bikes, which allows an even wider tire in the same frame.
Why it matters: Uncommon on entry-level bikes. If you see it, it is a deliberate choice for comfort over outright speed.
700x40c
A tire size: 700c wheel, 40mm wide.
Why it matters: The second number is the one that changes how the bike feels. Road bikes run 25-32; gravel bikes run 40-45.
ETRTO (e.g. 40-622)
The unambiguous international way of writing a tire size: width in millimeters, then rim diameter in millimeters.
Why it matters: '700x40c' and '40-622' are the same tire. The second version is the one to trust when checking compatibility.
Tire clearance
The widest tire the frame will physically accept before it starts rubbing.
Why it matters: A hard physical limit, not a setting. This single number is what separates a gravel bike from a road bike.
Tubeless
Running a tire without an inner tube, sealed to the rim, with liquid sealant inside that plugs small punctures automatically.
Why it matters: Fewer punctures and you can run lower pressure. It is fiddlier to set up and needs sealant topped up. Not essential for a first bike.
Presta valve
The narrow valve with a small threaded nut you unscrew before pumping. Standard on road and gravel bikes.
Why it matters: Different from the fat car-style Schrader valve. Make sure your pump handles Presta, or you cannot inflate your own tires.
PSI
Pounds per square inch — how hard the tire is inflated.
Why it matters: The most under-used adjustment on a bike. Lower pressure in a wide tire is more comfortable and more grippy; too low and you risk pinching the tube.

Frame and fit

Stem
The short component clamping the handlebars to the frame.
Why it matters: Swapping it for a longer or shorter one is a ten-minute job with a cheap part, and it is how a slightly small frame is adjusted to fit.
Stack and reach
How tall the front of the bike is (stack) and how far forward the handlebars sit (reach).
Why it matters: The two numbers that actually describe fit. Most budget listings do not publish them, which is why manufacturer size charts matter.
Standover height
How much room there is between you and the top tube when you straddle the bike, feet flat.
Why it matters: You want an inch or two on a road bike and two to three on a gravel bike. Zero is a genuine safety issue.
Wheelbase
The distance between the front and rear wheel centers.
Why it matters: Longer is calmer and more stable; shorter is quicker to change direction. Gravel bikes are longer than road bikes on purpose.
Bottom bracket
The bearing assembly the pedal cranks spin on, inside the frame.
Why it matters: You will only think about it when it starts creaking, which on a cheap bike ridden through a wet winter is roughly when the unsealed bearings give up.
Headset
The bearings the fork turns on, at the front of the frame.
Why it matters: The bolts here are one of the two things most often wrong on a bike assembled out of a box. Have a shop check them.
Thru-axle
A rod that passes right through the wheel hub and threads into the frame, instead of the older quick-release skewer.
Why it matters: Stiffer and more secure, and standard on disc brake bikes. Only relevant when you buy a spare wheel.

Brakes

Rim brake
Pads that squeeze the wheel rim to slow you down.
Why it matters: Light, cheap and easy to adjust. Needs a moment to clear water off the rim in the wet before it bites.
Disc brake
Pads that squeeze a metal rotor attached to the wheel hub.
Why it matters: Consistent in the wet, and it leaves the rim free for a wide tire. Standard on gravel bikes for both reasons.
Mechanical disc
A disc brake pulled by a cable.
Why it matters: Works well, and needs occasional cable adjustment — a ten-minute job you can learn.
Hydraulic disc
A disc brake operated by fluid in a sealed line.
Why it matters: Much less hand force, self-adjusts as pads wear. Needs a shop when it eventually needs bleeding.

Pedals and shoes

Clipless pedals
Pedals your shoes clip into. Confusingly named, because the thing they replaced was called a toe clip.
Why it matters: More efficient on climbs. You will fall over at least once learning. Everyone does.
Cleat
The metal or plastic piece that bolts to the sole of a cycling shoe and clicks into the pedal.
Why it matters: Two systems exist and they do not mix. Two-bolt cleats recess into the sole and you can walk in them; three-bolt road cleats stick out and you cannot.
SPD
Shimano's two-bolt pedal and cleat standard. Effectively the default for gravel and commuting.
Why it matters: Recessed, walkable, and available everywhere. The sensible place to start.
Float
How much your foot can rotate while still clipped in.
Why it matters: More float is kinder to knees. If clipping in gives you knee pain, this is usually why.

The four terms that actually change your purchase

If you only remember four things from this page, make them these — they decide almost everything about whether a bike suits you:

  1. Frame size, because it is the only thing you cannot change later. Do this properly.
  2. Groupset, because it decides whether a shop can service your bike. The ladder is here.
  3. Tire clearance, because it decides where you can ride.
  4. Brake type, because it decides how the bike behaves in the rain.

Everything else on this page is useful context. Those four are the decision.

Questions people actually ask

What does 700x40c mean on a bike tire?

700c is the wheel diameter used on almost all road and gravel bikes, and 40 is the tire width in millimeters. The same size is written unambiguously as 40-622 in the international ETRTO standard, where 622mm is the rim diameter.

What is the difference between a cassette and a chainring?

The cassette is the stack of sprockets on the rear wheel; the chainrings are the toothed rings at the front, attached to the pedal cranks. You have one or two chainrings and typically 8 to 12 sprockets, and multiplying them is how listings get numbers like '24 speed'.

Why are clipless pedals called clipless when you clip into them?

Because they replaced toe clips — the cages and straps riders used before the modern system existed. 'Clipless' meant 'without toe clips'. The name outlived the thing it was distinguishing itself from, which is a fairly common fate for technical vocabulary.

What is tubeless and do I need it?

Running a tire sealed directly to the rim with liquid sealant inside instead of an inner tube. Small punctures seal themselves and you can run lower pressure for more comfort. It is fiddlier to set up and the sealant needs topping up a few times a year. Not necessary on a first bike.

What is a Presta valve?

The narrow valve found on road and gravel bike tubes, with a small threaded nut at the tip you unscrew before pumping. It is different from the fat car-style Schrader valve. Make sure any pump you buy handles Presta, or you will not be able to inflate your own tires.

Sources

Specifications come from the manufacturer or the retailer listing, dated. Where a figure is not published, we say so rather than estimating it.

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