Glossary

A quick reference for terms used throughout the guide.

Axle — the metal rod that the wheel rotates around. Modern bikes use thru-axles (12 or 15 mm threaded into the frame) or quick releases (older standard).

B-tension screw — adjusts the gap between the upper jockey wheel of the rear derailleur and the largest cog. Affects shift quality.

Banjo — the angled fitting on a hydraulic brake hose where it connects to the lever or caliper.

BB — bottom bracket. The bearings the crankset rotates on, housed in the frame.

Bead — the inner edge of a tire that hooks onto the rim.

Bedding-in — the process of building up an even layer of pad material onto a brake rotor for new pads.

Bleed — the process of removing air from a hydraulic brake system.

Carbon paste — friction-enhancing assembly compound used at carbon interfaces to allow lower torque without slipping.

Cassette — the cluster of cogs on the rear wheel.

Chainstay — the frame tube running from the bottom bracket to the rear dropouts.

Cleat — the metal piece that bolts to the bottom of a cycling shoe and clips into a clipless pedal.

Cog — an individual sprocket. The rear cluster has multiple cogs of different sizes; the front rings are sometimes also called cogs informally.

Crown race — the bearing race that sits on top of the fork crown, where the lower headset bearing rests.

DOT fluid — a brake fluid used in SRAM, Hayes, and some other hydraulic brakes. Corrosive; absorbs water.

Dropout — the slot in the frame or fork where the wheel’s axle sits.

Float — the angular freedom your foot has when clipped into a clipless pedal before the cleat releases.

Freehub — the splined drum on the rear hub that the cassette slides onto. Contains the ratcheting mechanism that lets you coast.

Gauge — a measuring tool. Hanger alignment gauge, dish gauge, tension gauge.

Hanger — the small replaceable plate on the rear dropout that the rear derailleur bolts to. Designed to bend in a crash to save the frame and derailleur.

HG (Hyperglide) — Shimano’s freehub spline standard, also adopted by SRAM for cassettes up to 11-speed.

Hood — the rubber covering on a road brake/shift lever where you typically rest your hands.

Hose — the fluid-carrying line of a hydraulic brake.

Indexing — the process of setting cable tension on a derailleur so each click of the shifter results in a precise gear change.

Jockey wheel (pulley) — the small toothed wheels in the rear derailleur cage that route the chain.

Lockring — a threaded ring that secures the cassette to the freehub (and similar applications).

Mineral oil — the brake fluid used in Shimano, Magura, and some other hydraulic brakes. Less aggressive than DOT.

Pedaling under load — applying significant force through the pedals (climbing, sprinting).

Pinch bolt — a bolt that compresses something around something else (e.g., crank arm pinch bolts compress the arm onto the spindle).

Pivot — a hinging joint, e.g., suspension pivots on a full-suspension MTB.

Press-fit — a BB shell standard where bearings are pressed directly into a smooth bore (no threads).

Quick link / master link — a removable chain link that allows the chain to be opened/closed without a chain breaker.

Rotor — the disc that rotates with the wheel and is gripped by the brake caliper.

Sag — the amount the suspension compresses under static rider weight, expressed as a percentage of total travel.

Sealant — the latex liquid inside tubeless tires that automatically seals small punctures.

Stanchion — the upper polished tube of a suspension fork, which slides into the lower legs.

Star nut — a star-shaped fitting installed inside the steerer tube of an aluminum or steel fork; the top cap bolt threads into it.

Steerer — the part of the fork that extends up through the head tube and is clamped by the stem.

Stiction — friction in suspension or other moving parts that resists initial movement (low-speed friction).

Threadless — a headset standard where the fork’s steerer is smooth (no threads) and the stem clamps onto the outside.

Through-axle — the modern wheel-attachment standard where a long bolt threads through the dropouts and hub.

Toed-in — for rim brakes, when the front of the pad contacts the rim 1 mm before the rear, reducing squeal.

Tubeless — a tire system without an inner tube, sealed at the bead with sealant.

XD / XDR — SRAM’s freehub standards for 11s+ cassettes (XD for MTB, XDR for road).