Bicycle Wheel Building & Maintenance Glossary
25 essential terms for wheel building and bicycle service, with their Japanese originals.
Nomu Lab is, above all, a wheel-building workshop. The posts on this site are full of technical
vocabulary that can be hard to follow without context. This glossary explains the core terms in
plain English and pairs each with the Japanese original used in the source articles.
Wheel Building
- ERD Effective Rim Diameter（リム内径有効径）
- The diameter at which the spoke nipples seat, used as the key input for spoke-length calculation. Measured by stringing two spokes across the rim and adding twice the protrusion needed for the nipple.
- Spoke Length スポーク長
- The required length of each spoke, derived from ERD, hub flange diameter, flange-to-center distance, spoke count, and lacing cross. Even a 1–2 mm error can leave nipples under- or over-threaded.
- Lacing Pattern 組み方（スポークパターン）
- How spokes interlace between hub and rim. Common patterns are radial (0-cross), 2-cross, and 3-cross. More crosses transfer torque better; radial is lighter but unsuitable for driven or disc-braked wheels.
- Cross (3-cross, 2-cross) クロス（３クロス・２クロス）
- The number of other spokes each spoke crosses on its way from hub to rim. 3-cross is the durable standard for most road and touring wheels.
- Radial Lacing ラジアル組み
- A 0-cross pattern where spokes run straight from hub to rim. Light and stiff laterally, but it transmits no torque, so it is used only on non-driven, rim-brake front wheels.
- Inpoke / Outpoke ヌポーク／反ヌポーク（当ブログ独自語）
- Nomu Lab's own terms for the direction a spoke is laced through the hub flange. 'Inpoke' means the spoke is laced from the inside of the flange outward, so its head (elbow) sits on the inner face — heads-in. 'Outpoke' is the opposite, laced from outside inward with the head on the outer face — heads-out. The choice affects how the spoke head seats against the flange, which matters most on radial and low-flange builds.
- Spoke Tension スポークテンション（張力）
- The tensile load in each spoke. Even, adequate tension is what makes a wheel strong and durable; uneven tension causes fatigue cracks, broken spokes, and wheels that won't stay true.
- Tensiometer テンションメーター（スポーク張力計）
- A tool that measures spoke tension by deflecting the spoke a fixed amount. Essential for building wheels with consistent, correctly balanced tension.
- Dish / Dishing センター出し（ディッシュ）
- Centering the rim exactly between the hub locknuts. Rear wheels are 'dished' asymmetrically because the freehub body forces unequal flange spacing and therefore unequal left/right tension.
- Truing 振れ取り
- Adjusting nipple tension to remove lateral (side-to-side) and radial (up-and-down) deviations so the rim spins straight and round.
- Nipple ニップル
- The small threaded fastener at the rim end of each spoke. Turning it changes spoke tension. Available in brass (durable) and aluminum (lighter, more prone to seizing).
- Butted Spoke バテッドスポーク
- A spoke drawn thinner in the middle than at the ends (single-, double-, or triple-butted). It saves weight and adds elasticity to resist fatigue, while keeping strong, full-diameter ends.
- Bladed Spoke エアロ（偏平）スポーク
- A spoke flattened into an aerodynamic blade. Reduces drag and resists wind-up during tensioning, but usually requires slotted hub holes or special holders.
- J-bend vs Straight-pull Ｊベンド／ストレートプル
- Two spoke head styles. J-bend spokes have a 90° elbow and fit traditional flanges; straight-pull spokes have no bend and need purpose-built hubs, eliminating a common fatigue point at the elbow.
- Flange フランジ（ハブつば）
- The raised disc on each side of a hub where the spoke heads anchor. Flange diameter and spacing strongly affect spoke length and wheel stiffness.
Components
- Hub ハブ
- The central component of a wheel, containing the axle and bearings on which the wheel rotates. The rear hub also carries the freehub body for the cassette.
- Freehub フリーハブ
- The ratcheting body on a rear hub that lets the wheel coast while the cassette stays still. Its engagement mechanism (pawls or ratchet rings) determines how quickly the drive engages.
- Cassette カセット（スプロケット）
- The cluster of sprockets mounted on the freehub body, providing the rear gear range.
- Rim リム
- The outer hoop of the wheel that holds the tire and, on rim-brake wheels, provides the braking surface. Rim material, depth, and internal width all affect ride and tire fit.
- Tubeless / Clincher / Tubular チューブレス／クリンチャー／チューブラー
- The three tire systems. Clinchers use an inner tube; tubeless seal directly to the rim with sealant for lower pressures and fewer flats; tubulars are sewn-up tires glued to a special rim.
- Bottom Bracket ボトムブラケット（ＢＢ）
- The bearing assembly in the frame's bottom bracket shell that supports the crank spindle and lets the cranks rotate.
- Headset ヘッドセット
- The bearings in the head tube that allow the fork steerer—and thus the handlebars and front wheel—to turn smoothly.
Maintenance
- Overhaul オーバーホール
- A full disassembly, cleaning, regreasing, and reassembly of a component (typically hubs, bottom brackets, or headsets) to restore smooth operation and prevent wear.
- Bearing Adjustment / Preload 玉当たり調整（プリロード）
- Setting the correct bearing tightness on cup-and-cone or adjustable bearings: snug enough to remove play, loose enough to spin freely without binding.
- Spoke Prep / Threadlocker ねじ止め剤（スポークプレップ）
- A compound applied to spoke threads that prevents nipples from loosening over time while still allowing future adjustment.