# BMX Parts Depot > Used and mid-school BMX parts, sold through eBay. This site is a fitment and identification reference: what the BMX standards are, what dimensions they use, and how to tell which one you have before buying a used part. Sales happen on eBay, not here. There is no checkout on this site. Inventory links point out to the eBay store. ## How specs on this site are sourced Dimensions are taken from component manufacturer and established retailer documentation, and each figure carries its status in the page: confirmed by two or more independent sources, single source, or sources in conflict. Where sources disagree the range is published rather than a single figure picked for tidiness. Blocks marked as caliper verification are bench measurements taken in the shop. This site does not publish sales figures, review counts, or years in business. Where a figure could not be traced to a manufacturer specification or a published standard, the page says so in place of the number rather than repeating a figure that circulates without a source. Those gaps are deliberate and some of them are permanent: no BMX brand publishes a tire casing TPI or a Shore A durometer, and the old school, mid school and modern era year boundaries could not be traced to any primary source, so this site describes eras by their features and publishes no year ranges for them. An absent figure here means it was looked for and not found. ## Fitment Guides and Key Pages - [Home](https://bmxpartsdepot.com/) : Used and mid-school BMX parts reference and shop portal. - [BMX Fitment Guide and A-Z Parts Glossary](https://bmxpartsdepot.com/guides/) : The master index page and searchable dictionary of all BMX fitment standards. - [Bottom Brackets and Spindles](https://bmxpartsdepot.com/guides/bottom-brackets-and-spindles/) : American, Mid, Spanish, and Euro bottom brackets compared, with shell diameters, bearing sizes, and which crank spindles fit each one. - [Frame ID, Materials and Geometry](https://bmxpartsdepot.com/guides/bmx-frame-identification-and-geometry/) : Chromoly against hi-ten, butted tubing, gussets, dropouts and brake mounts, plus what top tube length, chainstay length and head angle actually change on a BMX frame. - [Wheels, Hubs and Axles](https://bmxpartsdepot.com/guides/bmx-wheels-hubs-and-axles/) : Cassette, freecoaster and freewheel hubs compared, plus axle diameters, male and female axles, hub spacing, rim wall construction, bead seat diameter and spoke count. - [Drivetrain, Chains and Sprockets](https://bmxpartsdepot.com/guides/drivetrain-chains-and-sprockets/) : Chain width 1/8 inch against 3/32 inch, half links, gear ratio and gear inches, micro drive, sprocket bolt patterns and spline drive, sprocket bore, chainline and chain tension. - [Cranks and Pedals](https://bmxpartsdepot.com/guides/bmx-cranks-and-pedals/) : One-piece, two-piece and three-piece BMX cranks explained, with how spindles attach, what crank arm length changes, and which pedal thread goes with which crank. - [Brakes, Cables and Detanglers](https://bmxpartsdepot.com/guides/bmx-brakes-and-gyros/) : How BMX U-brakes mount, what 990 mounts and gyro tabs are, how a detangler actually works, and what a brakeless frame is missing when you try to put a brake back on it. - [Headsets, Forks and Stems](https://bmxpartsdepot.com/guides/bmx-front-end-headsets-and-forks/) : Integrated, zero stack and threaded BMX headsets explained, with how threadless compression works, what fork offset changes, and how to tell a quill stem from a threadless one. - [Handlebars, Grips and Cockpit](https://bmxpartsdepot.com/guides/bmx-handlebars-and-cockpit/) : How BMX bars are measured, what rise, width, backsweep and upsweep each change, two-piece against four-piece construction, clamp diameter, and how grips and stem choice finish the cockpit. - [Seats, Posts and Clamps](https://bmxpartsdepot.com/guides/bmx-seats-and-seatposts/) : Pivotal, railed and tripod seats explained, how seat post diameter is measured, integrated against external clamps, slammed setups, and how to get a seized post out of a frame. - [Era, Dating and Restoration ID](https://bmxpartsdepot.com/guides/vintage-bmx-identification/) : What old school, mid school and modern actually mean, why the year boundaries are contested, and how to read a frame's era from its bottom bracket, headset, cranks, bars and construction. - [BMX FAQ](https://bmxpartsdepot.com/bmx-faq/) : Sizing by height, what separates street from race, gearing, chromoly against hi-ten, brakes, wheel size, what a first bike costs, crank length and tubeless, answered with sources. - [BMX Exploded View](https://bmxpartsdepot.com/bmx-exploded-view/) : An exploded 3D view of a 20 inch street BMX naming 33 components, plus a fifteen second spin game. - [BMX Wheelie Run](https://bmxpartsdepot.com/bmx-wheelie-run/) : A browser game: balance a BMX wheelie and steer through the gates. ## Section and Glossary Term Anchors Every section heading and every glossary term is deep-linkable. A term appears once, under the guide that owns its definition. ### Bottom Brackets and Spindles - [How to identify your bottom bracket](https://bmxpartsdepot.com/guides/bottom-brackets-and-spindles/#identify) : Section of the guide covering how to identify your bottom bracket. - [American bottom bracket](https://bmxpartsdepot.com/guides/bottom-brackets-and-spindles/#american-bottom-bracket) : A bottom bracket standard using a large unthreaded frame shell with bearing cups pressed into each side. - [Mid bottom bracket](https://bmxpartsdepot.com/guides/bottom-brackets-and-spindles/#mid-bottom-bracket) : A pressed-in bottom bracket standard using a shell smaller than American, with bearings pressed straight into the frame. - [Spanish bottom bracket](https://bmxpartsdepot.com/guides/bottom-brackets-and-spindles/#spanish-bottom-bracket) : A pressed-in bottom bracket standard with a shell narrower than Mid. - [Euro bottom bracket](https://bmxpartsdepot.com/guides/bottom-brackets-and-spindles/#euro-bottom-bracket) : A threaded bottom bracket that screws into a threaded frame shell, common on older race frames. - [The four standards side by side](https://bmxpartsdepot.com/guides/bottom-brackets-and-spindles/#comparison) : Section of the guide covering the four standards side by side. - [Crank spindle diameter](https://bmxpartsdepot.com/guides/bottom-brackets-and-spindles/#crank-spindle-diameter) : The diameter of the axle running through the bottom bracket, with 19mm, 22mm, and 24mm all in circulation. - [How bore and outer diameter work together](https://bmxpartsdepot.com/guides/bottom-brackets-and-spindles/#sealed-bearing-sizes) : The numeric code stamped on a cartridge bearing that gives its bore, outside diameter, and width. - [Swapping standards and spindles](https://bmxpartsdepot.com/guides/bottom-brackets-and-spindles/#compatibility) : Section of the guide covering swapping standards and spindles. - [Cross-brand compatibility](https://bmxpartsdepot.com/guides/bottom-brackets-and-spindles/#cross-brand) : Section of the guide covering cross-brand compatibility. - [Bottom bracket shell width](https://bmxpartsdepot.com/guides/bottom-brackets-and-spindles/#bottom-bracket-shell-width) : The measured width of the frame's bottom bracket shell between its two faces. - [Press-fit bottom brackets and how they go wrong](https://bmxpartsdepot.com/guides/bottom-brackets-and-spindles/#press-fit-bottom-bracket) : A bottom bracket where bearings or cups press into an unthreaded shell. - [Loose ball bearings, and when to bin them](https://bmxpartsdepot.com/guides/bottom-brackets-and-spindles/#loose-ball-bearings) : Individual bearing balls running in cups and cones rather than in a sealed cartridge. - [Unsealed bearings on used parts](https://bmxpartsdepot.com/guides/bottom-brackets-and-spindles/#unsealed-bearings) : Bearings running without a cartridge seal, usually loose ball with cups and cones. - [Questions](https://bmxpartsdepot.com/guides/bottom-brackets-and-spindles/#questions) : Section of the guide covering questions. - [Thread pitch](https://bmxpartsdepot.com/guides/bottom-brackets-and-spindles/#thread-pitch) : The distance between thread crests, which makes two same-diameter threads incompatible and is the root of most stripped parts. ### Frame ID, Materials and Geometry - [How to identify a used BMX frame](https://bmxpartsdepot.com/guides/bmx-frame-identification-and-geometry/#identify) : Section of the guide covering how to identify a used bmx frame. - [Chromoly, hi-ten and what the sticker means](https://bmxpartsdepot.com/guides/bmx-frame-identification-and-geometry/#4130-chromoly) : A chrome-molybdenum steel alloy used for stronger and lighter frames, forks, and bars. - [Butted tubing](https://bmxpartsdepot.com/guides/bmx-frame-identification-and-geometry/#butted-tubing) : Tubing with thinner walls in the middle and thicker walls at the ends to save weight without losing strength at the joints. - [Gussets and where frames get reinforced](https://bmxpartsdepot.com/guides/bmx-frame-identification-and-geometry/#frame-gusset) : A reinforcing plate welded at a high-stress joint, usually at the head tube or bottom bracket. - [Dropouts, slot width and brake mounts](https://bmxpartsdepot.com/guides/bmx-frame-identification-and-geometry/#dropout-slot-width) : The width of the axle slot in the frame or fork ends. - [Top tube length and how a frame is sized](https://bmxpartsdepot.com/guides/bmx-frame-identification-and-geometry/#top-tube-length) : The measured length of the top tube, the headline size number on a BMX frame. - [Chainstay length and head tube angle](https://bmxpartsdepot.com/guides/bmx-frame-identification-and-geometry/#chainstay-length) : The distance from the bottom bracket centre to the rear axle. - [Standover and wheelbase](https://bmxpartsdepot.com/guides/bmx-frame-identification-and-geometry/#wheelbase) : The distance between the front and rear axle centres. - [Serial numbers and dating a frame](https://bmxpartsdepot.com/guides/bmx-frame-identification-and-geometry/#serials) : Section of the guide covering serial numbers and dating a frame. - [Checking a used frame for damage](https://bmxpartsdepot.com/guides/bmx-frame-identification-and-geometry/#damage) : Section of the guide covering checking a used frame for damage. - [Telling hi-ten from chromoly on an unlabelled frame](https://bmxpartsdepot.com/guides/bmx-frame-identification-and-geometry/#hi-ten-steel) : High tensile steel, heavier and cheaper than chromoly, common on entry-level bikes. - [Chainstay yoke, and what fails there](https://bmxpartsdepot.com/guides/bmx-frame-identification-and-geometry/#chainstay-yoke) : The shaped bridge or plate joining the chainstays near the bottom bracket. - [Quad-butted tubing](https://bmxpartsdepot.com/guides/bmx-frame-identification-and-geometry/#quad-butted-tubing) : Tubing with four different wall thicknesses along its length. - [Vertical dropouts, and why BMX does not use them](https://bmxpartsdepot.com/guides/bmx-frame-identification-and-geometry/#vertical-dropout) : A dropout with a vertical slot rather than a rearward-facing horizontal slot. - [Junior and Pro XL frame sizes](https://bmxpartsdepot.com/guides/bmx-frame-identification-and-geometry/#junior-bmx-frame-size) : A BMX race frame size class sitting between mini and expert. - [Questions](https://bmxpartsdepot.com/guides/bmx-frame-identification-and-geometry/#questions) : Section of the guide covering questions. - [Effective Top Tube](https://bmxpartsdepot.com/guides/bmx-frame-identification-and-geometry/#effective-top-tube-length) : The horizontal top tube measurement used to compare frame size between brands. - [Head Tube Angle](https://bmxpartsdepot.com/guides/bmx-frame-identification-and-geometry/#head-tube-angle) : The angle of the head tube relative to the ground. - [Frame Reach](https://bmxpartsdepot.com/guides/bmx-frame-identification-and-geometry/#frame-reach) : The horizontal distance from the bottom bracket to the head tube top. - [Pro XL Frame Size](https://bmxpartsdepot.com/guides/bmx-frame-identification-and-geometry/#pro-xl-frame-size) : The largest common BMX race frame size class. ### Wheels, Hubs and Axles - [Telling the three rear hub types apart](https://bmxpartsdepot.com/guides/bmx-wheels-hubs-and-axles/#identify-rear-hub) : Section of the guide covering telling the three rear hub types apart. - [Cassette hub](https://bmxpartsdepot.com/guides/bmx-wheels-hubs-and-axles/#cassette-hub) : A rear hub with an internal ratchet and a removable driver that carries the sprocket-side cog. - [Freecoaster](https://bmxpartsdepot.com/guides/bmx-wheels-hubs-and-axles/#freecoaster) : A rear hub with an internal clutch that lets the bike roll backwards without turning the cranks. - [Freewheel](https://bmxpartsdepot.com/guides/bmx-wheels-hubs-and-axles/#bmx-freewheel) : A threaded cog cluster that screws onto an older rear hub rather than driving from inside it. - [Drivers and cog sizes](https://bmxpartsdepot.com/guides/bmx-wheels-hubs-and-axles/#cassette-driver) : The removable splined body on a cassette hub that the cog is part of or bolts to. - [Axle diameter, male axles and female axles](https://bmxpartsdepot.com/guides/bmx-wheels-hubs-and-axles/#bmx-axle-diameter) : The outside diameter of a hub axle, commonly 14mm on modern rear hubs and 3/8 inch on older and lighter builds. - [Hub spacing and over locknut dimension](https://bmxpartsdepot.com/guides/bmx-wheels-hubs-and-axles/#over-locknut-dimension) : The measured width of a hub across the outer faces of its locknuts. - [Rims, wall construction and bead seat diameter](https://bmxpartsdepot.com/guides/bmx-wheels-hubs-and-axles/#rim-wall-construction) : Whether a rim is single, double, or triple wall in cross section. - [Tires, tubes and what actually fits](https://bmxpartsdepot.com/guides/bmx-wheels-hubs-and-axles/#tire-fitment) : Section of the guide covering tires, tubes and what actually fits. - [Spoke count and lacing](https://bmxpartsdepot.com/guides/bmx-wheels-hubs-and-axles/#spoke-lacing-pattern) : The pattern spokes follow between hub and rim, commonly three cross on BMX. - [Pegs and what decides whether one fits](https://bmxpartsdepot.com/guides/bmx-wheels-hubs-and-axles/#bmx-pegs) : Tubes that bolt onto the axle for grinding and standing. - [Hub guards, drive side and left hand drive](https://bmxpartsdepot.com/guides/bmx-wheels-hubs-and-axles/#left-hand-drive) : A setup where the sprocket, chain, and driver sit on the left side of the bike. - [Questions](https://bmxpartsdepot.com/guides/bmx-wheels-hubs-and-axles/#questions) : Section of the guide covering questions. - [Axle Nuts and Bolts](https://bmxpartsdepot.com/guides/bmx-wheels-hubs-and-axles/#axle-nuts-and-bolts) : The threaded hardware that clamps a wheel into the dropouts, either nuts on a male axle or bolts into a female axle. - [Wheel Dish](https://bmxpartsdepot.com/guides/bmx-wheels-hubs-and-axles/#wheel-dish) : How centred the rim sits between the hub locknuts. - [Effective Rim Diameter](https://bmxpartsdepot.com/guides/bmx-wheels-hubs-and-axles/#effective-rim-diameter) : The diameter a rim measures at the spoke nipple seats, used to calculate spoke length. - [Hub End Caps](https://bmxpartsdepot.com/guides/bmx-wheels-hubs-and-axles/#hub-end-caps) : The spacers or caps at each end of a hub axle that set the overall width. - [Female Axle](https://bmxpartsdepot.com/guides/bmx-wheels-hubs-and-axles/#female-axle) : A hub axle that is internally threaded and takes bolts rather than external nuts. - [Hub Guard](https://bmxpartsdepot.com/guides/bmx-wheels-hubs-and-axles/#hub-guard) : A disc that sits against the hub to protect the flange and spokes during grinds. - [ISO Bead Seat Diameter](https://bmxpartsdepot.com/guides/bmx-wheels-hubs-and-axles/#iso-bead-seat-diameter) : The ISO measurement of the rim diameter at the tire bead seat, the true way to match tire to rim. - [J-Bend Spoke](https://bmxpartsdepot.com/guides/bmx-wheels-hubs-and-axles/#j-bend-spoke) : A spoke with a bent elbow head that hooks through a hub flange, the standard BMX spoke type. - [Male Axle](https://bmxpartsdepot.com/guides/bmx-wheels-hubs-and-axles/#male-axle) : A hub axle threaded on the outside that takes nuts. - [Spoke Nipple](https://bmxpartsdepot.com/guides/bmx-wheels-hubs-and-axles/#spoke-nipple) : The small threaded fitting that joins a spoke to the rim and sets tension. - [Right Hand Drive](https://bmxpartsdepot.com/guides/bmx-wheels-hubs-and-axles/#right-hand-drive) : The conventional setup with the sprocket, chain, and driver on the right side. - [Valve Hole Size](https://bmxpartsdepot.com/guides/bmx-wheels-hubs-and-axles/#valve-hole-size) : The drilled hole diameter in a rim, sized for either a Schrader or a Presta valve. - [Wheel Size](https://bmxpartsdepot.com/guides/bmx-wheels-hubs-and-axles/#bmx-wheel-sizes) : The nominal wheel diameter of a BMX bike, with 20 inch standard and other sizes used for cruisers and smaller riders. - [3X Lacing](https://bmxpartsdepot.com/guides/bmx-wheels-hubs-and-axles/#3x-lacing) : The three cross spoke pattern, where each spoke crosses three others on its way to the rim. - [ISO 406](https://bmxpartsdepot.com/guides/bmx-wheels-hubs-and-axles/#iso-406) : The bead seat diameter of a standard 20 inch freestyle and street rim, and the number that actually defines 20 inch. - [ISO 451](https://bmxpartsdepot.com/guides/bmx-wheels-hubs-and-axles/#iso-451) : The larger 20 inch bead seat diameter used on some race and fractional-sized wheels, which will not interchange with 406 in either direction. - [Tire Size Marking](https://bmxpartsdepot.com/guides/bmx-wheels-hubs-and-axles/#tire-size-marking) : How a tire states its size on the sidewall, where decimal and fractional markings of the same nominal diameter are different standards. - [Wire Bead Tire](https://bmxpartsdepot.com/guides/bmx-wheels-hubs-and-axles/#wire-bead-tire) : A tire with a steel wire bead, heavier, cheaper, and not foldable, which is what most used tires will be. - [Folding Bead Tire](https://bmxpartsdepot.com/guides/bmx-wheels-hubs-and-axles/#folding-bead-tire) : A tire with a flexible aramid bead that folds for shipping and saves rotating weight, the lighter and more expensive option. - [Bead Hook](https://bmxpartsdepot.com/guides/bmx-wheels-hubs-and-axles/#bead-hook) : The lip inside the rim wall that retains the tire bead under pressure, absent on some rim designs and part of what caps safe pressure. - [Tire Seating](https://bmxpartsdepot.com/guides/bmx-wheels-hubs-and-axles/#tire-seating) : Bringing the bead evenly onto its seat so the moulded line sits parallel to the rim, which is what stops a tire running out of round. - [Casing TPI](https://bmxpartsdepot.com/guides/bmx-wheels-hubs-and-axles/#casing-tpi) : Threads per inch in the tire casing, which trades suppleness against puncture resistance and sidewall support. - [Tire Pressure Range](https://bmxpartsdepot.com/guides/bmx-wheels-hubs-and-axles/#tire-pressure-range) : The minimum and maximum pressures marked on the sidewall, which are a property of the tire and rim together rather than rider preference. - [Durometer](https://bmxpartsdepot.com/guides/bmx-wheels-hubs-and-axles/#tire-durometer) : The rubber hardness rating, which trades grip against wear life and is why two identical-looking tires behave differently. - [Tread Pattern](https://bmxpartsdepot.com/guides/bmx-wheels-hubs-and-axles/#tire-tread-pattern) : Slick, semi-slick or knobby, which is a surface decision rather than a fitment one but changes effective width on the same casing. - [Sidewall Marking](https://bmxpartsdepot.com/guides/bmx-wheels-hubs-and-axles/#tire-sidewall-marking) : The full set of stamped markings on a tire sidewall and how to read them, which is how a used tire is identified with no packaging. - [Skinwall Tire](https://bmxpartsdepot.com/guides/bmx-wheels-hubs-and-axles/#skinwall-tire) : A tire with an unreinforced tan sidewall, both a period identifier and a real durability difference against a black wall. - [Directional Marking](https://bmxpartsdepot.com/guides/bmx-wheels-hubs-and-axles/#tire-directional-marking) : The rotation arrow on a directional tire, which decides which way round it mounts and is routinely ignored on used builds. - [Inner Tube Size Range](https://bmxpartsdepot.com/guides/bmx-wheels-hubs-and-axles/#inner-tube-size-range) : The span of tire widths a tube is rated for, and why a tube outside its range either folds or over-stretches. - [Tube Valve Type](https://bmxpartsdepot.com/guides/bmx-wheels-hubs-and-axles/#tube-valve-type) : Schrader against Presta, which has to match the rim's valve hole and the pump, and is a different question from the hole's size. - [Valve Stem Length](https://bmxpartsdepot.com/guides/bmx-wheels-hubs-and-axles/#valve-stem-length) : How far the valve protrudes past the rim wall, which has to clear deep sections and be long enough to take a pump head. - [Tube Gauge](https://bmxpartsdepot.com/guides/bmx-wheels-hubs-and-axles/#tube-gauge) : The wall thickness of a tube, trading weight against puncture resistance, and the difference between a standard and a thorn-resistant tube. - [Rim Tape](https://bmxpartsdepot.com/guides/bmx-wheels-hubs-and-axles/#rim-tape) : The strip covering the spoke nipple holes inside the rim, without which the tube punctures on the nipples rather than from outside. - [Tubeless BMX](https://bmxpartsdepot.com/guides/bmx-wheels-hubs-and-axles/#tubeless-bmx) : Whether a given BMX rim and tire can run without a tube, which requires both a compatible bead seat and a sealed rim bed. ### Drivetrain, Chains and Sprockets - [What a BMX drivetrain is made of](https://bmxpartsdepot.com/guides/drivetrain-chains-and-sprockets/#overview) : Section of the guide covering what a bmx drivetrain is made of. - [Chain width, 1/8 inch and 3/32 inch](https://bmxpartsdepot.com/guides/drivetrain-chains-and-sprockets/#bmx-chain-size) : Single speed BMX chain is normally 1/8 inch wide, with narrower 3/32 inch chain used on some setups. - [Half links](https://bmxpartsdepot.com/guides/drivetrain-chains-and-sprockets/#half-links) : Section of the guide covering half links. - [Gear ratio and gear inches](https://bmxpartsdepot.com/guides/drivetrain-chains-and-sprockets/#bmx-gear-ratio) : The relationship between front sprocket teeth and rear driver or cog teeth. - [Micro drive](https://bmxpartsdepot.com/guides/drivetrain-chains-and-sprockets/#micro-drive) : A drivetrain using a small front sprocket with a small-tooth-count driver. - [Drivers and cog sizes](https://bmxpartsdepot.com/guides/drivetrain-chains-and-sprockets/#cassette-driver) : Section of the guide covering drivers and cog sizes. - [Sprocket bolt patterns](https://bmxpartsdepot.com/guides/drivetrain-chains-and-sprockets/#sprocket-bolt-pattern) : The number and spacing of mounting bolts on a bolt-on sprocket. - [Spline drive and sprocket bore](https://bmxpartsdepot.com/guides/drivetrain-chains-and-sprockets/#spline-drive-sprocket) : A sprocket that mounts directly to splines on the crank spindle rather than bolting to a spider. - [Chainline](https://bmxpartsdepot.com/guides/drivetrain-chains-and-sprockets/#chainline) : Section of the guide covering chainline. - [Chain tension and tensioners](https://bmxpartsdepot.com/guides/drivetrain-chains-and-sprockets/#internal-chain-tensioner) : A tensioner that sits inside the dropout slot to hold axle position under load. - [Drive side and non-drive side](https://bmxpartsdepot.com/guides/drivetrain-chains-and-sprockets/#non-drive-side) : The side of the bike opposite the sprocket and chain. - [Sprocket guards](https://bmxpartsdepot.com/guides/drivetrain-chains-and-sprockets/#sprocket-guard) : A plastic or alloy disc that protects the sprocket teeth during grinds. - [Questions](https://bmxpartsdepot.com/guides/drivetrain-chains-and-sprockets/#questions) : Section of the guide covering questions. ### Cranks and Pedals - [Telling the three crank types apart](https://bmxpartsdepot.com/guides/bmx-cranks-and-pedals/#crank-types) : Section of the guide covering telling the three crank types apart. - [One-piece cranks](https://bmxpartsdepot.com/guides/bmx-cranks-and-pedals/#one-piece-crank) : A crank where both arms and the spindle are a single bent steel piece, also called Ashtabula. - [Two-piece and three-piece cranks](https://bmxpartsdepot.com/guides/bmx-cranks-and-pedals/#three-piece-crank) : A crankset made of two arms and a separate spindle. - [Spindle attachment, boots and pinch bolts](https://bmxpartsdepot.com/guides/bmx-cranks-and-pedals/#pinch-bolt) : A bolt that clamps a slotted part, such as a stem on a steerer or a seat clamp on a post. - [Crank spindle diameter](https://bmxpartsdepot.com/guides/bmx-cranks-and-pedals/#crank-spindle-diameter) : Section of the guide covering crank spindle diameter. - [Crank arm length](https://bmxpartsdepot.com/guides/bmx-cranks-and-pedals/#crank-arm-length) : Section of the guide covering crank arm length. - [Pedal thread size](https://bmxpartsdepot.com/guides/bmx-cranks-and-pedals/#pedal-thread-size) : The thread size of the pedal spindle, which differs between one-piece and three-piece crank setups. - [Pedal bodies](https://bmxpartsdepot.com/guides/bmx-cranks-and-pedals/#nylon-pedals) : A plastic-bodied pedal with a metal spindle, lighter and cheaper than an alloy body. - [Sprocket mounting](https://bmxpartsdepot.com/guides/bmx-cranks-and-pedals/#spline-drive-sprocket) : Section of the guide covering sprocket mounting. - [Checking used cranks and pedals](https://bmxpartsdepot.com/guides/bmx-cranks-and-pedals/#crank-condition) : Section of the guide covering checking used cranks and pedals. - [Questions](https://bmxpartsdepot.com/guides/bmx-cranks-and-pedals/#questions) : Section of the guide covering questions. - [One-piece to three-piece conversion](https://bmxpartsdepot.com/guides/bmx-cranks-and-pedals/#one-piece-to-three-piece-conversion) : Fitting three-piece cranks into a frame built for one-piece, using an adapter kit in the American shell, the most common upgrade question on old frames. - [Left-hand thread](https://bmxpartsdepot.com/guides/bmx-cranks-and-pedals/#left-hand-thread) : A thread tightening anticlockwise, used where normal rotation would loosen a part, and why a forced pedal or cup comes out damaged. - [Cross-threading](https://bmxpartsdepot.com/guides/bmx-cranks-and-pedals/#cross-threading) : Starting a fastener off-axis so it cuts across the existing thread, the failure that ruins crank arms and bottom bracket shells. - [Thread insert](https://bmxpartsdepot.com/guides/bmx-cranks-and-pedals/#thread-insert) : A helical or solid insert restoring a stripped thread in a frame or crank, the repair deciding whether a damaged part is scrap. ### Brakes, Cables and Detanglers - [U-brakes and how they work](https://bmxpartsdepot.com/guides/bmx-brakes-and-gyros/#u-brake) : The standard BMX rim brake, mounted on two posts either side of the wheel. - [Brake mounts and the 990 name](https://bmxpartsdepot.com/guides/bmx-brakes-and-gyros/#u-brake-mounts) : The welded posts on the seat stays or chain stays that a U-brake bolts onto. - [Removable brake mounts](https://bmxpartsdepot.com/guides/bmx-brakes-and-gyros/#removable-brake-mounts) : Brake mounts that bolt on rather than being welded to the frame. - [Detanglers and how they actually work](https://bmxpartsdepot.com/guides/bmx-brakes-and-gyros/#gyro-detangler) : A rotor unit that lets the bars spin while keeping the rear brake connected. - [Gyro tabs](https://bmxpartsdepot.com/guides/bmx-brakes-and-gyros/#gyro-tabs) : The small welded tabs on the head tube that a detangler bolts to. - [Straddle cable and yoke](https://bmxpartsdepot.com/guides/bmx-brakes-and-gyros/#straddle-cable-yoke) : The small carrier that links the main brake cable to the straddle cable on a U-brake. - [Brake levers](https://bmxpartsdepot.com/guides/bmx-brakes-and-gyros/#brake-lever-reach) : How far the lever blade sits from the bar, sometimes adjustable by a screw. - [V-brakes and calipers on BMX](https://bmxpartsdepot.com/guides/bmx-brakes-and-gyros/#v-brake) : A linear pull rim brake mounted on posts, uncommon on BMX but found on some builds. - [Cable routing and quick release](https://bmxpartsdepot.com/guides/bmx-brakes-and-gyros/#quick-release-brake-cable) : A cable or straddle fitting that unhooks quickly so the wheel can pass the brake pads. - [Brakeless frames and what gets left behind](https://bmxpartsdepot.com/guides/bmx-brakes-and-gyros/#brakeless) : Section of the guide covering brakeless frames and what gets left behind. - [Keyed washers](https://bmxpartsdepot.com/guides/bmx-brakes-and-gyros/#keyed-washer) : A washer with a tab that locates in the dropout slot to stop the axle rotating. - [Questions](https://bmxpartsdepot.com/guides/bmx-brakes-and-gyros/#questions) : Section of the guide covering questions. - [990 mounts](https://bmxpartsdepot.com/guides/bmx-brakes-and-gyros/#990-mounts) : The post spacing standard most BMX U-brakes and frames are built to, and the number needed before a used brake bolts to a used frame. - [Straddle cable hanger](https://bmxpartsdepot.com/guides/bmx-brakes-and-gyros/#straddle-cable-hanger) : The piece carrying the straddle cable above the brake, whose height changes the mechanical advantage of the whole brake. - [Cable pull ratio](https://bmxpartsdepot.com/guides/bmx-brakes-and-gyros/#cable-pull-ratio) : How much cable a lever pulls per unit of hand movement, which the brake has to be designed for or the lever either hits the bars or the pads never bite. ### Headsets, Forks and Stems - [Headset standards, and why the head tube decides](https://bmxpartsdepot.com/guides/bmx-front-end-headsets-and-forks/#bmx-headset-standards) : The set of head tube and cup designs, including integrated, semi-integrated, and older threaded types. - [Integrated headsets](https://bmxpartsdepot.com/guides/bmx-front-end-headsets-and-forks/#integrated-headset) : A headset where the bearings drop directly into a machined seat inside the head tube with no pressed cups. - [Zero stack and pressed cup headsets](https://bmxpartsdepot.com/guides/bmx-front-end-headsets-and-forks/#zero-stack-headset) : A semi-integrated headset where cups press into the head tube and the bearings sit inside it. - [Threaded headsets and quill stems](https://bmxpartsdepot.com/guides/bmx-front-end-headsets-and-forks/#threaded-headset) : An older headset design where the top race threads onto a threaded fork steerer. - [Threadless headsets and compression](https://bmxpartsdepot.com/guides/bmx-front-end-headsets-and-forks/#threadless-headset) : A headset used with an unthreaded steerer, where a stem clamps the steerer directly. - [Top load and front load stems](https://bmxpartsdepot.com/guides/bmx-front-end-headsets-and-forks/#front-load-stem) : A stem with a removable faceplate that clamps the bars from the front, as opposed to a top load. - [Steerer tube length and stack](https://bmxpartsdepot.com/guides/bmx-front-end-headsets-and-forks/#steerer-length) : Section of the guide covering steerer tube length and stack. - [Fork offset](https://bmxpartsdepot.com/guides/bmx-front-end-headsets-and-forks/#fork-offset) : How far the dropouts sit ahead of the steerer tube centreline, also called rake. - [Fork dropouts and axle sizing](https://bmxpartsdepot.com/guides/bmx-front-end-headsets-and-forks/#dropout-slot-width) : Section of the guide covering fork dropouts and axle sizing. - [Headset play, wear, and checking a used front end](https://bmxpartsdepot.com/guides/bmx-front-end-headsets-and-forks/#headset-play) : Section of the guide covering headset play, wear, and checking a used front end. - [Aheadset](https://bmxpartsdepot.com/guides/bmx-front-end-headsets-and-forks/#aheadset) : A trade name for the threadless headset design that is now the common freestyle standard. - [Quill stems](https://bmxpartsdepot.com/guides/bmx-front-end-headsets-and-forks/#quill-stem) : A stem with a long shaft that slides inside a threaded fork steerer and locks with a wedge. - [Unicrown forks](https://bmxpartsdepot.com/guides/bmx-front-end-headsets-and-forks/#unicrown-fork) : A fork where the legs bend in to meet the steerer directly, with no separate crown. - [Questions](https://bmxpartsdepot.com/guides/bmx-front-end-headsets-and-forks/#questions) : Section of the guide covering questions. - [Steerer tube diameter](https://bmxpartsdepot.com/guides/bmx-front-end-headsets-and-forks/#steerer-tube-diameter) : The outside diameter of the fork's steerer, which has to match both the headset and the stem clamp. - [Steerer tube length](https://bmxpartsdepot.com/guides/bmx-front-end-headsets-and-forks/#steerer-tube-length) : How much steerer the fork has, which caps how many spacers fit under the stem and whether the fork suits a longer head tube at all. - [Star nut](https://bmxpartsdepot.com/guides/bmx-front-end-headsets-and-forks/#star-nut) : A sprung nut driven into the steerer giving the top cap something to pull against when setting headset preload on a threadless front end. - [Compression cap](https://bmxpartsdepot.com/guides/bmx-front-end-headsets-and-forks/#compression-cap) : The cap whose bolt pulls the fork up to preload the headset bearings, and which is not a structural clamp. - [Internal compression bolt](https://bmxpartsdepot.com/guides/bmx-front-end-headsets-and-forks/#internal-compression-bolt) : A compression system running inside the steerer rather than pulling on a star nut, which is what a hollow-steerer fork needs. - [Crown race](https://bmxpartsdepot.com/guides/bmx-front-end-headsets-and-forks/#crown-race) : The bearing race seating on the fork crown, which has to match the headset's bearing angle and diameter or the front end never adjusts properly. - [Split crown race ring](https://bmxpartsdepot.com/guides/bmx-front-end-headsets-and-forks/#split-crown-race-ring) : A split race that clips onto the fork crown rather than being pressed, common on modern BMX and the piece most often missing from a used fork. - [Headset bearing angle](https://bmxpartsdepot.com/guides/bmx-front-end-headsets-and-forks/#headset-bearing-angle) : The contact angles on a cartridge headset bearing, which decide whether a bearing physically seats in a given cup and race combination. - [Headset stack height](https://bmxpartsdepot.com/guides/bmx-front-end-headsets-and-forks/#headset-stack-height) : How much height the assembled headset adds above and below the head tube, changing bar height and usable steerer. - [Headset spacer](https://bmxpartsdepot.com/guides/bmx-front-end-headsets-and-forks/#headset-spacer) : Spacers between top race and stem that set bar height and take up spare steerer, which still have to leave the stem fully clamped on the tube. - [Top load stem](https://bmxpartsdepot.com/guides/bmx-front-end-headsets-and-forks/#top-load-stem) : A threadless stem clamping the bars from above, giving a different bar height and clamping feel than a front load stem on the same fork. - [Stem reach](https://bmxpartsdepot.com/guides/bmx-front-end-headsets-and-forks/#stem-reach) : The horizontal distance from steerer centre to bar clamp centre, moving the bars forward or back independently of bar sweep. - [Torque specification](https://bmxpartsdepot.com/guides/bmx-front-end-headsets-and-forks/#torque-specification) : The tightness a fastener is designed for, which matters more on alloy and titanium parts than on the steel they replace. ### Handlebars, Grips and Cockpit - [The four numbers on a set of bars](https://bmxpartsdepot.com/guides/bmx-handlebars-and-cockpit/#bar-numbers) : Section of the guide covering the four numbers on a set of bars. - [Handlebar rise](https://bmxpartsdepot.com/guides/bmx-handlebars-and-cockpit/#handlebar-rise) : The vertical height from the bar clamp area to the top of the grip area. - [Handlebar width](https://bmxpartsdepot.com/guides/bmx-handlebars-and-cockpit/#handlebar-width) : The overall width of the bars measured end to end. - [Backsweep and upsweep](https://bmxpartsdepot.com/guides/bmx-handlebars-and-cockpit/#handlebar-backsweep) : The angle the bar ends are swept back toward the rider. - [Two-piece, three-piece and four-piece bars](https://bmxpartsdepot.com/guides/bmx-handlebars-and-cockpit/#bar-construction) : Section of the guide covering two-piece, three-piece and four-piece bars. - [Bar clamp diameter](https://bmxpartsdepot.com/guides/bmx-handlebars-and-cockpit/#oversize-bar-clamp) : A larger-than-standard bar clamp diameter used on some stems and bars. - [Bar material and butting](https://bmxpartsdepot.com/guides/bmx-handlebars-and-cockpit/#bar-material) : Section of the guide covering bar material and butting. - [Grips, flanges and barends](https://bmxpartsdepot.com/guides/bmx-handlebars-and-cockpit/#bmx-grips) : The inner diameter and end style of a grip, including flanged and flangeless types. - [Stems and where they put the bars](https://bmxpartsdepot.com/guides/bmx-handlebars-and-cockpit/#front-load-stem) : Section of the guide covering stems and where they put the bars. - [Questions](https://bmxpartsdepot.com/guides/bmx-handlebars-and-cockpit/#questions) : Section of the guide covering questions. - [Two-piece bar](https://bmxpartsdepot.com/guides/bmx-handlebars-and-cockpit/#two-piece-bar) : Bars made from two tubes, lighter with fewer welds, distinguishable by eye and both a durability and an era marker. - [Four-piece bar](https://bmxpartsdepot.com/guides/bmx-handlebars-and-cockpit/#four-piece-bar) : Bars made from four tubes with a crossbar, the common freestyle construction, with more welds and a different feel under load. - [Crossbar](https://bmxpartsdepot.com/guides/bmx-handlebars-and-cockpit/#bar-crossbar) : The tube bracing a four-piece bar between the uprights, adding stiffness and giving a mount point for a number plate or cable. - [Lock-on grip](https://bmxpartsdepot.com/guides/bmx-handlebars-and-cockpit/#lock-on-grip) : A grip clamped by a collar rather than held by friction, needing bar end room for the clamp and no glue. - [Knurled Bar Clamp Area](https://bmxpartsdepot.com/guides/bmx-handlebars-and-cockpit/#knurled-bar-clamp) : The roughened band in the middle of a handlebar that helps the stem grip. - [Handlebar Upsweep](https://bmxpartsdepot.com/guides/bmx-handlebars-and-cockpit/#handlebar-upsweep) : The angle the bar ends rise from the horizontal cross section. ### Seats, Posts and Clamps - [Pivotal, railed and tripod](https://bmxpartsdepot.com/guides/bmx-seats-and-seatposts/#seat-types) : Section of the guide covering pivotal, railed and tripod. - [Pivotal seats](https://bmxpartsdepot.com/guides/bmx-seats-and-seatposts/#pivotal-seat) : A seat and post interface using a splined face and a single bolt through the seat. - [Seat post diameter](https://bmxpartsdepot.com/guides/bmx-seats-and-seatposts/#seat-post-diameter) : The outside diameter of the seat post, with more than one size in common use. - [Seat clamps, integrated and external](https://bmxpartsdepot.com/guides/bmx-seats-and-seatposts/#integrated-seat-clamp) : A seat clamp built into the frame's seat tube rather than a separate collar. - [Post length, slammed setups and offset](https://bmxpartsdepot.com/guides/bmx-seats-and-seatposts/#post-length) : Section of the guide covering post length, slammed setups and offset. - [Stuck and seized seat posts](https://bmxpartsdepot.com/guides/bmx-seats-and-seatposts/#stuck-post) : Section of the guide covering stuck and seized seat posts. - [Seat and post material](https://bmxpartsdepot.com/guides/bmx-seats-and-seatposts/#seat-material) : Section of the guide covering seat and post material. - [Combo seat and post units](https://bmxpartsdepot.com/guides/bmx-seats-and-seatposts/#combo-units) : Section of the guide covering combo seat and post units. - [Buying a used seat, post or clamp](https://bmxpartsdepot.com/guides/bmx-seats-and-seatposts/#condition) : Section of the guide covering buying a used seat, post or clamp. - [Questions](https://bmxpartsdepot.com/guides/bmx-seats-and-seatposts/#questions) : Section of the guide covering questions. - [Railed seat](https://bmxpartsdepot.com/guides/bmx-seats-and-seatposts/#railed-seat) : A seat on twin rails clamped by a railed post, the main alternative to pivotal and not cross-compatible with it. - [Seat clamp diameter](https://bmxpartsdepot.com/guides/bmx-seats-and-seatposts/#seat-clamp-diameter) : The outside diameter of the seat tube at its top, which is what a clamp must match, and a different number from post diameter. - [Tripod post spline](https://bmxpartsdepot.com/guides/bmx-seats-and-seatposts/#tripod-post-spline) : A third seat mounting interface using a three-point pattern, compatible with neither railed nor pivotal parts. - [Standover Height](https://bmxpartsdepot.com/guides/bmx-seats-and-seatposts/#standover-height) : The height of the top tube above the ground at its lowest useful point. - [Yield Strength](https://bmxpartsdepot.com/guides/bmx-seats-and-seatposts/#yield-strength) : The stress at which a material starts to deform permanently. - [Zero Offset Seat Post](https://bmxpartsdepot.com/guides/bmx-seats-and-seatposts/#zero-offset-seat-post) : A seat post with the clamp directly above the post centreline rather than set back. - [Zinc-Plated Hardware](https://bmxpartsdepot.com/guides/bmx-seats-and-seatposts/#zinc-plated-hardware) : Bolts and small parts with a zinc coating for corrosion resistance. ### Era, Dating and Restoration ID - [Why the year ranges are contested](https://bmxpartsdepot.com/guides/vintage-bmx-identification/#era-boundaries) : Section of the guide covering why the year ranges are contested. - [Old school](https://bmxpartsdepot.com/guides/vintage-bmx-identification/#old-school-bmx) : The earlier era of BMX, generally covering the sport's first generation of bikes and parts. - [Mid school](https://bmxpartsdepot.com/guides/vintage-bmx-identification/#mid-school-bmx) : The loosely defined era of BMX between old school and modern, marked by specific part standards. - [Modern](https://bmxpartsdepot.com/guides/vintage-bmx-identification/#modern-bmx) : Section of the guide covering modern. - [Dating a frame from its features](https://bmxpartsdepot.com/guides/vintage-bmx-identification/#dating-by-feature) : Section of the guide covering dating a frame from its features. - [Construction giveaways](https://bmxpartsdepot.com/guides/vintage-bmx-identification/#construction) : Section of the guide covering construction giveaways. - [The front end: threaded to threadless](https://bmxpartsdepot.com/guides/vintage-bmx-identification/#threaded-to-threadless) : Section of the guide covering the front end: threaded to threadless. - [Mag wheels and period wheel details](https://bmxpartsdepot.com/guides/vintage-bmx-identification/#mag-wheels) : Section of the guide covering mag wheels and period wheel details. - [Buying and valuing vintage](https://bmxpartsdepot.com/guides/vintage-bmx-identification/#buying-vintage) : Section of the guide covering buying and valuing vintage. - [Before you restore](https://bmxpartsdepot.com/guides/vintage-bmx-identification/#restoration) : Section of the guide covering before you restore. - [Questions](https://bmxpartsdepot.com/guides/vintage-bmx-identification/#questions) : Section of the guide covering questions. - [Adjustable Cone](https://bmxpartsdepot.com/guides/vintage-bmx-identification/#adjustable-cone) : A threaded cone on a loose-ball hub or headset that sets bearing preload. - [Expander Bolt](https://bmxpartsdepot.com/guides/vintage-bmx-identification/#expander-bolt) : The long bolt that pulls a wedge up inside a quill stem to lock it in the steerer tube. - [Jam Nut](https://bmxpartsdepot.com/guides/vintage-bmx-identification/#jam-nut) : A second nut tightened against a cone or locknut to stop it backing off. - [Neck](https://bmxpartsdepot.com/guides/vintage-bmx-identification/#bmx-neck-stem) : Old-school slang for the stem, still used in listings for period parts. - [Wedge Stem](https://bmxpartsdepot.com/guides/vintage-bmx-identification/#wedge-stem) : A quill stem locked in place by an angled wedge pulled up by the expander bolt. ### BMX FAQ - [What size BMX bike do I need for my height?](https://bmxpartsdepot.com/bmx-faq/#what-size-bmx-bike-do-i-need-for-my-height) : On a modern freestyle BMX the wheel is 20 inch whatever your height, and the size you actually choose is the top tube length. Adult bikes run roughly 20 to 21.25 inches of top tube... - [What size wheel does a BMX bike use?](https://bmxpartsdepot.com/bmx-faq/#what-size-wheel-does-a-bmx-bike-use) : Twenty inch, and that number means a bead seat diameter of 406mm rather than anything you can measure across the tire. The trap is that a second 20 inch standard exists at 451mm, m... - [What crank arm length should I run?](https://bmxpartsdepot.com/bmx-faq/#what-crank-arm-length-should-i-run) : Almost every BMX crank sold is 160, 165, 170 or 175mm, and 170mm is what most complete bikes ship with. Beyond that this is rider preference rather than a specification, and the on... - [Street, park, dirt or race, what is actually different about the bike?](https://bmxpartsdepot.com/bmx-faq/#street-park-dirt-or-race-what-is-actually-different-about-th) : Race bikes are a different machine. Street, park and dirt bikes are the same machine set up differently. That is the honest split, and most buying guides blur it. A race bike is bu... - [Freestyle and race BMX, are they the same bike?](https://bmxpartsdepot.com/bmx-faq/#freestyle-and-race-bmx-are-they-the-same-bike) : No, and the clearest tell is the size chart. Freestyle is near enough one size with a 20 inch wheel and roughly 20 to 21.25 inches of top tube. Race is a graded set of named sizes... - [Chromoly or hi-ten steel, is the price difference worth it?](https://bmxpartsdepot.com/bmx-faq/#chromoly-or-hi-ten-steel-is-the-price-difference-worth-it) : Yes for anything that gets landed on, and the difference is a real material property rather than marketing. Chromoly is roughly twice as strong as hi-ten for the same weight of tub... - [What gear ratio should a beginner run, and what does the ratio number mean?](https://bmxpartsdepot.com/bmx-faq/#what-gear-ratio-should-a-beginner-run-and-what-does-the-rati) : Ride what the bike came with. The ratio is the front sprocket teeth divided by the rear cog teeth, and a modern complete almost always ships at 25/9, which is 2.78 to 1. There is n... - [U-brake, caliper, or no brakes at all?](https://bmxpartsdepot.com/bmx-faq/#u-brake-caliper-or-no-brakes-at-all) : A modern BMX runs a U-brake on the back or nothing. Calipers are not a current BMX part. The real decision is brake or brakeless, and it is not only a style question, because a fra... - [How much should a first real BMX bike cost, and what do you get at each price point?](https://bmxpartsdepot.com/bmx-faq/#how-much-should-a-first-real-bmx-bike-cost-and-what-do-you-g) : We are not publishing a price tier table, because the spec is what you are buying and the price does not track it. At around the same money you can buy an all hi-ten bike from one... - [Can I run tubeless on a BMX?](https://bmxpartsdepot.com/bmx-faq/#can-i-run-tubeless-on-a-bmx) : Usually not, and it needs both the rim and the tire to be built for it rather than just sealant in a normal setup. The requirement is a rim bed that seals and a bead that locks, an... ## Optional - [eBay Store](https://www.ebay.com/usr/bmx-parts-depot) : The live eBay inventory store. - [Privacy Policy](https://bmxpartsdepot.com/privacy.html) : Privacy policy for the website. - [Terms of Use](https://bmxpartsdepot.com/terms.html) : Terms and conditions of using the website.