Understand bike standards before checkout.

Fit Checklists

Every interface a frame must match before it fits in a build — this is the exact list the MACH4 builder checks automatically.

• Steerer ↔ Head tube — checked against your fork. Tapered steerers need a lower bearing seat that handles 1.5" (ZS56 / IS52 / EC44). Moto forks never fit bicycle frames. Standards: tapered, straight-1-1/8, moto. • Headset cups ↔ Head tube — checked against your headset. The headset's upper and lower cups (SHIS codes like ZS44/ZS56) must both match the frame's head tube bores exactly. Standards: zs44/zs56, zs44/zs44, is41/is52, is42/is52, ec34/ec34, ec44/ec44. • Fork wheel size ↔ Frame — checked against your fork. A mullet (mx) frame runs a 29" fork; otherwise fork and frame wheel sizes match exactly. Standards: 26, 29, 27.5, mx, 700c. • Fork travel ↔ Frame rating — checked against your fork. Frames are designed around a fork travel window (~rear travel to +20mm). Big deviations change geometry and can void warranty. Adapter path: Outside the typical range for this frame's rear travel — check the frame maker's approved fork travel before buying. • Shock size ↔ Frame mount — checked against your shock. Eye-to-eye (e.g. 205mm) must match the frame's shock spec exactly; stroke and trunnion vs standard mounting must match too. • Rear axle ↔ Frame spacing — checked against your wheels. Boost 148, 142, and Super Boost 157 are mutually exclusive — no adapters. Standards: 12x148, 12x142, 12x157, 10x135. • Wheel size ↔ Frame — checked against your wheels. Match diameters; mullet frames take 29 front / 27.5 rear. Standards: 26, 29, 27.5, mx, 700c. • T-Type ↔ UDH frame — checked against your rearDerailleur. SRAM Transmission mounts to the UDH interface itself — no UDH frame, no T-Type. • BB shell ↔ Frame — checked against your bottomBracket. The bottom bracket's shell side must name the frame's exact shell (BSA 73, PF92, T47…). Standards: bsa-73, bsa-68, t47, pf92, pf30, bb30. • Seatpost diameter ↔ Frame — checked against your seatpost. Match exactly; shims only size DOWN. Adapter path: A skinnier post can run in a bigger frame with a shim (e.g. 30.9 in 31.6). A fatter post never fits. • Motor ↔ Frame platform — checked against your motor. E-MTB frames are molded for one motor system — no cross-brand swaps. • Battery ↔ Frame platform — checked against your battery. Batteries fit only their platform and downtube shape. • Display ↔ Frame platform — checked against your display. Displays/remotes are platform-and-generation specific.

Also called: frame compatibility, does a frame fit

Fit Checklists

Every interface a fork must match before it fits in a build — this is the exact list the MACH4 builder checks automatically.

• Steerer ↔ Head tube — checked against your frame. Tapered steerers need a lower bearing seat that handles 1.5" (ZS56 / IS52 / EC44). Moto forks never fit bicycle frames. Standards: tapered, straight-1-1/8, moto. • Headset ↔ Fork steerer — checked against your headset. A tapered steerer needs the headset's lower bearing to be a 1.5" seat (ZS56 / IS52 / EC44 lower). • Fork wheel size ↔ Frame — checked against your frame. A mullet (mx) frame runs a 29" fork; otherwise fork and frame wheel sizes match exactly. Standards: 26, 29, 27.5, mx, 700c. • Fork travel ↔ Frame rating — checked against your frame. Frames are designed around a fork travel window (~rear travel to +20mm). Big deviations change geometry and can void warranty. Adapter path: Outside the typical range for this frame's rear travel — check the frame maker's approved fork travel before buying. • Front axle ↔ Fork — checked against your wheels. Front hub spacing/diameter must match the fork dropouts. Adapter path: Many hubs convert between 15x110 and 20x110 with end caps — check the hub maker's spec. Standards: 15x110, 15x100, 20x110.

Also called: fork compatibility, does a fork fit

Fit Checklists

Every interface a rear shock must match before it fits in a build — this is the exact list the MACH4 builder checks automatically.

• Shock size ↔ Frame mount — checked against your frame. Eye-to-eye (e.g. 205mm) must match the frame's shock spec exactly; stroke and trunnion vs standard mounting must match too.

Also called: rear shock compatibility, does a rear shock fit

Fit Checklists

Every interface a wheels / hubs must match before it fits in a build — this is the exact list the MACH4 builder checks automatically.

• Rear axle ↔ Frame spacing — checked against your frame. Boost 148, 142, and Super Boost 157 are mutually exclusive — no adapters. Standards: 12x148, 12x142, 12x157, 10x135. • Front axle ↔ Fork — checked against your fork. Front hub spacing/diameter must match the fork dropouts. Adapter path: Many hubs convert between 15x110 and 20x110 with end caps — check the hub maker's spec. Standards: 15x110, 15x100, 20x110. • Wheel size ↔ Frame — checked against your frame. Match diameters; mullet frames take 29 front / 27.5 rear. Standards: 26, 29, 27.5, mx, 700c. • Tire diameter ↔ Rim — checked against your tires. A tire only mounts a rim of the same bead-seat diameter. No exceptions. Standards: 26, 29, 27.5, mx, 700c. • Cassette ↔ Freehub body — checked against your cassette. HG, Micro Spline, XD, and XDR are different splines. Most good hubs sell swappable driver bodies. Adapter path: XD cassette on an XDR driver: add the 1.85mm spacer behind the cassette. Standards: hg, microspline, xd, xdr. • Rotor mount ↔ Hub — checked against your rotors. Six-bolt vs Centerlock — the rotor must match the hub (or use the CL→6-bolt adapter). Adapter path: 6-bolt rotors mount on Centerlock hubs with an adapter; the reverse doesn't exist. Standards: 6-bolt, centerlock.

Also called: wheels / hubs compatibility, does a wheels / hubs fit

Fit Checklists

Every interface a tires must match before it fits in a build — this is the exact list the MACH4 builder checks automatically.

• Tire diameter ↔ Rim — checked against your wheels. A tire only mounts a rim of the same bead-seat diameter. No exceptions. Standards: 26, 29, 27.5, mx, 700c.

Also called: tires compatibility, does a tires fit

Fit Checklists

Every interface a cassette must match before it fits in a build — this is the exact list the MACH4 builder checks automatically.

• Cassette ↔ Freehub body — checked against your wheels. HG, Micro Spline, XD, and XDR are different splines. Most good hubs sell swappable driver bodies. Adapter path: XD cassette on an XDR driver: add the 1.85mm spacer behind the cassette. Standards: hg, microspline, xd, xdr. • Speeds: cassette ↔ chain — checked against your chain. Chain width is speed-specific — 12s chain for a 12s cassette. • Speeds: cassette ↔ derailleur — checked against your rearDerailleur. Derailleur cage/pull geometry is designed per speed count.

Also called: cassette compatibility, does a cassette fit

Fit Checklists

Every interface a chain must match before it fits in a build — this is the exact list the MACH4 builder checks automatically.

• Speeds: cassette ↔ chain — checked against your cassette. Chain width is speed-specific — 12s chain for a 12s cassette.

Also called: chain compatibility, does a chain fit

Fit Checklists

Every interface a rear derailleur must match before it fits in a build — this is the exact list the MACH4 builder checks automatically.

• Speeds: cassette ↔ derailleur — checked against your cassette. Derailleur cage/pull geometry is designed per speed count. • Speeds: shifter ↔ derailleur — checked against your shifters. Click count must equal cog count. • Shift protocol — checked against your shifters. Same brand, same family: SRAM mech ↔ SRAM mech, AXS ↔ AXS, Di2 ↔ Di2. Pull ratios and wireless protocols don't cross brands. • T-Type ↔ UDH frame — checked against your frame. SRAM Transmission mounts to the UDH interface itself — no UDH frame, no T-Type.

Also called: rear derailleur compatibility, does a rear derailleur fit

Fit Checklists

Every interface a shifters must match before it fits in a build — this is the exact list the MACH4 builder checks automatically.

• Speeds: shifter ↔ derailleur — checked against your rearDerailleur. Click count must equal cog count. • Shift protocol — checked against your rearDerailleur. Same brand, same family: SRAM mech ↔ SRAM mech, AXS ↔ AXS, Di2 ↔ Di2. Pull ratios and wireless protocols don't cross brands.

Also called: shifters compatibility, does a shifters fit

Fit Checklists

Every interface a bottom bracket must match before it fits in a build — this is the exact list the MACH4 builder checks automatically.

• BB shell ↔ Frame — checked against your frame. The bottom bracket's shell side must name the frame's exact shell (BSA 73, PF92, T47…). Standards: bsa-73, bsa-68, t47, pf92, pf30, bb30. • BB bore ↔ Crank spindle — checked against your crankset. DUB, 24mm, and 30mm spindles each need matching BB bearings. Standards: dub, 24mm, 30mm.

Also called: bottom bracket compatibility, does a bottom bracket fit

Fit Checklists

Every interface a crankset must match before it fits in a build — this is the exact list the MACH4 builder checks automatically.

• BB bore ↔ Crank spindle — checked against your bottomBracket. DUB, 24mm, and 30mm spindles each need matching BB bearings. Standards: dub, 24mm, 30mm.

Also called: crankset compatibility, does a crankset fit

Fit Checklists

Every interface a rotors must match before it fits in a build — this is the exact list the MACH4 builder checks automatically.

• Rotor mount ↔ Hub — checked against your wheels. Six-bolt vs Centerlock — the rotor must match the hub (or use the CL→6-bolt adapter). Adapter path: 6-bolt rotors mount on Centerlock hubs with an adapter; the reverse doesn't exist. Standards: 6-bolt, centerlock.

Also called: rotors compatibility, does a rotors fit

Fit Checklists

Every interface a handlebar must match before it fits in a build — this is the exact list the MACH4 builder checks automatically.

• Bar clamp ↔ Stem — checked against your stem. 31.8 and 35mm are the two clamp sizes; no adapters. Standards: 35, 31.8.

Also called: handlebar compatibility, does a handlebar fit

Fit Checklists

Every interface a stem must match before it fits in a build — this is the exact list the MACH4 builder checks automatically.

• Bar clamp ↔ Stem — checked against your handlebar. 31.8 and 35mm are the two clamp sizes; no adapters. Standards: 35, 31.8.

Also called: stem compatibility, does a stem fit

Fit Checklists

Every interface a seatpost must match before it fits in a build — this is the exact list the MACH4 builder checks automatically.

• Seatpost diameter ↔ Frame — checked against your frame. Match exactly; shims only size DOWN. Adapter path: A skinnier post can run in a bigger frame with a shim (e.g. 30.9 in 31.6). A fatter post never fits.

Also called: seatpost compatibility, does a seatpost fit

Fit Checklists

Every interface a e-bike motor must match before it fits in a build — this is the exact list the MACH4 builder checks automatically.

• Motor ↔ Frame platform — checked against your frame. E-MTB frames are molded for one motor system — no cross-brand swaps.

Also called: e-bike motor compatibility, does a e-bike motor fit

Fit Checklists

Every interface a e-bike battery must match before it fits in a build — this is the exact list the MACH4 builder checks automatically.

• Battery ↔ Frame platform — checked against your frame. Batteries fit only their platform and downtube shape. • Controller ↔ Battery voltage — checked against your controller. System voltage (60V/72V…) must match across battery, controller, and motor.

Also called: e-bike battery compatibility, does a e-bike battery fit

Fit Checklists

Every interface a e-bike display must match before it fits in a build — this is the exact list the MACH4 builder checks automatically.

• Display ↔ Frame platform — checked against your frame. Displays/remotes are platform-and-generation specific.

Also called: e-bike display compatibility, does a e-bike display fit

Fit Checklists

Every interface a controller must match before it fits in a build — this is the exact list the MACH4 builder checks automatically.

• Controller ↔ Battery voltage — checked against your battery. System voltage (60V/72V…) must match across battery, controller, and motor.

Also called: controller compatibility, does a controller fit

Frame & Fit

The frame is the one part that decides almost every other purchase. It fixes your wheel size, rear axle spacing, bottom bracket shell, head tube (and therefore headset and fork steerer), seat tube diameter, rear shock size, brake mount, derailleur hanger, and max fork travel.

How to check fit: find the frame's spec sheet and write down seven numbers before buying anything — wheel size (29 / 27.5 / MX), rear axle (e.g. 12x148 Boost), BB shell (e.g. BSA 73mm threaded), head tube standard (e.g. ZS44/ZS56), seatpost diameter (e.g. 31.6mm), shock size (e.g. 205x60 trunnion, full-suspension only), and max fork travel. Every part page you look at afterwards gets compared against that list. The MACH4 builder does this automatically once a frame is in your build.

Also called: frameset, front triangle, what fits my frame

Frame & Fit

Reach (horizontal) and stack (vertical) measure the distance from the bottom bracket to the top of the head tube — together they describe how big a frame really is, far better than seat tube length or S/M/L letters.

Sizing isn't compatibility, but it is fit: compare reach between your current bike and a candidate frame. ±5mm feels the same, 15mm+ is a size change. Head angle, seat tube angle, and chainstay length shape handling; none of them affect whether parts bolt on.

Also called: reach, stack, frame geometry

Frame & Fit

The head tube's inner diameter at top and bottom sets which headset — and therefore which fork steerer — fits. Written in SHIS code: ZS44/ZS56 (zero-stack cups pressed inside), IS41/IS52 (drop-in integrated bearings), or EC34/EC44 (external cups). The number is the bore in millimeters.

How to check fit: the frame spec lists something like 'ZS44/28.6 | ZS56/40'. The first half must match your headset's upper cup, the second half the lower cup. Nearly every modern MTB frame accepts a tapered steerer (1-1/8" top, 1.5" crown) through a ZS44/ZS56 or IS41/IS52 head tube. If the head tube is straight 44mm inside top and bottom ('44mm head tube'), you can still run a tapered fork with an external-lower headset (EC44).

Also called: zs44, zs56, is41, is52, ec44, headtube standard, shis

Frame & Fit

Modern MTB fork steerers taper from 1.5" at the crown to 1-1/8" at the stem. Straight 1-1/8" steerers survive on older and budget bikes; straight 1.5" is rare.

How to check fit: fork spec says 'tapered' → needs a head tube/headset combo whose lower end handles 1.5" (ZS56, IS52, EC44 lower). Stems always clamp the 1-1/8" top (28.6mm), so stems are universal on modern forks. A straight-steerer fork in a tapered frame needs a reducer crown race; a tapered fork will never fit a straight 1-1/8"-only head tube (e.g. EC34 lower).

Also called: steerer tube, 1 1/8, 1.5 taper

Frame & Fit

The frame's BB shell is a fixed diameter/width/thread situation: BSA 73mm threaded (most modern MTB), T47 (threaded, oversized), PF92 (press-fit, 41mm bore, 92mm wide), BB30/PF30 (30mm-bearing press-fit, mostly older/road). The shell never changes — the bottom bracket you buy adapts the shell to your crank's spindle.

How to check fit: match TWO things — (1) bottom bracket's shell side to the frame ('BSA/English/threaded 73mm' must say the same on both), and (2) bottom bracket's bore to the crank spindle (DUB 28.99mm, Shimano 24mm, or 30mm). Example: BSA 73 frame + SRAM DUB crank → 'DUB BSA 73mm' bottom bracket. Press-fit shells can usually run any spindle via the right BB; threaded shells too. What you can't do is thread a BSA bottom bracket into a PF92 shell.

Also called: bsa 73, pf92, bb92, t47, pressfit, threaded bb, bottom bracket shell

Frame & Fit

Rear dropout spacing × axle diameter: 12x148 'Boost' rules modern MTB. 12x142 is the previous thru-axle norm, 12x157 'Super Boost' appears on some enduro frames (Pivot, some Knolly), 10x135 QR is rim-brake/older era.

How to check fit: frame spec 'rear axle: 148x12' → the rear hub/wheelset must say 'Boost 148' — no adapters exist that make a 142 hub into a 148 (offset end caps don't change flange spacing legally for the chainline; some hubs are convertible with kits — check the hub maker's compatibility chart). Super Boost 157 wheels are NOT Boost-compatible in either direction. Watch for it: buying wheels is where this bites most people.

Also called: boost 148, 12x142, super boost, 157, rear spacing, thru axle

Frame & Fit

Set by the fork, not the frame: 15x110 'Boost' on almost all modern MTB forks; 15x100 on older forks; 20x110 on DH and some heavy enduro forks; 9mm QR on old/budget forks.

How to check fit: fork lowers say '15x110 Boost' → front hub must be 15x110. Many nicer front hubs convert between 15x110 and 20x110 with end caps — check the hub's spec page for 'convertible'. A non-Boost 15x100 wheel cannot space out to Boost correctly (rotor and tire center off).

Also called: 15x110, 20x110, boost front, front hub spacing

Wheels & Tires Fit

29" (622mm bead seat) and 27.5" (584mm) are the two MTB diameters; 26" survives on dirt jump and kids bikes. 'MX' or mullet means 29 front + 27.5 rear.

How to check fit: frame and fork each state their wheel size — match the wheel's diameter to each end. A 27.5 wheel physically bolts into most 29 forks/frames but wrecks the geometry (BB drops ~19mm) — treat sizes as non-interchangeable unless the frame explicitly offers a flip-chip/mullet mode. Tires must match rim diameter exactly: a 29 tire never mounts a 27.5 rim.

Also called: 29er, 650b, 26 inch, wheel diameter

Wheels & Tires Fit

A mixed-wheel bike: 29" front for rollover, 27.5" rear for clearance and agility. Factory MX frames (and many with flip chips) are designed around the geometry.

How to check fit: an MX frame wants a 29 fork + 29 front wheel and a 27.5 rear wheel — so 'wheelset' listings must be MX-specific or bought as separate front/rear. Converting a 29 frame to mullet drops the BB and slackens it ~1°; only do it if the frame maker documents a mullet setting.

Also called: mixed wheel, mx wheels, mullet bike

Frame & Fit

The seat tube's inner diameter: 30.9mm, 31.6mm, and 34.9mm cover almost all modern MTB; 27.2mm is gravel/road/oldschool. Dropper posts come in each size.

How to check fit: match exactly — a 30.9 post in a 31.6 frame needs a 0.35mm shim (fine); a 31.6 post will never enter a 30.9 frame. Shims only size DOWN a frame's bore to a skinnier post, never the reverse. For droppers also check insertion depth: measure how much post the seat tube swallows before internal bends/pivots stop it, and compare with the dropper's 'total length' and 'insertion' figures.

Also called: 30.9, 31.6, 34.9, 27.2, post diameter, dropper size

Drivetrain Fit

SRAM's standardized replaceable derailleur hanger, adopted by most frames since ~2020. Besides being a cheap crash part, UDH is the mounting interface required by SRAM T-Type/Transmission derailleurs, which bolt straight to the axle in place of the hanger.

How to check fit: frame spec or the frame maker's site says 'UDH compatible'. If yes → any regular derailleur (with the UDH hanger installed) or any T-Type Transmission derailleur fits. If no (proprietary hanger) → T-Type is off the table entirely; regular cable/AXS derailleurs still fit that frame's own hanger.

Also called: universal derailleur hanger, udh hanger

Drivetrain Fit

SRAM's hangerless electronic drivetrain (XX/X0/GX/S1000 Eagle Transmission, 12s). The derailleur clamps the frame's UDH interface directly, shifts under full load, and only pairs with T-Type cassettes, chains, and cranks' chainrings.

How to check fit: needs (1) a UDH frame, (2) an XD driver rear hub for the T-Type cassette, (3) a T-Type flattop chain, (4) AXS pod controller — no mechanical option. Mixing T-Type with older Eagle 12s parts doesn't work: chains, cassettes, and derailleurs are all T-Type-specific.

Also called: t-type, eagle transmission, gx transmission, hangerless

Drivetrain Fit

A shifter and derailleur only work together if they speak the same 'language': the cable pull per click (mechanical) or the wireless/wired protocol (electronic). SRAM mechanical ≠ Shimano mechanical; SRAM AXS ≠ Shimano Di2.

How to check fit: stay same-brand, same-speed, same-family. Shimano 12s MTB shifter → Shimano 12s MTB derailleur. SRAM Eagle mechanical → Eagle mechanical. AXS pairs with any AXS-generation SRAM derailleur (but T-Type pods pair only with T-Type). Cassette and chain then just need matching speed count — those two are cross-brand tolerant (a 12s Shimano chain runs fine on a SRAM cassette in practice, with HG+ being the picky exception under load).

Also called: pull ratio, cable pull, axs, di2, brand mixing

Drivetrain Fit

The cassette's interface must match the wheel's freehub body: Shimano HG (8–11s, and 12s 'HG or 8-10 driver' cassettes), Shimano Micro Spline (12s, 10t-capable), SRAM XD (10t MTB cassettes), SRAM XDR (road, 1.85mm longer).

How to check fit: cassette listing names its driver ('XD driver body required') — match to the hub listing. One legal crossover: an XD cassette fits an XDR driver with a 1.85mm spacer behind it (XDR cassette on XD driver: never). Most nice hubs sell swappable freehub bodies ~$40–80, so a 'wrong' wheelset is usually a driver-swap away from right.

Also called: xd vs microspline, hg driver, xdr spacer, driver body swap

Drivetrain Fit

The axle through your cranks: SRAM DUB (28.99mm), Shimano Hollowtech II (24mm), and 30mm (RaceFace Cinch, e*thirteen, Hope). The spindle decides which bottom bracket bearings you need — not the frame.

How to check fit: crank spec names the spindle; buy the bottom bracket named '<spindle> for <your frame shell>' (e.g. 'DUB BSA73', 'Hollowtech II PF92', '30mm T47'). Also check chainline/spacing flavor: Boost frames want Boost-chainline cranks (52mm, sometimes sold as '3mm offset chainring'); Super Boost wants 56–57mm.

Also called: dub, hollowtech, 30mm spindle, cinch, gxp

Drivetrain Fit

The distance from the frame centerline to the chainring, ideally aligned with the cassette's middle. Boost 148 frames want ~52mm chainline; Super Boost 157 wants ~56.5mm; older 142 frames ~49mm.

How to check fit: crank or chainring listings state chainline ('52mm Boost'). A wrong chainline still pedals but shifts worse at the extremes and wears faster. Direct-mount chainrings with different offsets (0/3/6mm) let one crank serve multiple chainlines — match ring offset to your frame's spacing.

Also called: 52mm chainline, chainring offset, boost chainline

Drivetrain Fit

The sacrificial aluminum link between frame and derailleur, meant to bend or snap in a crash instead of your dropout. Pre-UDH, nearly every frame used its own proprietary shape.

How to check fit: search your exact frame + year on a hanger database (wheelsmfg.com is the canonical one) — hangers are frame-specific, cheap, and worth carrying a spare of. If your frame is UDH, the spare is just 'UDH' and any shop stocks it.

Also called: mech hanger, dropout hanger, replaceable hanger

Drivetrain Fit

Chains narrow as cassettes gain cogs: 12-speed chains (5.25mm) are not interchangeable with 11s (5.5mm) or 10s. Within a speed count, cross-brand mostly works — except SRAM T-Type flattop and Shimano 12s HG+ which prefer their own.

How to check fit: match the chain's stated speed to the cassette/derailleur speed, full stop. For 1x MTB also pick the matching chainring tooth profile (narrow-wide). Flattop road/T-Type chains need flattop-compatible derailleur pulleys and rings.

Also called: 12 speed chain, flattop, hg+ chain, narrow wide

Suspension Fit

A rear shock is sized 'eye-to-eye × stroke' (e.g. 205×60, 210×55). Trunnion mounts bolt the shock body directly from the sides (shorter for the same stroke); standard mounts use eyelets both ends. The frame dictates both numbers and the mount style exactly.

How to check fit: frame spec sheet lists shock size ('205x62.5 trunnion') — the replacement shock must match eye-to-eye, stroke (or the frame maker's approved alternates ±2.5mm stroke), and mount style. Also match mounting hardware width/bolt diameter (e.g. 30x8mm bushings) and check the shock reservoir clears the front triangle — Fox/RockShox both publish frame-fit databases; use them before buying.

Also called: eye to eye, stroke, trunnion, 205x60, metric shock

Suspension Fit

Frames are designed (and warrantied) around a fork length range. More travel raises the front, slackens the head angle ~0.5°/10mm, and increases dropout leverage on the head tube.

How to check fit: frame spec lists recommended fork travel (e.g. '150–160mm'). Staying within ±10mm of stock is safe; +20mm or more voids most warranties and can genuinely overload short head tubes on XC frames. Also confirm the fork's wheel size and axle match your front wheel, and its steerer is long enough for your head tube + stack of spacers (used forks: measure steerer!).

Also called: overforking, max fork travel, axle to crown

Suspension Fit

How far the front axle sits ahead of the steering axis — 44mm and 51mm are the common 29er options, 37/44mm for 27.5. Less offset = more trail = calmer steering.

Fit-wise any offset bolts on; it changes handling only. Match the frame designer's intended offset (spec sheet) unless you're deliberately tuning. Not a compatibility blocker — buy whichever your frame was designed around when in doubt.

Also called: rake, 44mm offset, 51mm offset

Brakes Fit

Rotors attach to hubs one of two ways: six M5 bolts on a 44mm circle, or Shimano's Centerlock spline with a lockring. Functionally equal — but the rotor must match the hub.

How to check fit: hub listing says '6-bolt' or 'Centerlock'. Centerlock hubs can take 6-bolt rotors via an adapter; 6-bolt hubs cannot take Centerlock rotors. If your wheels and rotors disagree, the cheap fix is new rotors, not new hubs.

Also called: centerlock, 6 bolt, lockring rotor

Brakes Fit

Rotor diameters run 160/180/200/203/220mm. Forks and frames have post-mount tabs natively sized for one rotor (often 180 front, 160–180 rear); adapters step the caliper up 20 or 40mm. Every fork/frame also has a MAX rotor it's rated for.

How to check fit: fork spec lists 'max rotor 230mm' etc. — stay at or under it. Then buy the adapter matching your jump ('PM 180→200 +20mm'). Note 200 vs 203: SRAM uses 200, Shimano 203 — calipers need the right-size adapter, a 3mm mismatch is shimmable with washers but best avoided by matching brand conventions.

Also called: post mount, 203 vs 200, max rotor, brake adapter

Cockpit Fit

MTB bars and stems come in two clamp diameters: 31.8mm and 35mm. The bar's center section and the stem's clamp must be the same number — there is no adapter.

How to check fit: both listings state clamp diameter. Grip end diameter is universal 22.2mm, so grips/brakes/shifters fit any MTB bar. Stem-to-steerer is universally 28.6mm (1-1/8") on modern forks.

Also called: 31.8, 35mm bar, bar clamp

Wheels & Tires Fit

Frames and forks publish a max tire size ('29 x 2.5"'). Rim internal width also sets a sensible tire range: ~30mm internal suits 2.3–2.6" tires.

How to check fit: tire diameter must equal rim diameter exactly; tire width must be ≤ frame/fork max clearance (leave mud room — a claimed 2.6 max means a 2.6 measures tight). On the rim side, stay within the rim maker's tire-width range so the casing isn't pinched or bulbed.

Also called: tire clearance, internal width, 2.4 vs 2.6

Wheels & Tires Fit

Tubeless-ready rims + tubeless-ready tires + tape/valves/sealant. Modern MTB default; hooked vs hookless matters mostly for road pressure limits, not MTB.

How to check fit: both rim and tire listings say 'tubeless ready'. Any TR tire seats on any TR MTB rim. Non-TR ('tube type') casings can burp/weep — run tubes in them.

Also called: tubeless ready, tlr, hookless

E-Bike Systems

Mid-drive e-MTB frames are molded around ONE motor system: Bosch (CX/SX Smart System), Shimano EP8/EP801, DJI Avinox, Brose, Fazua Ride 60, TQ HPR, Specialized SL, Yamaha, or Bafang M-series. Motor, battery, display, and controller must all come from that platform.

How to check fit: the frame listing names its motor ('Bosch Performance CX Gen 5'). Batteries are further constrained to the exact platform generation and downtube shape (a Bosch 750Wh PowerTube fits only frames molded for it). There is no cross-brand mixing — an EP8 motor never mounts in a Bosch frame. Displays/remotes must be same-system, same generation.

Also called: bosch smart system, ep8, avinox, motor mount, powertube

E-Bike Systems

Kits like Bafang BBS02/BBSHD replace the bottom bracket of a normal bike, turning it into an e-bike. The kit clamps through the BB shell, so the shell type and width are the whole fitment story.

How to check fit: BBSHD fits threaded BSA shells 68–73mm (standard MTB) with longer-shell versions for 100/120mm fatbikes; press-fit frames need adapter cups and are a headache. Also budget for: chainline (kit ring sits further out), battery mounting space in the triangle, and brake levers with cutoff sensors if wanted. Frame warranty: gone. Legal class depends on power/speed settings.

Also called: bbshd, bbs02, tongsheng tsdz2, conversion kit

E-Bike Systems

A motorized wheel replacing your front or rear wheel. Fitment = dropout spacing + axle type + freehub for rear kits.

How to check fit: most cheap kits are 135mm QR rear / 100mm QR front — they do NOT fit modern 148 Boost thru-axle frames without specialty kits (rare). Check dropout width, axle style, rotor mount, and cassette/freewheel type. Torque arms are mandatory on aluminum dropouts — hub motors twist axles out of frames without them.

Also called: hub motor kit, torque arm, motorized wheel

E-Moto

E-moto parts are model-specific the way motorcycle parts are: a swingarm, triple clamp, or controller listing names the bikes it fits — Sur-Ron Light Bee (X), Ultra Bee, Storm Bee; Talaria Sting (R/MX4), XXX, Dragon; Segway X160/X260; E-Ride Pro SS.

How to check fit: match your exact model AND year/revision in the listing's fitment line — 'Light Bee' parts often don't fit 'Ultra Bee'; Talaria Sting and Sur-Ron LBX share some bolt patterns but not motor mounts (Talaria uses a gearbox, Sur-Ron a belt/chain primary). 'Universal e-moto' parts (grips, levers, some pegs) are the exception. The MACH4 builder reads these fitment tags automatically.

Also called: sur-ron light bee, talaria sting, segway x260, ultra bee, fitment

E-Moto

E-moto electrical systems are built around a nominal voltage — 60V (stock Light Bee), 72V (Ultra Bee, common upgrades), up to 96V+ race builds. Battery, controller, and motor must be rated for the same system voltage.

How to check fit: a 72V battery into a stock 60V controller = fried controller; a 72V controller on a 60V battery = weak output at best. Upgrading voltage means battery + controller (+ often motor and display) as a matched set — aftermarket ecosystems (EBMX, Torp) sell paired kits per bike model. Also match connector types (QS8/XT90) and BMS discharge rating to the controller's phase amps.

Also called: 72v conversion, 60v, phase amps, x9000 controller

E-Moto

E-motos use motorcycle-style upside-down forks held by triple clamps, not bicycle-style tapered steerers. Fitment = stanchion diameter, steerer/stem length, and the clamp's offset for your frame's head tube.

How to check fit: buy forks + triple clamps as a model-specific package ('DNM/Fastace for Sur-Ron Light Bee'). A bicycle fork can't replace a moto fork (and vice versa) — the head tube bearings, axle, and brake mounts all differ. Front wheel must then match the moto fork's axle (usually 20mm+) and rotor spacing.

Also called: usd forks, triple tree, dnm forks, fastace

E-Moto

E-moto drivetrains use motorcycle chain sizes: 420 pitch stock on Light Bee/Sting class, 428 or 520 on bigger/converted builds. Front (counter) sprocket, rear sprocket, and chain must share one pitch.

How to check fit: all three parts must say the same number (420/428/520). Rear sprockets additionally match the wheel's bolt pattern for your model, front sprockets match the motor's output shaft spline. Changing gearing (e.g. 48T→54T rear) may also need a longer chain — count links.

Also called: 420 chain, 428 conversion, 520 chain, sprocket swap

Drivetrain

A cassette is a stack of rear cogs that slides onto a splined freehub body.

It is different from a threaded freewheel. Common cassette bodies include HG, XD, XDR, MicroSpline, N3W, and Campagnolo patterns.

Also called: sprocket cluster, rear cogs

Drivetrain

A freewheel threads directly onto the hub and contains its own ratchet mechanism.

A cassette uses a separate freehub body, while a freewheel does not. That difference matters immediately for compatibility.

Also called: thread-on freewheel, threaded freewheel

Drivetrain

A single-speed bike runs one front chainring and one rear cog with no derailleur shifting.

Single-speed cogs can use cassette-style drivers or freewheel threading depending on the hub.

Also called: single speed, singlespeed, ss

Drivetrain

A fixed-gear drivetrain locks the rear cog to the hub so the pedals always turn with the rear wheel.

Track hubs, lockrings, cog threading, and chainline all matter more than they do on a standard cassette bike.

Also called: fixed gear, fixed cog, track cog, fixie

Wheel Systems

The freehub body is the splined driver that a cassette mounts onto.

Common body standards include HG, XD, XDR, MicroSpline, N3W, Campagnolo, and threaded freewheel systems.

Also called: cassette body, driver body, driver

Bearings

A cartridge bearing is a self-contained bearing unit that presses into a frame, hub, headset, or bottom bracket part.

The other common service style is cup-and-cone. Sealed cartridge does not automatically mean ceramic.

Also called: sealed cartridge, sealed bearing

Wheel Systems

The hub is the center of the wheel and carries the axle, bearings, spoke flanges, and rear driver or freewheel mount.

Axle spacing, brake rotor mount, freehub body, spoke count, and bearing style all affect compatibility.

Also called: front hub, rear hub

Wheel Systems

The rim is the outer wheel hoop that supports the tire and the spoke nipples.

Rim brake rims need a brake track. Tubeless, hookless, clincher, and tubular rims all have different use cases.

Also called: wheel hoop

Wheel Systems

A spoke connects the hub to the rim and sets wheel strength, stiffness, and lacing geometry.

J-bend, straight-pull, bladed, butted, and spoke-count differences matter for wheel building and replacement parts.

Also called: j-bend spoke, straight-pull spoke

Cranksets

Cranks are commonly described as one-piece, two-piece, or three-piece based on how the arms and spindle are built.

One-piece is common on older or BMX bikes. Modern MTB cranks are usually two-piece or three-piece depending on the spindle design.

Also called: one-piece, two-piece, three-piece

Cranksets

Square taper is a crank spindle interface with four tapered flats that press into the crank arm.

It is different from ISIS, PowerSpline, Octalink, DUB, 24 mm, 30 mm, Ultra-Torque, and Power-Torque systems.

Also called: square taper, cotterless square taper

Cranksets

PowerSpline is a splined spindle interface used on some SRAM and Truvativ cranksets.

It is not interchangeable with ISIS or square taper even though all three can look similar from a distance.

Also called: power spline, poweer spline

Cranksets

Campagnolo Ultra-Torque uses two half-spindles joined in the center with a Hirth joint.

It needs its own bearing and extraction logic and is not the same as Campagnolo Power-Torque.

Also called: campagnolo ultra-torque, ultra torque

Cranksets

Campagnolo Power-Torque uses a different spindle and extraction method than Ultra-Torque.

When a build uses Campagnolo or Fulcrum parts, the exact spindle system has to be identified before buying tools or bearings.

Also called: campagnolo power-torque, power torque

Cranksets

A self-extracting crank uses a captive cap or ring so the crank arm can be removed without a separate puller body.

The fixing bolt still matters, but the removal procedure is different from a standard square-taper or splined crank puller setup.

Also called: self extracting, self-extracting

Tools

Different drivetrains and bottom brackets need different Park Tool removers, pullers, sockets, and bearing tools.

Examples include FR cassette tools, BBT bottom-bracket tools, and CCP or CWP crank pullers. Tool fit is part-standard specific.

Also called: park tool, cassette tool, bb tool, crank puller

Bottom Brackets

Bottom bracket standards describe the frame shell diameter, width, and whether the system is threaded or press-fit.

Common standards include BSA, T47, PF41, BB90, PF42, PF46, BB30, PF30, 386EVO, and BBRight.

Also called: bb standard, bb shell

Bottom Brackets

PF41 is a 41 mm press-fit shell family used by standards such as BB86, BB89.5, BB92, and some road and MTB frames.

The shell width still matters, so PF41 by itself is not always enough to guarantee fit.

Also called: bb86, bb89.5, bb92, pf92

Bottom Brackets

BB90 is a Trek-specific 37 mm shell system that places bearings directly in the frame.

It is not the same as PF41, BB30, or PF30 even though spindle diameters can overlap.

Also called: bb95

Bottom Brackets

PF42 and BB30 both use a 42 mm shell family but differ in shell style and bearing arrangement.

BB30 is typically a bearing-in-frame setup, while PF42 variants use cups. Spindle and frame details still need checking.

Also called: bb30, pf42

Bottom Brackets

PF46 and PF30 use larger press-fit shell diameters and usually support 30 mm spindles.

PF30 uses 46 mm shells with cups sized for 30 mm spindles. Some 24 mm or DUB conversions need reducer cups or different bearings.

Also called: pf46, pf30

Bottom Brackets

386EVO combines a wide shell layout with a long 30 mm spindle format.

It is common on road and gravel builds but still shows up in compatibility discussions because of spindle length and shell width.

Also called: 386 evo, bb386evo

Bottom Brackets

BBRight is Cervelo's asymmetrical shell standard based on a 46 mm shell family with extra width on the non-drive side.

It is not interchangeable with PF30 even when some dimensions look close on paper.

Also called: bbright, bb right

Drivetrain

A chainring is the front toothed ring that drives the chain from the crankset.

Tooth count, chainline, direct-mount pattern, BCD, and 1x or 2x use all affect fit.

Also called: front ring, front sprocket

Drivetrain

Chain compatibility depends on chain width, speed family, chainring profile, and rear sprocket spacing.

Single-speed and track chains often use 1/8. Derailleur systems usually use 3/32 or speed-specific 6 through 13-speed chains.

Also called: chain width, 1/8 chain, 3/32 chain

Pedals

Pedal threads are commonly 9/16 inch on modern two-piece and three-piece cranks, while older one-piece cranks often use 1/2 inch.

If the crank and pedal thread do not match, the pedals cannot be installed safely.

Also called: 1/2 pedal, 9/16 pedal

Shifting

A derailleur system combines the shifter, derailleur, cassette, chain, and chainring strategy into one matched shift family.

Speed count, cable pull or electronic protocol, clutch design, cage capacity, and mount style all matter.

Also called: rear derailleur, front derailleur

Shifting

Shifters come in flat-bar trigger styles, twist grip, thumb shifters, drop-bar integrated controls, downtube shifters, and bar-end shifters.

The control style is separate from the pull ratio or electronic protocol, so style alone does not guarantee compatibility.

Also called: shift lever, twist grip, bar end shifter, brifter

Shifting

Electronic shifting systems use batteries, wiring, or wireless communication instead of a standard mechanical cable pull.

AXS, Di2, and EPS are all electronic systems, but they are not cross-compatible with each other.

Also called: e-derailleur, axs, di2, eps, etap

Brakes

Brake calipers can be disc, dual-pivot road, cantilever, V-brake, U-brake, roller, drum, or coaster styles depending on the bike.

Mounting standard and actuation type matter just as much as the broad caliper family.

Also called: disc caliper, rim brake caliper

Brakes

Brake pads are the friction material used by a disc caliper or rim brake to slow the bike.

Disc pads vary by backing-plate shape and compound. Rim pads vary by holder style and rim material compatibility.

Also called: disc pad, rim pad, cartridge pad

Brakes

A disc rotor bolts or locks onto the hub and gives the caliper a braking surface.

Rotor size, thickness, mount type, and maximum fork or frame clearance all affect fit.

Also called: brake rotor, disc rotor

Brakes

Brake systems can be hydraulic, fully mechanical cable, or cable-actuated hydraulic hybrids.

The lever and caliper must use the same actuation family for the system to work correctly.

Also called: hydraulic brake, cable brake, mechanical brake

Cockpit

Upright handlebars place the rider in a taller hand position than a low drop-bar setup.

Flat, riser, swept-back, BMX, and alt-bar shapes all change posture, clamp fit, and control layout.

Also called: flat bar, riser bar, swept bar

Cockpit

The stem clamps the steerer tube and the handlebar, fixing reach and handlebar clamp diameter.

Steerer clamp size, handlebar clamp size, rise, and length all matter.

Also called: threadless stem, quill stem

Fit

The saddle supports the rider and clamps to the seatpost by its rails.

Rail material and rail shape can matter when matching certain seatpost clamps.

Also called: bike seat

Fit

The seatpost fits inside the frame seat tube and supports the saddle.

Diameter, insertion depth, dropper routing, and clamp style matter more than people expect.

Also called: dropper post, rigid post

Headsets

Headsets are usually integrated, zero-stack, or external-cup systems, each with their own upper and lower cup codes.

IS, ZS, and EC codes describe cup style and bore size. Crown-race seat and steerer type must also match.

Also called: integrated headset, zero stack, external cup

Headsets

The crown race is the lower bearing seat that interfaces with the fork crown and the headset lower bearing.

Straight and tapered steerers often use different crown-race diameters.

Also called: fork crown race

Hardware

Bike hardware includes bolts, nuts, spoke nipples, pinch bolts, lockrings, screws, and threaded inserts used across the build.

Thread pitch, head shape, torque limits, and material all matter when replacing tiny parts.

Also called: bike screws, hardware, lockring

Ecosystems

Campagnolo and Fulcrum use several ecosystem-specific standards for cassettes, freehub bodies, wheels, and crank interfaces.

That is why terms like N3W, Ultra-Torque, and Power-Torque have to be parsed explicitly instead of treated like generic parts.

Also called: campagnolo, fulcrum

Brands

S-Works is Specialized's top-tier product branding rather than a single compatibility standard.

It can appear on frames, cockpits, wheels, saddles, shoes, and drivetrain parts, so the actual underlying standard still needs to be parsed separately.

Also called: sworks, s-works

Geometry

The angle of the head tube relative to the ground. Slacker head angles usually feel more stable on steep descents, while steeper angles can feel quicker at slower speeds.

Geometry always works as a system, so head angle should be considered with reach, fork offset, wheelbase, and stack.

Drivetrain

The bottom bracket is the bearing system the crank spins on. Different frames and cranksets require different shell standards and widths.

This is one of the most common mismatch points in a custom build, so it is worth checking carefully before buying parts.