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Folding

Brompton C Line 12-speed

Selected build : Brompton C Line 12-speed · United Kingdom

We have not verified this bike yet.

2 of the 14 measurements on file · 0 verified. Fit is checked for each part.

Model year not documented

Representative silhouette: Folding. Explore the bike’s regions.
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Market: UK

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We have not verified this bike yet

2 of the 14 measurements are on file; 0 confirmed by two independent sources.

A documented replacement can be recommended even while unrelated bike measurements are missing.

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My build and size · Brompton C Line 12-speed

Documented original equipment. Replacements and upgrades remain in the fitment lists.

Observed specification market: UK. Captured 2026-10-07. Manufacturer observation for UK. Exact production substitutions and revision remain unconfirmed; it does not establish another regional build.

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Documented factory parts for this build

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PositionOriginal equipment
SeatpostSeatpost: Extended, Black (35") ×1
FrameBrompton steel main frame ×1
FrameBrompton Advance rear frame ×1
ForkBrompton steel fork ×1
CockpitBrompton lock-on grips ×1
SaddleBrompton standard saddle ×1
SeatpostComposite seat clamp and rear-frame clip ×1
FrameComposite hinge clamp levers ×1
PedalsLeft folding pedal ×1
PedalsRight non-folding pedal ×1
CranksetBrompton 50-tooth crank with guard ×1
DrivetrainSquare-taper bottom bracket — interface unprinted ×1
CockpitBrompton headset — exact code unprinted ×1
CockpitFour-speed derailleur shifter ×1
CockpitThree-speed hub shifter ×1
Cassette11–18-tooth sprockets ×1
Rear derailleurBrompton direct-mount derailleur ×1
FrameBrompton mudguard set ×1
FrameBrompton reflector set ×1
FrameAdvance roller-wheel assembly ×1
FrameFront carrier block ×1
CockpitBell ×1
Front wheelFront wheel ×1
Rear wheelRear wheel ×1
Front brakeBrompton dual-pivot caliper — front ×1
Rear brakeBrompton dual-pivot caliper — rear ×1
BackReset view

No documented exploded view for this assembly.

Coverage and remaining work

Size-dependent parts are excluded until you select a size.

Factory assemblies
26 · inventory incomplete
Parts with a drawing or manual
0/36
Components with a service manual
0/36 · 0 indexed procedures
Parts selectable in a schematic assembly
64/90
Parts with reviewed exact geometry
0/90
Exact purchase destinations
0/36 · 0 via kit
  • Model year/generation is unestablished; the catalog reading date is not a model year.
  • Corroborate applicable fitment claims with a second independent publisher.
  • Obtain the full manufacturer service inventory, revisions, fasteners, tools and connection-specific torque conditions.
  • Establish exact marketplace ASIN variants and official purchase destinations; search and documentation links do not establish availability.
  • Factory listing does not publish a complete hardware inventory. Hub/axle revisions, cables, fasteners and internal dimensions require component-specific documentation.
  • The 12-speed system combines a three-speed internal hub with four sprockets. Do not order a conventional twelve-speed derailleur chain by the total gear count. Identify hub/chain/axle/hinge revisions and all unprinted hardware. Rack is not included.
Complete documented parts tree — usable without 3D

Documented specifications

United Kingdom · Brompton C Line 12-speed
These details describe this reference build. They do not automatically apply to another market or build.

The Brompton C Line 12-speed is a folding bike — representative silhouette: Folding. We have read 1 specification sheet (Brompton Bicycle) and recorded 5 fit facts from it. 2 of the 14 measurements a folding bike needs to answer fit questions are on file; 0 are confirmed by two independent sources. Where a measurement is missing, we say so below — we do not guess.

Wheel size (ISO bead seat)16" Brompton / 16 × 1 3/8 (ISO 349)
Rotor interface (hubs)No rotor interface (rim brake)
Brake actuationCable rim brake
Brake pad shape (fitted calipers)Rim pads: Brompton dual-pivot caliper
Shift actuationMechanical (cable)

Confidence: every fact above comes from a single cited source — "derived" on our lattice; none is verified by a second independent publisher yet. A verdict that rests on a safety-critical fact therefore stops at "unknown" rather than "fits".

Not on file (required for a folding bike): Bottom bracket shell · Derailleur hanger · Rear axle spacing · Seatpost diameter · Maximum tyre width (frame) · Front axle spacing · Brake mount, front · Brake mount, rear · Freehub body · Rear speeds · Chain standard · Pedal thread. The sheet we read does not state them; until a source does, confirm these measurements before choosing a part that depends on them.

Why do so many verdicts on this bike read "unknown"?
Because a verdict needs the bike's measurement for every dimension a part requires, and 12 of the 14 required measurements are not on file. "Unknown" means we could not check — not that it fits, and not that it does not.
Will the verdicts change?
Yes. When a second independent source confirms a measurement — or a first one states a missing one — the verdicts are recomputed from the new facts. Nothing on this page is typed by hand.

Regions of this bike

Not on file (required)

  • Bottom bracket shell
  • Derailleur hanger
  • Rear axle spacing
  • Seatpost diameter
  • Maximum tyre width (frame)
  • Front axle spacing
  • Brake mount, front
  • Brake mount, rear
  • Freehub body
  • Rear speeds
  • Chain standard
  • Pedal thread

Sources

The spec sheets we read. Every fact above cites one of them.

Source limitations: Model year is not printed; 2025 is the catalogue year the page was read in. Left absent: hub spacing (Brompton's 112/74 mm proprietary spacing is not stated on the page), seatpost diameter (only 'Extended'), bar clamp, bb_shell, freehub/speeds (a 3-speed hub gear plus 4-speed derailleur does not map onto the cassette dimensions).

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