A noise rarely comes from where you hear it. The frame transmits vibration like a resonator. Professional diagnosis does not start by replacing parts; it starts by isolating variables until the sound is trapped in one assembly.
Identify the Noise Source
Define context first: only while pedaling, only while braking, only while standing and rocking the bike, or only on bumps. Then map the zone by action:
Pedaling under load: bottom bracket, cranks, pedals, chainrings, cassette, derailleur hanger, rear axle. Standing and rocking: seatpost, clamp, saddle rails, pivots. Braking: rotors, calipers, axles, headset. Turning the bar: headset, cables, front hub bearings.
Bottom Bracket Noise vs Crank Noise
The common mistake is blaming the bottom bracket every time. Practical separation:
Bottom bracket: deep, repeatable creak under torque, changes with cadence and often worsens out of the saddle. It can also show up when rocking the bike side to side.
Cranks/pedals: a sharper click or localized creak that appears on one side. It changes if you swap pedals, change shoes/cleats, or pedal seated without rocking the bike.
Quick check: verify correct torque, then inspect interfaces (spindle–crank, spider–ring, pedal–crank) and clean/grease where appropriate. A loose chainring bolt can impersonate a “dead” bottom bracket.
Carbon Creaks
Carbon does not creak because it is carbon. It creaks because parts move against each other: seatpost–frame, stem–bar, spacers/caps, saddle rails, or micro-movement at an interface. Carbon assembly paste and correct torque usually solve it. If the noise changes with torque, it was an interface problem, not the material.
Internal Cable Rattle
With internal routing, a housing or cable can hit the inside of the frame on vibration. It sounds like a hollow rattle on bumps. Diagnosis: push the housing at entry/exit points, change the routing, or temporarily immobilize it with foam or internal guides. This is damping, not indexing.
Diagnosis by Elimination
1) Clean and torque-check critical points (axles, calipers, stem, seatpost, chainrings). 2) Change one variable at a time. 3) Reproduce in place: brake front wheel and rock (headset), brake rear wheel and rock (axle/dropouts), pedal with the rear wheel off the ground (drivetrain).
4) Swap components if possible: pedals, rear wheel, saddle/seatpost. 5) If the noise disappears, you have the zone. If not, go back to step 2. Speed does not help; control does.
When a Noise Signals Structural Damage
Red flags: a creak that appears suddenly after an impact, noise with a visible crack, delamination, paint lifting in a linear pattern, or a geometry change (wheel out of center, derailleur indexing changes overnight). Also: rapidly increasing play in the headset or bottom bracket area.
A constant noise is not always structural damage, but a fast-progressing noise plus play or marks demands inspection. Priority is safety, not “silence”.
Noise diagnosis is the first step before a professional tune-up or structural analysis.
[ SCIENTIFIC_BASIS_REPORT ] This procedure complies with structural integrity protocols documented in our Carbon Footprint Analysis.