Blog
Notes on carbon.
Carbon fiber inspection, used-bike economics, NDT methodology, and the failure modes we see in the field.
hairline-crack-carbon-framecarbon-frame-hairline-crackmatrix-microcrackingHairline crack in a carbon bike frame: the inspection protocol before you ride again
7 min readA hairline crack on a carbon frame gets resolved by a loupe under angled light, a thumb palpation, and a referral to NDT if either of those returns positive. A test ride is not part of the protocol, because a frame can lose substantial local strength and still feel fine.
pultrusioncomposite-manufacturingpultrudedWhat is pultrusion in composite manufacturing
4 min readPultrusion is a continuous composite manufacturing process in which fiber rovings are pulled through a resin bath and a heated die to yield a solid profile of constant cross-section. Its name is a portmanteau of pull and extrusion.
used-bike-inspectionbuyer-checklistpre-inspection-triageHow to check a second hand bike before you pay for a full inspection
7 min readA buyer-side triage protocol for a second-hand carbon bike before committing to paid NDT. The test ride covers fit and function; it cannot validate composite integrity. The visual sweep covers the four high-stress junctions in good light.
carbon-frame-dentbvidbarely-visible-impact-damageCarbon frame dent: what a dent on a carbon tube actually means
7 min readA dent on a carbon tube is not a dent in the aluminum sense. Carbon does not deform plastically, so a permanent indentation is evidence of energy that has already done something to the laminate underneath.
prepregb-stage-resincomposite-materialsWhat is prepreg in composite manufacturing
4 min readPrepreg is reinforcement fiber (tape or cloth) pre-impregnated with a metered amount of partially cured B-stage resin. The name is a portmanteau of pre-impregnated. It is the workhorse of high-performance aerospace layups, high-end sporting goods, and cleanroom lamination.
bike-east-bayeast-bay-bikesoaklandEast Bay used-carbon market: Craigslist Oakland and the Laney College flea market history
6 min readEast Bay's used carbon scene runs through a highly active Craigslist Oakland market coexisting with the historical Laney College Flea Market fencing problem. Bike East Bay interventions, the multi-agency San Jose bust, and the vetted alternatives (The Bikery, Biketopia Swap Meet, Valley Spokesmen, Wrench Science, Allen's Bicycles).
ruckus-compositesultrasoundultrasonic-thickness-gaugeRuckus Composites and ultrasound-led carbon bike inspection, explained
8 min readRuckus Composites runs portable pulse-echo ultrasonic thickness gauges and prices a full frame-and-fork inspection at around $250. Ultrasound is the workhorse method for carbon bikes, with specific geometries where it gives way to radiography or thermography.
cracked-carbon-handlebarcarbon-handlebar-crackcomponent-replacementCracked carbon handlebar: why component cracks default to replacement
7 min readA cracked carbon handlebar is the case where the inspection report skips the Safe-Serviceable-Unsafe ladder and writes replace. The reasoning is load margin and stress concentration, not pessimism, and it changes what the bar inspection actually covers.
delaminationcomposite-delaminationcarbon-fiber-delaminationWhat is delamination in a composite laminate
5 min readDelamination is the separation of adjacent plies along their interlaminar plane within a composite laminate, the layers peeling apart at the bond between them. It is essentially an interlaminar crack and is the dominant subsurface failure mode in composite structures.
carbon-fiber-crackvisual-triageraking-lightCarbon fiber crack on a bike frame: how to read what you are looking at
7 min readVisual triage on a carbon bike frame asks two questions: is this clearcoat or laminate, and is the area in a high-stress zone. Raking light, cotton-glove passes, and the four critical junctions are the methods that answer them.
carbon-frame-scratchscratch-on-carbon-bike-framecosmetic-vs-structuralCarbon frame scratch: how depth, location, and pattern decide whether to ride it
8 min readA practical scratch-evaluation framework for the top tube, down tube, and seatstays: how to read scratch depth against the underlying laminate, where the high-stress junctions sit, and when a scratch crosses from Serviceable to a referral for subsurface NDT.
rtmresin-transfer-moldinghp-rtmWhat is resin transfer molding (RTM) in composite manufacturing
5 min readResin transfer molding (RTM) is a closed-mold process: a dry fiber preform is placed in matched rigid tooling, the mold closes, and liquid resin is injected under low-to-moderate pressure to impregnate the fibers and cure in situ. HP-RTM and VARTM are the related variants.
bike-shop-san-franciscobike-indexserial-verificationBuying a used carbon bike in San Francisco: serial-number clearance through Bike Index before any cash transaction
6 min readSF's high theft rate and low recovery rate (5 to 10 percent) means peer-to-peer carbon inventory carries elevated stolen-frame risk. Bike Index serial clearance before any meeting, the four high-stress junction audit at a police safe-exchange zone, and the four-step pre-purchase verification protocol that the local environment demands.
carbon-repair-kitdiy-repaircosmetic-vs-structuralBicycle carbon fiber repair kit: what a kit actually fixes, and what it cannot
7 min readConsumer carbon fiber repair kits address cosmetic chips, surface scratches, and clearcoat damage. They cannot resolve subsurface delamination or fiber fractures, and a previously applied kit layer interferes with the methods an inspector relies on.
carbon-fork-scratchcracked-carbon-forkcarbon-fork-crackCarbon fork scratch: when surface damage on a fork is cosmetic and when it isn't
9 min readA scratch on a carbon fork is not the same as a scratch on a top tube. The fork is a load path with no fallback, the steerer is a clamp zone, and the triage protocol that clears a fork has to account for both.
ndtnon-destructive-testingcompositesWhat is non-destructive testing (NDT) in composite materials
5 min readNon-destructive testing (NDT) evaluates a material's structural integrity and defect state without altering its function or serviceability. The central rule: a clearance never proves absence, only that no flaws exceed the equipment's detection threshold.
marin-gravel-bikesea-otter-classicsunshine-bicycle-centerMarin County carbon bikes: the gravel and mountain aftermarket the Sea Otter Classic feeds
6 min readMarin's premium carbon gravel and MTB aftermarket runs on a one-to-two-season-old churn driven by the April Sea Otter Classic in Monterey. The dominant inspection risk is minor fire-road scuffing masking deeper trail-impact damage at the four high-stress junctions.
carbon-fiber-crack-repairrepair-vs-replaceinspection-reportCarbon fiber crack repair: when a crack can be repaired and when the frame should be replaced
7 min readThe repair-versus-replace decision rests on the inspection report. Damaged carbon bars, stems, and lightweight steerers default to replacement. Components engineered to low weight margins do not tolerate post-repair stress concentrations.
crack-in-carbon-framecarbon-frame-crackcarbon-bike-frame-crackCrack in a carbon frame: how to tell paint cracks from structural cracks
10 min readThe field framework for evaluating a crack on a carbon bike frame: clearcoat crazing and star cracks versus matrix microcracking and fiber fracture, the load-flexion test that most protocols rely on, and where the field method stops and NDT takes over.
compositesdefine-compositesanisotropyWhat are composite materials: the working definition
6 min readA composite material is a fiber-plus-matrix system in which the fibers carry load along their length and the matrix transfers shear between fibers. A single ply is therefore anisotropic; stacking plies at multiple angles builds the multi-axial laminate.
mikes-bikeshuckleberry-bicyclessummit-bicyclesWhere to buy a used carbon bike in the Bay Area: trade-in chains, CPO channels, and the adverse-selection problem
6 min readThe Bay Area's used carbon bike channels split between commercial trade-in chains (Mike's Bikes, Sports Basement, Huckleberry, Summit), non-profit clearinghouses (BikeX, The Bikery), and an unregulated peer-to-peer market that concentrates structurally compromised frames the commercial channels reject.
carbon-fiber-delaminationdelaminationcfrp-delaminationCarbon fiber delamination: what it is, what it looks like, and why a clean paint surface guarantees nothing
13 min readDelamination is the central failure mode in carbon bicycle frames, and most of it is invisible from outside. A reference on the physics of ply separation, the surface signatures that hint at subsurface damage, and how visual triage and NDT slot together to confirm it.
autoclavecomposite-cureprepregWhat is an autoclave (composite cure cycle), in plain terms
5 min readA composite-cure autoclave is a sealed pressure vessel that cures prepreg laminates under simultaneous heat and gas pressure. The combination drives void content below 1 percent and is the quality benchmark for primary aerospace structure and high-performance racing parts.
carbon-bike-inspectionsan-franciscobay-areaCarbon bike inspection in the San Francisco Bay Area: who does what, where, and what it costs
8 min readNorthern California's carbon repair capacity is mature but geographically decentralized. Local shops do triage; structural repair concentrates in Monterey Bay specialists; quantitative NDT ships to a national mail-in network. The full Bay Area carbon inspection and repair landscape, with the operational terms that matter.
carbon-bike-frame-repaircarbon-fiber-frame-repairndtCarbon bike frame repair: what inspection determines before any work begins
14 min readCarbon bike frame repair starts with an inspection that sorts findings into Safe, Serviceable, or Unsafe, separates cosmetic marks from structural ones, and where damage is found returns an actionable remediation quote that may advise replacement over repair.
kbb-for-bikeskelley-blue-book-for-bikesbicycle-blue-bookIs there a Kelley Blue Book for bikes? The state of the used carbon bike market in 2026
10 min readThere is no audited registry-based KBB for bikes. Bicycle Blue Book is the nearest analog, and its limits (no VIN, no audited transactions, depreciation multipliers, conflict of interest) are precisely the gap that explains the used carbon bike market's structural information asymmetry. The 2026 state of the market in one structural reference.
bicycle-accident-lawyerbicycle-accident-attorneybike-crash-lawyerBicycle accident lawyer: what a documented carbon inspection adds to the legal file
11 min readA bicycle accident lawyer building a defensible file on a carbon-frame failure needs a third-party NDT report that separates observation from opinion, preserves the failed part, and survives Federal Rule of Evidence 702 and the Daubert standard.
open-mold-carbon-framedirect-to-consumeruci-approvalInspecting open-mold and direct-to-consumer carbon frames: layup, BB tolerance, certifications
14 min readThe cluster reference for open-mold and DTC carbon frames. What UCI, TÜV Rheinland, and ISO 4210 do and do not certify; how the Xiamen and Shenzhen manufacturing ecosystem actually works; the inspection methodology a buyer can run themselves; and where independent NDT escalation fits.
specialized-turbo-creoturbo-creocarbon-ebike-inspectionInspecting a carbon e-bike: motor mounts, battery cavities, and bonded inserts
13 min readCarbon e-bike inspection is not pedal-bike inspection with extra attention paid to the battery. Interface failures (motor mounts, battery cavities, bonded inserts) matter more than mid-tube cracks. Visual inspection misses what NDT catches.
used-triathlon-bikeused-tri-bikesused-tt-bikesUsed triathlon bike inspection: what to check on a Canyon Speedmax, Cervelo P5, Trek Speed Concept, or BMC Timemachine
11 min readA used tri bike isn't really a frame. It's a tightly integrated system of frame, fork, proprietary cockpit, hidden routing, storage, and fit hardware, and 'no cracks in the frame' is far too low a bar. The inspection burden is structurally different from a used road bike.
used-carbon-mountain-bikepivotssuspensionBuying a used carbon mountain bike: pivots, suspension, and the harder-impact lifecycle
8 min readThe buyer-side inspection framework for a used carbon mountain bike. Pivot-bore ovalization, shock-tunnel cracking, inner-ply delamination from rock strikes that leaves outer paint intact, and the discipline-specific risk pattern that road-bike triage does not catch.
pulsed-thermographyinfrared-thermography-ndtflash-thermographyPulsed thermography for composite NDT: the physics, the defect envelope, and the 3 to 5 mm depth limit
16 min readPulsed thermography reads how a subsurface feature perturbs heat flow at the surface, not the defect itself. The 3 to 5 mm depth rule on standard CFRP is a working guideline set by diffusion physics, not a material constant, and tight vertical cracks are a documented blind spot.
bike-crash-insurance-claimbike-accident-insurance-claimtotal-lossBike crash insurance claim: how to document a carbon frame so the claim survives an adjuster
12 min readA bike crash insurance claim on a carbon frame succeeds or fails on the documentation built in the first hours after the crash: a forensic photo set, a total-loss case for any lateral vehicle impact, Loss of Use accrual, and strict component segregation if the bike is bought back as salvage.
bike-resale-valuebicycle-resale-valuebike-valuationBike resale value: how condition, comps, and documentation set a used carbon bike's real price
10 min readThe reference page on what a used carbon bike is actually worth: the depreciation curve, the private-versus-CPO spread, how to normalize comps across model year and groupset generation, and the documentation that moves a private listing from mid-band to the top of the private range.
buy-used-bicycleused-carbon-bikeinspectionBuy used bicycle: the carbon-frame due-diligence playbook for the secondhand market
14 min readThe buyer-side reference for evaluating a used carbon bike: why carbon hides damage that metal would show, the 20-minute hands-on triage that runs in a seller's driveway, the listing photo red flags to filter on before traveling, the financial math for walking away, and the script for requesting an independent inspection without killing the deal.