The creak starts subtle. A faint tick on the first pedal stroke after a rough section. By the end of the ride it's constant, rhythmic, maddening — every push answered with a sound that makes other riders look over. You regrease the BB. You re-press the cups. You spend €150 on an aftermarket threaded insert. Six months later: tick, tick, tick. If this sounds familiar, you're not dealing with a maintenance failure. You're dealing with an engineering decision that was made on your behalf, without your knowledge, to save money at the factory. This article explains exactly why press-fit bottom brackets creak on gravel bikes — and what the permanent fix actually looks like.
Press-fit bottom brackets creak on gravel bikes because carbon shells cannot maintain the precise interference tolerance that press-fit requires. Gravel vibration, thermal expansion, and moisture accelerate the degradation. T-47 threading with mould-integrated alloy sleeves eliminates the tolerance problem at the source — no workaround, no insert, no regreasing schedule required.
In This Article
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What is press-fit and why did the industry adopt it?
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The physics of why press-fit creaks on gravel
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Why the standard fixes don't actually fix it
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T-47 threading explained
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What 'mould-integrated alloy sleeves' means — and why it matters
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What to look for when choosing a gravel frame
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Frequently asked questions
What Is Press-Fit and Why Did the Industry Adopt It?
Press-fit bottom brackets are secured by forcing an oversized bearing cup into a carbon or aluminium shell — no threading, just interference pressure. The industry adopted press-fit primarily because it is cheaper and faster to manufacture at scale than threaded alternatives.
The logic made superficial sense. Threaded BB shells require precise machining, additional components, and more assembly time. Press-fit shells are essentially just round holes — the bearing cup is pressed in at assembly using a simple tool. For a factory producing thousands of frames, the cost difference is significant.
The most common press-fit standards you'll encounter are BB86 and BB92 (Shimano-originated), PF30 (SRAM-originated), and BB90/BB95 (Trek proprietary). They are mutually incompatible. According to a 2023 survey by cycling forum WeightWeenies polling 1,400 riders, press-fit BB creak was cited as the most frustrating recurring maintenance issue across road and gravel disciplines — ahead of tubeless sealant failure and electronic shifting gremlins combined.
Why Does Press-Fit Creak? The Physics Explained
Press-fit creak on gravel bikes is caused by micro-movement between the bearing cup and carbon shell — a movement that cannot be permanently prevented using a press-fit interface.
The interference fit requires that the outer diameter of the bearing cup be slightly larger than the inner diameter of the shell bore. When pressed together correctly, friction holds everything still. The problem is that 'correctly' depends on tolerances that carbon layup cannot reliably guarantee.
Carbon frames are constructed by laying fibre sheets in a mould and curing under pressure. The inner diameter of the BB shell bore varies by fractions of a millimetre between frames — an acceptable variation for most structural purposes, but critical for a press-fit interface. A bore that is even 0.03mm oversized creates a loose fit that will move under load.
Four Mechanisms That Accelerate Creak on Gravel
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Vibration fatigue: Gravel surfaces transmit impact forces directly through the BB shell. Each rock strike is a micro-impact loosening the interference fit incrementally. Road-specific frames experience roughly 20–30% of the off-road impact energy that gravel frames do on rough terrain.
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Thermal cycling: Carbon and aluminium have different coefficients of thermal expansion. As temperatures swing between a cold morning start and a warm afternoon climb, the cup and shell expand and contract at different rates — the fit loosens and tightens repeatedly, ratcheting gradually toward permanent slop.
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Moisture ingress: Water penetrates the interface between the aluminium cup and carbon shell, causing galvanic corrosion. The resulting material degradation further loosens the fit.
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Load eccentricity: Gravel riding produces uneven lateral and torsional loads through the BB — dismounts, bike-handling corrections, rough-surface power delivery — that a road frame rarely experiences. These eccentric loads accelerate micro-movement.
The result is audible: a tick or creak that occurs under power, typically felt through the pedals and heard by everyone within 10 metres.
Why the Standard Fixes Don't Actually Fix Press-Fit Creak
Common remedies for press-fit creak — including regreasing, re-pressing, Loctite application, and aftermarket threaded inserts — provide temporary relief but do not address the root cause.
Regreasing reduces friction momentarily. Re-pressing restores the interference fit to its original state — which was already marginal for gravel use. Loctite compounds fill the tolerance gap chemically but degrade over time under thermal and vibrational load.
Aftermarket threaded inserts — products from Hambini, Wheels Manufacturing, and TOKEN — are more durable solutions and do provide significant improvement. They work by replacing the carbon-to-metal interface with a metal-to-metal interface. However, they still rely on a press fit to secure the insert sleeve into the carbon shell. The fundamental problem — a pressed interface in a carbon bore — remains one layer deeper.
The Hambini threaded insert, for example, retails at approximately £120–£180. Installation requires either a workshop press or careful DIY technique. Multiple independent tests have shown recurrence of creak symptoms within 12–24 months of install, particularly in heavier riders or those riding technically demanding terrain regularly.
The honest conclusion: aftermarket threaded inserts are the best available remedy for a frame that already exists. They are not equivalent to a frame that was designed correctly from the start.
What Is T-47 and How Is It Different?
T-47 is a threaded bottom bracket standard featuring a 47mm bore diameter, designed by the Bottom Bracket Standards Working Group to provide a modern threaded interface compatible with current crankset spindle diameters.
Unlike older threaded standards such as BSA (English thread, 33mm bore), T-47 accommodates the wider spindles used in contemporary road and gravel groupsets from SRAM, Shimano, and other manufacturers. It uses the same M47×1.0 thread pitch across all applications, and a T-47 shell is compatible with any T-47 BB cup regardless of crankset brand.
The key difference over press-fit is mechanical: threading provides engagement through contact across the full helix of the thread interface. The clamping force is distributed across dozens of thread contact points rather than relying on a single radial interference fit. A correctly torqued threaded interface does not loosen under vibration or thermal cycling in the way a press-fit does — this is basic mechanical engineering, not cycling-specific innovation.
The key difference over press-fit is mechanical: threading provides engagement through contact across the full helix of the thread interface. The clamping force is distributed across dozens of thread contact points rather than relying on a single radial interference fit. A correctly torqued threaded interface does not loosen under vibration or thermal cycling in the way a press-fit does — this is basic mechanical engineering, not cycling-specific innovation.
What 'Mould-Integrated Alloy Sleeves' Means — and Why It Matters
Mould-integrated alloy sleeves represent the manufacturing approach that distinguishes a frame designed around T-47 from one where threading is added post-manufacture. The sleeve is placed inside the carbon mould before layup, and the carbon is cured around it — making the sleeve structurally part of the frame.
This is a critical distinction. Two frames can both be labelled 'T-47 compatible', but through fundamentally different manufacturing approaches:
Approach 1: T-47 Threads Machined Post-Cure
After the carbon frame is cured, the BB shell bore is machined and a threaded insert is bonded or pressed in. This is an improvement over press-fit, but the insert's connection to the carbon frame still relies on bonding or press-fit at that junction.
Approach 2: Mould-Integrated Alloy Sleeves
The alloy sleeve — precisely machined to T-47 specification — is placed in the mould before carbon layup begins. Carbon fibre is then laid over and around it. When cured, the sleeve is encapsulated within the frame structure. There is no secondary bonding step, no press-fit junction, and no tolerance degradation point. The sleeve's bore concentricity is guaranteed by machined metal, not carbon layup.
The structural benefit extends beyond creak prevention: the alloy sleeve reinforces the highest-load junction on the frame. The BB shell bears both torsional and compressive forces from the drivetrain simultaneously — an area where carbon-only construction benefits from the rigidity of an integrated metal component.
The Altera G21 uses T-47 threading with mould-integrated alloy sleeves. The sleeves are CNC machined and positioned during layup, not added post-cure. This is a more expensive manufacturing process than either press-fit or post-cure threading — it requires greater precision at the layup stage and cannot be implemented as a retrofit. It is a frame-level design decision.
What to Look For When Choosing a Gravel Frame
When evaluating a gravel frame's bottom bracket specification, two questions matter more than the standard name alone.
Question 1: Threaded or press-fit?
Threaded is the correct answer for gravel. This includes T-47, BSA/English, and Italian threading. Press-fit in any form — BB86, BB92, PF30, BB90, BB95, BB386 — introduces the tolerance problems described above. The severity varies with rider weight, terrain, and mileage, but the mechanism is always present.
Question 2: Integrated at manufacture or added post-cure?
This question separates genuinely engineered solutions from adequate ones. Ask the brand directly, or look for technical documentation. If the answer is 'T-47 compatible via insert' or 'our frame accepts T-47 BBs', the threading was added after manufacture. If the answer is 'mould-integrated alloy sleeves' or 'integrated during layup', the frame was designed from the start with the correct BB solution.
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Standard
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Type
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Creak Risk on Gravel
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Verdict
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T-47 (integrated sleeves)
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Threaded
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Very Low
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Best-in-class. Permanent fix by design.
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BSA / English thread
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Threaded
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Very Low
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Proven standard. Limited spindle compatibility.
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T-47 (post-cure insert)
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Threaded
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Low
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Better than press-fit. Not equivalent to integrated.
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Aftermarket insert (PF→T47)
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Press-fit shell
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Low–Medium
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Best available retrofit. Not a designed solution.
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BB86 / BB92
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Press-fit
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High
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Marginal on road. Inadequate for gravel.
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PF30
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Press-fit
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Very High
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Widest bore = widest tolerance variation.
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BB90 / BB95 (Trek)
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Press-fit
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Very High
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Proprietary. Creak rate well-documented.
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The Altera G21 uses T-47 threading with mould-integrated alloy sleeves — CNC machined and encapsulated during carbon layup, not added after. It is compatible with any T-47 crankset from SRAM, Shimano, Praxis, and Enduro.
Frequently Asked Questions
What is the difference between press-fit and threaded bottom brackets?
Press-fit BBs are held by interference pressure — an oversized cup forced into a round shell. Threaded BBs use mechanical thread engagement across multiple contact points. Threaded interfaces resist loosening under vibration and thermal cycling; press-fit interfaces do not.
Does T-47 actually eliminate bottom bracket creak?
T-47 threading with mould-integrated alloy sleeves eliminates the primary creak mechanism: the carbon-to-metal tolerance gap. Independent field reports from T-47-equipped gravel frames consistently show near-zero creak recurrence compared to press-fit equivalents in the same conditions.
Can I convert my press-fit gravel bike to threaded?
Aftermarket threaded inserts (Hambini, Wheels Mfg, TOKEN) convert most press-fit shells to T-47 or BSA threading and significantly reduce creak. They are the best available retrofit, but the insert itself still uses a press-fit connection to the carbon shell — performance is better than stock press-fit but not equivalent to a frame designed with integrated threaded sleeves from manufacture.
Is T-47 compatible with my crankset?
T-47 is compatible with SRAM DUB, Shimano (using a BSA→T47 adapter), Praxis, Enduro, and most modern cranksets. Check the BB manufacturer's compatibility chart for your specific crankset spindle diameter. The Altera G21 T-47 shell accepts all major T-47 BB cups.
Why do some expensive bikes still use press-fit?
Press-fit reduces manufacturing cost and allows thinner BB shells, which marginally simplifies frame design. Some premium brands retain press-fit for these reasons. As T-47 adoption has grown among DTC and boutique brands, the argument that 'press-fit is necessary for performance' has become harder to sustain.
Further Reading
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