27g for a Pair: How OVERFAST Engineered the World's Lightest Carbon Fibre Thru Axle
Carbon fibre thru axles have existed before, but the reason nobody switched was never really about the weight; it was about trust.
Here's how OVERFAST spent two years solving every problem standing in the way.
Why Thru Axles Were the Last Holdout
Carbon fibre is ubiquitous with performance bicycles in this day and age. Walk around any serious road/ gravel/ mountain bike, and you'll find carbon fibre everywhere. Stems, handlebars, seatposts, saddle rails - the industry has gone all-in.
So, why have thru-axles largely remained in aluminium, steel or titanium?
It's because carbon as a material for thru-axles has several real-world concerns, such as:
1) Would the carbon shaft twist under torque?
2) Would a glued metal thread eventually corrode and fail?
3) Would the head crack under repeated clamping force?
4) Is it durable/strong/safe enough?
These are legitimate questions, and for a component that keeps your wheels on as you are flying down a mountain range, "it should be fine" isn't good enough.
OVERFAST is an engineering company that takes cycling seriously. After two years of development, lab testing, and real-world athlete use, they've built a carbon thru axle that addresses each of those concerns specifically and patented the solutions to back it up.
The Weight Case: Real Numbers
A standard pair of aluminium thru axles typically weighs around 110g. OVERFAST's carbon axles weigh approximately 27g per pair (May 2026), which is a saving of around 83g!
To put that in context:
The OVERFAST pair weighs less than a single lightweight quick-release skewer designed for rim brake bikes. That's a remarkable figure for a component that has to deal with torque, tightening loads, and vibration.
The Engineering: Four Problems, Four Solutions
Let's dive into how OVERFAST addressed cyclists' concerns for a carbon thru-axle >>
1. The Twist Problem. Solution: Double Groove Anti-Twist Design
Torsion is the primary structural challenge with a carbon thru axle. When you tighten a thru axle, you're applying significant rotational force, and if the metal threaded end rotates relative to the carbon shaft, it means the joint failed and cannot be tightened to spec.
OVERFAST forms two concave grooves on the carbon axles. The metal end piece has matching protruding ridges that key into those grooves. This mechanical interlock means that rotational force is transferred through geometry, not just adhesive. The two parts physically cannot rotate against each other under load.
2. The Glue Failure Problem. Solution: MagicLock Physical Bonding
Relying solely on adhesive to bond carbon to metal is a known long-term risk. Galvanic corrosion between carbon fibre and aluminium can degrade adhesive bonds over time, and in a worst-case scenario, the threaded insert simply pulls out. This is the failure mode that makes most riders uneasy, and rightfully so.
OVERFAST uses a 7075 aluminium threaded insert that has been internally machined to create a mechanical locking structure. The carbon shaft interior uses an expanding design that physically interlocks with this structure. The result: even without any adhesive, the metal-to-carbon bond has been tested to withstand 500 kgf of tensile pull without separation. With adhesive added as a secondary measure, that figure rises to 1,000 kgf. Real-world thru axle loads are a fraction of either number.
3. The Head Failure Problem. Solution: One-Piece Moulded Carbon Cap
When aluminium thru axles are weight-optimised, the cap (the flanged head that bears against the fork or dropout face) has to be made very thin. Thin aluminium caps are susceptible to metal fatigue. Small cracks develop over thousands of clamping cycles, eventually leading to fracture. This is why you occasionally see the head of a budget lightweight axle crack or deform.
The cap on the OVERFAST axle is moulded as a single piece with the carbon shaft. No separate bonded or pressed cap.
The material properties of carbon fibre are also such that it doesn't suffer from metal fatigue. This means it maintains its properties under repeated loading cycles indefinitely, without accumulating damage.
Not only that, but the interface between the axle and the cap is made angular with a curved radius. With a corresponding angular washer, this curved design increases the contact area compared to a standard flat washer, allowing it to withstand a higher lateral impact force.
4. The High-Torque Tool Problem. Solution: Built-In Titanium Hex Insert
Race-neutral service vehicles routinely use high-torque electric wrenches to swap wheels at speed. A standard carbon hex socket would risk stripping under an impact driver at high torque settings.
OVERFAST installs a 0.8mm thick titanium liner inside the hex socket. This titanium liner is made using Wire Electrical Discharge Machining (WEDM), commonly known as "line cutting". It is used specifically to achieve high-precision, intricate shapes on hard, conductive metals like titanium without mechanical stress or deformation.
Titanium provides the hardness and toughness needed to survive impact wrench use while adding minimal weight, far less than a steel insert would. The hex socket is effectively race-ready straight from the box.
Bonus (let's hope it never gets there): Special Tool Slot
In the worst-case scenario where the axle breaks within the frame, these slots allow the removal of the aluminium threaded part.
Is It Actually Safe? The Testing Behind the Product
Before launch, every OVERFAST thru axle had to pass a comprehensive series of destructive and non-destructive tests. These include recognised international standards.
- Thru axle fatigue test with wheelset (EN standard)
- Impact test with wheelset (UCI standard)
- Maximum torque test - passed at 45 Nm
- Maximum tensile strength - 1,250 kgf before failure
- X-ray internal inspection of every production batch
- Carbon cap impact and fatigue test - 20J impact, 12 Nm torque, 500 continuous twist cycles
- Over two years of real-world testing with competitive athletes
Tensile Test
Torque Test to over 45Nm. Typical torque recommendations are 10-12 Nm.
X-ray inspection of each batch. Spot the double groove interface.
The Bottom Line
Overfast has done the work of properly engineering carbon thru axles: the anti-twist geometry, the mechanically bonded insert (plus adhesive for good measure), the fatigue-resistant one-piece cap, the titanium hex liner. Each of those is a direct answer to a real failure mode.
At around 27 grams for a front and rear pair, these are some of the lightest thru axles available today. The excellent test scores also make the weight saving worth taking seriously.
Compatibility: Over 20 Frame Brands Supported
OVERFAST thru axles are available in multiple lengths and thread specifications to fit the most popular disc brake road and gravel frames on the market.
Confirmed compatible brands include Pinarello, Bianchi, Giant, Colnago, Merida, Specialized, Trek, Cannondale, Factor, Cervelo, BMC, and Scott, among others.
If your frame isn't on the standard list, OVERFAST can produce custom axles to your measurements. You'll need to know your thread specification (M12 x 1.0, 1.5 or 1.75mm pitch), effective length, and total length. Please see the measurement guide below to get the right numbers before ordering.
Custom colour options are also available beyond the standard black. White, pink, purple, orange-red fade, and purple-green fade can be ordered, though these are made to order and carry longer lead times.
A Note on Materials and Packaging
OVERFAST acknowledges that carbon fibre production is not the most environmentally-friendly manufacturing process. In response, all packaging is fully recyclable and paper-based. The company has committed to sourcing and recycling materials responsibly as the product line grows.
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