TAG Heuer is marking the rollout of its new-and-improved, and in-house, carbon hairsprings – timed to coincide with the 350th anniversary of the hairspring’s invention – with a pair of chronographs: the Monaco Flyback Chronograph TH-Carbonspring and Carrera Chronograph Tourbillon Extreme Sport TH-Carbonspring.

More than just two new watches, the TH-Carbonspring is a notable technical achievement that might promise an entirely new generation of TAG Heuer movements equipped with oscillators that boast all of the advantages of silicon, but with added robustness. Protected by several patents, TH-Carbonspring is also the result of a fascinating process of research and development to overcome a surprising problem.

Kitted out in carbon composite dials and cases, the two watches are centred on TAG Heuer’s latest-generation carbon-nanocomposite balance springs, with each being a limited edition of just 50 pieces

Initial thoughts

Both models serve as a launch platform for TAG Heuer’s improved and industrialisation-ready carbon hairspring. While the brand has been flirting with carbon hairsprings since 2019, its use of the technology has been intermittent and on limited scale.

TAG Heuer explains previous attempts at carbon springs were not up to the brand’s standards, which is to say the hairsprings did not perform as expected and could not be produced at scale. The new TH-Carbonspring indicates TAG Heuer has perfected the technology to make reliable hairsprings, which might lead to broader adoption within the LVMH’s stable of watch brands. In fact, the material might even rival silicon in the future, at least for LVMH marques.

The main advantages of carbon hairsprings are the total magnetic resistance (since carbon is naturally non-magnetic), lightness, and ability to be formed in any shape imaginable — especially useful when optimising hairspring geometry. These qualities are very close to silicon’s traits, but carbon holds an advantage, higher yield strength, making it more robust when handled by a watchmaker during assembly or service.

Assuming TAG Heuer can industrialise the carbon hairspring and install it across its production, as is the goal, the technical achievement of TH-Carbonspring is significant. Ironically, the two watches are fairly low-key symbols of this achievement, both have a similar monochromatic aesthetic  due to the overwhelming use of carbon composite on the exterior — though they are as different as they come. 

Notably, the movements in the two watches are distinguished not only by the carbon hairspring, but in terms of decoration as well. Both the Monaco and Carrera share a distinctive chequerboard finish that was first implemented on the one-of-a-kind Monaco made for the Only Watch charity auction. Though not hand applied as with the unique piece, the decor does set these calibres apart.

The Monaco Flyback TH-Carbonspring is undoubtedly the better looking of the two – though I admit I’ve always been a fan of the Monaco. Fashioned out of forged carbon, the square Monaco case is very different from the colourful piece that famously graced Steve McQueen’s wrist. The monochromatic look suits the square design well, all while keeping the dial sufficiently legible. 

The classic dial layout of the Monaco is retained, but with a clever touch in the form of a spiral motif on the dial. In keeping with the iconic twin register look, the Monaco Flyback employs a “ghost” register for the running seconds at six o’clock. 

At CHF17,000 the Monaco in carbon is a little pricey compared to the standard Monaco models, but it offers a lot more in all respects, from the case material and the movement technology. That, combined with the small edition size, rationalises the price.

The Carrera, on the other hand, is still a value-minded complication, but dressed in a full carbon ensemble. The result is not as appealing as the Monaco, with some design choices here looking forced. The marbled texture of forged carbon are more prominent than on the Monaco, while the lugs attempt to resemble an integrated bracelet. Much of the aesthetic result is due to the design of the Carrera Extreme Sport rather than the carbon livery.

While the Carrera might not be to everyone’s taste, its value lies in the in-house chronograph movement, adapted for a flying tourbillon regulator which puts the TH-Carbonspring front and center.

The two movements employed to showcase the new TH-Carbonspring point to TAG Heuer moving upmarket in terms of both industrialisation capability and quality. Performance chronographs from the likes of Rolex, Omega and Breitling are almost all chronometer-certified while also employing advanced technology, especially in the oscillator.

TAG Heuer was always a little behind in that respect. With its new hairspring technology, TAG Heuer has finally a fighting chance of reaffirming its place as a chronograph maker of note, with innovation-fuelled creations.

The carbon evolution

With the hairspring turning 350 years old, we already delved substantially into its history and evolution driven by materials science. The final important development in the evolution was the silicon hairspring with its easy mass-production, tight tolerances, and isochronal geometries, not to mention a useful resistance to magnetic and temperature influence.

Carbon, however, might do one better. For all its qualities, silicon still suffers from inherent brittleness, which makes such hairsprings susceptible to snapping due to shock or even mishandling during service. This weakness, combined with the fact that the patent for silicon hairsprings limits their use to a select few companies, drove the engineers at the TAG Heuer Institute (now renamed the TAG Heuer Lab) to search for other non-metallic materials that to replace alloy springs.

TH-Carbonspring sample, with a distinctive geometry.

TAG Heuer’s first carbon nanocomposite hairsprings hit the market in 2019. The new oscillator promised all the advantages of silicon (non-magnetic, isochronal geometry) while boasting a superior yield strength. At the time, TAG Heuer claimed the new hairsprings could withstand 5,000 G of acceleration — a value which would snap silicon and severely bend alloy springs. 

These first versions the carbon spring were made out of carbon nanocomposite, essentially a vertical bundle of carbon nanotubes (with diameters of 3 to 7 nanometers), held together by a rigid carbon matrix, almost like a forest of nanotube trees. The tubes were arranged perpendicular to the spiral’s plane, with each nanotube parallel to the rotational centre of the hairspring, namely the balance staff. 

PVD chamber with wafer plate.

The patent WO2017220672A1 filed back in 2017 detailed an original two-part production process for these carbon nanotube hairsprings. The first step was “growing” the nanotube structure with a PVD (Physical Vapour Deposition) method, and the second step was filling in the core carbon matrix, the adhesive that held the tubes together. The process was done on wafers similar to those used for silicon etching. 

The resulting carbon nanocomposite hairspring was elastic and strong, with the particular structure lending it a high elastic limit. A different patent addressed the issue of temperature self-compensation and the thermo-elastic coefficient. Paired with a proprietary geometry that would keep the rotation center coincident with the balance axis (an issue broadly covered in a past story on hairspring overcoils), the new carbon springs looked like a strong rival to replace silicon.

The promising system was only used sporadically by TAG Heuer (and sister company Zenith), clearly a sign that the hairspring was not as performing as intended — although the concept looked foolproof. A few select timepieces featured the new spring, but the carbon technology never reached the industrialised scale of its silicon counterpart. 

With the new TH-Carbonspring, TAG Heuer hints at the full potential for industrialising its improved carbon springs – the brand’s annual production of mechanical watches is into six figures. The fact that the two new models are each limited to 50 pieces is most probably related to their costly forged carbon cases and carbon accented dials, rather than the hairsprings themselves. 

Now watertight

Though TAG Heuer hints at a new and improved manufacturing process for the carbon springs, it has kept quiet about the details that make the invention ready for mass production. We did however manage to trace patent WO2025114588A1, filed at the end of last year and published earlier this year in June, which describes the additional manufacturing steps and hints at the issue that plagued the past versions of its carbon hairspring.

The patent heavily builds on the initial one from 2017, but explains how the composite material, in its raw form, is water permeable. This means that the original springs absorbed water and other liquids, which in turn affected their qualities (mass, natural frequency). In any watch there are plenty of lubrication points — not to mention the ever-present humidity in the air, all which seem to have negatively affected the original carbon springs. 

The issue of material permeability does not immediately come to mind in the field of hairspring design, since metal alloys and silicon are inherently non-permeable. The issue of oxidation was an issue, especially with alloy springs, but separate from permeability.

In the earlier version of TAG Heuer’s carbon hairspring, the nanotube “forest” turned into a sponge of sorts, with its porous surface absorbing humidity into the spaces between the tubes. The new patent explains the unwanted effect was only noticed in serial-production springs, so it was completely unforeseen during the design and development phase.  

At its core, the new patent describes a method of surface passivation, such that the hairsprings become hydro- and oleophobic. In other words, the hairspring will not absorb any liquids that may come in contact with its surface.

Through a bend of chemistry and physics, TAG Heuer engineers developed a process of treating the nanocomposite springs with specific carbon chains that render the final product impervious to humidity. The process itself is similar to electrolysis in some ways, but requires specialised chemical reactors and needed some extensive experimentation to be fine-tuned. 

With the implementation of this final step, the TH-Carbonspring seems to be a mature technology that is finally able to fulfil its potential. While it shares some qualities with silicon springs, mainly the imperviousness to magnetic fields and optimised geometry, it surpasses silicon in two ways: lightness and much higher yield strength. 

A lighter hairspring is more faithful to the theoretically perfect sprung regulator, which doesn’t take into account the spring’s own mass and inertia. The higher yield strength allows the TH-Carbonspring to withstand shocks, and important allows watchmakers to handle them like alloy springs during assembly and servicing, without fear of breakage.

The Monaco

Perhaps the most emblematic model in TAG Heuer’s line, the Monaco is dressed in carbon for this limited edition, while keeping the design cues of the original.

The square chronograph retains its classic, well-proportioned 39 mm case that is now sculpted from carbon composite. Being fashioned out of carbon, the case is light and durable. The material not only gives the watch a stealthy and raw look, but also makes each piece unique, since the carbon graining has a different orientation in each batch of material.

Also rendered in carbon composite, the dial is milled with a circular motif made up of wide bands that spiral from the center — a nod to the coils of a hairspring. 

The white hands and numerals maximise legibility, while the intentional omission of a defined sub dial for the small seconds is laudable, since it preserves the original Monaco look. The small seconds hand itself is blackened and only visible under close scrutiny. 

The Monaco Flyback TH-Carbonspring is powered by the TH20-60, an in-house movement derived from the more basic TH20-00 developed by Carole Forestier-Kasapi and her team. Compared to the basic version of the caliber, the TH20-60 is updated with a flyback function as well as the TH-Carbonspring system. 

The TH20-60 caliber is at its core a competent and modern chronograph movement, with a respectable power reserve of 80 hours and a standard 4 Hz rate. It benefits from a column wheel actuation system and a vertical clutch — both marks of modern performance chronographs. This new version updates the regulator with a TH-Carbonspring, while curiously keeping the simplistic raquette regulating system. 

The choice of an inexpensive index regulator, compared to the more advanced free-sprung option is odd — especially for a timepiece which is centred around a new high-performance regulator. Although it is not advertised on the dial, the TH20-60 is COSC-chronometer certified.

The caliber is clearly machine-finished, with the bridges finished with a chequered flag motif inspired by the brand’s motorsport ties. Being a round movement fitted into a larger square case, the TH20-60 requires a substantial movement ring, which is also tastefully finished with the same pattern.

A chronograph and tourbillon

Compared the almost-subdued Monaco, the Carrera Chronograph Tourbillon Extreme Sport TH-Carbonspring is an aggressively styled 44 mm. Whereas the Monaco leans into classic looks, the Carrera TH-Carbonspring is modern. The large case follows the lines of the traditional Carrera form, but is bulked up and accented with touches like the “integrated” strap.

It is fashioned from forged carbon, as are the chronograph pushers and crown. Also in carbon is the tachymeter bezel that features lacquered numerals. 

Much like the Monaco, the Carrera is very legible, something which can’t be said for many monochromatic watches. The carbon spiral motif is present on the dial as well, although it is decidedly larger than the one used for the Monaco. The spiral pattern is emanates from the tourbillon cage, as opposed to the center of the dial, which is a thoughtful design choice.

The defining visual trait of the model is surely the flying tourbillon regulator, positioned a little too low at the 6 o’clock position. The cutout aperture is larger than the chronograph sub registers and for some reason makes the tourbillon look a little small. This and the fact that it cuts into the outer minute track leaves the impression of a slightly lopsided dial. 

Powering the Carrera is the TH20-61 — yet another iteration of the basic TH20-00. For this version, TAG Heuer kept the chronograph works and only altered the going train and base plate to accommodate the dial-side tourbillon regulator.

The TH-Carbonspring is paired here with a free-sprung balance, which is fitting at this price point. The TH20-61 manages 65 hours of power reserve while beating at 4 Hz. This is less compared to the TH20-60 in the Monaco and the difference speaks of to the energy consumption of a tourbillon regulator. The TH20-61 is chronometer certified as well and shares the same finishing as the TH20-60. 

Key facts and price

TAG Heuer Monaco Flyback Chronograph TH-Carbonspring
Ref. CBL5190.FT6313

Diameter: 39 mm
Height: 14.1 mm
Material: Forged carbon, DLC-coated titanium caseback
Crystal: Sapphire
Water resistance: 100 m

Movement: Cal. TH20-60
Functions: Hours, minutes, seconds and flyback chronograph
Frequency: 28,800 beats per hour (4 Hz)
Winding: Automatic
Power reserve: 80 hours

Strap: Rubber strap with DLC-coated titanium folding clasp

Limited edition: 50 pieces
Availability: Starting from December 2025
Price: CHF17,000

TAG Heuer Carrera Chronograph Tourbillon Extreme Sport TH-Carbonspring
Ref. CBU5091.FT6305

Diameter: 44 mm
Height: 15.4 mm
Material: Forged carbon, DLC-coated titanium caseback
Crystal: Sapphire
Water resistance: 100 m

Movement: Cal. TH20-61
Functions: Hours, minutes, chronograph, and flying tourbillon
Winding: Automatic
Frequency: 28,800 beats per hour (4 Hz)
Power reserve: 65 hours

Strap: Rubber strap with DLC-coated titanium folding clasp

Limited edition: 50 pieces
Availability: Starting from the first quarter of 2026
Price: CHF40,000

For more, visit Tagheuer.com.