Jamie Weiss
Hairsprings (also known as balance springs) are one of the most vulnerable yet most important components of mechanical watches. Invented by Polymath Christian Huygens of the Netherlands in 1675, this small spiral spring controls the vibration of the balance wheel of the watch movement and thus adjusts the speed of the watch. It is figuratively literally at the heart of a mechanical watch. But as anyone who has tried to assemble a watch movement knows, they are sensitive. They are so thin that they are easy to stretch out. But more importantly, they are also very sensitive to shocks, temperature changes and magnetic fields.
For most of the history of watchmaking, hairsprings were made of steel. In the late 20th and 21st centuries, the brand has embraced silicon hairsprings because silicon is nonmagnetic, highly temperature-resistant, impact-resistant and has light. However, over the past decade, Tag Heuer has quietly developed carbon hairspring, the next quantum leap in hairspring technology. And, in time for the 2025 Geneva Watch, this technology, which appears to have been finalized, has been released two of the most iconic chronograph versions, using what was called the “Th-Carbonspring” technology.
History of some carbon hairsprings
Before diving into these two watches, including the Carrera Chronograph Tourbillon Extreme Sports Th-Carbonspring and the Monaco Flyback Chronograph th-Carbonspring, we explain why these carbon hairspring are so important and provide a background to tag Heuer’s development. First, the obvious one: why carbon? Well, simply put, carbon (or rather, carbon nanotubes, the basis of Th-carbonspring) is even lighter than silicon, making it even more accurate because it is even more resistant to gravity.
It is also worth mentioning that the development of silicon hairsprings from 2002 to 2022 is patented and limits its commercial use to consortiums of brands such as Rolex, Patek Philippe, Swatch Group and Ulysse Nardine. This probably caused Tag’s movement towards carbon hairspring, but given that the silicon patent expired three years ago, Tag is confident that carbon is still relevant. Until now, only Zenith and Tag Heuer have been active in developing carbon hairsprings, and Tag has truly become the only horse in this race at the time of publication.
In 2019, Tag unveiled its first production watch using carbon hairsprings, a limited edition Carrera Caliber Heuer 02t Tourbillon Nanograph, and the Autovia Isograph Collection. However, these have not been proven to be the assumed Game Chonger tags, with Autavia returning to standard hairspring and the Elite Tag Heuer Lab R&D department returning to the drawings. TAG Heuer in 2021 also used carbon hairsprings, which was a unique piece. Carrera Chronograph Tourbillon Extreme Sports Th-Carbonspring and Monaco Flyback Chronograph Th-Carbonspring are extremely exciting watches as they represent the maturation and commercialization of carbon hairspring technology.
case
So let’s go to the clock. It makes sense that Tag wants to present his coolest and most impressive movement technology within the two most iconic chronographs, and it also makes sense to place a carbon hairspring on a watch in a Forged Carbon Fibre case. There are many carbons on display. Case back ring and strap clasp made from Grade 2 titanium, all parts of both the Carrera Chronograph Tourbillon Extreme Sports Th-carbonspring and the Monaco Flyback Chronograph feature end links for the Curra case, the case of the cover graph.
The Carrera Chronograph Tourbillon Extreme Sports Th-carbonspring is 44mm in diameter, with a lug two and lugs of 49.7mm and a thickness of 15.4mm. Carrera Extreme Sports aims to make Carrera bold and rude, and large dimensions can be forgiven because this is a complicated watch. Another lightweight touch that brings to the table is the motorsport-style fillet on the case barrel and the lug side.
The Monaco Flyback Chronograph Th-carbonspring is a slightly more approachable 39mm diameter, with a 47.4mm lug-to-lug and a thickness of 14.1mm. That said, Monaco wears naturally on the larger side. It’s not a meek watch. Forged carbon, used in both IT and Carrera, has a comfortable matte finish, with a spotted carbon appearance giving it a proper SF look.
Dial
Both of these Th-Carbonspring models have similar dials. Made from the same forged carbon fiber as their cases, they feature an almost meditative ripple pattern, like their hairspring, which is in the shape of a snail rather than a completely concentric circle. It’s a great nod to the impressive development that these watches are intended to showcase. I especially like the Carrera ripples appear to be emitted from the opening of the large tourbillon at 6 o’clock.
strap
The rubber straps are the order of the day here, but at first glance you might think that Monaco’s is actually textile. No, it’s just a pattern. Both straps are secured to the wrist with the familiar black DLC grade 2 titanium folding fragments.
Movement
Now, let’s go back to the hairspring! To showcase these Th-carbonsprings, Tag chose to combine two of the most complex movement technologies available at Arsenal, along with flyback chronographs, chronographs and flying tourbillons. Tag had just performed Th-Carbonspring on a simple three-person lattice, and I love how they really got all over here. Both are COSC certified.
The Monaco movement is designated as the Caliber Th20-60. This is an evolution of the HEUER 02 flyback caliber, which is particularly utilized in the 2023 similarly carbon-covered Monza flyback chronometer, but is based on the brand’s current TH20-00 movement architecture. Despite the inherently power-hungry nature of the complexity of the flyback chronograph, it features a thick, 80-hour power reserve.
Similarly, the Carrera caliber Th20-61 is a reworking of the Heuer 02 Tourbillon movement seen in an array of Carrera Tour Billon models over the years, and was also reworked with the addition of Th-Carbonspring. It also has an impressive 65-hour power reserve.
verdict
Modern Tag Heuer is not a brand that many people are immediately associated with cutting edge innovation in the watch industry. This is probably a bit unfair and takes everything into consideration. Tag, for example, does pioneering things with lab-grown diamonds, adding more and more mature movements of the watch into its range, including the TH81-00 Rattrapante Caliber, developed by Vaucher-Co. Now it appears they have finally completed their carbon hairspring technology. I have to wait and see…
But in the meantime, these two super cool carbon chronoes are just as aesthetic as technical knockouts. Carrera gets the points to put the front and center of that th-carbonspring, but personally I want a Monaco in the collection.
Pricing and availability of the Tags Heuer Carrera Chronograph Tourbillon Extreme Sport Th-Carbonspring and Monaco Flyback Chronographth-Carbonspring
Tags Heuer Monaco Flyback Chronograph Th-Carbonspring and Carrera Chronograph Tourbillon Extreme Sport Th-Carbonspring are limited editions of 50 individually numbered pieces available from December 2025.
Brand Tag Heuer Model Monaco Flyback Chronograph Th-Carbonspring Carrera Chroneragraphhologht Tourbillon Extreme Sport Th-Carbonspring Reference Number CBL5190.FT6313 CBU5091.FT6305 Case Dimension 39mm(D) x 14.1mm(T) x 47.4mm Case Materials Forged Carbon Fiber, Grade 2 Titanium Case Back Ring Forged Carbon Fiber, Grade 2 Titanium Case Back Ring Water Back Water Resistance 100m 100m Sapphire Front and Back Sapphire Front and Back Dial Dial Dial Dial Dial Carbon Fiber Dial Folding Clasp Black Rubber Strap, Forged Carbon End Link, Black DLC Gray Do2 Titanium Folding Class Claver TH20-60, In-house, Automatic, COSC, TH Carbon Spring Oscillator Caliber Caliber TH20-61, In-house, Automatic, Auto, COSC, TH Carbon Equipment Oschrator Power Plant Reserve Running Time, Running, Seconds, Chronograph, Flying Tourbillon Availability Limited to 50 Pieces, Limited to 50 Pieces from December 2025, Price CHF for December 2025 Available from 17,000 CHF 40,000
