Win Fin, Flow Fork, Speed Sniffer: Specialized launches 'fastest road bike ever made' in the S-Works Tarmac SL9

Today is the day many Specialized road bike fans will have been waiting for; the launch of the American brand's latest flagship race bike.

But no, it's not a Venge as many predicted. It follows in its many predecessors' footsteps (tyre prints?) and is called the Tarmac SL9.

Its launch has been a typically turbulent Tarmac launch. It started, as it often does, with an early digital imagery leak courtesy of a farflung retailer and the WeightWeenies forum. It was then followed by social media leaks courtesy of Red Bull-Bora-Hansgrohe's in-team photographer (who no doubt got a slap on the wrist before he duly deleted his post).

And it was then followed up by Dauphine spy photos courtesy of our very own Will Jones, who had to go full Daily Mail paparazzi and hide in a bush to get them, and was subsequently threatened on social media by a Red Bull-Bora-Hansgrohe mechanic. Fun.

What's new

At first glance, and second, the SL9 looks very similar to the SL8, but having been up close with one – I have one next to me right now as I type this – it's fair to say a lot of work has gone into the bike that will probably go unnoticed.

In fact, every single tube has been reshaped in some way. The ones that stand out the most, however, are:

• The seat tube now curves rearward to follow the shape of the tyre.
• The fork legs are now deeper and thus hide the deep 'speed sniffer' head tube.
• The seatpost has a narrowed section for extra aero gainz between the rider's legs.

In brief, that leads to a bike that is four watts more aero than its predecessor. The claimed frame weight is two grams heavier at 687g (size 56cm in Raw Carbon / Gloss Amethyst Frost finish), but full builds now start at 6.5kg thanks to lighter-weight components.

Tyre clearance remains at 32mm, but the specced option has bumped up to 30mm.

For today, the only version being revealed is the S-Works model. It's safe to say that more budget-friendly models will follow in due course, but today is all about the flagship product and as we gear up for the Tour de France, the team replica framesets too.

The equation of speed

When the brand launched the Tarmac SL8, it came with all the usual claims of being stiffer, lighter, more aero and so on, but quietly tacked on at the bottom were some calculations claiming it was 20 seconds quicker than the SL7 up the Col du Tourmalet or 128 seconds over the 294km course of Milan-San Remo. Without much context on how the brand landed on those numbers, they went largely ignored by most media and readers.

Returning to the present day, those claims are no longer tacked on quietly, but front and centre. Specialized has said it before, but this time it led its presentation with the statement: "Time to the finish is all that matters."

With that in mind, Specialized says the SL9 is "Fourteen seconds faster [than the SL8] over the last 80km of the final stage of the 2024 Tour de France Femmes," which conveniently is the stage in which FDJ United-Suez leader Demi Vollering lost the yellow jersey by four seconds to Kasia Niewiadoma.

I'm told that when Vollering heard the claim, she wasn't best pleased (in a 'thanks, but I wish you hadn't told me that' sense).

Specialized says that 'Time to Finish' is a "physics-based simulation output that predicts total elapsed race time over a specific real-world course, using measured inputs from aerodynamics, weight, rolling resistance, surface roughness, environmental conditions, and rider power. It is not a slogan. It is not theoretical. It is the result of measured data applied to real courses."

And that all takes us to Specialized's 10-year 'Equation of Speed' journey.

In 2016, Specialized hired Marcel Keyser from Scuderia Toro Rosso F1 team as a Senior Engineer for Race Simulation, and in the ensuing decade, he has developed a piece of software that looks at every force acting upon a cyclist, which he calls the Equation of Speed, effectively replicating software used in Formula 1 to predict lap times and guide the design of the cars.

The aforementioned sextet of inputs (aerodynamics, weight, rolling resistance, surface roughness, environmental conditions, and rider power) are also joined by other metrics such as tyre grip and rider skill.

A neat example is that Keyser can measure a rider's cornering speed using .FIT files, assign a cornering ability score to each rider, and then advise on their appropriate setup for an upcoming race – do they need the slower, grippier winter tyre when it's raining, or can they handle the 80km/h descent on the faster-rolling summer tyre?

With this software and by developing tests that measured each of these things in isolation, such as a test that measures the rolling resistance of tyres or the CdA of each rider on each bike, he could input known variables, and it would spit out a simulation telling him how long it would take a rider to finish a specific course.

How does that relate to the Tarmac SL9?

Specialized took this software, initially created to choose the optimal equipment for race day, and applied it to designing the optimal equipment for race day.

With key races in mind, Specialized designed the Tarmac SL8, and now of course the SL9 (as well as the recently released Crux) not only to be more aerodynamic in a wind tunnel or lighter on a scale, but to be faster to the finish line on a variety of important course profiles.

You could say that it went to a lot of trouble to land on the same end goal that most bike brands aim for: lighter, more aero, better handling. But Specialized will tell you the special sauce lies in finding the right balance with a measured, scientific approach.

I feel this points us towards the resurgence of a dedicated Specialized aero bike like the Venge. Specialized argues the Tarmac SL9 can be optimised via configuration, and for the upcoming Tour de France the riders will have three wheelset options: Rapide CLX III, Alpinist CLX III, and Rapide Sprint, which they can choose between depending on various factors.

But why shouldn't it also extend to frame choice? I struggle to believe that when designing a frame with specific courses in mind, one single design is optimal for Paris-Roubaix, a flat sprint stage, and the Col du Tourmalet concurrently. I shan't hold my breath, though.

The differences, in detail

I've used a lot of words there to explain Specialized's thinking. Now let's dig into what's actually changed.

Deeper fork

The most divisive feature of the SL8 - the protruding 'Speed Sniffer' head tube - has technically not gone anywhere, but thanks to a deeper fork, which Specialized is calling the 'Flow Fork', with its further-forward leading edge, the front end of the bike looks seamless once again.

Lower down tube

Behind the fork, the SL9's down tube has also been dropped slightly to better manage the airflow coming from the fork and the front wheel.

Narrower head tube

The 'Speed sniffer' head tube shape remains largely unchanged when viewed from the side, but head on it has shrunk by 4mm, bringing its frontal area down by 10 per cent. Of course, that's just the frontal area of the head tube itself, meaning the rider's total frontal area will be reduced by a much smaller percentage.

This led to a few design challenges for the Specialized team, as the reduced space meant less room for the brake hose to pass through the head tube around the steerer inside. As a result, the fork's steerer tube actually kinks to the right inside the head tube, then kinks back to the centre again at the top of the head tube. This allows the rear brake hose to sit alongside it.

Curved 'Win Fin' seat tube

It wouldn't be a Specialized Tarmac launch without a strange descriptor of one of its design elements, and this time it's the turn of the 'Win Fin' seat tube, which curves rearward and follows the shape around the rear tyre.

Specialized says that after studying WorldTour riders during the key parts of races where breaks are formed or races are won and lost, they invariably have ejected one of their bottles and are running an empty cage. As a result, the Tarmac SL9 was designed with this in mind, and this move alone is reportedly worth 0.5 watts at 45km/h.

Narrower seat post

North of the Win Fin is a new S-Works Rapide seatpost, which, incidentally, can also fit into the new Crux, and is narrower at the top half. This is essentially to remove material in an area where airflow is accelerated as it travels between a rider's legs.

Spec changes

Since my review of the Tarmac SL7, I have bemoaned Specialized's reluctance to embrace narrower handlebars, but there is at last some movement and improvement in this regard.

Previously, a 58cm bike would be shipped with 44cm bars, and the solution last time was to simply send cockpits in their own retail packaging so that shops could more easily swap them out when a customer wanted.

This time round, a 58cm bike will shipped with 42cm bars, but what's even better than that is that the measurement at the base of the hoods is now 36cm thanks to the flare of the Rapide cockpit. That's much narrower than they would have been on Tarmacs of old, where a 42cm outside-to-outside bar would still be around 40cm at the hoods.

In addition, all bikes now come with shorter cranks, to the tune of 2.5mm shorter across the board.

Bikes still ship with the 15mm offset seatpost, so those looking for the 'modern' aero position with an effective steep seat tube, short cranks and narrow bars will probably be looking to swap this out, which is possible but not without the support of an amicable bike shop.

But I can see why Specialized didn't flip the well-loved geometry of its flagship bike on its head to appease a growing-yet-still-small subsection of the market. Maybe that's where the Venge fits in.

The other change I really appreciate is that the S-Works Tarmac now ships with 30mm Turbo Cotton Tubeless tyres. This is at odds with most brands who have ballooned their tyre clearance to 32 or 34mm, yet still send bikes out with 28 or even 25mm tyres.

Tarmac SL9 vs Cervelo S5, Colnago Y1Rs and Factor ONE

It's becoming incredibly common for new bikes to launch with claims of being 'better' – in some metric, but often aerodynamics – than a named competitor. And almost ubiquitously, one of those named competitors is the S-Works Tarmac.

It could be seen as a compliment, but Specialized has become a little fed up with it and has decided to reciprocate the honour with a comparison of its own.

It has benchmarked the Tarmac SL9 against the Cervélo S5, the Colnago Y1Rs and the Factor One. Given the Remco Evenepoel connection, it's not a surprise to see the Cervélo and Colnago (ridden by Jonas Vingegaard and Tadej Pogačar respectively) in there, but the Factor One is an interesting addition that evidences Factor's rise to relevance over the past few years; no doubt aided by its unconventional design too.

These comparisons don't simply quote a single metric such as CdA, they input the CdA and weight into the Equation of Speed simulation to quantify the speed differences over a variety of courses.

Using bikes set up as follows:

Specialized measured each bike as follows:

Note that the delta between Tarmac SL8 and the competitors is different to what we found in our own wind tunnel tests, but within the error margin of our tests (using a real rider).

Our tests were performed at a slower speed (40km/h vs 45km/h), and the different yaw angles were weighted differently. Specialized says weighting more favourably towards zero yaw offers better real-world relevance for cyclists. Existing accepted methods – including ours – are based on the automotive standard of environmental wind speed, measured at 3m above the ground. Specialized's data argues that measurements at 1m above ground - as experienced by a cyclist - see a lower wind speed, thus increasing the likelihood of experiencing lower yaw as the rider's own forward momentum is what creates the wind.

I'll save the full breakdown, but over three laps of a relatively flat 2026 Montreal Worlds course, the differences are as follows:

• SL9 Time to Finish: '00:19:17.100'
• SL8: +3.7
• Cervelo S5: +0.5
• Colnago Y1RS: +1.9
• Factor ONE: +2.1

And in a single ascent of Alpe D'Huez, the differences are as follows:

• SL9 Time to Finish: ‘00:38:18.000'
• SL8: +5.5
• Cervelo S5: +16.4
• Colnago Y1RS: +18.2
• Factor ONE: +30.9

Early review

At the time of publishing, I still want to put more miles through the Tarmac SL9 (and put it in a wind tunnel) before I write a full review, but having ridden the SL6, SL7, SL8 and SL9, (as well as the Venge Vias, Venge, Roubaix, Allez, old and new Aethos and probably a few I've forgotten over the years), I can confidently say the SL9 retains the well-loved Tarmac handling and ride feel.

That's not to say it's exactly the same though.

Firstly, an important caveat. I am now a proud father, and two things have happened since January when our son was born.

1. I've not ridden as much as I normally would, so my fitness has tanked.
2. My willingness to rail around corners has reduced as my sense of mortality has increased.

The reason I mention this is that the perceived performance of a bike is quite correlated to my ability to ride it. It's the "all bikes feel slow at altitude" dilemma, but framed differently.

Take 40 watts off my FTP, and bikes won't feel as sprightly uphill, because my reference point of the SL8 is on legs I had two years ago. Nor will a bike feel as telepathic on descents. I'm comparing today's apples against last year's oranges.

Therefore, despite jumping onto the Tarmac SL8 in 2023 and immediately feeling like I could throw it into hairpins, that took around 4-5 hours of riding this time round, and only came on a fast descent of Coe, a spicy climb north of Morgan Hill. I was following a group of Specialized employees and locals that knew the roads inside out. Hanging off the back of the group to follow their lines helped me to judge the otherwise never-before-seen corners and let the bike shine.

And shine it did. It was stable, predictable and planted when you wanted it to hold a line around wider corners, but agile on the tighter corners and easy to accelerate back to speed on the other side of them. The SRAM Red brakes were reliable as ever for late braking into tight hairpins, and the wide tyres added a level of composure that really helped on rough and gritty roads I'd never ridden before.

The flare of the handlebars meant leverage wasn't lost when you wanted it for those tiny steering inputs on fast descents, but the narrower spacing between the hoods was perfect for getting small in the slipstream when the roads straightened up or levelled off. It really was a fun experience that, without getting too sentimental, was one of those that reminds you why you love riding bikes so much.

One thing that's not affected by my fitness, however, is the comfort and ride feel, and the balanced quality that has long shone through in previous generation S-Works Tarmacs remains abundant here. It's a lovely blend of snappy and punchy responsiveness under power, but smooth, stable and refined the rest of the time.

Price and availability

For now, as mentioned, Specialized is only launching the S-Works model Tarmac SL9.

When the lower-spec models will come is to be confirmed, but that at least simplifies your options if you want to buy one this side of the Tour de France.

Team edition colourways

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