Is it possible to create the world’s fastest road bike without the ‘wild’ wide-stance forks, V-stems, bayonet head tubes, gull-wing bars, split seat tubes and slammed-forward geometry that characterise the current crop of WorldTour weapons? This is exactly what Specialized is claiming to have done with its new flagship road race bike, the Tarmac SL9, which is at a glance alarmingly normal looking. But, everything depends on the definition of ‘fast’.
In Specialized’s words: “Fastest doesn’t mean lowest drag in a wind tunnel. Fastest doesn’t mean lightest on a scale. Fastest doesn’t mean best lab numbers in isolation. Fastest means crossing the finish line sooner – period.”
The new Tarmac SL9 is a claimed 4 watts faster at 45kph than the outgoing SL8 and 2 grams heavier at 687 grams – impressive given the new, deeper tube profiles – but the big headline is that it beats not only the old Tarmac but also the Colnago Y1Rs, the Cervélo S5 and the Factor ONE using Specialized’s Time to Finish equation. This is, says Specialized, 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.”
The US brand introduced Time to Finish when it launched the new aero-ised Crux earlier this month, and used it to illustrate the time its athletes would have saved at Unbound versus the old Crux. With the SL9, Specialized has gone further. Not only do its illustrations show how Demi Vollering would have won the 2024 Tour de France Femmes instead of losing it by four seconds had she been riding the Tarmac SL9 but also – as if to hit back at all the comparisons by its rivals against the SL8 – it has included data against competitor WorldTour bikes on simulated Tour de France stages, the 2026 Worlds and Liège-Bastogne-Liège. In each of the illustrations the SL9 is quickest to the line.
Specialized explains that this method of number-crunching all of the separate inputs rather than relying on the most aerodynamic or the lightest in isolation is well established in other performance-driven sports such as Formula One and sailing: “While the equation of speed itself is grounded in fundamental physics, the magic lies in how our team applies it and in the accuracy of the data we use to populate it. Every variable is measured independently, then integrated into a single simulation.” Let’s take a look at how the SL9 does it.
Aero exactness
Specialized has its own Win Tunnel at its HQ in Morgan Hill, California, which of course gives it an unfair advantage. But for the aerodynamics section of the SL9 presentation, its engineers wanted to talk in detail first of all about the new mannequin they used to develop the bike. This is of course the correct order for any science experiment – presenting the method of analysing the data after asking the question and forming the hypothesis.
Specialized’s mannequin is in its sixth generation and was built from a scan of a real rider. It pedals so that legs and wheels are rotating. It’s as close as you can get to a real rider with robotic repeatability, says the brand. Unlike static mannequins, leg-only mannequins or bike-only testing, Specialized says its own system captures how a rider’s full body in motion alters airflow across the bike at race-relevant speeds: any aero number without the rider is incomplete. None of this means anything without the mannequin being precisely positioned each time, and a millimetre-accurate laser projector system is used to ensure every time a bike is swapped the mannequin is in exactly the same place relative to each bike’s bottom bracket. According to Specialized, if the mannequin’s position is off by even half a centimetre, it can make a bigger drag difference than swapping the bike it’s riding.
So the claim was not that a superior mannequin necessarily leads to a faster bike but that it allows Specialized to measure more accurately and more realistically, to iterate faster – which it can do as it owns its own wind tunnel – and to reach the conclusion of the experiment (the faster bike) with more precision and therefore certainty.
Shapes of the future
At the presentation we were shown some slides of Mad Max-style mule bikes in the Win Tunnel, using the SL8 frame as a starting point with new tube shapes grafted/bonded in. The result is a completely new bike that looks almost the same at a glance – it’s instantly recognisable as a Tarmac – but every tube is different.
Starting at the front, a new ‘Speed Sniffer’ head tube reduces the frontal area by 10% by going narrower by 4mm. Normally the head tube – with the conventional steerer tube system – has to accommodate hydraulic brake cables as well as the fork steerer, so there’s a limit to how narrow it can go. For the SL9 Specialized designed a patent-pending offset steerer that allows the rear brake cable to run past it on the right without taking up extra space. We passed it around at the presentation and all marvelled at its cleverness. It’s a shame there’s no picture in the press pack (I wish I’d taken my own).
The redesigned fork – the Flow Fork – visually has a bigger, more arched crown, but something not so obvious is the angle of the blades, which are twisted outwards slightly like an intake to direct the airflow more efficiently over the frame. Specialized says this reduces drag over the entire front half of the bike.
A dropped down tube reduces the distance the airflow has to ‘jump’ when it leaves the trailing edge of the fork blades, and as it travels yet further back over the seat tube it stays attached longer thanks to a new ‘Win Fin’ – a deeper section that hugs the rear wheel. Interestingly, Specialized engineered this feature and the rest of the rear of the SL9 around a single bottle in the down tube cage. This appears to go against the idea that frames are faster if they’re developed around two bottles, which has been around at least since the Pinarello Dogma F8 of 2015.
“In a breakaway, team cars sit close behind the move,” says Specialized, “so riders can grab fresh bottles whenever they need them. With no second bottle required, the airflow around the seat tube and rear triangle changes dramatically compared to traditional two‑bottle test assumptions. The result is the Win Fin, tuned for the aero reality of winning moves, saving 0.5 watts.”
The other key aerodynamic feature of the SL9 is the new S-Works Rapide seatpost. It has a deeper profile with a reduced frontal area, which is said to deliver a cleaner airflow. Specialized says it is the thinnest seatpost section it has ever made where it matters most.
Lightest in category
We were told that Specialized’s engineers gave themselves a ‘budget’ of 50 grams over the 685 grams of the SL8, and the first revision frame came back at 710 grams. The team went ply-by-ply over the entire frame and got the weight down to 687. “Obviously there’s a minimum overlap between plies, so if we see anything that is over that, we are essentially trimming where we can, cutting away the excess material that we don’t need, explained product manager Alex Jerome. At the end of the day you have this little stash of material that you can put on the scale and see how much you saved.” He continues: “It’s not just something you can do on the laptop. Our whole team was there with our partners in Asia in the pre-forming room. It was quite a journey and definitely took more effort than the last 10 seconds of this conversation.”
The Tarmac SL9 starts at 6.5kg in the S-Works version and Specialized had on display hanging on a set of Park Tool scales a 6.14kg build with SRAM Red XPLR and Roval Alpinist CLX III wheels.
Strength in low numbers
Despite the low weight, the new bike has improved structural integrity compared with the SL8, says Specialized. It says the tube shapes rather than the material are designed to carry the load, and that the 687-gram S-Works frame, made with the flagship FACT 12r carbon, withstands over 100,000 cycles at 2,377 watts – far beyond industry standards. As before, each size gets a size-specific layup to ensure consistent handling.
Stiffness, compliance and geometry are the remaining pieces of the SL9 jigsaw, and Specialized says: “We were so committed to making you feel one with your bike that, despite the new aerodynamic profiles and the aggressive tube shaping required for Time To Finish gains, Tarmac SL9 matches the exact compliance and stiffness targets of the universally loved Tarmac SL8.”
Geometry is also the same as the SL8’s. It has clearance for 32mm tyres, a BSA 68mm threaded bottom bracket. And the price is the same as before too – the S-Works builds are priced at £11,999/€13,999/$14,000. Lower-priced frames and builds are to be announced shortly.
First impressions
I rode the Tarmac SL9 at a pre-launch press camp in Tossa de Mar, Spain last month – a stunning location right next to a perfectly semi-circular little bay with white sand and turquoise water. I know – brand takes journalists off to stunning location with lovely smooth roads and they say nice things about bike. Except when we rolled out it was sheeting with rain, the temperature was well below the 15°C that’s the mandatory minimum for shorts and short sleeves and we were immediately onto a treacherous descent with hairpin bends flanked by steel barriers.
Brand new disc brakes were squealing – or even howling – but we all felt comfortable and confident immediately. Later we all agreed we probably should have been a little more careful but at the time that was how it felt, and none of us was going to take a performance rain check. Fortunately it dried up before we had a chance to unstick the envelope.
In order to avoid any fit issues, Specialized had got me to visit approved fitter Jake Yarranton at Precise Performance before heading out to Spain, and he’d made sure I was Retül compliant (Specialized of course owns Retül). So I’d been able to hop onto the glossy red S-Works Tarmac SL9 without adjusting a thing and was able simply to focus on the ride.
I just felt as though I was riding ‘my’ bike, and not just because the fit was already dialled. As I’ve mentioned, the geometry is the same as the SL8 and so are the stiffness and compliance – it’s just that Specialized has designed it to go almost imperceptibly faster. Riding it, there are no surprises. It still feels supremely balanced, it is wonderfully light and ultra responsive when climbing or accelerating. And it really is fast. Cornering on it is an incredible amount of fun. We had some elite riders in our group and it was pretty humbling to watch them corner on the SL9 – it’s a bike designed for the likes of Remco Evenepoel and Demi Vollering after all, and I’d be flattering myself if I thought I was pushing it to its limits.
There will be people who say Specialized has been too cautious, they could have done something radical to trump Factor, Colnago, Cervélo et al but instead they played safe and just tweaked their old bike. I’ve ridden a couple of the more progressive aero bikes recently. I understood what the Felt Nexar is trying to do, and found it fascinating when its designer, Cesar Rojo, criticised traditional road riders for expecting a new bike to feel like their old one. I appreciated what Factor was doing with the ONE’s geometry, even though it wasn’t right for me personally.
Meanwhile, the Tarmac SL9 is right for me personally. The proportions were perfect – the size 56 could have been custom designed for me. There was no need to understand or get used to anything – everything felt right and it looked right, too. Specialized is saying that a bike can be fast while still looking and riding like a bike, and it has the data to back it up. Normal might be the new normal.
For all the information and pricing visit Specialized’s website.
