It was bound to happen. Aero bikes and all-around bikes have finally become one. With the launch of the Tarmac SL7, Specialized has made clear its intentions to redefine the superbike as the machine that can do both: combine the weight and ride characteristics of an all-rounder with the aero advantages of the aero bike.
As such, Specialized will phase out its dedicated aero bike, the Venge, which will only be available in certain markets as a frameset going forward. That’s how confident Specialized is that the Tarmac SL7 is the future of race bikes. That’s a safe bet, too.
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Tarmac SL7 weight
Specialized was already headed in the direction of combining the two categories with the launch of the Tarmac SL6 in 2017, which essentially looked like a slimmed-down Venge. Over the course of those three years of racing, it became clear that the morphing between aero and all-around was likely to continue, but the idea of having a selection of bikes to choose from still seemed like the optimal way to handle the widely-varying terrain of grand tours and other stage races. “If you’re picking a bike to climb on, or a bike to sprint on, that’s kind of old thinking now,” says Cameron Piper, road product manager at Specialized. “We believe the luxury of choosing between two different bikes is not a luxury anymore.”
In other words, riders crave the one tool that can do it all, and Specialized says it has created just that with the Tarmac SL7. Of course, that’s what every brand says. What exactly has Specialized done to back up its claims?
For starters — and perhaps unsurprisingly — Specialized has made the Tarmac SL7 lighter using its carbon layup the called Fact 12R Carbon. According to Specialized, a size 56cm Tarmac SL7 weighs 6.7kg out of the box, with an 800g frame. In other words, it’s exactly the UCI weight limit out of the box.
The carbon layup allows Specialized to create a lighter package without sacrificing stiffness. Again, this is a pretty common claim, and brands generally won’t reveal the secret sauce within its specific carbon products. But Specialized reps did say that the 12R carbon layup was created to minimize weight, both in terms of the actual carbon fibers and the resin used to bond it. That allowed engineers to eliminate materials where it wasn’t necessary, and reinforce areas that did need the extra material.
All told, A Tarmac SL7 built with exactly the same wheels and components as a Venge will be over 350g lighter.
The integrated handlebar and stem also weigh in lighter than the previous version. The stem alone shaves 45 grams, but more notably, you can still dial in your fit without having to re-cable your bike completely. That’s a very good way to do integration, as more brands come to the conclusion that there are aero advantages in the cockpit. That often comes at the cost of adjustability and convenience; not so here.
The Tarmac SL7, like many of the most recent race bikes that have come to market, has abandoned press-fit systems in favor of threads. In this case, the Tarmac gets a BSA threaded bottom bracket, which is notable as more and more bikes are coming stock with T47 bottom brackets. I asked why Specialized chose BSA over T47, and it largely comes down to weight savings. The BSA standard also accommodates more cranks and axles currently on the market.
Tarmac SL7 aerodynamics
One look at the bike also indicates it’s got plenty of aerodynamic benefits built-in. When the Tarmac SL6 launched in 2017, the bike’s silhouette made waves because it looked like a skinny Venge. That silhouette remains, but the Venge does not. As far as Specialized is concerned, that’s a testament to how well the Tarmac has performed for pro riders — and to the notion that the Venge’s deeper tube shapes don’t offer much beyond what the Tarmac SL7 does.
To keep the Tarmac SL7 aerodynamically competitive, Specialized went through nearly-endless CFD iterations to figure out which tubes needed to be aerodynamically shaped, and which tubes were less relevant to aero gains. Engineers found that the top tube and down tube were not as vital to aerodynamics, so it was possible to optimize these particular tubes for other things like stiffness and compliance.
Not surprisingly, the front of the bike matters quite a lot when it comes to aerodynamics, so the Tarmac SL7 has an aerodynamically optimized head tube, and it comes stock with Specialized’s integrated cockpit.
The Roval Rapide CLX wheels factor into aerodynamics significantly, and they’re attention-grabbing for sure. Take a look at the outer rim width and you’ll find yourself wondering if you lean the bike far enough over, whether the rim might make contact with the pavement before the tire. (You won’t, by the way.)
The wheels are wide, of course, to optimize the shape of the tire, and Specialized says you can fit up to a 32mm tire in the Tarmac SL7. At this point, we know wider is better when it comes to tires, but Specialized says a larger tire can also create significant drag effects in crosswinds. The wider rim ensures the best aero performance, according to Specialized, while still allowing for the advantages of a wider tire.
How exactly? Representatives didn’t give too much in the way of specifics, but when I asked whether the wide rim, which appears to sit outboard from the walls of the tire, can create something like a boundary layer trip — which would, in theory, help air adhere longer to the surface of the rim, essentially turning the flow from laminar to turbulent. That in essence reduces the drag-inducing eddy of air behind the rim had the air flow separated earlier. That seemed to be an affirmative part of the equation.
The silhouette of the Tarmac SL7 looks a lot like the SL6, and the dropped seatstays certainly draw the two together aesthetically. While Trek has largely avoided the dropped seat stay design with its new Emonda launched earlier this year, Specialized says its dropped seatstay design offers both aerodynamic advantages and compliance allowances. The lower junction of the seat stays with the seat tube allows strategic flex in the top tube, seat post, and seat tube.
The seatpost also features an aerodynamic airfoil shape, again to improve aerodynamics where it matters. For Shimano Di2 riders, you’ll find the junction box integrated into the back of the seatpost just below the saddle clamp. SRAM eTap-equipped bikes include a blank that goes in the spot where the junction box would otherwise live.
What does all that aerodynamic optimization lead up to? In a flat, solo TT effort, the aero difference is about 2.5 watts at 40kph, or 9 seconds over 40km. To put this in perspective, the Tarmac SL7 is as aero as the Venge ViAS, yet over 1kg lighter.
A few more details
Not surprisingly, the Tarmac SL7 will be available in a disc-brake option only.
The halo S-Works Tarmac SL7 Dura-Ace Di2 and Red eTap AXS models you’ll see under WorldTour riders starting at Strade Bianche in August sell for $12,000. The Shimano version comes equipped with a Specialized Power Pod power meter. Specialized worked with 4iiii to develop this dual-sided power meter that we have previously seen on the company’s carbon Power cranks. It’s important to note that carbon Power cranks are no longer compatible with the Tarmac SL7 due to the switch to the BSA bottom bracket.
There are several less expensive models as well, including the mid-level Tarmac Pro at $7,000. It comes dressed in a SRAM Force eTap AXS 1x setup, and features a removable front derailleur hanger should you want to make the switch to 2x. A Quarq power meter comes stock, too. The frame doesn’t feature the Fact 12R carbon layup that the S-Works version has; instead, the Tarmac Pro gets a Fact 10R frameset, which is 120 grams heavier. It is, however, still 40 grams lighter than the S-Works Venge frame.
Specialized says it has customized the ride quality across all sizes. which range from 44cm to 61cm. That essentially means the geometry and layup may differ from size to size in order to obtain the best handling and ride quality for each individual size. There is no women’s-specific version of the bike, as Specialized says it has devoted all its resources to one platform that’s best for any rider, regardless of gender.
The new Tarmac SL7 is available in shops today. Editorial director Ben Delaney has been testing out the new Tarmac SL7 and has a review ready and waiting for you here.