Just in time for the Tour de France and Peter Sagan’s quest for continued Green Jersey domination, Specialized has unveiled the latest version of its pure bred road race bike, the 2018 Tarmac SL6. In what is the sixth iteration of this roundly praised racer, Specialized said its primary development aim was to create a platform that was not just good at one thing (climbing, aero, sprinting, compliance), but instead delivered top end performance across all desired characteristics.
“Road racing has changed,” said Specialized’s Kevin Franks. “It used to be very clear what a day would hold, a sprint or climbing. But now there is more diversity. Our goal was to create something appropriate for those varied days. That meant being lighter and faster, but also with improved handling.”
And Specialized says they did just that. The new Tarmac, which will only be available in rim brake versions initially with a disc-equipped model coming in early 2018, delivers a claimed frame weight of just 733 grams in a size 56cm, which is 200 grams less than its predecessor. Much of this weight savings comes from a redesigned bottom bracket area, which is much less substantial than its predecessor, yielding a 30-gram weight saving and a more efficient way of dealing with cable routing. They also obsessed over the placement and angle of all cable/wire ports, aiming to use less overall material.
As demonstration of this weight savings, the top (top) of the line Specialized S-Works Ultralight Tarmac, which uses EE brakes, low profile Roval CLX 32 carbon wheels, and a special paint that only adds 10 grams, has a claimed weight of 13.7 pounds. Of course all that weight savings comes with a premium, in this case a $10,500 price tag. Fortunately there are other less eye-watering options, including a S-Works Dura-Ace Di2 build for $10,000, Ultegra Di2 for $6500, and an expert level spec for $4000.
The new Tarmac is also said to be more aero that its predecessor, a feat achieved in part by dropping the seatstays, using a D-shaped seatpost, refining fork leg shape, and implementing less fork crown height, which also increased tire clearance to 30mm. The bike also uses direct mount brakes, and instead of a brake bridge use of a titanium plate has been implemented.
Choosing the Right Fork
In order to keep the Tarmac’s ride quality, three different sized fork blades are being used, one each for frames 44cm-52cm, 54-56, and 58-64. All feature a truncated airfoil shape and vary depending on stiffness requirements. This results in forks that are visually different in size, but work to minimize the frontal profile as much as possible. Specialized is also using a 1.5-inch lower bearing, allowing them to move the fork further up inside of the head tube, and reducing the height of the crown by allowing carbon to move from the fork’s crown through the steerer tube without creating harsh angles that cause stress on the material. This reduction in height reduces frontal area and creates a smoother, faster shape.
Additionally, each steerer tube tapers depending of stiffness requirements, so smaller forks have no taper to allow for more deflection when ridden by small riders, while larger frames feature forks that use a taper running the entire height of the head tube. The new frame layup also features 500 pieces, as opposed to the 350 in the previous Tarmac, all but eliminating the overlap between plies.
As for the dropped seatstays, the rationale is that it both brought the Tarmac in line with other bikes in its family (Venge, Shiv TT, Roubaix, etc.), and more importantly by lowering the attachment of the seatstays on the seat tube, they say there were able to hide the tube from the wind with little to no cost to stiffness.
Specialized claims that in testing of a 45km distance, the new Tarmac was 45 seconds faster than the Trek Emonda or Cannondale SuperSix EVO, both similar bikes in weight and intended purpose. That’s about the same difference as using a set of box section rims versus seep section aero rims. Understand, though, that these are claims from Specialized, not independently verified stats.
D is for Speed
The D-shaped seatpost, meanwhile, was a nod to both aero efficiency and comfort. The initial goal was to match deflection numbers of the previous round-post-equipped Tarmac, while also gaining in the wind tunnel. To do this, they opted for a truncated airfoil seatpost shape that performs better aerodynamically. They then adjusted layup to progressively add stiffness as it moved down the length of the seatpost. This, claims Specialized, means that engineered flex is added near the seatpost head to provide the most possible comfort, while the shape provides a tangible aerodynamic advantage in the high-speed airflow zone between rider’s legs.
Finally, handling was examined, which Specialized says was not just a process of changing tube sizes and layups across sizes, but also finding the right handling for all sizes and then individually engineering to be able to hit those targets. That means using a huge amount of carbon fiber plies to introduce a different feel into frame.
Other enhancements of the new bike include a new rear derailleur hanger that’s said to be stiffer for more precise shifting. Sizing comes in a broad range, with the new Tarmac utilizing a shared platform for men and women from 44cm to 61cm. This concept came via the company’s partnership with the Retül fit system, which meant access to over 40,000 digital fit points. Through this, Specialized changed its approach to product development. By utilizing fit graphs, they looked at how men and women are fitting on their bikes and then ensured that the geometries served the riders and the experience they’re looking for.
The end result was the development of overlapping geometries, meaning there are now Tarmacs for women and Tarmacs for men. There’s no longer just a men’s Tarmac, but a Tarmac family that serves men and women, where the experience is built around the combination of a responsive front end and short wheelbase that’s aim is to deliver rapid response and efficient power transfer. Here are the complete men’s and women’s geo charts.
Rider First Approach
This rider-first approach was first introduced in 2014 on the Tarmac, with the goal that each individual frame size was developed around stiffness targets that were specific to the rider of each bike. The idea being you get a uniform experience for all riders, regardless of frame size.
For the new Tarmac, Specialized updated that process to take more than just handling into consideration. Using structural analysis simulation that provides a ply-by-ply analysis of each frame’s layup schedule, plus wind tunnel testing and CFD experimentation, they were able to measure each performance metric against each other, ensuring that a change made to increase one performance target didn’t erode another.
“By co-optimizing around all of our different performance targets, we were able to achieve an overall system performance that would be unobtainable without looking at them simultaneously,” explained R&D director Chris Yu. “Think about the target performance that we wanted to achieve like the peak on a pyramid. There are different competing sides, whether it’s weight, handling characteristics, or aerodynamics. Developing every feature on the new Tarmac was an exercise in finding that peak. There are tube shapes on the bike that, with a sub-millimeter change, would cause the system performance to fall off that peak and result
in a bike that is several watts less aero, several grams heavier, or would compromise handling performance. We applied this approach to every design element and engineering decision on the Tarmac.”
First Ride Impressions
During a 3-day media event at Mountain Creek Resort in Vernon, New Jersey, RoadBikeReview got the chance to log two rides on a Dura-Ace Di2 equipped 2018 Tarmac. Roads on the two routes were a mix of flat and rolling, with a few solid 10-20-minute climbs mixed in. Pavement condition was mostly smooth, but there were occasional choppy bits and even a little dirt.
While this is obviously a tiny test sample, initial impressions were highly favorably. Acceleration was quick and snappy, with not a hint of flex even in our size 61cm test rig. And just as Tarmacs of the past, the bike handled like a well-tuned sports car, carving in and out of turns with confidence and control. The Tarmac tracks exceptionally well, easily holding tight lines, and encouraging its rider to lean it over further and push it farther and faster.
I was also impressed with overall ride feel and comfort. While we didn’t drag it over the cobbles of Paris-Roubaix, the bike never felt overly harsh, even when zipping across bumpy sections of Tarmac. Our second test ride was an aggressive 75-miler, and while physically smoked at the end, I didn’t feel beat up like some race bikes can leave you. We’ll need to log some more test time before passing final judgment, but if those first few rides are any indication, the legacy of the Tarmac will live on.
For more information please visit www.specialized.com and check out the expansive photo gallery below.