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What bike did Peter Sagan ride during stage 4 of last year’s Tour de France? The race’s longest stage was 237 kilometers of flat and rolling terrain that trended upward in the final half. Sagan’s choice was a toss up between the lighter Specialized Tarmac and more aerodynamic Venge Vias. Sagan eventually went with the Venge, sprinting to third behind Marcel Kittel and Bryan Coquard. But the uncertainty underlined an underserved need: an all-around race bike with aerodynamic touches.
Based on our initial impressions of the new Tarmac SL6, we think Sagan will be happy with Specialized’s updated race bike.
“We found that every 10 kilometers, the decision of what bike to ride switched,” said Kevin Franks, Specialized brand manager, referring to stage 4 in 2016. “The course was too diverse and one bike wasn’t the clear answer. Over the past few years, the dynamics of racing has changed so the rider’s needs have evolved.”
The goal was to create something lighter, more aerodynamic, and more compliant. “They were asking us to design a unicorn,” Franks said.
The new Tarmac SL6 is the lightest frame Specialized has ever offered at 733 grams (size 56cm). It boasts new tube shapes and carbon layups as well as new compliance features. The new, well-rounded Tarmac ticks nearly all the boxes. Possible unicorn status will have to wait, however, until the disc-brake Tarmac arrives early next year.
Handling, aero, compliance
The Tarmac SL5 was already an exceptional race bike, in large part due to its nimble handling. It’s twitchy in a good way, easy to maneuver in a congested peloton. That said, steering remains stable and confident through high-speed corners.
Thankfully, not much changed in terms of geometry between the SL5 and new SL6. That means most of the updates come from the frame’s new tube shapes and carbon layups.
Specialized designed each SL6 frame size individually with specific stiffness goals based on the expected rider for each bike and model. Shorter riders are typically lighter and don’t need the same bike stiffness as those on 60cm frames. Specialized says this design process creates a uniform ride for all riders, regardless of frame size.
Of course, testing this theory is tricky since we only rode a 56cm test bike. However, smaller riders at the Specialized launch said they noticed similarly quick steering and a snappy ride without the harshness that can plague smaller bikes. It sounds as if this fine-tuning of each frame size may have paid off.
Three new fork designs also play into the uniform ride feel across the full Tarmac line. Each fork uses a 1.5-inch lower bearing but the steerer tube tapers differently depending on its stiffness requirements — the smallest fork has no taper for maximum deflection while the largest fork tapers the entire length of the head tube for more rigidity. The result is precise steering that had us pushing descents with confidence and sticking corners with ease.
When designing the Tarmac SL6, Specialized used structural analysis simulations that examined the entire bike as a whole rather than in pieces. This allowed engineers to pinpoint three areas they could improve the aerodynamics without affecting the bike’s ride qualities, without adding weight. The new, more aerodynamic Tarmac has an updated fork shape, dropped seat stays, and a D-shaped seatpost and seat tube.
The new fork design features truncated airfoil fork blades. A 1.5-inch lower bearing helps move the fork further up inside the bike’s head tube, reducing the height of the fork crown. This makes for a sleek transition from fork to head tube — again, aerodynamics.
The dropped stays and D-shaped seatpost improve the bike’s aerodynamics. They also make for a more compliant rear end. The seatpost’s carbon layup gets progressively stiffer as you move down the post. It flexes more near the top and helps isolate the rider from bumps and road chatter.
The Tarmac’s improved compliance is the most noticeable update to the race-worthy ride and it’s the biggest win for Specialized’s new design. While the previous model was fast and responsive, even Specialized admits that the SL5 was on the limit of harshness. The new SL6 pulls back into more comfortable territory. Don’t panic, though, the Tarmac is not an endurance or comfort bike. You still get plenty of road feel and will get rattled on rough roads. However, the bike minimizes bumps for a more manageable buzz rather than chatter.
Other features include a stiffer rear derailleur hanger for more precise shifting and direct-mount rim brakes for added tire clearance — up to 30mm tires. The added versatility that comes with bigger tires rounds out the Tarmac. It feels like what a race bike should feel like with quick steering and a responsive ride. It’s predictable without being boring. And it weighs merely 13.7 pounds. For riders not ready to make the switch to disc brakes, the Tarmac SL6 is the catch of the year. For the rest of us, a disc brake model that weighs a claimed 14.5 pounds will be available early 2018.
While the featherweight S-Works Ultralight model comes in at a harsh $10,500 with Dura-Ace Di2, more modest models are also available for less. The Shimano Ultegra Di2 Tarmac Pro will run $6,500 while the Expert model with an Ultegra mechanical drivetrain will cost $4,000.