New Tarmac SL7: lightweight AND super aero, says Specialized

Specialized has launched a new version of its Tarmac, the SL7, which it claims is almost as aerodynamically efficient as its current Venge aero road bike while being at the UCI's minimum weight limit for racing.

Here's our First Ride Review of the Specialized S-Works Tarmac SL7 Dura-Ace Di2

Specialized believes that there is no longer a need to have both an aero road bike and a lightweight road bike in its range because the Tarmac SL7 is both.

"This is one bike to rule them all, putting an end to the idea of a climbing bike and an aero bike," says Cam Piper, the product manager behind the Specialized Tarmac SL7.

"That idea is simply old fashioned. We have the technical ability to create a bike that's as aero as rules allow and as light as rules allow in a single package. Anything else would be forcing riders to make a compromise on race day, and we just weren't okay with that anymore. Asking riders to pick between two different bikes is so 2019! 

"We worked to create the best possible package at the UCI's [6.8kg minimum] weight limit. Anything lighter is illegal [in racing]. If you want to go lighter you'll have to hand in your racing licence!"

Specialized doesn't do understatement.

Over the past few years – quite a lot of years, actually – major bike brands have had an aero race bike and a lightweight race bike in their range. With Specialized it's the Venge and the Tarmac, with Trek it's the Madone and the Emonda, with Giant it's the Propel and the TCR, and so on.

If you want the best aerodynamics you need deep tubes and that means more material and more weight. Them's the rules, so which do you want, the aero one or the lightweight one? Of course, brands have lightened their aero bikes, and aero-ed their light bikes, but you've always had to decide where your priorities lie.

Specialized reckons that it has changed all that with the Tarmac SL7. 

"Aero, stiff, light – pick three," says Specialized (presumably a reference to Keith Bontrager's "Strong, light, cheap: pick two" line from back in the day).

In other words, Specialized is saying that you can have the lot here, putting an end to the umming and ahing. 

"The Tarmac SL7 puts an end to compromise, and racing will never be the same," says Specialized. "Climb on the lightest bike the rules allow, sprint on the fastest – all with legendary Tarmac handling. It’s like we combined Julian Alaphilippe’s attacking, climbing style, and Peter Sagan’s aggressive power in a single rider with no weaknesses. The only choice you need to make is when to attack."

Okay, that's enough hyperbole, what has Specialized actually produced here?

Aerodynamics

Specialized says that the quest for aerodynamic efficiency has been the driving force in the development of the Tarmac SL7.

"By targeting the tubes that truly impact the aero performance of the frame, whether it's the seat tube, the seatstays, the head tube or the fork blades, all with shapes from our FreeFoil Shape Library [the collection of airfoil shapes that Specialized has developed], and then mating them with the fastest components that we have at our disposal and integrating the cabling, we created a package that is 45secs faster over 40km than the Tarmac SL6," says Cam Piper.

The "fastest components" referred to here are the SL7's Aerofly II handlebar – taken from the Venge – a new Tarmac stem, and Roval Rapide wheels (details below).

"We started with our doctrine of a new shape for speed," says Cam Piper. "It takes the idea that are aero advantage does not need to come at the expense of weight or ride quality. A Tarmac SL7 is the ultimate expression of what that is. 

"We endlessly refine the shapes of our FreeFoil Shape library and put them on the frame where they matter the most... and then focused on the weight and the ride quality for some of the other tubes to create the most balanced bike."

Specialized says that it went to its in-house wind tunnel – the Win Tunnel – to validate its designs. It claims that the new Tarmac SL7 is right up there with the Venge in terms of aerodynamics, and considerably lighter – speaking of which...

Weight

Weight was considered alongside aerodynamics throughout the development process, according to Specialized, the aim being to produce a bike that hit the UCI's 6.8kg minimum weight limit for racing.

"Creating the Tarmac SL7 was an exercise in patience," says Cam Piper. " It took years of dedication from our engineers, starting even before the release of the SL6, to push every feature to the limit.

"We were able to limit the frame surface area and strategically reduce the wall thickness across the frame on our painted FACT 12r layup in order to create a frame that's 800g, without sacrificing aerodynamics, stiffness or ride quality."

It's a long and detailed process.

"The first samples out of the mould were extremely aggressive and basically experimental: the bare minimum material required to make a frame – we knew they’d fail lab tests, we knew they’d miss stiffness targets, but they were almost 20% under the weight target," says Specialized.

"From there we strategically over-wrapped these frames with carbon in our composites shop to hit stiffness targets. In the lab we tested many different overlaps to improve stiffness, but we went even further analysing them in FEA [finite element analysis software] which allows you to infinitely vary ply size, shape, angle, location, material, and stack.

"We're talking hundreds of layups, with thousands of ply iterations, confirming the final design had the best stiffness-to-weight ratio. Taking this approach means the final product is lightweight, aero and capable: no compromises."

The FACT (Functional Advanced Composite Technology) 12r carbon fibre used for the top-level S-Works Tarmac SL7 was also used for the S-Works Tarmac SL6. Specialized's 800g weight claim (see above) relates to a painted frame in the lightest finish.

The complete S-Works Tarmac SL7 Di2 model is a claimed 6.7kg (14lb 12oz) in the carbon/colour run silver green finish.

The Tarmac SL7 Pro and Expert models (see below) are made from Specialized's FACT 10r carbon and have a claimed frame weight of 920g – 15% heavier than the S-Works frame. Specialized says that the aero performance, the stiffness and the ride quality are all the same as those of the FACT 12r SL7.

A complete Tarmac SL7 Pro Ultegra Di2 has a claimed weight of 7.3kg (16lb 15oz).

Geometry

The new Tarmac SL7 "features identical fit and handling geometry" to the Tarmac SL6 and Venge, according to Specialized, although the stack and reach measurements are slightly different.

How does that work? Stack and reach are measured between the centre of the bottom bracket and the top of the head tube (they're the vertical and horizontal distances, respectively), but the SL7 has a top tube cutout and a taller than normal headset cover. Specialized has accounted for this. 

"Once you compensate for the height of the necessary headset cover on each bike, your stem’s lowest position ends up at the same point in space on any of them," says Specialized.

Brakes and shifting

The Specialized Tarmac SL7 is available only with hydraulic disc brakes (Shimano flat mount standard); there is no rim brake version, not even as a frameset only. 

Both the 12r and 10r SL7 versions are compatible with electronic and mechanical shift systems.

You get three headset covers with every Tarmac SL7. These have different routing holes allowing for different builds:

• Integrated Tarmac Stem with electronic shifting
• Integrated Tarmac Stem with mechanical shifting
• Universal cap for a standard stem, plus round spacers with either electronic or mechanical shifting

The Tarmac SL7's front derailleur hanger is removable, allowing you to tidy things up if you want to run a 1x (single chainring) setup. A cover for the cable routing hole and the two bolt holes is included with the bike.

The new S-Works Tarmac Carbon Seatpost provides an integrated location for a Shimano Di2 Junction Box. It provides easy access to the charging port and function button. 

If you use a wireless SRAM drivetrain, a cover for the seatpost port is included with all Tarmac SL7s.

Handlebar and stem

The handlebar and stem are essential to the Tarmac SL7's overall aerodynamic performance, according to Specialized, the higher end models (from the Tarmac Pro upwards) featuring the S-Works Aerofly II handlebar first introduced on the Venge. The bar comes in 380mm, 400mm, 420mm and 440mm widths.

The new Tarmac integrated stem used on all the SL7 models is said to save 45g over the previous version. It is available in 11 sizes. There are two angles: 6°, which is specced on SL7 models, and 12°, which is available aftermarket. 

"As fast and as light as the new frame is, we couldn't have achieved all our goals without the fastest components in the world," says Cam Piper. "The Aerofly II bar is paired with the new S-Work Tarmac stem... to not only reduce weight but to improve the overall integration of the cabling, allowing riders to achieve whatever fit they need, or travel without having to re-cable their bike."

Brake hoses and gear cables are now fully hidden both to improve the appearance and reduce drag. 

Wheels and tyres

The top-level Tarmac SL7s are fitted with new Roval Rapide CLX wheels – 51mm deep with a 35mm external width at the front, 60mm deep with a 30mm external width at the rear. Roval calls these "the fastest all-around road wheels in the world” – but then, it would.

Roval says that the extra rim width helps to boost stability, while the claimed weights are 649g (front) and 751g (rear).

Find out all about the Roval Rapide CLX wheels here

Interestingly, these wheels aren't tubeless ready, even though Roval says that it is committed to tubeless technology. When the design team looked at what it wanted to achieve in terms of aerodynamics, weight, stability and ride quality, going tubeless wasn't possible. The brand says that it wanted the highest performing package, and that dictated an inner tube-type wheel.

Roval Rapide CL wheels feature on the Tarmac Pros, with other wheels from Roval and DT Swiss used further down the range.

Complete Tarmac SL7s are shipped with 700 x 26mm tyres, but Specialized says there's enough clearance to fit 32mm-wide tyres on 21mm rims with 4mm of clearance all around. 

The wheels are held in place by 12mm thru axles.

Ride

A Specialized Tarmac SL7 review bike was delivered to road.cc a couple of weeks ago, and Stu has had the chance to write a First Ride, so make sure you check that out. A full review will follow in the next few weeks.

In the meantime, let's look at what Specialized has to say about the ride.

"We're taking a lot of what was great about the Tarmac SL6 when it comes to compliance and the ride balance to ensure that the overall feel is at the perfect spot for the best possible handling," says Cam Piper.

"It's not always about increasing stiffness, it's about properly using the stiffness values where it matters the most for the rider. From the SL6 to the new SL7, there is a difference in stiffness across the frame [the SL7 being stiffer overall] but it's comparable to where we are with our Venge platform. We have worked with our teams [Specialized is the bike supplier to Deceuninck-Quick-Step and Bora-Hansgrohe pro teams] to make sure that the stiffness is optimal for racing, based on their feedback.

"The tube shapes of the SL7 are a bit deeper [than those of the SL6] so the compliance is not going to be as great at the rear, but it is better balanced. The front end of the SL6 might have been a little too stiff or harsh and the rear was a bit more compliant; we've really worked to make sure that the ride feel is more balanced on the SL7."

Models

There are six Specialized Tarmac SL7 complete bikes:

S-Works Tarmac SL7 Red eTap AXS £10,500
Frame FACT 12r carbon
Groupset SRAM Red eTap AXS (inc Quarq power meter)
Wheels Roval Rapide CLX

S-Works Tarmac SL7 Dura-Ace Di2 £10,500
Frame FACT 12r carbon
Groupset Shimano Dura-Ace Di2 (inc Specialized power meter)
Wheels Roval Rapide CLX

Tarmac SL7 Pro SRAM Force eTap AXS 1x £6,500
Frame FACT 10r carbon
Groupset SRAM Force eTap AXS 1x
Wheels Roval Rapide CL

Tarmac SL7 Pro Ultegra Di2 £6,250
Frame FACT 10r carbon
Groupset Shimano Ultegra Di2
Wheels Roval Rapide CL

Tarmac SL7 Expert Ultegra Di2 £4,750
Frame FACT 10r carbon
Groupset Shimano Ultegra Di2
Wheels DT R470 Disc

Tarmac SL7 Expert £4,750
Frame FACT 10r carbon
Groupset Shimano Ultegra
Wheels Roval C 38 Disc

The Tarmac SL7 FACT 12r frameset is £3,750.

All of these models are designed for both men and women.

"As there is likely more difference between two male cyclists than there are between a male and a female, gender alone doesn't provide nearly enough data to specialise," says Cam Piper.

"Separating the SL7 into two separate platforms would be arbitrary and outdated so we used all our resources to develop the perfect bike for any rider, regardless of their gender.

All Tarmac SL7 models have a 68mm threaded bottom bracket.

Fed up of pressfit bottom brackets? Find out if something better is on the way

The Tarmac SL6 lives on

Although the SL7 takes over the higher levels of the Tarmac range, the FACT 9r carbon version of the SL6 is still available.

Two Tarmac SL6 complete bikes are available in the UK:

Tarmac SL6 Comp £3,200 (above)
Frame FACT 9r carbon
Groupset Shimano Ultegra (mechanical)
Wheels DT R470 Disc

Tarmac SL6 Sport £2,500
Frame FACT 9r carbon
Groupset Shimano 105
Wheels DT R470 Disc

Where does this leave the Specialized Venge?

All of these big claims for the Tarmac SL7 leave Specialized's Venge aero road bike looking surplus to requirements.

"For this upcoming model year, the Tarmac SL7 will be the platform of choice for race performance," says Cam Piper. "We will no longer have complete models in the line for the Venge, although it will still exist as a frameset. 

"It doesn't now feel right to sell riders a bike that's offering a compromise."

Read our review of the Specialized S-Works Venge Di2

Go to www.specialized.com for more info.