Pro bike: Tejay Van Garderen's HTC-Highroad Specialized Project Black S-Works McLaren Development Bike Tour de France

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Specialized is on a bit of a tear this year, scoring several key wins on brand new bikes nearly right after they were introduced to the public. The latest chapter is the company's new-bike saga is its S-Works Tarmac SL4 and one of the HTC-Highroad riders with the potential to do something big this time around is young American hotshot Tejay Van Garderen.

The Tarmac SL4 continues with the light-and-stiff theme of the SL3 predecessor but with the usual tweaks expected of a newer version. The lower steerer tube diameter has been slimmed down to 1 3/8in to save weight while the down tube and top tube have grown in width to boost torsional stiffness; the seat stays boast a flattened upper section for a more comfortable ride; chain stays have been puffed up to bolster pedaling efficiency; and the rear dropouts have been upgraded to hollow carbon fiber.

In total, Specialized claims a 19 percent boost in stiffness and a 50g weight savings relative to the SL3.

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Van Garderen's bike isn't an off-the-shelf SL4, though. Technically speaking, it's a "Specialized Project Black S-Works McLaren" development bike according to company PR man Nic Sims - otherwise known as a test mule built in conjunction with partner McLaren for a possible higher-end version of the standard SL4.

Naturally, Sims couldn't say exactly what differences exist between a standard SL4 and Van Garderen's bike but based on the companies' previous collaboration on the Venge model, weight and stiffness are obvious targets for improvement. Sims did tell us, however, that Specialized will make a final decision on whether or not to truly bring an "S-Works McLaren Tarmac SL4" to market based on what sort of performance gains can be had and how much they would cost. Team test riders such as Van Garderen will be providing feedback to Specialized during the Tour and then we'll know after things wrap up in Paris.

One obvious change, however, is the routing. Consumer bikes use convertible internal routing that will work with either mechanical or electronic systems but Van Garderen's machine is notably Di2-only - the entry ports on the down tube are shaved clean and the result is an impressively tidy appearance (that in all honesty, is a welcome departure from early season Di2-equipped team bikes that were occasionally a little clumsy in comparison).

The main wiring harness now enters the top tube just ahead of the brake housing, there's a port on the front of the seat tube for the front derailleur line, and the rear derailleur wire runs all the way through the driveside chain stay. Oh, but where's the battery? It isn't visible through the unused bottom bracket cable guide port, there is no mounting bracket hardware on the exterior surface of the frame, and it doesn't rattle around when the bike is shaken. In addition, there's also no obvious method by which the battery is charged.

HTC TechDev manager Lars Teutenberg would only say on the record that the battery is safely tucked away inside the frame - and that's as far as he would go. He was much more forthcoming off the record, though, and we're unfortunately restricted to saying that the system is remarkably clever - to the point where once word gets out, other Di2 users will undoubtedly have a "why didn't I think of that?" moment.

Shimano also rounds out most of the rest of Van Garderen's build, including the 35mm-deep carbon tubular wheels, carbon-bodied SPD-SL pedals, and previous-generation PRO stem and anatomic-bend bar. Tires are from Continental, fi'zi:k provides its top-end Aliante saddle with Twin Flex carbon shell and braided carbon rails, and Elite supplies its latest Sior carbon fiber and titanium bottle cages. That Aliante saddle is mounted atop an unmarked 3T Dorico seatpost instead of the team-issue PRO one, however, as PRO as yet still doesn't produce one with Van Garderen's requisite zero-offset head.

Final touches are filled in with SRM power meters and computer heads (though Van Garderen's bike went with a standard crank just prior to the start of the Tour), a custom etched K-Edge chain catcher from AceCo, and CeramicSpeed bearings and lower derailleur pulleys.

Total weight as pictured is 6.84kg (15.08lb).

Full Specifications

Bike specifications

Frame: Specialized McLaren Tarmac SL4, 56cm
Fork: Specialized McLaren Tarmac SL4
Headset: Cane Creek integrated, 1 1/8-to-1 3/8in
Stem: PRO Vibe, 140mm x -6°
Handlebars: PRO Vibe Anatomic, 42cm (c-c)
Tape/grips: PRO cork
Front brake: Shimano Dura-Ace BR-7900 w/ carbon-specific pads
Rear brake: Shimano Dura-Ace BR-7900 w/ carbon-specific pads
Brake levers: Shimano Dura-Ace Di2 STI Dual Control ST-7970
Front derailleur: Shimano Dura-Ace Di2 FD-7970
Rear derailleur: Shimano Dura-Ace Di2 RD-7970
Shift levers: Shimano Dura-Ace Di2 STI Dual Control ST-7970
Cassette: Shimano Dura-Ace CS-7900, 12-27T
Chain: Shimano Dura-Ace CN-7900
Crankset: Shimano Dura-Ace FC-7900, 175mm, 53/39T
Bottom bracket: CeramicSpeed
Pedals: Shimano Dura-Ace SPD-SL PD-7900
Wheelset: Shimano Dura-Ace WH-7900-C35-TU
Front tire: Continental Competition Pro Limited Allround tubular, 22mm
Rear tire: Continental Competition Pro Limited Allround tubular, 22mm
Saddle: fi'zi:k Aliante Carbon Twin Flex
Seat post: 3T Dorico (unmarked)
Bottle cages: Elite Sior (2)
Computer: SRM Power Control 7
Other accessories: Custom internal battery configuration

Critical measurements

Rider's height: 1.85m (6' 1")
Rider's weight: 67kg (148lb)
Saddle height, from BB (c-t): 817mm
Saddle setback: 75mm
Seat tube length, c-t: 548mm
Seat tube length, c-c: 499mm
Tip of saddle nose to C of bars (next to stem): 604mm
Saddle-to-bar drop (vertical): 135mm
Head tube length: 160mm
Top tube length: 565mm
Total bicycle weight: 6.84kg (15.08lb)