Overview

NOTHING IS LIGHTER AND STIFFER

The goal of the Tarmac SL2 was simple. Make the best complete race bike in the world. We knew we had to satisfy Tom Boonen, Paolo Bettini and Davide Rebellin. To do this, we set aggressive performance targets. Then we conducted extensive tests throughout the development process to ensure that we hit the mark. Our riders demanded that we develop the highest torsional, lateral and rear-end stiffness to ensure the most precise handling, ultimate pedaling efficiency and the fastest acceleration. When it came to weight, we knew that it had to be lighter than anything that was as stiff.

Once our goals were established, all preconceived notions and standards were eliminated. Our design, material choices, manufacturing methods and systems integration were applied without constraint. From the asymmetrical seat tube, to chainstays that feature a thirty 30% larger cross section, to size- specific seatstays, down tubes and top tubes, to pioneering the radical new FACT IS manufacturing method, our team of engineers, designers and material experts pursued every conceivable method to enhance the performance of the Tarmac SL2. The result is the best complete road bike in the world: Nothing is lighter and stiffer.

Testing

THIS IS NOT ONLY A TEST

At Specialized, we test for two reasons: to make our bikes perform as well as possible and to make them reliable for a lifetime of hard riding. To achieve these two goals, we have developed the most accomplished crew of test riders (including Tom Boonen, Paolo Bettini and Davide Rebellin) and the most advanced test lab in the industry, run by the best engineers.

Many different types of tests are conducted to provide the most complete understanding of what Specialized bikes and components will encounter and endure when pushed to extremes, including:

  1. Performance / Lab.
    Once the performance goals of the Tarmac SL2 were set, we had a quantifiable target. An initial frame design was crafted, new molds created and a first round of prototypes built. Lab tests were performed measuring ultimate strength, fatigue strength, stiffness and compliance in every key area and aspect of the frame. The goal was to deliver maximum performance in terms of efficiency, ride quality and light weight.
  2. Performance / Field.
    Extensive field testing of prototypes is performed by the world’s best professional riders and the fanatical staff at Specialized. Together, we log untold of hours of real world riding in grueling conditions. Quantitative data from the lab is compared with the qualitative test rider feedback, and the frame design is revised. We repeated this process over a dozen times to achieve the performance goal set for the Tarmac SL2: Nothing is lighter and stiffer.
  3. Safety.
    Safety and reliability are paramount concerns. While most frames pass industry standard safety tests, Specialized has established its own parameters that exceed international standards and extra tests that international bodies do not require. Any cyclist can ride with complete confidence that the Tarmac SL2 will deliver countless kilometers of riding and racing.

FACT

Functional Advanced Composite Technology

FACT (Functional Advanced Composite Technology) defines our carbon development process, one that takes an integrated approach to engineering, material application, manufacturing methodology and testing. This integrated approach enables us to achieve the performance goal for the Tarmac SL2: Nothing is lighter and stiffer.

FACT IS "fact is" Chassis. The Tarmac SL2 FACT IS (Integrated Structure) frame integrates several different manufacturing methods to create an optimized structure that is incredibly light, unbeatably stiff and super-strong. Drawing on years of experience with composites, Specialized engineers combined monocoque and Az1 sequential curing fabrication methods to achieve breakthrough performance.

Material study: pitch carbon fibers. Every Tarmac SL2 frame is a combination of different materials with varying strength and stiffness properties, determined by the requirements of any given area of the frame. The SL2 spares no expense and employs the most advanced technology in material application to achieve its performance goals. Pitch fibers--with the highest tensile modulus values in the bike industry--are placed in strategic locations to dramatically boost overall frame stiffness. Once utterly impractical to utilize in frame construction, we developed a unique process that enables us to take advantage of the exceptionally high stiffness of this material.

Testing: In the lab and in the field. The racers who ride our bikes compete at the highest level and are an integral part of our R&D team. All of the feedback they provide not only helps them win races, it help us provide a performance benefit to every rider. The SL2 was developed with intense involvement from former world champion and 2008 Paris-Roubaix winner Tom Boonen, who challenged us to develop a race bike with the highest lateral and torsional stiffness in the world. To complement the input that all kinds of riders give us, we’ve developed one of the world's foremost testing facilities in our Morgan Hill, California headquarters. Our staff of engineers and technicians monitor countless hours of safety and performance-based testing to ensure the SL2 meets our lofty weight and stiffness targets.

Rear End

BUILT FOR BOONEN

Frequent and precise feedback from Tour de France Green Jersey winner Tom Boonen compelled us to completely rethink the design of the rear end of a bicycle frame. Not only is his input directly reflected in the shape and materials used in the chainstays and seatstays of the SL2, but Boonen’s incredible power output and ability to clearly communicate his keen insight helped us develop new testing methods to continuously improve our designs.

The seatstays are triangulated at the seat tube, increasing in width as they approach the brake bridge, then continuing outward toward the carbon dropouts. This wide, triangulated stance required a specifically designed and tooled seatstay for each of the six Tarmac SL2 sizes and ensures maximum lateral rear end stiffness.

Full carbon dropouts with a replaceable alloy derailleur hanger help make the rear end as beautiful as it is light, while unidirectional fibers and intelligent layup help the carbon dropout transfer load between the chainstay and seatstay.

Was it worth the added time and expense? Tom says it’s the best race bike he’s ever ridden.

BB Cluster

THE STIFFEST BY DESIGN

The midsection of the Tarmac SL2 is engineered as a system to maximize stiffness. In fact, the SL2 has the highest BB stiffness of any frame we have tested. Greater stiffness at the bottom bracket allows more efficient and direct power transfer from the rider to the rear wheel. Improved acceleration and better use of your energy are the result—extremely valuable when sprinting for the finish or hammering out a long climb.

The down tube, BB shell and seat tube employ a carbon-centric design. By eliminating sharp edges in the structure that have not been optimized for carbon fiber, we have exceeded the stiffness of bikes with wider BB shells and larger diameter tubing.

The seat tube is another noteworthy piece of engineering. The asymmetrical design provides adequate clearance for the crank and drivetrain on the drive-side, but flares outboard on the left side of the bike to maximize lateral rigidity at the BB—much like taking a wider stance with your feet keeps you more stable.

Chainstay size was increased by over 30% and features a refined shape to position maximum material where it strategically enhances stiffness. What is the result of all of these design, material and manufacturing details? Simply put, nothing we have measured is stiffer at the BB.

Cranks

TOTAL INTEGRATION. MAXIMUM PERFORMANCE.

Like the Tarmac SL2, nothing is stiffer and lighter than the integrated FACT carbon crank and bottom bracket. Because we control the design of every chassis that features a FACT carbon crank, we’re able to optimize both the frame and crank for maximum efficiency and performance.

An oversized bottom bracket shell houses a pair of large diameter bearings directly in the frame for maximum torsional rigidity and eliminates redundant bottom bracket hardware. Total integration also allows us to employ a dramatically oversized two-piece bottom bracket spindle, one that saves weight and boosts efficiency under peak loads.

Crank arm stiffness is improved through a hollow and more efficient 'D' shape. The two crank arms are attached in the middle using a Hirth coupling for maximum stiffness. In addition, the carbon fiber is continuous from pedal threads into the alloy spindles at the Hirth coupling. Shifting performance is improved by refining tooth profiles, reengineering the spider (to increase stiffness) and adding a proprietary 3-19 Ni Boron plating to the chainrings.

Front End

Forward Thinking

Like the rest of the Tarmac SL2, the front end was developed as a whole. All conventions and constraints were abandoned, and our engineers were free to develop the fork, head tube, top tube, down tube and headset from scratch to achieve our performance goals. The result? Nothing is lighter and stiffer.

To maximize stiffness and minimize weight, we employed a carbon-centric design. For example, the fork’s steerer tube tapers from 1.125” at the top, to 1.5” at the crown. This over-sizing not only enhances stiffness, it also provides a gradual transition for the carbon to flow from the steerer tube to the crown. The smooth transition is key to unlocking the strength and stiffness potential of carbon fiber.

The head tube is also oversized, which enables the use of a massive down tube and top tube cross-section. These precisely engineered, shaped and frame size-specific tubes give the SL2 best-in-class front end torsional rigidity for improved steering precision.

The interface between the fork and the head tube is also a unique example of integrated design. Because we are in control of the frame, fork and headset design, our engineers were able to align force transferred from the fork directly to the point that the down tube meets the head tube.

Intelligent front-end design details enabled us to use less material and actually increase the strength and stiffness of the bike. Together, these key features of the Tarmac SL2 make it an agile bike with razor-sharp handling that inspires confidence, while improving upper body power transfer during out-of-the-saddle efforts.

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