Materials Selection


Stiffness & Strength

Not all carbon fiber is created equal. Some fiber has higher tensile strength (represented by the letter Y in the FACT chart), meaning “stronger”, and other fiber has superior stiffness properties (represented by the letter E in the FACT chart). Both properties are considered in any carbon project, but to varying degrees; road bikes are usually more concerned with stiffness, while mountain bikes focus more on strength.

To help us rank our composite bikes against ourselves and the competition, we’ve developed a chart that compares the material strength and stiffness, manufacturing methods, and finish layers applied to each FACT frame.

Bike FACT Rating Material Manufacturing Method Final Layer
S-Works Tarmac SL3 FACT 11R E630 FACT IS UNI
Tarmac Pro / Expert SL FACT 10R E390 FACT IS 12K
Tarmac Comp & Elite FACT 8R E240 Triple Monocoque 12K
S-Works Roubaix FACT 10R E390 FACT IS UNI
Roubaix Pro & Expert FACT 9R E285 FACT IS 12K
Roubaix Comp & Elite FACT 7R E285 Triple Monocoque 12K
Roubaix (BASE) FACT 6R E240 Triple Monocoque 12K
Ruby S-Works FACT 10R E390 FACT IS UNI
Ruby Pro/Expert FACT 9R E285 FACT IS 12K
Ruby Comp/Elite FACT 7R E240 Triple Monocoque 12K
Amira S-Works FACT 10R E390 FACT IS UNI
Amira Expert/Comp FACT 8R E285 FACT IS 12K
S-Works Hardtail FACT 10M Y579 Triple Monocoque UNI
SJ Marathon & Expert HT FACT 8M Y579 Triple Monocoque 12K
S-Works Hardtail, 29ER FACT 10M Y579 Triple Monocoque UNI
SJ Marathon & Expert HT, 29ER FACT 8M Y579 Triple Monocoque 12K
S-Works Epic FACT 11M Y579 FACT IS UNI
Epic Marathon & Expert FACT 9M Y579 FACT IS 12K
S-Works Era FACT 10M Y579 FACT IS UNI
Era Expert FACT 10M Y579 FACT IS UNI
S-Works Safire FACT 10M Y579 AZ1 UNI
Stumpjumper FSR Pro & Expert FACT 8M Y579 FACT IS 12K
Safire Expert FACT 9M Y579 AZ1 12K
S-Works Enduro FACT 10M Y579 FACT ISX UNI
Enduro Pro FACT 9M Y579 FACT ISX 12K
S-Works Tricross FACT 10M Y579 AZ1 UNI
Tricross Pro FACT 10M Y579 AZ1 UNI
S-Works Transition FACT 9R E390 Triple Monocoque UNI
Pro, Expert & Comp Transition FACT 7R E285 Triple Monocoque 12K
The column in the chart that’s titled “FACT Rating” is an internal numbering system we’ve created to represent the materials and manufacturing applied to each FACT bike. When comparing the E and Y-series carbon used for each bike, keep in mind that the higher the number, the greater the stiffness/strength.

Fiber Types

Modulus is an engineering term for fiber stiffness. Though high modulus carbon is good for stiffness, it tends to have lower elongation at failure. In general, you wouldn’t want to build a whole frame out of high modulus material, so we hybridize (mix) our high modulus carbon with a number of other materials and in varying modulae (stiffness ratings) to make our frames as light and stiff as possible without sacrificing strength or durability. The general idea is to align the higher strength material with loads and to save as much weight as possible everywhere else with stiffer high modulus material.


Pitch fiber is nearly double the stiffness of high modulus fiber, but lacks strength compared to lower modulus materials. It’s also very expensive and difficult to manipulate. Because of this, we use it very sparingly and strategically—only on S-Works bikes like the Tarmac SL3 and Epic and only in places that will benefit the most from a major boost in stiffness.


Rated at 40 Ton or 57Mpsi (millions of pounds per square inch). That’s about 62% stiffer than the standard aerospace-grade material most carbon bicycles use. At triple the cost of standard modulus fiber, this fiber is used extensively in S-Works and Pro-level frames.


Used to maximize strength and keep weight low in the highly stressed parts of the frame, like the top and down tubes. Because of its relatively high modulus and superior strength, this material is a good all-around workhorse for premium composite frames. “Intermediate” might not sound like the pinnacle of technology, but don’t be fooled—this material has an optimum blend of stiffness and strength to make your bike as damage-tolerant and stiff as you expect it to be.


Aerospace-grade carbon fiber used in conjunction with other materials for improved impact strength in specific areas. Note: Some companies call any aerospace-grade material “high modulus” when, in fact, it’s industry standard modulus material.

Weave Types

Most efficient use of materials because fibers remain the straightest
Difficult to get perfect cosmetics
Where We Use it:
Almost eveywhere – All frames use uni-directional fiber as their main structure
3K or 12K Weave
3K or 12K
Abrasion resistance, impact resistance, cosmetics
Not as stiff as equivalent uni-directional plies
Where We Use it:
In damage-prone areas
Twill Weave
Twill Weave
Conforms to radical shapes
Not as efficient as equivalent uni-directional plies
Where We Use it:
On very difficult parts such as Shiv seat tube
Prepreg Manufacturing
We use the hot melt process for making prepeg — the most sophisticated method available

Prepreg Manufacturing

Prepreg is defined as flexible sheets of carbon that have been “impregnated” with resin. During the layup process, these sheets are strategically layered into pre-form shapes before getting baked in a mold. Unique to Specialized, we make our own prepreg from both uni-directional and woven materials, even weaving our own fabric. This allows us to control exactly what goes into our bikes, from the fiber to the resin content to the process by which the prepreg is manufactured.

After determining the appropriate materials selection for each family of bike (and even each bike size within that family), our engineers use 100+ pieces of carbon fiber to create specific carbon layups that yield the perfect combination of stiffness, compliance, strength, and weight. Whether it’s the super stiff Tarmac or more balanced Roubaix, we can optimize performance for any given experience.