The EPX Bicycle Company first caught our attention with their sleek, carbon fiber, monocoque-framed city bikes. These creations included features like disc brakes, RockShox Judy SL forks, Rohloff 14-speed Speedhubs and even a model propelled by belt drive instead of a chain. When the company introduced a line of mountain bikes (they make the high-end TerraShark models and the budget-minded Reef line for cross-country riding), MBA jumped at the chance to put an EPX through our usual thrashing.
THE SHARK FAMILY
EPX offers three flavors of the TerraShark (the 1, 2 and 3). They all share the same frame and they are all intended for cross-country riding. The difference is the parts that are hung on the carbon. The bikes were designed in America and are manufactured in Taiwan. We opted for the top-of-the-line TerraShark 1.
There was the usual mix of Shimano XTR and XT components and the Mavic CrossMax tubeless tire wheels that you?ve become accustomed to seeing on a bike of this pedigree. What?s unique (if the frame isn?t unique enough for you) are the stem, handlebar and seatpost. All are EPX-made components (labeled EPXtras) and are constructed from carbon fiber. Heck, even the steering stem spacers are carbon fiber and made by EPX.
The bike has such a clean profile that you almost think something is missing. You?re right. There is no suspension linkage. There aren?t multiple mounts for changing the suspension travel (EPX gives you four inches, front and back). Cables hug the frame and swingarm. Esthetically, this is as sleek as you can design a mountain bike without going the single-speed route!
SWIMMING WITH THE SHARK
It was almost too pretty to take into the dirt, but we had to christen the TerraShark on our favorite trails. We were pleasantly surprised.
Hitting the dirt: The riser bars, five-degree-rise stem and multiple spacers positioned below the stem end up positioning your hands at about chest level. Luckily, lowering the bar is simple. Remove the bar (the stem has a split bar clamp, so you don?t need to remove the controls or grips), flip the stem, move some spacers from below to above the stem and you?re ready to go (in a more aggressive position). We were now ready to hammer.
On the flats: The TerraShark feels fast. If you are thinking, ?it is the rider, not the bike? that accounts for speed, you haven?t ridden as many bikes as the wrecking crew has. There are definitely bikes that feel fast, and this is one of them. Every pedal stroke translates to an increase in forward momentum. It feels light and stiff under pedaling.
The rear suspension is very active. Some riders went up higher on the shock pressure, but the best solution was to set the suspension for the rough stuff and flip the lock-out lever for hammering on smooth surfaces.
Climbing: We loved climbing on the TerraShark. The most effective technique was to engage the shock lockout, stay in the saddle, let the tubeless Michelins hook up and try pushing one gear larger than normal. If the terrain is rough or loose, leave the shock active, position your hands on the bar ends, and slide to the front of the saddle.
Descending: While not a downhill racer or a big-drop hucker, the TerraShark can hold its own on the descents. It is stable at high speeds, and seems to feel the best in high-speed fire-road flying mode. The TerraShark will stinkbug under heavy braking into corners, so you have to consciously shift your weight to the rear to balance things out. The Marta brakes worked great, even for riders with a tendency to ride their brakes on long downhills.
In the tight stuff: The TerraShark is not a quick-steering bike, but you can use the bike?s light weight and peppy acceleration to compensate by exiting corners with a burst of speed. The brakes are helpful in the tight, because they modulate very well. Scrub the speed you need to and leave the rest to get you out of the corner.
In the rough: The bike is well balanced and light. Four inches of wheel travel is plenty for cross-country race conditions and adequate for any epic trail rides. Let the TerraShark float over the rough stuff and it will never take a bite out of you.
Jumping: Want to huck the TerraShark off your favorite boulder or cliff? You got the wrong bike. Go get a steel hardtail.
SHARK BAIT
There were a couple of things that bugged us about the TerraShark that you should be aware of when taking a test ride. Some of our crew (the guys with large calves) rubbed their calves on the swingarm while pedaling from the rear of the saddle (a familiar position for long, steady climbs). There is no simple way to cure this, short of changing your riding position. This problem can be detected on a test ride. If you don?t have big calves, it is not an issue.
Finally, we broke an EPX seatpost (see sidebar below) during our testing. It was our fault, but our mistake could easily be made by others. Carbon fiber is a sensitive material, especially when it is used with aluminum, titanium or steel hardware.
SHARK ATTACK
If you hate the cluttered look of dual-suspension mountain bikes, but still want dual-suspension, the TerraShark is one solution. If you want a bike that is totally responsive to your legs? input, this bike delivers. The TerraShark rider will stand apart from other trail riders, and that?s half the fun of a bike like this. This is one shark attack that trail riders and cross-country racers alike won?t mind at all.
A LESSON LEARNED CARBON FIBER EDUCATION
l Hitting a g-out ditch at the bottom of a hill, the rider heard what sounded like a crack of lightning and the saddle disappeared from underneath him. Our EPX seatpost had snapped in two. Back at the MBA workshop, we carefully removed what was left of the seatpost from the seat mast. There were marks on the post that revealed the reason for the part failure. That reason was us!
When assembling the TerraShark, we found the seatpost fit very tightly into the frame. This is a good thing. You don?t want a sloppy fit, because that will cause seat creep later in the bike?s life. In a rush to get our TerraShark on the trail, we forced the seatpost in and, in doing so, unintentionally scratched the post. This caused what is called a stress riser. Think of a stress riser as a weak link in a chain. We made one more assembly error. We over-torqued the seatpost clamp, slightly crimping the seatpost. This added another stress riser.
Unlike steel and aluminum, which will both bend before breaking, carbon fiber just lets go. No warning, no flex, no visible cracks?just a loud crack and failure. The broken seatpost reminded us that more attention has to be paid when working and living with carbon fiber components. Budget extra time for assembly, read instructions carefully and be sure to use a torque wrench. If you scratch a carbon fiber bar, seatpost or stem (and we?re not only talking about crash damage; we?ve seen carbon bars scratched by a tie-down during transportation), trash it. l
LIGHT AND RIGID HOW EPX DOES IT
l Curious how EPX constructs their TerraSharks? First off, they?ve had a lot of help. EPX?s parent company, the EP Group, is a two-billion-dollar conglomerate and major carbon fiber player in aerospace, home entertainment and the automotive business (one of their divisions makes parts for Dodge?s PT Cruiser). The bike guys get to pick everybody?s brains about what works and what doesn?t when designing and manufacturing with carbon fiber. Here is what they have come up with.
THE EPX FRAME IS CUT
Carbon material (it has a grain) is cut into shapes (similar to how a tailor cuts out the pattern for a suit). Each piece is cut with a specific job in mind. Some will be cut with the carbon fiber grain running one way, others with the carbon grain opposing. This lay-up allows the frame to be tuned so it is strong and stiff in one area (like the bottom bracket), but with compliance in another (the seat mast).
THE FRAME IS MOLDED
The carbon fiber (already impregnated with resin) is ready to be cured. The cut pieces are laid up into the mold with a specially formed nylon bladder inside the ?wrap.? At this stage the frame looks like a deflated balloon in the shape of a bike frame.
Once the lay-up procedure is finished, the steel molds are closed and the whole package is gradually brought up to curing temperature with the pressure inside the bladder increasing to assist the forming of the carbon against the mold. The final pressure of about 110 psi and temperature of 180 degrees Celsius are achieved about 45 to 60 minutes into the process. At this point, the pre-impregnated resin has saturated the carbon fibers and the whole matrix is bonded together. Then the mold is allowed to cool to about 80 degrees Celsius before the new frame is ready to be released.
ALUMINUM MEETS CARBON FIBER
l Pretreated aluminum parts, such as the threaded nuts for the suspension mounts, bottom brackets and steerer tubes, are positioned in the frame during the lay-up process. This ensures that the parts are captured within the matrix of the material itself, and so no bonding agents are required to bind the aluminum to the carbon. Careful pretreatment of these parts ensures that surface oxides and contaminants are removed prior to bonding.
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