Giant's 2015 Defy Has Disc Brakes, Through Axles and A Lot More
(article from roadbikereview.com)
Giant
has made a giant-sized statement. Last week at a press event in
Scotland, the world’s largest bike maker rolled out a fully revamped
version of its Defy endurance road bike, claiming it’s both the lightest
road frame it’s ever produced (890 grams for size medium Advanced SL),
and that it smoked comparable competition when lab tested for weight,
stiffness and compliance
(more details below).
Perhaps more significant is that Giant is going all in with disc
brakes, outfitting all eight carbon fiber 2015 Defy models with the
burgeoning road braking standard. Top of that line is the wallet-busting
Defy Advanced SL 0, which comes stock with Shimano Dura-Ace Di2
shifting, Zipp 202 Disc carbon clinchers, and a $10,300 price tag. If
you want traditional rim brakes (and/or to spend a whole lot less money)
you’ll need to choose from one of five lower-tier alloy models.
The development project started with a basic goal: make a Defy with
disc brakes, but add no weight and strike the coveted balance between
stiffness and compliance. “This was a purely engineering driven
project,” said Jon Swanson, Giant’s global road category manager. “There
are no gimmicks and no fluff. The only thing that did not change
between the new Defy and its predecessor was the geometry.”
Swanson’s knock on “gimmicks” was clearly aimed at the competition,
many of which use various add-in bump-absorbing technologies in their
endurance road frames; see Zertz (Specialized Roubaix) and IsoSpeed
Decoupler (Trek Domane) for examples. “It’s not easy to make a frame
without stuff in it,” added Swanson. “I had to fight to not just add
something in so we can show a picture in a magazine.”
Instead, Swanson and his team claim to have increased compliance
primarily through the use of the D-Fuse integrated seatpost in the two
Advanced SL models, a design originally used in Giant’s top end TCX
cyclocross bikes. The thin D-shaped post is claimed to add 12mm of
ride-smoothing flex, but have no effect on power transfer. Once cut,
there is 25mm of adjustment, which Giant feels is adequate to alleviate
concerns about resale, a common complaint leveled at integrated post
designs.
The new Defy uses two forms of its
ride smoothing D-Fuse seatpost. Top end SL models utilize an integrated
set-up, while mid-tier bikes have an integrated seat clamp.
The rest of the composite frame models use a more traditional
seatpost binder that has an expander bolt easily be accessed at the top
tube. Swanson says the ride characteristic of the two systems will vary
some, and the non-integrated posts are less stiff and a little heavier.
All the new frames also utilize dramatically thinned
compliance-enhancing seat stays, which attach lower on the seat tube.
Ride feel is further enhanced by the stock 25c tires, and Swanson says
28s are no problem.
“The stays are basically as thin as we can possibly make them while
keeping them hollow,” explained Swanson of the leaf spring design. “By
keeping the stays hollow and eliminating the need for a brake bridge, we
get vertical compliance without sacrificing stiffness. Lowering the
junction point gives the frame balance. The upper half of the bike is
compliant, the lower half maintains stiffness.”
Check out the video below to see the integrated seatpost in action.
Weight was also a huge design driver. Swanson says the top end frame
is the lightest road frame Giant has ever produced. “The perception is
that with road disc you have to pay a weight penalty,” said Swanson. “We
approached it as how do we offset that weight. And we actually dropped
50 grams on our top end frames, which is pretty significant when you see
our competition having to add 40-50 grams to get disc tabs on.”
That weight was shed in part by using hollowed carbon dropouts,
eliminating the brake bridge, and generally minimizing the need for
reinforcement frame material by reducing the number of holes in the
carbon frame. The front brake hose is routed externally; all other
cables/hoses go into one side of the frame because when you punch a hole
in frame you have to add weight with reinforcing material. Instead
Giant made a single slightly larger hole on the non-driveside.
“That’s where having our own factory is huge,” said Swanson. “From
conception to in-house engineering to design to development to
prototyping, all the way through manufacturing, it’s all completely in
house and completely controlled by Giant. The only thing we get from the
outside is raw carbon fiber. We sit in offices above factory floor and
if there is a problem or question, we can simply walk down a flight of
stairs and are right in front of it. That level of control is huge and
we feel it’s a massive advantage over everyone else. Nobody else has
that level of control.”
Giant also opted for traditional quick releases rather than
thru-axles. Swanson said this was both a weight saving measure, and a
nod to the wait-and-see approach the company is taking toward the
increasing use of disc brakes on road bikes, but the lack of an
established standard when it comes to axles.
“People will say that once in a while you can get your rim brakes to
hit your wheel so wont the same thing happen with rotors,” explained
Swanson. “But that’s a wheel issue, not the core axle assembly. When
there is an industry standard that goes beyond a couple third party
players, and there are the same tolerances with the same designs, then
we’ll go with that. But at this point I was not comfortable building a
product that would lock someone in to a limited number of wheels.”
In an attempt to validate all the highlights of the new Defy, Giant
says it conducted a series of comparative tests, focusing on weight,
stiffness and compliance. The test field included the new Defy Advanced
SL frame, along with Cannondale’s Synapse Hi-MOD Disc, the Specialized
S-Works Roubaix SL4 Disc, and Trek’s Domane 6 Disc. Not surprisingly,
the information shared painted Giant in glowing light.
Weight comparison was based on size medium/56cm production frames
with fork, headset, derailleur hangers and seatpost/ISP. Stiffness was
tested by fixing the rear drop-out, then measuring how much force it
took to move the frame. Pedaling stiffness looked at force put into the
bottom bracket with front end fixed and the rear end placed in a dummy
hub. Bikes were then leaned at an angle representative of sprinting to
measure how much force it took to deflect the bottom bracket side to
side.
Finally, Giant looked at compliance, using methods created by a
third-party auto/motorcycle tester. This pair of tests measured the
amount and effect of vibration transmitted to a rider’s hands, and the
force coming through the saddle. Giant, as illustrated in these four
screenshots displayed during the press launch, claims it topped the
weight and stiffness comparisons, and was the second most compliant
behind Cannondale’s Synapse Hi-MOD Disc.
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