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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