2015 Giant Defy and Liv Avail endurance road bikes announced

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The internal routing system can be set up with either electronic or mechanical drivetrains. Giant has bundled up the various ports into as few holes as possible, too(Image credit: James Huang/Future Publishing)

Giant claims that the new Defy Advanced SL is built on a lighter-weight chassis (frame, fork, headset, seatpost/ISP, and associated hardware) than the Specialized S-Works Roubaix SL4 Disc, Trek Domane Disc 6.9, and Cannondale Synapse Hi-Mod Disc. In addition, Giant claims its new bike is stiffer than all of those competitors while also delivering a measurably smoother ride than all but the Cannondale(Image credit: James Huang/Future Publishing)

Giant – and its recently pseudo-independent women-specific brand, Liv – have completely overhauled their Defy and Avail collection of endurance road bikes for 2015. According to Giant, they're lighter, smoother, more efficient, and with the addition of disc brakes nearly across the line, more consistently controllable in all conditions. The previous version won the coveted Cycling Plus Bike of the Year award in 2013, and this new one seems like an easy candidate for another shot at the title.

The new Defy Advanced SL and Avail Advanced SL flagships blur the lines even further between what many riders might expect from a 'race bike' and a so-called 'endurance bike'. The more sharply engineering-centric frame shapes are still less than 900g – a number many dedicated competition frames struggle to hit – and yet Giant also claims that they're more comfortable than their previous versions.

Even so, several design concepts borrowed from the more racing-oriented TCR range place an emphasis on tuned stiffness that reportedly encroaches that bike's rigidity territory. The OverDrive 2 extra-oversized 1 1/4-to-1 1/2in steerers are bolstered by extremely wide MegaDrive down tubes, which are then connected to PowerCore bottom bracket shells that measure a healthy 86.5mm across. That extra width also lends additional room for the adjoining asymmetrical chain stays to spread apart in order to keep the rear end from wagging under power.

Giant backs this all up with bold in-house testing claims. As compared to the Specialized S-Works Roubaix SL4 Disc, Trek Domane Disc, and Cannondale Synapse Hi-Mod Disc, Giant claims the Defy Advanced SL is the lightest chassis by about 230-310g (including the frame, fork, headset, seatpost/seatmast, seatmast head, seatpost collar, derailleur hangers, headset expander plug, and all cable routing hardware). Torsional stiffness and pedaling stiffness values are also supposedly best in class (by as much as 40 percent in some situations) while overall front and rear 'compliance' is topped only by the Cannondale, all without any "marketing gimmicks" such as elastomeric dampers or integrated pivots.

Of course, not all of those specs apply across the rather wide Defy and Avail ranges. Second-tier 'Advanced' frames get slightly heavier carbon fiber blends, telescoping carbon 'D-Fuse' seatposts, and OverDrive 2 forks with aluminum rather than carbon fiber steerer tubes. Base-level Defy and Avail models, meanwhile, will get aluminum frames and aluminum/carbon forks with downsized 1 1/8-to-1 1/4in tapered steerer sizes.