2015 Giant Defy and Liv Avail endurance road bikes announced

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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.

Meet the all-new Giant Defy Advanced SL 0

High performance, low stress

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.

Key ride-oriented features include seat tubes, and top tubes that are supposedly more apt to flex over bumps than rounder sections; similarly D-shaped seatmasts and seatposts with slim diameters and lots of extension; lowered seat stays that are said to act more like leaf springs than conventional rear-end layouts; and slender fork blades that balance out the ride from front to back.

D-shaped tubing supposedly adds flex over the bumps

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.

Trademark features such as the extra-wide 'PowerCore' bottom bracket design carry over

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.

Giant goes all-in on disc brakes

While all of the Defy and Avail models are brand new, geometry is wholly carried over – a good thing since they were already highly refined with stable manners and modestly raised front end that's just 15mm taller on average. Giant has taken the bold step, however, of exclusively using disc brakes nearly across the board for more consistently predictable all-weather stopping performance.

All of the new carbon Giant Defy and Liv Avail models will come with disc brakes only

All carbon models will be disc-equipped for 2015; aluminum bikes will all be rim brake-only. Impressively, Giant looks to have done this without adding any weight – and in fact, says certain complete bikes even end up about 50g lighter than their comparable rim brake-equipped versions. We measured a top-end Defy Advanced SL 0 model at just 7.3kg (16.1lb)

"Our goal was to have a net zero increase," said road product manager Jon Swanson.

Officially, eliminating the rim brake calipers also yields easy clearance for tires up to 28mm-wide – although we think many 30mm ones will fit, too.

Tire clearance is outstanding on all disc-equipped models

Giant has not paired those disc brakes with thru-axles, though – a move that we definitely question.

According to Swanson, this was done so as to provide disc-equipped Defy and Avail owners with more wheel choices. Swanson also isn't satisfied with current thru-axle standards as they pertain to road bikes, saying they're overbuilt for the application and insufficiently elegant for the genre.

We're still a bit disappointed in that move, however, and can't help but wonder if this means a new road-specific thru-axle system with more behind-the-scenes industry support is pending.

Either way, things look to be heading in a very good direction here and are looking forward to spending more time aboard the new models. So far, we've developed a solid taste over two solid days on some rather rough roads in northern Scotland. Look for a First Ride Review shortly.

Women get the similarly ambitious Liv Avail Advanced SL 0

Key specs and retail prices for the complete US-spec Giant Defy and Liv Avail ranges are as follows (UK and AUS models and prices are TBD):

· Defy Advanced SL 0 (US$10,300): Shimano Dura-Ace Di2 drivetrain; Shimano R785 hydraulic Dual Control levers and brakes; Zipp 202 Disc carbon clincher wheels

· Defy Advanced SL 1 (US$4,950): Shimano Ultegra drivetrain; Shimano RS685 mechanical Dual Control levers and R685 hydraulic disc brakes; Giant P-SLR0 Disc carbon clincher wheels

· Defy Advanced Pro 0 (US$4,900): Shimano Ultegra Di2 drivetrain; Shimano R785 hydraulic Dual Control levers and brakes; Giant P-SL0 Disc aluminum clincher wheels

· Defy Advanced Pro 1 (US$3,500): Shimano Ultegra drivetrain; Shimano RS685 mechanical Dual Control levers and R685 hydraulic disc brakes; Giant P-SL0 Disc aluminum clincher wheels

· Defy Advanced 1 (US$2,600): Shimano Ultegra group; TRP Spyre mechanical disc brakes; Giant P-R2 Disc aluminum clincher wheels

· Defy Advanced 2 (US$2,075): Shimano 105/RS500 drivetrain and levers; TRP Spyre mechanical disc brakes; Giant P-R3 Disc aluminum clincher wheels

· Defy Advanced 3 (US$1,750): Shimano Tiagra group; TRP Spyre mechanical disc brakes; Giant S-R2 Disc aluminum clincher wheels

· Defy 1 (US$1,375): Shimano 105 group; FSA Gossamer Pro cranks; Tektro TK-R540 rim brakes; Giant P-R2 aluminum clincher wheels

· Defy 2 (US$1,075): Shimano Tiagra group; Tektro TK-R312 rim brakes; Giant S-R2 aluminum clincher wheels

· Defy 3 (US$950): Shimano Sora group; Tektro TK-R312 rim brakes; Giant S-R4 aluminum clincher wheels

· Defy 5 (US$620): Shimano Claris group; FSA Tempo cranks; Tektro TK-R312 rim brakes; Giant S-R2 aluminum clincher wheels

· Avail Advanced SL 0 (US$8,750): Shimano Dura-Ace Di2 9070 drivetrain; Shimano R785 hydraulic Dual Control levers and brakes; Giant P-SLR 0 Disc wheels

· Avail Advanced SL 1 (US$5,150): Shimano Ultegra Di2 drivetrain; Shimano R785 hydraulic Dual Control levers and brakes; Giant P-SL0 Disc aluminum clincher wheels

· Avail Advanced Pro (US$3,500): Shimano Ultegra drivetrain; Shimano RS685 mechanical Dual Control levers and R685 hydraulic disc brakes; Giant P-SL0 Disc aluminum clincher wheels

· Avail Advanced 1 (US$2,600): Shimano Ultegra group; TRP Spyre mechanical disc brakes; Giant P-R3 Disc aluminum clincher wheels

· Avail Advanced 2 (US$1,925): Shimano 105/RS500 drivetrain and levers; TRP Spyre mechanical disc brakes; Giant P-R2 Disc aluminum clincher wheels

· Avail Advanced 3 (US$1,750): Shimano Tiagra group; TRP Spyre mechanical disc brakes; Giant S-R2 Disc aluminum clincher wheels

· Avail 1 (US$1,375): Shimano 105 group; FSA Gossamer Pro cranks; Tektro TK-R540 rim brakes; Giant P-R2 aluminum clincher wheels

· Avail 2 (US$1,075): Shimano Tiagra group; Tektro TK-R312 rim brakes; Giant S-R2 aluminum clincher wheels

· Avail 3 (US$950): Shimano Sora group; Tektro TK-R312 rim brakes; Giant S-R2 aluminum clincher wheels

· Avail 5 (US$620): Shimano Claris group; FSA Tempo cranks; Tektro TK-R312 rim brakes; Giant S-R2 aluminum clincher wheels