Endurance road bike head to head: Giant Defy Advanced SL 0 vs Specialized Roubaix SL8 Expert

This year has seen the launch of the latest Giant Defy and Specialized Roubaix endurance road bikes.

Both are steeped in cycling lore as leaders of the pack when it comes to embodying a more relaxed ride position and fast performance.

The Roubaix, of course, is named after the most famous spring classic of them all (and was born to conquer it), while the Defy helped make the endurance road bikes category what it is today.

However, which is best?

While the Roubaix is now firmly ensconced in the all-road bike genre and a compellingly versatile machine, the Defy bucks the latest trends and doubles down on what endurance bikes should be, to amazing effect.

Introducing the bikes

Giant Defy Advanced SL 0

Giant Defy Advanced SL 0 specifications

• Weight: 7.52kg (Large, including 2x bottle cages, out-front mount)
• Sizes: S, M, M/L, L
• Frame: Advanced SL-grade composite, disc
• Fork: Advanced SL-grade composite, full-composite OverDrive Aero steerer, disc
• Cassette: SRAM Force, 12-speed, 10x36t
• Chain: SRAM RED D1
• Crankset: SRAM RED D1 DUB, 33/46t with Quarq power meter, L:175mm
• Bottom bracket: SRAM DUB, press-fit
• Shifters: SRAM RED eTap AXS
• Front derailleur: SRAM RED eTap AXS
• Rear derailleur: SRAM RED eTap AXS
• Brakes: SRAM RED eTap AXS hydraulic, SRAM CenterLine XR rotors, [F]160mm, [R]160mm
• Brake levers: SRAM RED eTap AXS hydraulic
• Handlebar: Giant Contact SLR D-Fuse, 44cm
• Bar tape: Stratus Lite 3.0
• Stem: Giant Contact SLR AeroLight, L:110mm
• Seatpost: Giant SLR D-Fuse, composite, -5/ 15mm offset
• Saddle: Giant Fleet SLR
• Rims: Cadex 36 Disc WheelSystem, [F]36mm, [R]36mm
• Tyres: Cadex Classic, tubeless, 700x32c (33.5mm), folding
• Extras: Computer mount, fender mount, 2x bottle cages, factory tubeless setup
• Price: £11,499 / $12,000 / CAD$14,999 / €11,999 / AU$13,999

Giant has taken the legendary Defy design and put it on a diet.

It features much more integration than the previous bike, thanks to the use of the internally routed cockpit, while Giant has attempted to imbue it with a sportier ride.

The aerodynamics were also considered, with the fork legs and seat tube both having truncated profiles.

Overall, the design of the fork and frame resembles a slimmed-down version of the brand’s Propel aero bike.

Despite sharpening the design and integration, tyre clearance was upped to 38mm – a trend we see in anything related to road bikes these days.

The frame and fork have both shed considerable weight. A medium frame is claimed to weigh 785 grams, 195g less than the old model, and the fork is down to 350g (claimed) – 15 per cent lighter than the old one.

Those weights put the Defy in the realms of a race bike, yet the frame has mount points for mudguards, including a removable rear bridge.

Specialized Roubaix SL8

Specialized Roubaix SL8 specifications

• Weight: 8.62kg (19.1lb), 58cm
• Sizes: 44, 49, 52, 54, 56, 58, 61, 64
• Frame: FACT 10R, Rider First Engineered™ (RFE), FreeFoil Shape Library tubes, threaded BB
• Fork: Future Shock 3.2 w/ Smooth Boot, FACT Carbon 12x100mm
• Crankset: SRAM Rival AXS w/Power, 12-speed, 46/33t
• Chain: SRAM Rival, 12-speed
• Cassette: SRAM XG 1250, 10-36T
• Bottom bracket: SRAM DUB BSA
• Front derailleur: SRAM Rival eTAP AXS, 12-speed
• Rear derailleur: SRAM Rival eTAP AXS, 12-speed
• Shift levers: SRAM Rival eTAP AXS, 12-speed
• Handlebars: Specialized Hover Expert, Alloy, 125mm drop, 75mm reach w/Di2 Hole
• Stem: Future Stem Pro
• Tape: Supacaz Super Sticky Kush
• Seatpost: S-Works Pave
• Saddle: Body Geometry Power Expert
• Brakes: SRAM Rival hydraulic disc
• Wheels: Roval Terra C, 25mm inner width carbon rim, 32mm depth, DT 370 hubs, 24h, DT Swiss Comp Race spokes
• Tyres: S-Works Mondo 2BR, 700x32c
• Inner Tubes: 700x28 / 38mm, 48mm Presta valve
• Price: £6,000 / $6,500 / €6,500 / AU$9,400

Specialized has gone about things a little differently – the always all-road capable Roubaix has been given an aero overhaul.

The frame looks inspired by the Tarmac SL8, albeit with a taller front end.

It has also upped tyre clearances (the Roubaix can accommodate up to 40mm-wide rubber), but the geometry remains very similar to the previous generation.

That has an effect on the wheelbase of 1,031mm – the Giant in comparison is 6mm shorter.

Up-front, the latest incarnation of the Future Shock suspension system brings fluid damping and real springs together.

There are three versions of the new system, headlined by Future Shock 3.3, as seen on the higher S-Works and Pro models, with an adjustable fluid damper.

Future Shock 3.2, used here, has a fixed fluid damper, while Future Shock 3.1 relies on the sprung part only. All come with three springs to set the level of support.

I kept the mid-tension spring installed for damping in testing, and didn’t find myself needing more or less spring, regardless of the surface.

At the rear, a new seat tube shape fits a deeper aero seatpost, replacing the old super-flexible slender post.

The frame is lighter than the previous generation by a few grams (a claimed 50g on the S-Works level frame).

At 828 grams in a size 56cm, it’s 43g heavier than the Defy, although it claws back 20g with its lighter fork.

That said, the Future Shock system weighs 450g, rendering the frameset significantly heavier on paper.

However, even if the Roubaix frameset is heavier than the Defy, losing 50g from the previous version remains an achievement, considering the amount of aerodynamic restyling and provision for additional mounts.

On top of mudguard mounts, there’s a third set of bottle bosses underneath the down tube and a set of bento box mounts on the top tube.

It’s these details that push the Roubaix further towards ‘all-road’ – and gravel racing – than ever before.

Giant Defy Advanced SL 0 vs Specialized Roubaix SL8 Expert specifications

The Giant Defy Advanced SL 0 is the flagship specification, with the lightest frame Giant makes, costing £11,490 / $12,000 – that’s a superbike-level price.

The Specialized Roubaix SL8 Expert is a mid-tier bike, priced at £6,000 / $6,500.

Comparing specifications here is unfair to either bike, but of course, there are broadly equivalent specifications that can be bought.

What can you buy for similar money?

The Roubaix Expert is fitted with a SRAM Rival eTap AXS groupset, with a single-sided Quarq power meter and Roval Terra C carbon wheels. It has an alloy bar and stem from Specialized’s parts bin.

At £6,000, the equivalent Defy is the Advanced Pro 0. This is fitted with Shimano Ultegra Di2 (nominally a level up) with a dual-sided power meter, plus carbon wheels and a carbon bar.

Comparing top-spec bikes, the Giant Defy Advanced SL 0 features a SRAM Red eTap AXS drivetrain, dual-sided power meter, Cadex 36 carbon wheels and a carbon cockpit.

The S-Works Roubaix costs a little more at £12,000 / $14,000. This also gets you a SRAM Red eTap AXS groupset with the same power meter, carbon handlebar and Roval Terra CLX II wheels.

Overall here, the Giant edges it on relative value. That said, despite both being endurance bikes, they represent different propositions when you get out onto the road.

Giant Defy Advanced SL 0 vs Specialized Roubaix SL8 Expert ride comparisons

I’ve loved previous generations of both the Defy and Roubaix, and I’m a fan of both here too.

When plenty of brands are mashing up their endurance models into pseudo-gravel bikes, Giant has made the latest Defy more focused on the road – and it's all the better for it.

The steering geometry is unchanged from the previous Defy (and the one before that), but perhaps the most important element of the new Defy is the 9mm reduction in stack height.

This doesn’t sound much, but on the road, the Defy feels like a faster bike, backed up ably by the new slippery shape, and latest wheels and tyres.

Compared to the Roubaix, it’s 34mm lower (in a size L), while the reach is 4mm shorter.

Out on my most familiar roads, the Defy felt more like my own TCR (an all-round race bike), rather than the relaxed long-distance cruiser endurance bikes are often perceived to be.

For reference, the stack is only 15mm taller and the reach only 9mm shorter than a TCR (again, in a size L).

However, where a stiff race bike will usually dash and dart over poorer roads, the Defy simply wafts over them, maintaining its pace with ease.

The seatpost and handlebar isolate vibrations admirably, yet down in the drops, the bar feels sprint-ready stiff.

The Specialized Roubaix is also a quick bike and the steering swiftness adds plenty of fun.

The Future Shock-equipped front end feels constantly active, and this makes the bike’s ability to cope with road imperfections and obstacles (bumps, scars and even smaller potholes) impressive – you don’t have to take as much evasive action.

It’s especially good on descents, where corners have broken up on the surface or gravel has been washed onto the optimal line.

With the Roubaix, I found I didn’t need to back off, and the 700x32c S-Works Mondo tyres, which inflate closer to 34mm wide, added to the sense of confidence.

On rolling roads with changeable surfaces, the Roubaix’s ride feel is split between a soft and smooth front, and a firmer rear end.

On bigger bumps, rougher roads and choppy striated surfaces, the back end takes the edge off and reduces vibrations, but on better-kept roads, it's noticeably stiffer.

Trying to do too much?

Comparing the two side by side, the Defy is very much the roadie’s endurance bike, whereas the Roubaix is a bit more adventurous.

With that, though, the Roubaix feels a little more conflicted.

It's undoubtedly an impressive bike; the ride smothers rougher roads in a way few of its rivals can, and the 8.83kg complete weight is reasonable, though not that light for a bike running 32mm tyres with this specification level.

That said, the Roubaix’s reinvention feels somewhat unbalanced – the frame’s lighter, and more aero on paper, but at the same time has added features usually found on gravel bikes.

The combination of soft front and stiff rear reveals itself much more on smooth tarmac than it does on rough, ragged roads and light gravel. This is both the Roubaix’s strength and its weakness.

On one side, it’s a hugely versatile and comfortable bike with a great turn of pace, but on the other it’s a bit hefty and not quite as agile as the Giant Defy.

It’s a very good all-rounder, but I’d argue not quite a class-leader, either on the road or off it.

Giant Defy Advanced SL 0 vs Specialized Roubaix SL8 Expert bottom line

If you're looking for a bike that’ll do a bit of everything to a high level, the Roubaix joins a growing number of all-road-ready endurance bikes.

However, I love that the Defy keeps the riding experience focused on the road, and Giant hasn't felt the need to muddy the boundaries of endurance bikes.

The Defy’s latest iteration has kept the class-leading smoothness and handling of its predecessors. Wider tyre clearances modernise the bike, of course, but without sacrificing the element of race-bred excitement.

It's this exciting ride quality, matched to essential compliance that doesn’t erode that excitement, that makes it my favourite of the two.