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Specialized Roubaix SL4 Comp review

20 Sep 2016

The Specialized Roubaix SL4 Comp is superbly comfortable and the Ultegra Di2 really helps it sing.

Cyclist Rating: 
Unbelievably comfortable
Wheel & tyres on the heavy side

As its name suggests, the Specialized Roubaix takes its cue from the mother of all endurance races, Paris-Roubaix, a race that famously pummels its riders with cobbles over a day’s hard riding. There’s also a sportive version of the event, the Paris-Roubaix Challenge, which many of you may be contemplating entering, along with 4,500 other amateur riders. But does the Roubaix SL4 Comp have what it takes in the comfort department, as well as the ability to rattle along at pace over such gruelling terrain?

To read our first ride review of the new 2017 model, click here: Specialized Roubaix 2017 first ride review


Specialized Roubaix SL4 Comp Zertz

The Zertz inserts in the seatstays and fork were an innovation in 2004 and are still doing their comfort-giving thing brilliantly.

Zertz vibration-damping rubber inserts in the carbon fork and seatstays are intended to isolate the rider from jarring road surfaces but not at the expense of feel. The FACT carbon frame retains a level of stiffness you’d expect from a thoroughbred race bike, and a wide down tube extends from the relatively short 145mm head tube to meet a BB30 bottom bracket which provides excellent transfer of power. Meanwhile, an asymmetric seat tube, beefed up on the non-drive side, counters any potential flexing forces when you’re putting watts to the ground.

A wheelbase of 990mm is slap-bang in the sweet spot for endurance riding, providing enough stability to inspire confidence while still short enough to provide excitement and responsiveness in the corners. A head angle of 72.4° supplies a good balance of sure-footedness and agility.


Specialized Roubaix SL4 Comp Di2

The Di2 front mech gives a satisfying whirr as it shifts gear

By combining Shimano’s 11-speed Ultegra Di2 shifters and derailleurs with a 105 chain and cassette, Specialized has brought high-end electronic shifting to the masses at a surprisingly keen price. A 50/34 chainset and 11-32 cassette supplies the rider with a wide enough spread of gear ratios to conquer the toughest of climbs. Shimano 105 brakes are as impressive as ever, with good initial bite and well-modulated performance that means you can leave your braking late for downhill hairpins.

Finishing kit

Specialized Roubaix SL4 Comp seatpost

The CG-R - or 'Cobble Gobbler' - seatpost is designed for nullifying shocks from below

The highlight here is the 27.2mm carbon CG-R seatpost with its rubberised insert at the top. Predictably, this lessens the effect of poor road surfaces, but perhaps robs a little feel for what’s happening beneath your rear end. It’s topped with a near-perfect Body Geometry Phenom saddle. Own-brand 42cm compact-drop alloy bars flex enough to protect wrists and fingers from numbness on the worst roads.


Specialized Roubaix SL4 Comp wheels

Fulcrum’s Racing S-19 wheels aren’t the lightest at 3.06kg, including cassette, quick-release skewers and tyres. However, the real winners of this package are the 26c tyres themselves. Rolling on much lower pressures than required by a standard 23, they smooth the ride, absorb road imperfections admirably, and give stacks of cornering confidence. And they stayed puncture-free throughout our entire test. There’s even clearance for sizes up to 28c.

The ride

As soon as we clasped our hands around the deeply padded bar tape, we knew the ride would be comfortable at both ends. Indeed, with a miserly 85psi in the Specialized’s 26c tyres, within two miles of our test loop it was clear that those inserts in the stays and fork are more than just a gimmick. Initial impressions from the SL4 Roubaix are of a smooth ride that you’d happily stay on until the sun goes down. Or until the Di2 battery runs out of charge – whichever comes sooner.

Comfort levels put this in the premier league of endurance road bikes, with nothing our local roads could throw at it getting in the way of pure riding enjoyment. The only thing holding it back on the hills is its all-up bulk of 8.44kg, which shows as the gradients increase – although the 11-32 cassette gives you the best possible chance of selecting an appropriate gear, and on rolling roads and flatter terrain, it’s going to take some beating when it comes to high-speed mile-munching.

Specialized Roubaix SL4 Comp review

Shimano’s electronic shifting is faultless – it flatters even cack-handed shifts under load, and provides a space-age soundtrack with its ‘zipping’ noise as the rear mech shifts across the cassette.

Throw the Roubaix into a downhill sweeper and it surprises with its willingness to carve through at speed. It retains a direct feeling when your riding becomes more focused, not in the least tempered by its vibration-absorbing technology. If anything, the frame inserts flatter, even in high-speed cornering, taking any harshness out of small bumps and allowing you to get on with the business of hammering out of turns in a 50x11 gear. Composure is there in abundance, aided by an easy-going head angle and wide tyres. As with most bikes under £4,000, though, the first thing to go would be the wheels. If you’re planning to ride across northern France, we’ve no doubt they’d prove durable and dependable. But for sprint efforts approaching town signs, they’re a little on the portly side and unwilling to spin up as quickly as we asked. All-day comfortable when shod with Specialized’s excellent Turbo Pro tyres, but the weak link in the build.

Frame Bike frames don't come much more comfortable
Components A good mix of Di2 and 105, with superb finishing kit
Wheels The one weak spot in the build, ripe for an upgrade
The ride Sure-footed and agile, but perhaps not truly exciting


Geometry chart
Claimed Measured
Top Tube (TT) 536mm 534mm
Seat Tube (ST) 475mm 484mm
Down Tube (DT) 630mm
Fork Length (FL) 368mm 368mm
Head Tube (HT) 145mm 145mm
Head Angle (HA) 72 72.4
Seat Angle (SA) 74 74.5
Wheelbase (WB) 990mm 990mm
BB drop (BB) 73mm 78mm


Specialized Roubaix SL4 Comp as tested
Frame Specialized SL4 FACT 8r frame & fork
Groupset Shimano Ultegra Di2
Brakes Shimano 105
Chainset Praxis TURN Zayante, 50/34
Cassette Shimano 105, 11-32
Bars Specialized Comp, alloy
Stem Specialized Comp, alloy
Seatpost Specialized CG-R, FACT carbon, 27.2mm
Wheels Fulcrum Racing S-19
Saddle Specialized Body Geometry Phenom Comp
Tyres Specialized Turbo Pro, 26c

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