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When it comes to endurance road bikes, there exist two outright titans of the segment: the Specialized Roubaix and the Trek Domane SLR. Specialized arguably created the segment when it launched the first Roubaix in 2004, and although Trek followed closely afterward with the Pilot, it wasn’t until the company launched the Domane in 2012 that it could really go head-to-head. Ever since, the two bikes have been locked in a battle for sales supremacy.
Endurance road bikes are all about comfort and confidence, and the latest versions of the Roubaix and Domane are unquestionably the most progressive examples either company has put forward to date. Both feature new — and truly legitimate — pavement-specific suspension technologies designed to smooth out rough roads, powerful disc brakes, stable handling with back-friendly fits, and clearance for big, cushy tires.
The Roubaix and Domane are very similar, but they differ greatly on the road — and in this hotly contested market, there can be only one winner.
Specialized introduced the first Roubaix more than ten years ago, and in hindsight, that debut was little more than a toned-down race bike. The handling was slightly more stable, the ride quality smoother and more composed, the rider position more upright and relaxed. Zertz elastomeric inserts at the seatstays and fork blades supposedly helped attenuate road vibration (although it was highly debatable whether they ever worked), but the tires were still just 23mm wide.
That original Roubaix may not pass the sniff test for what an endurance road bike should be in modern terms, but it had a massive impact on the market back then. Whereas virtually every mainstream road bike at the time simply mimicked the look, feel, and fit of full-blown racing bikes, the Roubaix marked the first time a major brand took more of an everyday-rider approach instead of forcing everyone to ride bikes that didn’t make sense for what they were doing.
More than a decade later, the new Roubaix still holds rider comfort at the top of its design priorities, but it bears little resemblance to its grandfather.
Rider comfort is still very much at the top of the bike’s list of design requirements, but in place of those squishy Zertz inserts is the far more radical FutureShock coil-spring short-travel suspension cartridge up front, paired to a novel approach to a traditional solution out back.
Unquestionably the most intriguing aspect of the Roubaix’s design, FutureShock offers up 20mm of movement via a set of telescoping tubes, a pair of simple steel coil springs, and low-friction roller bearings — a concept very similar to Cannondale’s earliest Headshok designs. But whereas a conventional suspension fork moves the front wheel up and down below the frame, Specialized positions FutureShock above the head tube; the front wheel stays put while the bar and stem move up and down.
According to Specialized, conventional suspension forks are designed for bigger impacts. FutureShock, however, is aimed more at reducing vibration and protecting the rider’s upper body from fatigue over longer rides.
At the opposite end, the new Roubaix is more straightforward.
Seatpost flex is one of the primary sources of rider comfort while sitting in the saddle, and bike designers have long understood that decreasing the seatpost’s diameter and increasing its effective length can enhance that effect. As such, the new Roubaix’s seatpost collar is now 65mm lower than usual — well below the seatstays, in fact — and the seat tube opening is flared above that to provide room for the post to move. In addition, the Specialized CG-R carbon fiber seatpost incorporates an unusual kink up top that promises even more movement, and while the company could have gone further with a more undersized seatpost diameter (like Cannondale and others), the 27.2mm size is the smallest option that still allows for easy replacement as needed.
Trek’s latest Domane SLR endurance platform presents a very different approach to the same issue.
On any bike, it’s not just the seatpost that flexes when a rider hits a bump; the entire seat tube bends like a diving board. Frame designers — particularly those working with carbon fiber — have long attempted to enhance that movement without compromising other aspects of a frame’s performance.
With the Domane SLR, Trek incorporates the groundbreaking IsoSpeed “decoupler” that was first seen on the original Domane, launched in 2012. A mechanical pivot at the intersection of the top tube and seat tube separates those two elements from each other (hence the “decoupler” moniker). This allows the seat tube to flex much more than usual when hitting bumps, as it no longer is constrained by the top tube or seatstays, yet it also keeps the frame from flexing in ways you don’t want it to.
This latest version ups the ante by offering user-adjustable ride stiffness, tunable with a handy vertical slider that effectively changes the length of that diving board by altering the fulcrum point — just like what real-life competitive divers do, in fact.
The effectiveness of IsoSpeed has rarely been disputed, but earlier Domanes were criticized for delivering an unbalanced ride with the front end decidedly less cushy than the rear. The new Domane SLR, however, now incorporates a Front IsoSpeed mechanism to match. Here, the upper headset bearings sit in a pivoting cradle instead of the usual fixed seat, allowing the steerer tube to flex more than usual when hitting bumps. And just like with the rear IsoSpeed setup, the isolated two-dimensional movement on Front IsoSpeed promises to limit the undesirable out-of-plane movement that can yield unpredictable handling.
Otherwise, the new Roubaix and Domane SLR are quite similar to each other.
Typical for the segment, the geometry on both bikes features mellower handling and more upright riding positions relative to full-blown race bikes: the head tube angles are slacker, the front ends are taller, the wheelbases are longer, and the bottom brackets are lower, all of which prioritize stability and confidence over agility.
Also standard on both the Domane SLR and Roubaix are flat-mount disc brakes, 12mm-diameter thru-axles, and room for tires up to 32mm-wide (the Roubaix is disc-only, but the Domane SLR is also offered with rim brakes). A little extra practicality is on tap for the Trek with its hidden fender mounts; the Roubaix incorporates fittings for Specialized’s optional SWAT storage box down by the bottom bracket.
Carbon fiber construction keeps the frame and fork weights similar for both, too. Trek claims an official weight of 2,030g for its top-end 56cm Domane SLR Disc model, including the frame, fork, headset, integrated seat mast topper, front and rear IsoSpeed units, and all associated hardware. Specialized claims 1,975g for a 56cm Roubaix under similar conditions (and including the FutureShock cartridge).
For this head-to-head review, I rode both bikes for an unusually long period as compared to typical bike tests — 16 months for the Domane, five months for the Roubaix. I tackled a wide range of both paved and unpaved surfaces throughout, and also sampled a collection of wheels, tires, and saddles on both machines to get as well-rounded an opinion of their respective characters as possible.
It’s also worth noting at this point that I’m not comparing specific models here, but rather the performance of each platform in general. Both bikes are offered in a wide range of build kits and multiple grades of carbon fiber, and while the Domane SLR tends to be slightly more expensive for a given spec, they’re close enough to be considered direct competitors.
On paper, these bikes target the exact same type of rider and promise similar performance benefits. But in the end, they couldn’t be much more distinct.
The same, but different
The coil-spring front suspension on the Roubaix is easily the most polarizing feature of either bike so it makes sense to discuss that first. Say what you will about the FutureShock’s aesthetics, but in terms of function, it works far better than one might expect — myself included.
Coming from a mountain-bike background, I initially questioned Specialized’s decision to omit any sort of damping mechanism in the FutureShock design. But in fairness, it’s precisely that approach that allows the Roubaix front end to be so effective at protecting your hands from vibration. FutureShock isn’t so much a way to absorb individual bumps as it is a filter for the road buzz that can be so disruptive on longer rides. Provided you take the time to select the right spring for your weight and riding style — there are three different spring rates available — your hands essentially float in the sweet spot of the spring’s travel range while the front of the bike busily follows the contours of the road beneath you.
FutureShock isn’t just about comfort, either; there’s also a traction benefit, which I happily exploited while racing the mixed-surface Boulder Roubaix race earlier this year, where tires tend to skitter through the many loose-over-hardpack dirt turns that punctuate that course, and washboard sections make it hard to keep the front end on the ground. With FutureShock, I was able to push down harder on the front end than I normally would have, and the tire stayed more confidently planted for faster cornering and more effective speed control.
That said, the lack of damping can feel clunky on bigger bumps, and with such stiction-free movement, the bars are constantly moving up and down to some degree, especially in out-the-saddle sprints and climbs. How disruptive you find that movement will depend on your preferences, but there’s no way to eliminate it completely, even with the stiffest spring option.
There’s also no getting around the FutureShock’s ungainly appearance. Effective or not, it certainly challenges widely accepted notions of how an elegant, high-end road bike should look.
Trek drew plenty of criticism with the original Domane for its unbalanced ride quality: the rear end was pillowy smooth, but the front end was comparatively harsh. With the Roubaix, it’s the exact opposite. FutureShock is incredibly effective on vibration, but less so on individual bumps. The extended seatpost, meanwhile, works better on unexpected impacts, but feels considerably stiffer overall.
The effectiveness of the flexing CG-R seatpost head is also dependent on the amount of saddle setback and rider weight: heavier riders and/or riders running more saddle setback will notice some benefit, but lighter riders who ride with their saddles further forward likely won’t be able to tell the difference between the CG-R and a conventional carbon seatpost.
In comparison, the Domane SLR is far more balanced. Front IsoSpeed rides firmer than the FutureShock cartridge on the Roubaix: the latter eradicating vibration almost completely; the former behaving more like a filter that removes the harshness from the road surface. Nevertheless, it’s still very effective, and offers a vastly smoother ride than what the previous-generation Domane front end once offered. To put it in automotive terms, FutureShock is like an old Cadillac; Front IsoSpeed is more akin to a well-tuned German suspension.
Meanwhile, I continue to be in awe of how well IsoSpeed works out back, and the adjustable version only improves it further still. Whereas the rear end of the Roubaix is still occasionally jarring and buzzy, the tail end of the Domane SLR varies from eerily smooth to firm-yet-comfy, depending on where you place the slider. The system does bob more under power than what Specialized uses on the Roubaix, but that softer feel also leaves you feeling fresher after a long day.
As a bonus, Trek has done a great job of integrating both IsoSpeed units into the Domane SLR frame. They’re nearly invisible from a distance, and in profile, there’s almost nothing in the Domane SLR’s shape to suggest that there’s anything unusual baked into the chassis.
Ride comfort isn’t the only thing that matters when it comes to endurance road bikes, though, and while the two bikes once again share plenty of character traits, there are still notable differences.
Trek has achieved the once-dichotomous performance characteristics that bicycle frame makers have sought for ages: excellent stiffness where you want it; copious amounts of give elsewhere. The front end is rock-solid when climbing or sprinting out of the saddle (steerer tube flex notwithstanding), and that huge main triangle yields little when mashing the pedals.
Meanwhile, the Roubaix, with its more slender and svelte frame construction, feels slightly less stout, but arguably livelier beneath you — less muscle, more personality.
Nevertheless, Trek may have strayed too far toward the stability end of the spectrum when it comes to the Domane SLR’s handling.
By nature, endurance bikes are built to lend their riders more confidence while on the road (or dirt). And while the Roubaix’s bottom bracket is already lower to the ground than what you’d normally find on a race bike, the Domane SLR is practically scraping the asphalt with a full 80mm of drop relative to the axles (70mm is more common on road bikes). Likewise, the Roubaix geometry also features shorter chainstays and shorter wheelbases across the board, as well as longer trail dimensions.
As a result, the Domane SLR is stable almost to a fault, lending heaps of rider confidence when it comes to staying upright on the straight-and-narrow, but feeling less willing to snake its way through twisty stretches of road. The Roubaix is still steady in its demeanor, but not as extreme in its approach, requiring a less deliberate lean and less countersteering to hit your apexes. It’s nimbler through the corners, feels more eager to snake its way down through fast and twisty canyons, and generally seems more playful overall as compared to the sleepier Domane SLR.
Bits and baubles
Elsewhere, it’s more a question of subtle quirks and novel features when it comes to distinguishing between the Domane SLR and the Roubaix.
Both bikes are approved for tires up to 32mm-wide, but only Trek takes full advantage of that clearance from the factory. Depending on the model, Specialized equips each Roubaix model with 26mm or 28mm-wide tires instead, arguing that it’s a more appropriate size for the paved surfaces on which most Roubaix riders are expected to ride. Indeed, this contributes somewhat to the Roubaix’s spritelier personality straight of the box when riding on the road, but at the expense of multi-surface capability.
Specialized’s tire size argument holds some merit, but switching to 32mm-wide tires still substantially expands the comfort envelope in terms of what the Roubaix can handle. Given the minimal impact in terms of weight and rolling resistance, it’s a bit disappointing that Specialized decided against diving right into the high-volume pool straight from the factory, especially given the fact that the company obviously had no qualms building the entire bike around the FutureShock suspension unit.
The Domane also has the edge in terms of all-weather capability with its discreetly integrated fender mounts, which still leave room for those meaty 32mm-wide treads. Curiously, no fender mounts are included on the Roubaix at all.
Specialized does incorporate mounts down by the bottom bracket for the handy SWAT storage box, however — a tidy plastic container with enough room for a spare tube, an inflator cartridge and head, a tire lever, and a multi-tool. It’s more an issue of aesthetics and convenience (cue the anti-saddle bag crowd), but neat to have nonetheless.
I wouldn’t normally go into depth on bottom brackets when comparing two bikes, but given the proliferation of press-fit systems — and the annoying creaking that often goes with them — it’s worth mentioning that Specialized has the upper hand here.
On the Domane SLR, Trek uses its long-standing BB90 system, which features a 90mm-wide bottom bracket shell with cartridge bearings that press into recesses that are molded directly into the carbon fiber structure. From an engineering standpoint, BB90 makes a lot of sense: it’s always better to space bearings further apart on a rotating shaft, there’s more room for bigger frame tubes and broader chainstay spacing for extra tire clearance, and with no additional cups required, it saves a decent amount of weight.
But those bearing seats can loosen over time, and while Trek offers slightly oversized bearings to fit in those situations, no other aftermarket solutions exist. Meanwhile, Specialized has reversed course from recent years, outfitting every new Roubaix (save for the top-end S-Works version) with a conventional threaded shell. It’s a few grams heavier, but far easier to service at home, and offers more aftermarket options and greater compatibility with different crankset formats.
Unfortunately, that advantage is negated by the Roubaix’s woefully clumsy headset adjustment.
Instead of the usual single preload bearing and headset cap sitting atop the steerer tube, a pair of grub screws sit on either side of the upper headset cover. The lower ones adjust the bearing preload, and the upper ones are tightened on top of those to lock the setting in place — in theory, not unlike how an old threaded headsets work.
In reality, though, having just two points of contact (instead of the fully circumferential one you would normally get by evenly pushing the stem down on top of the upper headset cover) makes it tricky to get a balanced adjustment. Tightening the upper set screws on top of those can also add extra unwanted preload, and there’s no way to directly counter-rotate the lower and upper set screws against each other; thread-retaining compound is a must.
As a result, I found myself on more than one occasion with a headset that was either tighter than I ideally wanted, or one that refused to stay tight. In general, the design feels disappointingly unfinished and crude, to the point where it arguably should never have left the engineer’s computer.
Taking everything into consideration, then, which one would I choose?
Specialized deserves a lot of credit for incorporating something as radical as FutureShock on to its highest-volume road family. It’s undoubtedly polarizing, but it also works. That said, it also has a few rough edges, the ride quality of the rear end can’t keep up, and there are a few too many curious spec issues to ignore.
Had Specialized addressed all of this before the bike’s release, it might have been a closer fight. But as is, the Domane SLR’s ride quality is more balanced, it feels more refined and polished overall, it includes fender mounts for year-round usability, and at least in my opinion, its more cohesive design just flat-out looks better.
For me, my money is on the Domane SLR.