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by James Huang
October 13, 2016
Photography by James Huang
It’s a rare occurrence when a new technology truly moves the bar in the cycling industry. Specialized did just that when it first introduced the SmartWeld head tube on the Allez alloy road bike in 2012, and now it’s expanded the concept to a groundbreaking hollow bottom-bracket shell. According to U.S. technical editor James Huang, the new Allez DSW SL isn’t just an interesting bike because of that SmartWeld technology; it may just be the very best privateer race bike in the company catalog, regardless of material, signaling a new era in high-performance aluminum bikes.
The technology of aluminum bicycle frames has certainly progressed over the years, with newer alloys, advanced shaping processes, and refined heat-treating procedures all steadily improving the breed. Even so, nearly every frame is still assembled the same way: the tube joints are mitered for a tight fit, and then TIG-welded, just as they have been for ages. More wildly shaped tubing has made those interfaces increasingly complicated in terms of geometry, but the weld joints themselves really haven’t changed.
In contrast, SmartWeld – developed by Specialized “creative specialist” Chris D’Aluisio – turns all that on its head with a completely different take on how to join frame tubes together.
Instead of mitered joints, SmartWeld uses radically hydroformed frame sections that move the weld location away from the most highly stressed area. In addition, the joints themselves feature more of an end-to-end geometry — more like connecting the ends of two straws instead of making them into a “T” — along with rolled-in edges that create a natural channel for weld material.
The “SmartWeld” concept began a few years ago with this ingenious one-piece hydroformed head tube. Instead of being essentially cylindrical with the top tube and down tube mitered and welded as usual, the SmartWeld head tube provides a flatter surface and built-in channels for the welding rod for a stronger and more foolproof union.
According to Specialized, the SmartWeld concept not only makes for a lighter frame, since the tube walls can be made substantially thinner (especially at the joints), but also one that’s stronger and stiffer given the relocated weld locations and larger joint cross-sections. Those little channels supposedly make for more consistent welds that are easier to lay down and require less finish work, too. Ultimately, what results is an aluminum frame with a shape that more closely resembles a carbon fiber one.
Specialized first used SmartWeld four years ago to boost the front-end torsional strength and rigidity in the head tube area of the aluminum Allez. Now, a radical new bottom bracket with a wholly new construction method — conceived by Specialized senior advanced R&D engineer Chuck Teixeira — is now doing the same for drivetrain stiffness.
The SmartWeld concept has now been expanded to the ingenious bottom bracket shell, which is formed as two halves and then brazed together along a central seam. The carbon-like shape provides heaps of surface area for welding the adjoining tubes.
Just like that first SmartWeld head tube, the bottom bracket of the new Allez DSW SL is a radical departure from the norm, comprising an enormous hollow structure built in two hydroformed clamshells that are then brazed together down a central seam. There’s still a tube for the bottom-bracket cups, but it’s now just a separate thin-walled sleeve that’s inserted into the shell.
“Because of how carbon works, you can really add stiffness just by changing the direction of your materials,” said Conner Swarthout, the Specialized engineer who turned Teixeira’s idea into engineering reality. “But with aluminum, the only way to add stiffness is to add more weight, unless you can be creative with how you make your structure. That’s what’s so great about the shell. It’s putting material in the place where it needs to be to get the right stiffness.
“We were looking at the bottom bracket on the original Allez — and really, all aluminum frames — and you’re looking at this really small structure where all these forces are centralized on the frame. It just didn’t make a lot of sense. By opening up the shape and opening up the walls the way we did, it makes for much stiffer and more efficient structure.”
The lines around the bottom bracket on the Specialized Allez DSW SL closely resemble those of the carbon Tarmac — and not coincidentally, Specialized says the stiffness numbers of the two frames are virtually identical.
What results is a bottom-bracket area with a hugely increased cross-section that not only resists pedaling forces better than the original SmartWeld Allez — by 30%, according to Swarthout — but also allows the adjoining tubes to be bigger as well. In fact, Specialized claims stiffness test figures roughly on par with the previous-generation carbon-fiber Tarmac SL4, and with no weight penalty as compared to a more conventionally constructed aluminum chassis.
“This frame ended up heavier because we went with the aero seat tube,” Swarthout said. “But the weight of [the SmartWeld] bottom-bracket shell is the same as what it would on a current aluminum bike.”
Actual weight of my 52cm test frame is 1,187g – about 300g heavier than an S-Works Tarmac of the same size — plus 370g for the matching fork and compression plug. However, whereas the flagship carbon frameset retails for US$3,750, an Allez DSW SL is a comparative bargain at US$1,200, including the same full-carbon fork.
Specialized offers the Allez DSW SL in three complete builds, or as a bare frameset for riders who prefer to choose their own components.
Specialized sent my test sample as a custom spec to reflect what a well-heeled racer might build for themselves, including a SRAM Red eTap wireless groupset, 64mm-deep Roval carbon clincher wheels wrapped in speedy Specialized S-Works tires, an aero carbon-fiber seatpost and handlebar, and a Specialized S-Works Romin Evo saddle matched with grippy Specialized Roubaix handlebar tape.
Total weight was 6.93kg (15.28lb), without pedals or accessories.
Specialized’s latest road bikes have gone heavier on distinctive styling, but lighter on in-your-face branding. Even without the logo on the down tube, there would be no mistaking what this is.
I’ve ridden a lot of aluminum bikes in my day, and while they cover a wide spectrum in terms of performance characteristics, they nevertheless invariably share one common trait: a subtle, but distinct, stiffness gap relative to high-end carbon frames. Step on the gas, and even the best aluminum frames will exhibit a slight hesitation before squirting forward.
Not so on the Allez DSW SL.
In terms of drivetrain and torsional stiffness, the Allez DSW SL feels much closer to Specialized’s much more expensive Tarmac than any other aluminum frame — as perhaps should be expected given the frame’s Tarmac-like skin. Stabs at the pedals are rewarded with right-now accelerations, and there’s an immediacy to the bike’s handling reflexes that fits perfectly with its sporting intentions. Cast these comments as fluffy hyperbole if you wish, but even the most skeptical luddite won’t be able to deny the difference in feel on the road. It’s real, and dramatic.
The SmartWeld bottom-bracket shell is the key to the Allez DSW SL’s insanely stiff backbone. No one else has figured out how to make a shape that’s so big, and so hollow.
That stiffness dictates how the bike is ridden, too. Whereas some bikes seem content just to cruise and take in the scenery, the Allez DSW SL feels more like a muscle car stuck in rush-hour traffic, frustratingly unable to show off its potential. You certainly could soft-pedal, but on a bike like this, why would you? It feels more at home when treated with a little less respect, and doesn’t come into its own until given a little extra juice.
Even the surface finish seems chosen with competition in mind. While the anodized and bead-blasted surface is lighter than a paint job, it’s also tougher and much more resistant to scratches, with no paint to flake or chip — perfect for stuffing into travel cases or the back of a car week after week. As an added bonus, it’s easier to keep clean, too.
As are most things built for racing, there are some compromises — and in the case of the Allez DSW SL, what you gain in speed, you lose in comfort in equal measure.
With a huge down tube, a large-diameter head tube area, and aero-profile seat tube – along with a similarly deep carbon fiber aero seatpost to match — the Allez DSW SL isn’t exactly supple over bumps, nor does it damp road buzz as would a good composite chassis. And Specialized doesn’t include the option for fitting higher-volume rubber inside the frame, either, with a maximum officially allowed tire width of just 24mm.
Tire clearance is good, but not great. Specialized could certainly gain more ground here by abandoning the narrow-format BB30 bottom bracket shell.
In fairness, competitors focused on efficiency might not be too concerned about that aspect of things. However, bear in mind that even race courses aren’t always held on perfect pavement, and when it comes to going faster, narrower isn’t always the way to go (nor does it provide the utmost in cornering grip). It perhaps isn’t surprising, then, that Specialized first launched this frame as the Allez Sprint, a 1x-specific speed machine whose sole purpose in life was to dominate criteriums and corporate lunch rides — in other words, all-out sufferfests usually lasting about 90 minutes or less.
The geometry on Specialized’s racing-oriented aluminum machine is even edgier than the Tarmac’s, too. The reach dimension on the Allez DSW SL is up to 11mm shorter, depending on size, and the stack is about 10mm lower. And while the Tarmac’s bottom-bracket drop and chainstay length vary slightly with frame size, Specialized pegs those dimensions on the Allez DSW SL at 69mm and 405mm, respectively. Coupled with the correspondingly shorter wheelbase, what results is a more aggressive posture that’s better suited to repeated out-of-saddle sprints, hard cornering, and quick maneuvering than long and fast pulls in front of a peloton.
Specialized infuses the Allez DSW SL with a few aero details, such as the deep-section seat tube (and matching saetpost), and a triangular-profile down tube.
Assuming you’re okay with all of that, any remaining complaints I have are minor.
The cable routing is only partially internal, and the brazed-on housing stops on the chainstay and seat tube can’t be removed — so unless you’re running SRAM Red eTap, don’t bother trying to get a clean installation on a Shimano Di2 or Campagnolo EPS drivetrain. Full-length housing on the rear brake makes for a bit more squishiness than I’d prefer, too.
The internally routed derailleur ports can be capped on the down tube if they’re not used…
…but there are still vestigial housing stops on both the chainstay and behind the seat tube.
Riders who prize quiet-running bikes may also scowl at the Allez DSW SL’s press-fit bottom bracket shell. While I would certainly prefer a threaded fitment here (or at least one of the press-fit formats that use wider bearing spacing, such as PF86 or BB386EVO), I will admit to having much better luck on press-fit frames with metal shells, which respond better to requisite surface treatments such as retaining compounds and adhesives.
On the plus side, the 30mm-diameter (inner dimension) bearing cartridges press directly into the shell with no additional cups required, which means one fewer interface to potentially creak, and yes, a handful of grams saved, too.
Some may walk away from this review with the impression that I didn’t like the Allez DSW SL that much, but the opposite is true. I liked it a lot, in fact, and briefly even considered buying one. That it’s so single-minded in its purpose is hardly a bad thing. The only question is whether your needs and wants are the same as what the Allez DSW SL’s designers had in mind.
If your goal is a reasonably priced bike built specifically for racing, I can think of few bikes that fill this niche better — but also few bikes that would be as poorly suited if racing isn’t in your immediate future.
The Specialized Allez DSW SL is the most race-bred aluminum bike I’ve ever ridden.
These are among the tallest chainstays available on an aluminum frame.
The seat tube essentially flares out to the full width of the bottom bracket down below for extra rigidity. The welds admittedly aren’t exactly pretty, but the design of the SmartWeld system supposedly makes it much easier to build a weld that’s structurally correct.
The anodized finish on this Specialized Allez DSW SL does little to hide the lumpy welds, but Specialized sees them more as a feature than a blemish given the uniqueness of the frame construction.
The Allez has typically been associated with journeyman race machines, and that persona is certainly apt here.
The aluminum dropouts are very tidy.
Specialized supplied CyclingTips with a custom-built version of its Allez DSW SL frameset, including a SRAM Red eTap wireless electronic groupset.
The SRAM Red eTap wireless electronic group continues to impress with crisp and reliable shift performance. It’d be nice if multiple shifts were executed a little more quickly, though.
So-called “mid-compact” 52/36T chainrings have fast become the norm in recent years.
SRAM has done a good job of minimizing the visual bulk of the front derailleur, especially since it also houses its own battery and wireless hardware.
The “DSL” in the bike’s name pays homage to Chris d’Aluisio, the Specialized engineer who developed the original SmartWeld concept.
Specialized first introduced the Allez DSW SL frame as a 1x-specific version with no provision for a front derailleur. This one, however, includes a braze-on mount.
The included Roval Rapide CLX 64 carbon clincher wheels are plenty fast and reasonably stable in crosswinds. The S-Works tires are flat-out excellent, with extremely low rolling resistance and outstanding grip. They’re quite fragile, though.
The shape of the Roval hubs was penned by Specialized industrial designer Brian Szykowny, who also painted a fleet of track-prepped Allez DSW SL frames for a round of the Red Hook Criterium.
The Specialized aero road bars look rather unusual with their substantial built-in rise. The idea is to get the steerer tube as short as possible to minimize the frontal area. Thankfully, Specialized at least includes enough space directly next to the clamp for accessory mounts.
The untaped tops aren’t terribly comfortable (or grippy), especially if you prefer to wrap your thumbs around the back of the bars. Then again, that’s not really what they’re meant for.
The proprietary carbon fiber seatpost continues the aero profile of the seat tube. It certainly looks sleek, but it’s also completely unyielding to road impacts.
The seatpost clamp is nicely done, with a smooth profile and dual barrel nuts with fully replaceable hardware.
The Specialized Romin Evo was a supremely comfortable place to spend time — at least for me.