Specialized S-Works Aethos shuns aero, embraces low weight and ride quality

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Most of the performance drop-bar world has fully embraced the aero efficiency theme, with everything from racing bikes to gravel bikes regularly chasing free watts. With the new S-Works Aethos, however, Specialized casts all of that aside in favor of more traditional metrics like low weight, high stiffness, and good ride quality — just like the good old days.

Aethos isn’t a wholesale change in direction for Specialized by any means, but it’s a genuinely fantastic bike nonetheless, and hopefully a sign of things to come from the industry in general, because if you’re not racing, then #aeroreallyisnteverything.

Story Highlights

  • What it is: An ultralight carbon fiber road bike designed solely for structural efficiency and ride quality.
  • Frame features: Ultra-low weight, traditional carbon fiber tube profiles and shaping, threaded bottom bracket, partially external cable routing, standard 27.2 mm round seatpost.
  • Weight: 617 g (actual weight, painted 56 cm frame only); 310 g (actual weight, fork only, uncut steerer); 6.10 kg (actual weight, 52 cm S-Works Aethos Dura-Ace Di2 complete bike, without pedals)
  • Price: US$12,500 / AU$18,500 / £10,750 / €11,800 (Specialized S-Works Aethos Dura-Ace Di2 or SRAM Red eTap AXS)
  • Highs: Gloriously lightweight, outstanding stiffness, excellent ride quality, nimble handling, easy maintenance and serviceability, room for 32 mm tires.
  • Lows: Very expensive, proprietary front brake adapter.

Aero, schmero

Looking back through the years, it isn’t too hard to divide the progression of mainstream road bike technology into eras. There was the gradual switch from steel to aluminum, followed by the wholesale conversion to carbon fiber. Then there was the weight-weenie period, where “stiffness-to-weight ratio” become an everyday term amongst enthusiast road riders, and every gram saved was as good as gold.

But once those gains started leveling off — and especially with the introduction of the UCI’s 6.8 kg minimum weight rule — bike brands began looking at other areas to improve performance, and it didn’t take long before aerodynamic efficiency became priority number one. The original Cervelo Soloist certainly wasn’t the lightest or stiffest bike around, but when you considered the numbers, it wasn’t too hard to see where this was going.

Suddenly, the currency of progress transitioned from grams to watts, and everyone was off to the races to see how efficiently their bikes could be made to slice through the wind.

It’s all round(ish) tubes and straight lines on the Specialized S-Works Aethos.

Specialized certainly wasn’t going to let that train leave the station without hitching a car to the engine, and even the venerable S-Works Tarmac — long one of the torchbearers of stiffness-to-weight — began to surrender to the aero movement with the SL6 generation in 2018, and then went full-aero in 2020 with the SL7.

Throughout all of this, traditional performance metrics like structural stiffness and weight were still important, but when it all came down to it, as long as a bike could be made to hit 6.8 kg for the sponsored pros, it was all good. And what about ride quality? Wait, you did say you wanted to go fast, no? That’s not to say most of these bikes rode like concrete horses, but it’s safe to say that rider comfort wasn’t the main thing engineers were thinking about.

The seatstays are tiny, and the chainstays nowhere near as bulbous as what’s been commonly used on high-end carbon fiber road racing bikes in the last few years.

There’s nothing wrong with wanting to go faster, but while all of the attention was being paid to lopping off a second here and there, riders who still pined for bikes like the original Scott Addict and the pre-aero Cannondale SuperSix Evo were starting to feel left out in the cold. After all, that UCI limit only matters if you’re competing in UCI-sanctioned events. If you’re not — as is the case for the vast majority of us out there — one could easily argue that those traditional metrics matter more than wind tunnel tests, but in recent years, the number of choices that still subscribed to that philosophy dwindled in number almost to the point of being non-existent.

Now, however, we have a surprising new entry from Specialized to address those wants and needs, in the form of the S-Works Aethos.

What the heck is the Aethos?

Basically, the Aethos is what you get when you throw any and all concerns about aerodynamic performance out the window, and refocus on high stiffness, low weight, and rider comfort. It’s about structural efficiency instead of aerodynamic efficiency, function over form, and an unapologetic refutation of everything the bicycle industry marketing machine — Specialized included — has been spewing out for much of the past decade.

“It was hard for many people here to wrap their heads around a high-performance road bike that wasn’t focused on racing,” said Specialized road and gravel category leader Stewart Thompson. “We were afraid that the project would meet resistance and get cancelled, so our team worked in relative secrecy for over a year. No one knew about the project until the design was finalized, and we were making our first frames.”

The tubes on Aethos are nominally round throughout, and there’s nary a sharp corner to be found at any of the joints. The seatstays connect to the seat tube up high, right where Eddy Merckx intended. There are threaded metal inserts inside the 68 mm-wide bottom bracket shell. The steerer tube is tapered, but it’s round from top to bottom. The seatpost is round, too — as well as a totally normal 27.2 mm diameter — and held in place by a good ol’ fashioned external aluminum collar. The cables run — gasp — externally up front instead of hiding in fear from the wind, and the handlebar and stem are actually two separate components, held together with clamps and bolts.

Aside from the sloping top tube, traditionalists are sure to find much to like here.

While the profile should be very familiar to any road rider who’s been around a while, Specialized still says it went through over 100,000 computer simulations for frame shape before hitting its target numbers. After all, getting a frame close to where you want it isn’t terribly difficult when it’s already been done before. But moving things well past that takes some additional work.

As expected, the Aethos frame is light, but exactly how light is still fairly striking. Claimed weight for a painted 56 cm frame is just 585 grams, and actual weight for a sample we have here is pretty much spot-on at 617 grams (including the seatpost collar, rear derailleur hanger, and removable front derailleur mount), plus 310 grams for the matching fork (with an uncut steerer tube). Put in relative terms, that’s almost 300 grams lighter than a comparable S-Works Tarmac SL7 or Cannondale SuperSix Evo, 180 grams lighter than the new Giant TCR Advanced SL, and more than 100 grams lighter than Trek’s latest Emonda SLR (and that’s not accounting for paint).

Despite the feathery weight, Specialized claims the Aethos gives up little to the Tarmac SL7 in terms of stiffness. Bottom bracket and head tube stiffness are said to be virtually identical, although rear-end stiffness takes a 20% hit. Durability supposedly isn’t a concern, either, with tube walls that Specialized says are nearly as thick as they are on the Tarmac SL6. The Aethos’s structural efficiency apparently comes from the shape of the tubes, not due to some ultra-brittle mix of high-stiffness fibers.

The seat tube flares as it joins the bottom bracket shell, but only a little bit.

On the plus side, Specialized also claims a 20% boost in rear-end compliance for the frame alone. The intentionally more aggressively sloping top tube and shorter seat tube also make for more seatpost extension relative to a Tarmac, which adds another degree of flex to smooth out road imperfection. Front-end compliance is claimed to be substantially better than the SL7 too, although Specialized admits it doesn’t have a great metric for quantifying the improvement. Either way, if that’s still not enough, Aethos is approved for tires up to 32 mm wide.

“The sloping top tube was about ride quality as much as it was for weight savings,” Thompson explained. “It gives you a lighter, stiffer front triangle and more fore-aft compliance at the saddle because of the greater exposed seatpost. While no comparison like this is perfectly apples-to-apples, our simulations suggested approximately a 20 g difference between [a frame with a] horizontal top tube and where we ended up. I guess Giant was onto something with the first TCR back in the day, huh?”

Yep, threaded.

Also ranking high on the list of priorities was ease of maintenance, although I’m not sure Specialized really deserves a ton of credit here. Although the Aethos is claimed to be quite the marvel in terms of structural efficiency, it’s essentially a road bike from several years ago — and older bikes were just easier to work on. Those exposed cables up front don’t require hours of cursing and frustration when all you want to do is swap a stem length or raise or lower your bars a bit. Removing the bottom bracket doesn’t involve a hammer. And the conventional seatpost collar is so refreshingly functional that you almost forget that all bikes used to be this way.

About the only concession to normalcy is the front brake adapter. Despite the dedication to low weight, Aethos is only offered with disc brakes (that horse has left the stable, folks), and in trying to make something lighter that’s inherently heavier than older competing technology, Specialized went with a proprietary front caliper adapter with a lower mounting hole that’s a few millimeters higher than usual. The brake itself is the same as any other flat-mount caliper, though, which is obviously a huge relief.

A standard flat-mount setup (at left) features a lower bolt hole that’s closer to the dropout than what’s found on the Aethos. According to Specialized, going the proprietary route allows the fork tip to be more hollow and saves 12 grams. But is such a small weight decrease worth the potential long-term headache? Photo: Specialized.

“The lower mounting bolt position is higher, yes,” Thompson admitted. “You must use the included brake adapter. This allowed us to mold the fork blade hollow all the way to the dropout. With normal flat mount, the lower brake stud is too close to the dropout to get the EPS in that space and mold around it so you have to fill the whole area with solid material. This feature actually saved us about 12 g in total.”

Specialized didn’t take any risks at all when it came to the Aethos frame geometry, though: it’s exactly the same as the Tarmac SL7. Aside from the more compact frame, then, the fit and handling of the Aethos should be very familiar to long-time Specialized owners.

What’s far more surprising is the graphics Specialized has applied to each Aethos — because there basically aren’t any. Aside from the usual “S” logo on the head tube and a small “S-Works 1974” decal on the top tube, there isn’t a single bit of branding anywhere on the Aethos frame. No down tube logo, no contrasting color blocks or stripes, no feature call-outs. It’s the dark grey Mercedes-AMG against a sea of NASCAR wannabes.

Models, prices, and availability

Specialized is offering the new S-Works Aethos in just three complete builds to start, all with dual-sided power meters, Roval Alpinist CLX carbon clinchers, 26 mm Specialized Turbo Cotton tires, Roval Alpinist carbon seatposts, and Specialized S-Works Power Arc saddles. All S-Works Aethos frames are designed for use with electronic drivetrains only, and again, there are no rim-brake versions.

US$12,500 / AU$18,500 / £10,750 / €11,800 gets you your choice of Shimano Dura-Ace Di2 or SRAM Red eTap AXS on top of that (eTap-only in Australia, though), and there’s also the US$14,500 / AU$22,000 / £13,000 / €13,000 Founders Edition flagship (limited to 300 pieces). That version is identical to the regular Dura-Ace Di2 model, save for a special satin silver paint job and an upgraded Roval Alpinist one-piece carbon fiber handlebar-and-stem in place of the separate S-Works SL forged aluminum stem and S-Works Short & Shallow carbon fiber bar used elsewhere.

For DIYers, Specialized will offer the S-Works Aethos frameset for US$5,200 / AU$8,000 / £4,000 / €4,500, in a choice of seven different colors, including the intriguing “Jet Fuel”, which is sanded, primed, and prepped for custom paint, but is otherwise unfinished save for a couple of removable surface decals.

All of the Aethos models should be available at retailers effective immediately, with the exception of Australia. Select retailers will carry the frameset in-store, but complete S-Works bikes will only be sold via the “click and collect” channel where you order online and then pick the bike up at the brick-and-mortar Specialized retailer of your choice.

Test ride report: back to basics

Cast aside for a moment, if you will, whatever ill will you might harbor toward Specialized. True, the California company is viewed as the 600-pound gorilla, and doesn’t exactly have the reputation for being the nicest person on the block; the subject of far too many internet memes.

Instead, think for a moment what you like about riding road bikes. Is it speed? The sound of the tires rolling across fresh blacktop when you’re moving at exactly the same rate as that glorious tailwind? The feeling of effortlessly ripping through a downhill switchback? That sense of immediacy when you rise out of the saddle on a steep uphill pitch? If you think about it, the chances are good that your most memorable moments on the bike have involved something you felt, not something your computer said you achieved — a second here, a watt there.

If some of that resonates, I have some news to share with you: this bike is annoyingly good.

This is just about the only logo you’ll find on the Specialized S-Works Aethos.

I’ve ridden an awful lot of high-end road bikes lately, but the vast majority have subscribed to the same formula. Tarmac, Emonda, TCR, SuperSix, Ultimate. They’re all so similar that it sometimes can feel like there’s no difference at all.

But in voluntarily jumping off the bandwagon, the big S genuinely does seem to have created something a little, well, special here.

My 52 cm S-Works Aethos Dura-Ace Di2 sample tips the scales at just 6.1 kg without pedals — just a hair over 13 pounds in freedom units. Stiff and responsive or not, it’s hard to argue with a disc-equipped road bike that handily comes in under the 6.8 kg figure. But this thing is stiff and responsive, and when you combine that all together, it truly makes climbing a joy.


I have never been afraid to admit that I hate climbing (ok, “hate” may be a bit too strong a word, but it’s certainly not my favorite direction). The math doesn’t lie: I have too much weight, and not enough power. But the truth of the matter is that I genuinely love going uphill on this thing. It makes me smile when the bike squirts just that little bit faster upward when I exert the slightest bit of additional pressure on the pedals. There’s a sense of connectedness stemming from how something so light can somehow also feel so solid. The bike is lively and communicative in a way that so few production bikes seem to be these days.

Build kit obviously helps to some degree, in particular the shallow Roval Alpinist CLX carbon clinchers and supple 26 mm Specialized Turbo Cotton tires on my test sample (which measure 28 mm on those 21 mm-wide rims). With a claimed weight of just 1,248 grams, the wheels wind up quickly, and their somewhat springy nature suits the frameset well. I don’t need wind tunnel data to tell me they’re actually slower in most situations than the deeper and heavier Rapides. The combination feels so good that I don’t care.

As promised, the ride quality of the Aethos is superb. I wouldn’t characterize it as being pillowy smooth, though, because it’s not. It’s comfortable, but in a more tactile and controlled way, not an overly isolating one. In comparison, the Tarmac and Venge are good for what they are, but they’re still race bikes at heart, meant to go fast first, with everything else landing somewhere further down the priorities list. As such, they both tend to be a little more chattery through poorly paved corners than I’d prefer. In contrast, the Aethos feels confidently planted and surefooted. With 30 mm-wide Challenge open tubulars, it’s magical.

The Specialized Turbo Cotton tires are a perfect choice for a bike like this: smooth, supple, fast. History has shown these to also be fast-wearing and somewhat prone to punctures, but the person buying this bike is more likely to relish the ride quality they offer than outright durability.

As fun as it is to descend on the Aethos, I also can’t pretend to not notice the bike’s missing aero component. There are heaps of mountain descents around here — Boulder, Colorado — and I know them well: how long it takes to get down, how fast I can go, what they feel like. And the Aethos — even with more aggressive wheels fitted — just isn’t quite as capable of effortlessly hitting ridiculous speeds as the Tarmac, Venge, and other bikes of their ilk. Some of that is offset by how much more confident I feel ripping through certain corners than on those bikes, but if top speed is your drug, just keep in mind that you might not quite get the same fix here.

“I can say that the Aethos is more aero than a Tarmac SL5 and does quite a bit better than other ultralight bikes like the outgoing Emonda,” Stewart explained. “Regarding the top speed on descents – agreed. If your descents have you reaching terminal velocity and tucking or spun out, it’s likely not the fastest choice. But for the descents with a lot more corners and a little slower average speed, there is nothing like this bike in my opinion.”

Handling is without complaint, though, which is to be expected given that the geometry is lifted straight from the Tarmac and Venge. The Aethos is appropriately stable at high speed, agile at lower ones, and fluidly transitions from corner to corner everywhere in between. Nevertheless, I might argue that Specialized may have played it a bit too safe here. This bike will most likely appeal to connoisseurs, many of which I’m not entirely sure will want the level of nimbleness that comes with true race bike geometry. Surely there was discussion of doing something in between the Tarmac/Venge and Roubaix, no?

Geometry is borrowed from the Tarmac and Venge, but it seems like there should have been room for something more befitting the intent of the bike.

I know I turn to automotive analogies too often, but it’s too hard to resist doing so again here. If the Venge and Tarmac are Specialized’s pure sports cars, and the Roubaix something more akin to a highway cruiser, surely there was room for a grand tourer in the middle — something nearly as quick and agile as the thoroughbreds, but requiring just a bit less attention.

As expected, working on the Aethos is refreshing compared to most modern aero superbikes. A stem swap took all of five minutes. The seatpost doesn’t slip or creak. The bottom bracket is silent (and when and if it isn’t, that’ll also be a five-minute job). If this bike were actually mine and I had it long enough to need to replace the headset bearings, that might be a 10-minute job since I wouldn’t have to redo all of the cabling and rebleed two hydraulic disc brakes.

It’s all visible and straightforward. Nothing hidden. It’s relief in mechanical form.

Someone tell me again why companies stopped using these?

Put more bluntly, this is the road bike I’d pick from the Specialized stable if given the choice. I enjoy going fast, but I haven’t regularly pinned on a number for road racing in ages. My rides more typically comprise solo exploring, and the only time I’m counting seconds is if I’m running late to get home.

This bike makes me smile, and that’s not easy to do these days.

In all honesty, this should really be a first-ride review given the limited number of rides I have on this thing so far, but experience has demonstrated to me time and again that almost never do my long-term conclusions differ from my early impressions, and I’m not seeing much of anything on this bike (aside from potential durability questions) that I’d expect to toss me a curveball.

This bike is fantastic. I don’t want to give it back. And in fact, maybe I won’t. Hate me if you wish, or call me a shill, but it won’t change my opinion.

Back to the future

One thing Specialized mentioned while presenting the Aethos to CyclingTips does give me pause, though. According to Specialized road and gravel marketing manager Jeremy Dunn, Aethos is meant “to reshape the future of modern road bikes.”

Sorry, but … no.

From where I sit, Aethos isn’t so much a reinvention of contemporary road bikes as it is just a return to how things used to be before the aero craze went mainstream. It really wasn’t long ago when every bike company focused on low weight and high stiffness. Round tubes were the norm, as were the smooth transitions that characterize the Aethos and only look so unusual because of the current context.

The chainstays are basically straight from end to end, with only the most subtle curve to them as they make their way from the bottom bracket shell to the dropouts.

Ironically, one of the principal engineers on the Aethos project, Peter Denk, was the same person largely responsible for the first-generation Scott Addict (the bike that arguably brought the stiffness-to-weight philosophy out from the shadows of smaller German brands like Storck) and some of the most coveted versions of the Cannondale SuperSix Evo. Denk is an engineer through and through, and given that it’s always been known that round tubes are some of the most structurally efficient shapes around, it’s little surprise that there’s more than a little resemblance between the Aethos and high-end bikes of yesteryear.

That the Aethos is here at all shouldn’t be a surprise, either. This is what Peter Denk does, after all. And so, Specialized might be taking just a little too much credit in claiming ownership of this return to normalcy, especially given that the California brand has been pushing the aero message harder than just about everyone. #aeroiseverything, remember?

“I think you’re pretty spot on here,” Steward admitted when I brought this up. “These principles have always held true, and Aethos was really just the opportunity to take them to the next level with our modern carbon technology and leading analysis and simulation horsepower.”

This is a legitimately fantastic bike.

Nevertheless, I’m glad that the Aethos exists, and I do at least have to give Specialized credit for taking the bold step in moving away from even its own seemingly set-in-stone path toward objective speed. For now, the Aethos feels special. This is still the bike industry, though, and competitors are sure to follow.

I sincerely hope they do. Engineering is a game of numbers and formulas, and making the math work. Data is data, and the numbers don’t lie, but sometimes it’s the heart that matters more.


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