The new Specialized Aethos is simultaneously simple and amazing. Much like an iPhone, it appears sleek and minimal on the outside, but with incredible technology and performance hiding inside.

Admittedly, Specialized just sort of brought back “a road bike”. But that oversimplification underserves just how good this bike is. Yes, it pushes the boundaries of how light a mass production (or even a full custom, boutique) road bike frame and fork can get. It also pushes the ride quality beyond what I’ve found on other bikes recently.

This thing is an absolute joy to ride, and I had a really, really hard time finding any faults with it. Like, any. OK, maybe one. But let’s look at the details first…

Aethos Frame & Tech Details

specialized aethos pro ultregra di2 road bike closeup frame details

From a distance, you’d never know this was anything special. The Aethos’ presence is subdued, and I love it. On a recent group ride, I had two different friends ask what it was…the graphics are that subtle. Note the paint color in these photos…it’s blue, yet so thinly applied that you can still see the carbon through it. When the sun catches it just right, it’s gorgeous.

specialized aethos pro ultregra di2 road bike closeup frame details

Closer up, little curves and shapes appear. Slopes leading into the head tube…

specialized aethos pro ultregra di2 road bike closeup frame details

…a slight flare the the base of the seat tube, tapering at the ends of the head tube…

specialized aethos pro ultregra di2 road bike has a threaded bottom bracket

…and even a little bump at the front of the chainstays as they wrap under the bottom bracket. The tubes are all comparatively thin by today’s standards, which is part of how this frame ends up so light. Claimed weight for the Pro and Expert models is just 699g for size 56, with paint.

specialized aethos pro ultregra di2 road bike closeup frame details

It does this with normal features and standards, like a BSA threaded bottom bracket.

specialized aethos pro ultregra di2 road bike closeup frame details

The frames are designed around electronic drivetrains, so you’ll only find wire ports on the complete bikes. It’s cleaner, and also less hardware to save weight. But, on the Pro and Expert versions, there are cable ports and hardware you can attach if you want to build up a frameset with a mechanical group. But whyyyyyyyy….?

specialized aethos pro ultregra di2 road bike closeup frame details

Dropouts and thru axles are minimal…

specialized aethos pro ultregra di2 road bike closeup frame details

…with beautifully recessed ends. Even the brake hose routing is clean, leaving almost nothing visible.

specialized aethos pro ultregra di2 road bike closeup frame details

The Alpinist seatpost only comes in 27.2mm diameters, to the top tube wraps around the thinner seat tube, directly into the seatstays. This wider stance gives the bike decent tire clearance (pics below), and more laterally/torsional rigidity.

specialized aethos pro ultregra di2 road bike closeup frame details

Just a couple pics of the carbon layers visible through the paint.

specialized aethos pro ultregra di2 road bike closeup frame details

The front derailleur mount is removable, with a cover plate available for 1x setups.

specialized aethos pro ultregra di2 road bike tire clearance

The bikes come with 700×26 tires, but Specialized says it’ll clear up to 700×32.

specialized aethos pro ultregra di2 road bike cockpit details

The cockpit is comfortable, with their carbon handlebar with flattened ergonomic shaping on the tops.

specialized aethos pro ultregra di2 road bike with roval alpinist lightweight seatpost closeup

The Roval Alpinist seatpost is crazy light (claimed 136g), but you’ll want a saddle with a cutout in order to easily access the adjustment bolts.

Rounding out the spec are their Roval Alpinist CL wheels, which aren’t tubeless compatible. And this would be my only complaint – tubeless is the future.

The S-Works 120tpi Gripton tires have puncture protection, but that didn’t stop a piece of glass from cutting through to the tube and flatting me on my first ride.

As much as I love and prefer a tubeless setup, I’ll admit that these tires rode really well. And the wheels are so light, spooling up quickly and handling on par with expectations for a high end wheelset, maybe better considering their weight. More on their performance below.

Specialized Aethos Actual Weight

specialized aethos pro ultegra di2 road bike actual weight shown on a scale

I tested the Aethos Pro Ultegra Di2 in a size 58. Actual weight for this bike was 14.86lb (6.74kg). That’s without pedals, but does include the tubes in the tires as it comes out of the box.

Retail price for this model is $7,400. That gets you a complete Shimano Ultegra Di2 group, S-Works Short & Shallow carbon bar w/ Supacaz bar tape, Specialized alloy stem, and Body Geometry Pro saddle with hollow ti rails and carbon base. The standout components are the Roval Alpinist carbon seatpost, and their ultralight Alpinist CL wheels…which are not tubeless compatible, hence the tubes. They come wrapped with 700×26 Specialized S-Works Turbo 120tpi tires with BlackBelt puncture protection.

Aethos Ride Review

2021 specialized aethos pro lightweight road bike review and action riding photo

As we’d expect from a featherweight bike, it climbs like a dream. It feels light, in a good way. There’s “bad” light, and then there’s a well-spec’d bike that feels and rides light without getting noodly or scary. The Aethos is the latter, offering a solid, stable ride while also being ridiculously light.

But let’s be real…a bike that’s a couple pounds lighter is like throwing your water bottle off before ascending. It’s the sum of the parts that makes a bike climb well, and this one’s got some good parts.

2021 specialized aethos pro lightweight road bike review and action riding photo

Everything starts with the frame. Specialized has all the charts and graphs to prove the Aethos (even the much lighter S-Works version) is stiff in all the right ways and places.

On the road, that translates into a bike that handles power input smoothly and efficiently. There are bikes that feel like they have more instantaneous acceleration, but I’ll take the pleasant smoothness of this bike any day. Don’t get me wrong, the Aethos is no slouch, it just doesn’t have to prove itself by hammering your backside.

2021 specialized aethos pro lightweight road bike review and action riding photo

Its handling is spot on. Front to rear, it feels really well balanced and just drives through corners. I just want to keep saying smooth, smooth, smooth…but also precise. It just rolled into, around, and out of corners so well that I could really concentrate on my entry and exit points, maintain more speed, and not have to worry about whether the bike would obey my commands.

2021 specialized aethos pro lightweight road bike review and action riding photo

2021 specialized aethos pro lightweight road bike review and action riding photo

Descending on the Aethos is equally enjoyable. The bike was every bit as stable at 42mph as at 15mph. We have one particularly fast, sweeping descent near a quarry here, where pebbles and grit often litter the road, the pavement’s less than perfect, and it’s easy to hit 40+mph curving into the bottom of it. I’ve never felt more stable hitting that section than on this bike.

As much as I try to avoid heaping glowing praise on something (because, you know, we’re supposed to be objective-bordering-on-snarky, right?), hot damn do I love this bike! It honestly does everything well, it’s comfortable, and it’s light as sin. Win, win, win.


  1. mudrock on

    Such a fanboy you are, but that’s refreshing in the cycling press I suppose. Love that this bike stayed away from proprietary seat posts and cockpits. but the lack of tubeless compatibility is a huge mistake. Even the pros are going tubeless. So many advantages over tubes and sew-ups.

    • Gregory Thomas on

      The Alpinist rims have a tubeless-style inner rim wall shape. Nobody intentionally designing a rim strictly for tubes would use that shape. Considering also that the Light-Bicycle equivalent rims (almost guaranteed to be the manufacturer) are labeled as tubeless compatible, my guess is that they were supposed to be for tubeless and for one reason or another didn’t pass Specialized’s internal testing for tubeless use. It could be something like, due to the ultralight construction, too much rim compression happens with tubeless beads, lowering the spoke tension too much, and the nipple seat area cannot handle the required increase in spoke tension. Or that same tubeless bead deforms the rim irregularly or inconsistently… Etc etc.

        • Greg on

          “Medium” evidence. Specialized releases a new wheel or rim, and Light Bicycle has a matching new rim at the exact same time (not months later). Also more than one former Specialized employee being “99% sure”.

    • Tyler Benedict on

      The Tarmac SL7 seemed a bit stiffer overall, like when hammering out of the saddle or just cruising over rougher surfaces.

      The most illustrative example I can think of is, on the Tarmac, with an all out standing sprint effort I could sometimes pull the rear wheel up a bit (I tend to pull up with my hamstrings and hip flexors, too, when I really want to crush it) if I wasn’t super careful about keeping my power and weight balanced.

      I never felt this on the Aethos, despite it being lighter. It’s a subtle thing, having just a bit of “give” under hard pedaling. By no means was it a slouch, though, I looked down during the sprints to see if I could notice any flex, and otherwise really tried to pay attention for it, but didn’t ever notice it. If anything, I’d argue that feeling slightly less stiff is what made this bike such a joy to ride, able to accommodate the nuances of the rider and road without giving up any performance.

      The Tarmac was also surprisingly comfortable over long distances…for an aero road bike. But the Aethos is the one I’d choose for most rides.

      – T

  2. dang3rtown on

    Other than in TT, tubeless is actually falling off a bit for road. The biggest reason is that it just doesn’t offer much of a real advantage over a standard clincher with a latex tube. Weight and RR appear to be slighter better with latex if anything and the puncture resistance is nice but not a big enough issue that it makes the hassle of tubeless worth it.

    The other issue with tubeless is Freds have been destroying their nice carbon wheels at alarming rates by over-inflation. Outside a track exactly zero people need more than 80psi or so but fat old rich guys keep trying to ride tubeless at 100psi and their wheels are literally exploding.

  3. scottg on

    Looking forward to SeaOtter 2022, with the new 7.85% lighter and 26.7% stiffer Aethos IIs
    with 3.02% improved compliance. I have hefted a friends Aethos, best bike ever for roof rack

  4. Miclaroc on

    Must also say having seen them in person and side-by-side with Sl7s the Aethos is so minimalist as to be downright “generic” looking and certainly boring compared to the sexiness of the Sl7 in relative terms. However, that being said, this bike does sound really promising and innovative and perhaps next iteration of the Sl7 (8?) will be some hybrid of the two. Either way I wish I could afford both…. I really wouldn’t know how to choose just one. It’s also kind of a shame going for ultra lightweight they don’t make the s works mechanical compatible nor rim brake compatible given the aim here…

    • DY on

      I’d say it depends on the way you use it. If you race, get an SL7. It’ll be the faster bike.
      If you don’t race and like to cruise along and enjoy being outdoors over maximum speed, I could see someone choosing the Aethos.

  5. Jorge Tomé on

    The weight is really not impressive…
    At 6740g without bottle cages, without pedals, without GPS support…
    Almost achieved to underpass my gravel bike weight with 29er 2.1 tyres, including 2 pedals, 2 bottle cages, GPS support and rear light support.
    Well done Spezy!

  6. E B on

    I was looking at this in a shop the other day. It is beautiful. But the price tag… ouch.
    I have an original Cervelo R3. I’ve used a Dremel daintily to remove the original cable stops, and consulted with a carbon repair guy on where the most “meat” was on the layup when I couldn’t re-use the rivet hole. Anyway, I’ve Di2’d it.
    Rides amazing.
    Lighter as a complete bike than the Atheos as pictured.
    Has tubeless, but lacks disc brakes.
    Anyway, the point is you can achieve beautiful light nice riding bikes in different ways than expunging all the cash from your wallet. It feels new again, or just renewed.

    • jason d west on

      I was always under the impression that LB are a seller of high quality carbon hoops and not an actual manufacturer of carbon goods.

  7. tinkertowncycle on

    This is pathetic. It’s just another UGLY black-out (specialized) bike. It’s just a road bike! Nothing special. This bike is not doing anything (other than disc brakes) that a bike from a 100 years ago has already done. I like checking out bikerumor now to get a kick out of the advertising like this.

    You all do realize this is just another road bike? A cheaply made carbon toy. NOTHING SPECIAL GOING ON WITH THIS BIKE. NOTHING. Maybe designed complications, but it’s not SPECIAL.

    If anything it’s another specialized down grade.

    Why don’t ya’ll do some research into real bikes? Save up some money for a little while and get a real bike you love not a piece of garbage you’ll be sick of in a few months to maybe two years.

      • tinkertowncycle on

        Nobillete, Moots, Eriksen, Wiegle, Parlee, Gunnar, or anything bike made by a human being you can shake hands with. Doesn’t even have to be a “brand” anyone has heard of, but I’d say stay away from large brands like Specialized, Trek, etc. It’s like going to McDonalds, BurgeKing, Wendys, Etc. for what you think is a great burger.

    • Tom on

      That’s a pretty strong reaction. You do realize that there is convergence in bikes, correct? Using the same set of constraints (materials, form factor) and goals, bikes will become more alike. But there is certainly more difference between this and the SL7, vs the old Italian/French/American steel bikes that we all used to fetishize. maybe you are tired of the relentless commercialization of bikes. Guess what, that’s how the world has always/will always work in a consumer market. Ignore it or have an aneurysm, your choice. And no, I’m not a Spec fan boi, have never owned one. But I think they make good stuff. I just never got a bro deal, and never felt like dropping the $ for one.

    • Martin Hayman on

      What an interesting story! And, since I already own one of these Cannondales, it saves me the grief of wishing for this latest — very attractive — Spesh model. Oh, and no trouble ever with the Pressfit bb.

  8. Bryin on

    A good bike? Yes… Worth $7400? No way. This is a made in China bike (also wheels, bar, stem) with an Ultegra group. Costs Specialized about $1000 to make without marketing costs. We will see how “great” the frame is when Luther Teknick cuts one apart on YouTube. I have NOTHING against the bike or Specialized but the value of package is very low.

  9. Onrhodes on

    And with this mentality don’t but a Ford, Toyota, Honda, Chevy, etc. Buy a car from the small fabrication shop down the street. You’ll be fine.

    There is absolutely no reason not to buy a bike from a big manufacturer. Nor is there a reason not to go buy a moots, IF, Seven, etc. I think the big guys/gals like Specialized, Trek and Cannondale have way more $ to push engineering and test concepts. I can’t really think of the last time a small time builder really changed how the industry builds bikes.

    • Robin on

      ^This. Buy what you want and makes you happy, not what some anonymous commenter in an internet comment section says you need to buy. His agenda won’t necessarily make you happy or give you the ride you want.

  10. nphone on

    My Roval Alpinist CL HG Wheelset box says made in Taiwan. Light Bicycle is in Xiamen, China.
    Are you sure they are the same? At $1600 with US warranty at any dealer vs $1300 from light, you don’t save much.

    FYI The test sheet is in traditional Chinese, not Simplified.

  11. lolo on

    My 2017 Cannondale SuperSix Evo HiMod Disc is in fact lighter (6.85 kg complete with pedals, 2 water bottles, Garmin mount & cadence sensor), built with mechanical Dura-Ace and Mavic Cosmic wheels. It is also originally minimal/old school without the Ethos hype for the trendy ones.

  12. Bennett Shane on

    If you already had an aero race bike for fast group rides, and wanted a second road bike for super long and hilly days on mixed quality roads, would you rather have an Aethos, or a Canyon Endurace?

    • Chris on

      Aethos. But I do not know Canyon. Aethos is just so light that hilly rides feel flat. My husband has a Roubaix for longer endurance rides on less than smooth roads. He loves that. But it is about 2kg heavier than Aethos.

    • Jeff on

      I owned a Canyon Endurace…. The geometry didn’t suit me. If you are used to race bike geometry, you might not like endurance bike geometry. I don’t know how to describe the Endurace other than not too exciting.

      The Aethos is a dream if you want aggressive geometry but comfort and light weight. I just got mine (Pro) and have just a few rides on it, but love it. And yes, it does remind me my old SuperSix Evo… If only they had internally routed cabling down the tubes and didn’t have the odd thru axle in front, QR in back on the disc models. The Aethos feels like what the SuperSix could have been, but it’s definitely better than the previous generation S6.

  13. Chris on

    I bought the Aethos S-works Dura Ace Di2 last weekend. My first ride was an absolute dream – 84km around the lake here and was still wishing I could do more. I cannot get myself off the thing now and I look forward to biking everyday. Totally different bike than what I am used to, which is the Turbo Creo SL that I use for commuting (I live in Switzerland and do not have a flat ride into work). I do not regret for a second the purchase despite the horrifyingly high price tag. I tried the Pro model Aethos as well before deciding to go with S-Works. The weight difference between the two is almost not noticeable. Both are insanely light (especially when I compare it with my Creo!). The S-Works just felt better to me, so that’s what I went with. I have already ridden in a downpour on slick roads downhill, and I have to say that I felt more stable on the Aethos than I do on my Creo gravel, which was surprising to me. I will keep the Creo as my commuter bike so I don’t turn up to work a complete sweaty mess, but will ride the Aethos for workouts and fun the rest of the time.


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