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Specialized S-Works Aethos review

14 May 2021

The Aethos is virtually the perfect bike, from its razor handling to incredible climbing. If only it had tubeless wheels and cost a bit less

Cyclist Rating: 
Light and stiff • Incredible climber • Fantastic handling
Clincher-only wheels

Photography: Peter Stuart and Mike Massaro

Every day’s a school day. I recently learned from an article by fellow journalist Carlton Reid that British marque Carlton Cycles made a carbon-tubed, alloy lugged bike back in 1971.

Motor Cycle and Cycle Trader magazine reported at the time, ‘The weight of the complete machine is 13lbs 12oz,’ continuing that ‘most certainly the experimental Carlton in carbon fibre is the most exciting adaptation of modern materials to cycle building that we have seen for many years’.

Sadly the bike never went anywhere, but it struck me as wonderfully coincidental that I’m testing what’s claimed to be the world’s lightest production disc brake bike – the S-Works Aethos – and its weight? It’s 6.23kg, or 13lbs 12oz in old money. Is anything new under the cycling sun?

Number, number, weight, division

The foundation of the Aethos is its 585g frame and 270g fork (claimed, 56cm), 1,248g Roval Alpinist wheels and 136g Roval Alpinist seatpost. Yet that’s about where the ‘special’ components end – everything else is pretty standard.

Of course Dura-Ace Di2 and £240 S-Works saddles aren’t exactly run-of-the-mill, but time and again brands dress up average-weight frames in ridiculous components – notably entirely unsuitable tubular wheels – so they can label their bikes ‘lightest ever’.


The Aethos bucks that. It’s light but it has day-to-day usability. The wheels are clinchers; the bars and stem are two-piece, and the cables are – gasp – visible. So while you may want to change a tyre or cut the steerer, you won’t need an NVQ in needlework and brake bleeding. The saddle even has padding.

The only non-ordinary thing here is that the Aethos isn’t – further gasp – UCI approved, because it’s well under its 6.8kg minimum weight.

So (a) Specialized has saved itself €5,000 on getting the certificate (I’m told that’s what it costs) and (b) in theory this is not for pro racers, with the Big S proclaiming, ‘Sod the rules, we want to make a bike for you.’

And, my days, if it hasn’t gone and made the best mainstream bike out there. 

Buy the Specialized S-Works Aethos now from Tredz

Too talented by half

Think of everything you want a road bike to be and the Aethos is it. The handling is superb. Specialized has borrowed the geometry of its brilliant Tarmac SL7, but when combined with the lightness of the Aethos the result is a bike that’s just that bit more responsive than the SL7. Specialized has then blended this character with stability and a stiff punch.


Eddy Merckx said a lightweight bike cost Luis Ocaña the 1971 Tour when the Spaniard came unstuck on a bend, and you don’t argue with Eddy. But what Eddy can’t argue with is how well the Aethos descends, displaying none of the skittishness that plagues ultralight bikes, instead presenting the assured platform of a bike 2kg heavier.

The frame flexes enough to track undulations and offer grip, but never so much it feels wavy. However, as brightly as the Aethos shines in those departments, it is outright retina-eviscerating in one specific area: climbing.

All bikes can go uphill if you pedal them hard enough, but what the Aethos does is ride up first, hook a motor winch to the crest then abseil down to collect you. This bike climbs like an invisible force is pulling it. It’s just brilliant, and this extends to acceleration too, where stiffness and lightness combine to make rocket fuel.

Buy the Specialized S-Works Aethos now from Tredz

So are there any weaknesses? Well, it’s not an aero bike. To hit weight and stiffness targets Specialized has used round tubes. And again to save weight the paintjob is understated.


As a friend remarked, ‘Eleven grand for a bike that looks like it was made in 2012?’ And there’s a shred of truth to that, because although it blows every other mainstream bike out of the water, its pricetag moves it into a realm in which resides the Argonaut Road Bike and Prova Speciale. Both are custom, so different beasts in a sense, but they’re stunning to look at and amazing to ride. The Argonaut remains the best bike I’ve ever ridden.

Then – and this is not a criticism, just a point of interest – the idea this is not for pros is murky. I bet the Aethos will end up being raced with ballast, and it may even suggest Specialized knows the UCI is poised to lower weight limits.

Buy the Specialized S-Works Aethos now from Tredz

I do have one conjecture though: the wheels. These Alpinists are lovely to ride but they’re not tubeless, so I swapped in a pair of DT Swiss ARC 1100 50mm tubeless wheels with 28mm Schwalbe Pro One tyres.

That added 17mm to the rim depth and 2mm more rubber yet little more than 300g in weight, and on balance I preferred this setup. Tubeless wheels are faster, more comfortable and I hate punctures.

Still, however you look at it, while crazy-light carbon bikes may have existed since the 1970s, never has one ridden this well. The Aethos is an absolute triumph.

Pick of the kit

Castelli Estremo gloves, £95,

I’m a sensitive soul when it comes to my fingers, which means I have an alarming number of gloves, and at the top of the tree are the Estremos, the kind I would have given to Shackleton.

The Gore-Tex Windstopper fabric is only water-resistant, so a prolonged shower will see them start to wet out. But I can accept this given the Estremos’ fleece lining has rebuffed the coldest of rides, including through snow at -2°C up a Swiss mountain, and yet they offer enough dexterity to operate even Di2 buttons.

Buy the Castelli Estremo gloves now


The gilded lily

This Aethos not enough for you? The £13K 5.9kg (claimed) Founder’s Edition has lighter paint, a one-piece Alpinist cockpit (255g), custom saddle (134g), blacked-out Turbo Cotton tyres and a CeramicSpeed BB.

Buy the Specialized S-Works Aethos Founder's Edition now

Gain ounces, drop pounds

Lower-grade Fact 10r carbon means the Expert frame weighs 699g (claimed), and Ultegra Di2, DT Swiss R470 alloy wheels, alloy bars and 120tpi S-Works tyres add up to a claimed 7.14kg, but it costs £5,500.

Buy the Specialized Aethos Expert now from Cyclestore


Frame Specialized S-Works Aethos
Groupset Shimano Dura-Ace Di2 Disc
Brakes Shimano Dura-Ace Di2 Disc
Chainset Shimano Dura-Ace Di2 Disc
Cassette Shimano Dura-Ace Di2 Disc
Bars S-Works Short & Shallow
Stem S-Works SL alloy
Seatpost Roval Alpinist
Saddle S-Works Power
Wheels Roval Alpinist CLX, S-Works Turbo Cotton 26mm tyres
Weight 6.23kg (56cm)

All reviews are fully independent and no payments have been made by companies featured in reviews


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