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, saddleback.co.uk
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
Alternatively…
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
Spec
| 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) |
| Contact | specialized.com |
All reviews are fully independent and no payments have been made by companies featured in reviews
Specialized Aethos: First ride review on 5.9kg disc brake road bike
Words: Peter Stuart
Specialized has unveiled its brand new lightweight road bike platform, the Specialized Aethos, which boasts an incredible frame weight of 588g in a 56cm size, and hits only 5.9kg for an overall build.
The lightest production disc road bike we’ve ever seen, the Aethos has not been conceived for competition in the WorldTour, and it makes no attempt to stick to the UCI’s weight limit of 6.8kg.
Yet, despite it’s 5.9kg overall weight, this bike is not simply an exercise in cutting grams.
Specialized claims that the Aethos is the most technologically advanced bike the brand has ever produced, yet is designed around the needs and passions of the most dedicated bike lovers.
As a result, the Aethos is a rare example of a top-end Specialized bike not built purely around aerodynamics.
Buy the Specialized S-Works Aethos from Tredz for £10,750
This was down to a reconception of the goals for Specialized’s top road bike, with the brand acknowledging that the needs of pro riders and elite amateurs were becoming increasingly divergent from many of the most passionate bike consumers.
Watch: Specialized S-Works Aethos – first ride review
Buy the Specialized Aethos from Specialized now
Passion over pro performance
‘It became even more clear to us at the point of creating the Tarmac SL7 as a single solution to racing, that we were drifting even further from some of the priorities that core riders were after,’ says Stewart Thompson, road category leader at Specialized.
‘These riders are incredibly discerning – they value performance and their identity is largely defined by the riding experience. But they don’t always prioritise aerodynamic integration and performance criteria in the same way that competitive racers do.’
Specialized claims this is the lightest disc road bike ever produced on a mass market level. According to the Cyclist scales, this size 56cm Aethos comes in at 6.2kg with bottle cages, and Specialized claims the S-Works Aethos comes in at an average of 6.0kg. The Jet Fuel colourway Founders Edition weighs in at a more svelte 5.9kg.
Importantly, that isn’t down to lightweight components, as we often see on other special edition super-light bikes. The S-Works Aethos is equipped entirely with standard componentry – it even has a Dura-Ace crankset rather than an S-Works Praxis crank.
To hit this weight point, Specialized hasn’t employed exclusive super high-modulus carbon fibre, which is historically a favourite means of cutting weight. It uses the same Fact 12r carbon as used on the S-Works Tarmac, and rather it’s an altogether new shape and what Specialized call the ‘strategic use of this material’ that has allowed it to hit this low weight.
Finite Element Analysis
This bike was designed using something called Finite Element Analysis, or FEA for short, alongside a powerful supercomputer. Now that’s not uncommon amongst frame design, as most top-end frames will use FEA to determine shape and carbon layup. The difference with the Aethos is that it went through 100,000 simulations to create this finished product.
Buy the Specialized S-Works Aethos from Tredz for £10,750
The project was spearheaded by Peter Denk and Sebastian Servet, who are based in Germany, and involved extensive computations and data analysis.
The brand built more and more data before refining it down until they hit an effective golden bike design – a perfect sweet spot and an entirely new shape.
‘We often spend a few months working on analysis and validating a frame shape, and then spend a year or more working in layup,’ says Thompson. ‘This was a three-year project for us in which the first year was spent completely in an FEA stage, going deeper than we ever have before. That’s because the shape itself represents basically three quarters of bikes performance.’
The first prototype weighed an incredible 545g, and Specialized boasts that it didn’t need much material to be added to make it rideable.
Buy the Specialized Aethos from Specialized now
Despite the Aethos’ innovative new shape, it actually looks fairly classic, with tube shapes that remind us of earlier generations of Tarmac. Yet up close, there is some advanced design at work.
The entire frame uses a type of constant curvature across the tubes to ensure one tube flows into another and there are no blunt junctions. Amongst those 100,000 FEA simulations, Specialized created thousands to find exactly the right curvature where the seat tube flows into the BB and flows into the down tube.
Every single fibre in the bike is doing work, in what Specialized describes as a layup with no ‘lazy fibres’, which has helped cut wasted material and hit this low weight.
That has all come together to mean the bike is not only incredibly light, but also really rigid too. Specialized claims the Aethos has a stiffness to weight ratio that beats everything aside from the Tarmac SL7.
The ultimate goal for Specialized was the ‘perfect ride’. Not one for World Tour pros but people who simply love to ride bikes.
Geometry and components
While light weight was the most attention-grabbing goal, Specialized wanted the Aethos to offer a complete package in riding and handling terms. No surprise, that the geometry and fit is identical to the Tarmac SL7 that Specialized released a few months ago.
The S-Works Aethos comes with a new Roval Alpinist wheelset, which hit a very impressive weight of 1,248g.
Specialized has also used an Alpinist seatpost and the top tier Founders Edition comes with an integrated Alpinist bar and stem cockpit that will be available for purchase for other S-Works Aethos frames too. As standard the bikes come equipped with S-Works carbon bars and alloy stem.
The Aethos comes with S-Works 26mm Turbo cotton clincher tyres, though there is officially clearance for 32c tyres, which will be a big attraction for Aethos consumers eager to take on gravel or cobbled routes – which we expect to match the Aethos profile well.
At present, there’s no announcement of specs of Aethos that will sit below the S-Works tier. However, we can only assume that we’ll see the Aethos shape used across a range of new lightweight Specialized bikes hitting more affordable price points.
S-Works Aethos Founders Edition, with Alpinist cockpit, at a price of £13,000
At £10,750, the Aethos sits at the top of the Specialized tree in terms of price, but the extra £250 over the Tarmac SL7 is on account of currency exchange, rather than innately more expensive production costs.
There are three options for the Aethos in total – the Founders Edition equipped with Shimano Dura-Ace Di2 at £13,000. Then comes our Dura-Ace Di2 spec and an identically priced Sram AXS Red spec.
On paper, the Aethos hits some incredible stats, and so we were raring to take it out on the road to test its real-world performance.
Specialized S-Works Aethos: First ride review
When climbing, this bike really does feel weightless. It’s almost surreal when rocking the bike from side to side, it almost feels like there’s nothing beneath you. The kilogram or more of saving over most disc brake road bikes makes a really palpable difference, and it almost feels like having a hand on your back uphill.
Cyclist testing the Aethos, picture by Chris Sansom
Of course, light weight isn’t a huge gain if it comes at the cost of rigidity and with a loss of power, and this is where the Aethos really performs well. As it’s surprisingly rigid from front to back, it has a transfer of power and a turn of speed that is really striking, and while riding it I found myself dreaming of classic climbs I’d love to return to in search of a PB.
While geometry plays a huge part in handling, what really distinguishes top racing frames is making sure they’re stiff in the right places, and they have flex where it’s needed. That’s certainly the sensation aboard the rear-end of the bike, which handles road scarring and potholes really well – very reminiscent of the Tarmac SL6, in fact.
Coming downhill, the Specialized Tarmac has always been a champion. It historically leads the industry when it comes to stiffness across the bottom bracket, and the Aethos really mirrors that handling quality.
Aerodynamics hasn’t been a priority for this bike, where normally Specialized designs everything with aerodynamics at the heart of it. So in theory means it won’t carry the speed that we’re used to from the Venge or Tarmac.
On flat stretches, of course, it lacks a bit of the sheer speed of the Tarmac SL7 or the outgoing Venge, yet as a bike that encourages you to ride without a GPS unit and power and speed data, I didn’t really notice it. It still felt like a quick bike, and with the aerodynamic Roval Alpinist wheels it still probably performs relatively well against the wind as a whole system.
Ultimately, the Aethos almost captures opposing ride qualities all at once – it climbs like a light-footed mountain goat yet sprints and descends with all the resolution of an aero race bike.
So far, we can only make first impressions, but it seems that Specialized has really captured a sense of riding for passion rather than pure speed. In that sense it has achieved exactly what the brand set out to do.
We look forward to spending more time with the Aethos over the coming months to create a long-term review.
