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Specialized S-Works Aethos review

14 May 2021

Page 2 of 2Specialized Aethos: First ride review on 5.9kg disc brake road bike


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

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.


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Page 2 of 2Specialized Aethos: First ride review on 5.9kg disc brake road bike