The new Specialized S-Works Aethos is a 5.9kg non-racer built for the love of riding

“Lightest-ever” disc frame weighs just 585g claimed

The new Specialized S-Works Aethos

With the dust from the Tarmac SL7 launch just barely beginning to settle, Specialized has launched an entirely new 2021 road bike called the Aethos (pronounced AY-thoss).

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Built around a disc-only frame claimed to weigh an astonishing 585g in its lightest finish (size 56), the top spec S-Works Founders’ Edition is said to weigh just 6kg for a complete bike. 

This halo Founder’s Editions Aethos will cost £13,000 / $14,500 / AU$22,000, and the two other S-Works builds will be priced at £10,750 / $12,500 / AU$18,500.

Specialized S-Works Aethos: here’s what you need to know

  • All-new disc-only super lightweight road bike with a design focused on ride quality and weight
  • 585g claimed weight for a 56cm frame
  • Same geometry as Tarmac SL7
  • Design team lead by Peter Denk, the engineer behind the original Scott Addict and Cannondale SuperSix EVO.
  • Top-spec Founder’s edition costs £13,000 / $14,500 / AU$22,000 and weighs 5.9kg claimed
  • Tarmac SL7 remains the race bike – the Aethos has no aero features and teams won’t be riding it
  • Cables (hoses) notfully integrated
  • Clearance for 32mm tyres
  • Threaded bottom bracket
  • S-Works models cost £10,500 / $12,500 / AU$18,500

Specialized S-Works Aethos: all about the riding, not the racing

When the Tarmac SL7 launched, Specialized made a point of saying that it no longer made sense to differentiate between the aero (Venge) and lightweight (Tarmac) platforms, and so they were merged into one. 

With that in mind, you might question why the brand is now launching an exceptionally lightweight bike, but the Aethos is not intended to be a racer, and Specialized says we won’t be seeing sponsored teams riding the bike. Instead, the Aethos is a bike simply “for the love of riding”, one that offers “the purest imaginable road riding experience”. 

The Aethos is designed to be the best possible ride, not necessarily the fastest.

As a result, the Aethos has none of the aero features we typically see on modern road bikes, instead sporting round tubes and a remarkably traditional looking semi-compact profile, without dropped seatstays. 

Nevertheless, it shares fit geometry with the Tarmac SL7 (a medium gets 544mm of stack and 384mm of reach) and, should you wish to race it, the frameset is UCI-approved. 

There’s not a dropped stay in sight.

The engineering lead on the Aethos was none other than Peter Denk, the man behind legendary bikes including the original Scott Addict and the first two generations of the Cannondale SuperSix EVO. 

Specialized says it used “staggeringly large supercomputer simulations” to arrive at the Aethos’s final frame shape, focusing on ride quality, stiffness, style and weight.

While the Aethos nominally shares its carbon with the Tarmac SL7, getting the same FACT 12r grade stuff, Specialized says it used “an entirely new way to lay-up” the bike’s frame that involved reducing the number of “stiffness layers” and using “larger, longer and more continuous, unbroken [carbon] plies”.

The idea was to create a frame with “no lazy fibres” – i.e. ones that don’t pull their weight in forming part of the structure, if you’ll forgive the confusing choice of idiom. 

The Aethos is claimed to be the lightest disc road frame ever produced at 585g for a size 56 with the lightest finish, and the Founder’s Edition – which is limited to 300 bikes worldwide – weighs a claimed 5.9kg for a complete bike without pedals.

Specialized says the Aethos beats all the competition in stiffness-to-weight, citing figures of 162Nm/°/kg (newton meters per degree per kilo) for the new bike versus 146Nm/°/kg for the Cervélo Rca and 141 for the Canyon Ultimate CF EVO 10.0 Ltd.

Despite these remarkable numbers, the Aethos has a respectable rider weight of 275lbs (125kg).

Disc-only, electronic-only

The Aethos is a clean-sheet design with relatively traditional features.

In the virtual launch presentation, the team behind the Aethos variously described the new frame as “very classic looking” and, in a perhaps slightly unfortunate turn of phrase: “almost boring looking”. 

There’s no denying it’s a wonderfully pared-back design, with clean, simple lines. 

The Aethos is a truly elegant bike.

Interestingly, despite the general trend towards ever-higher levels of integration and the Tarmac SL’s fully-internal routing, the S-Works Aethos doesn’t hide its cables completely. 

The frameset is only compatible with electronic groupsets, though, so the front-end is still quite tidy. 

Like the Tarmac, the Aethos accepts tyres up to 32mm wide (26s are fitted as standard) and it features a conventional threaded bottom bracket. 

Threaded BBs seem to be experiencing a comeback.

It’s also disc-only, a statement of intent if ever there were one. When Specialized hinted that this bike was coming, we speculated that a so-called ‘pure’ road bike might feature rim brakes, but it seems Specialized really is all-in on discs. 

As you’d expect, Specialized will be offering the S-Works Aethos in some seriously fancy builds.

The halo Founder’s Edition Aethos gets a Shimano Dura-Ace Di2 groupset and features Specialized’s brand-new Alpinist cockpit, which weighs a claimed 247g (for a 110mm stem and 420mm bar width), while all builds get the new Alpinist seatpost (136g claimed for 27.2mm × 300mm). 

The Aethos Founder’s Edition is the only model to get the new Alpinist one-piece cockpit.

There are also ‘standard’ S-Works builds in a choice of Di2 and SRAM Red eTap AXS flavours, and all models are specced with Roval’s recently-launched and super light Alpinist CLX wheelset.

There’s a frameset option too, which gives you some truly lovely paintjob choices. 

You’re probably wondering how a sub-600g bike rides, so make sure you check out BikeRadar editor George Scott’s first ride review.

Specialized S-Works Aethos range: builds, weights and prices

S-Works Aethos Founder’s Edition

S-Works Aethos Founder’s Edition.
  • Claimed weight: 5.9kg (56cm)
  • Groupset: Shimano Dura-Ace Di2
  • Wheels: Roval Alpinist CLX
  • Price: £13,000 / $14,500 / AU$22,000

S-Works Aethos SRAM Red

S-Works Aethos eTap.
  • Claimed weight: 6.26kg (56cm)
  • Groupset: SRAM Red eTap AXS
  • Wheels: Roval Alpinist CLX
  • Price: £10,500 / $12,500 / AU$18,500

S-Works Aethos Shimano Dura-Ace

S-Works Aethos Di2.
  • Claimed weight: 6.0kg
  • Groupset: Shimano Dura-Ace Di2
  • Wheels: Roval Alpinist CLX
  • Price: £10,500 / $12,500 / AU$18,500

S-Works Aethos frameset

S-Works Aethos frameset.
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  • Claimed weight: 585g (56cm, frame only)
  • Price: £3,750 / $5,200 / AU$8,000