Specialized Aethos 2 Expert

Specialized’s new Aethos 2 Expert represents a revamp for its lightweight, versatile road bike range. It’s still very light, but it’s even more versatile thanks to geometry tweaks that make it more suitable for a larger collective of riders. Throw in excellent ride quality and you have all the ingredients for a fun, fast and responsive machine.

In my opinion Specialized went through a bit of meh period around ten years ago, at least when it came to the ride quality of its carbon frames. They were good, but they lacked the balance of performance versus ride quality, they all felt a bit rigid and clinical.

Consequently I remember riding the S-Works Tarmac SL7 back in 2020, because it was a massive revelation. Spesh had nailed it: it was light, stiff and rode absolutely beautifully. It was a major turning point in its carbon bikes, and something it built on with the SL8, and now this Aethos 2.

Many bike designs create comfort through specific parts of the frame or setup: narrow seatstays to promote flex, for instance, often in conjunction with a sloped top tube to increase seatpost length – again because that allows greater vibe-dampening flex.

It doesn’t stop there. The selected carbon grade and the exact nature of its layup affect the direction and nature of any flex too, and the whole frame and fork here feels sublime. It creates the stiffness required for this kind of race bike, while minimising harsh vibrations, and all without sacrificing feedback from the road. It’s a very hard balance to achieve, especially this well.

It’s worth pointing out that while the Aethos 2 will take much wider rubber, Specialized has specced 28mm tyres. I take that as a sign it hasn’t just dialed up the stiffness and relied on tyre volume to make it comfortable, something I think a few brands are guilty of as road tyres grow.

I’ve said it before, and I’ll keep saying it – you can’t hide a poor frame design behind soft tyres.

This smooth-but-connected ride quality provided the basis for everything I did on the Specialized. Because none of the contact points were beating me up, I could ride it hard for hours, and the whole bike just feels really planted.

Chunky chainstays and a large bottom bracket area create stiffness where it’s needed, and a sub-metre wheelbase means the Aethos 2 feels nippy and nimble. With those attributes it’s the perfect bike if you ride a lot of hills, and I found its now slightly higher and more relaxed geometry very comfortable on the long climbs. That sub-7kg weight certainly helps too.

It’s a confident descender. On my main test hill it handled all the technical sections with ease, including the off-camber chicane. The whole bike felt balanced, very sure-footed and responsive to shifts in body position as lined I up for the next apex. It really is a joy to ride, and I think it’s worth pointing out that this new Aethos is far from a full endurance bike.

Frame & Fork

While many post-launch headlines focused on the Aethos 2’s increased frame weight, in truth it was negligible – around 10g on the S-Works models, which are 595g in the 56cm size. In reality this remains an impressively light machine, with this 56cm Expert’s frame a claimed 705g, and the full bike weighing a very respectable 6,960g on our own scales.

That’s lighter than Specialized’s claimed 7.12kg (something we don’t see very often), and I’d say quite spectacular for an Ultegra Di2 bike.

Beyond a taller front end, the Aethos 2 looks much the same as its predecessor. It’s retained that rather retro, traditional road bike look thanks to tubing that’s ever so slightly ovalised, and there are no huge chunky aero sections to be seen.

Spesh has directed brake hoses and gear wiring through the frame for a modern, clean finish, while the standard round 27.2mm seatpost is almost niche by today’s standards.

The Expert model only comes in this Gloss Dolomite Metallic scheme which, as nice as it is, could be brighter – it’s a little dull for my taste. Shame there’s no choice.

As before, the Aethos 2 Expert uses Specialized’s FACT 10r grade carbon for the frame and fork, and runs a threaded BSA bottom bracket. Tyre clearance is up from 32mm to 35mm though, and the new bike runs Specialized’s own design of SRAM’s Universal Derailleur Hanger (UDH), which it says is lighter and less ugly. Though probably more politely than that.

Specialized says that data from over 100,000 Body Geometry fittings has gone into creating a better fit for the average rider here. The refinements give a position that increases comfort, and therefore – in the real world – increases performance.

In a nutshell, they have increased the stack height by 15mm for a slightly more upright riding position, while increasing the wheelbase by 7mm and slackening the head angle by half a degree for extra stability.

For comparison, a 56cm Aethos 2 has a stack and reach of 580mm and 391mm, versus the original’s 565mm and 395mm. The top tube of the new bike is 5mm shorter at 557mm, and the wheelbase is 998mm instead of 991mm.

The Aethos 2 has a head angle of 73 degrees, and a seat tube angle of 74 degrees. Fork offset has risen to 47mm from 44mm, and the BB drop is now 75mm compared to 72mm to accommodate wider, taller tyres.

Finishing kit

Entry into Aethos 2 ownership starts with this Expert model at £5,499. The £7,249 Pro model gets the same Ultegra Di2 groupset (or SRAM Force AXS if you prefer) but adds a 4iiii power meter, Roval Alpinist CLII wheels and tubeless ready tyres. It also gets an integrated cockpit.

The two S-Works frames get an upgrade to 12r carbon fibre and are built with either SRAM Red AXS or Shimano Dura Ace Di2 componentry. Whichever version you go for, it’s £11,499!

If you fancy the frameset-only route to create your own build, £3,499 will get you the FACT 10r carbon frameset found here, while the 595g-framed S-Works option will set you back £4,999.

The Shimano Ultegra Di2 groupset on our Expert model wears a 52/36T semi-compact chainset and a 12-speed, 11-30T cassette (for full details of how Ultegra Di2 works and feels check out our in-depth review). It gives a wide-ranging spread for all kinds of riding, while the 160mm front/140mm rear rotors provide a huge amount of stopping power for such a lightweight bike.

The Expert is the only model to get a two-part cockpit, in the shape of the alloy Pro SL stem and a carbon Roval Alpinist handlebar. That creates a fairly typical 125mm drop and 75mm of reach. On this 56cm bike the spec is for a 100mm stem and a 420mm-wide bar.

The carbon seatpost is a Roval Alpinist, and topped with Specialized’s own Body Geometry Power Expert saddle. It’s a setup I got on well with thanks to the seatpost being in-line (my preferred choice) and the saddle offering a good firm padding with a narrow profile.

The Roval C38 wheelset is a decent performer with a bit of depth (38mm) for slight aero gains, while staying shallow enough for versatility in climbing and on windy days. At around 1,600g they’re heavier than many rivals, but not by so much they held me back on the hills or anything. Both wheels run 24 spokes and have an internal width of 21mm. Throughout testing I found them reliable and issue-free.

The tyres are 28mm S-Works Turbos, which I’d describe as middling. The rim width of the Roval wheels make them look and feel much narrower than they are, too. On the upside they proved durable and trustworthy through all kinds of weather, but I’d definitely upgrade to something more supple and grippy.

The competition

In its latest guise the Aethos 2 has moved from competing with the likes of Giant’s TCR race bike to butting heads with its endurance machine, the Defy.

Back in 2025 I reviewed the Defy Advanced SL 1 in a M/L size, which corresponds well to this 56cm Aethos. With a stack and reach of 577mm/384mm there are a few millimeters here and there, but the biggest difference is in the wheelbase, which is 1,010mm on the Defy. The Giant can take larger tyres (40mm) which makes it a bit more all-road though, if that’s your thing.

The Defy Advanced Pro 0 has a similar spec to this Specialised and costs exactly the same at £5,499, though you get a power meter with it too.

It’s the same story when it comes to Merida: the Aethos used to sit alongside the Scultura, but now it’s closer to the Scultura Endurance for stack and reach. The Scultura Endurance matches the Aethos on tyre clearance at 35mm but does slightly better on value. The 9000 Ultegra Di2 equipped model includes a carbon cockpit and Reynolds deep section wheels, and costs £4,950.

I actually rode the latest Scott Addict 20, the firm’s endurance road bike, alongside the Aethos 2. In the M/54 size it has practically the same dimensions as the Specialized. I was really impressed with it, and at £4,299 with a near identical spec to the Aethos 2 Expert, it’s a relative bargain as well.

In terms of ride I’d put them all very much on par with each other. They all offer an excellent ride feel that’s stiff where it’s required, and exceptional comfort – especially at the rear end.

The Aethos 2 wins on weight however, and by quite a decent margin against the Merida.

Overall

Think of the Aethos 2 as a race bike with the edge taken off. It’s more suitable for long rides but is still quick, responsive, stiff and light – it has all the positives of the original, but it’s noticeably easier to live with for the average Joe.