Reviewed: The Aethos of the S-Works Crux

Described as ‘a quiver killer’ and fast, lightweight allround road and gravel bike, this S-Works Crux is one fascinating and drool-worthy machine, as Roderic Gill explains.

Watching Pogi win Strade Bianche this year (on his Colnago V4Rs road bike), you have to wonder about how far you can push a road bike into the dirt and how far you can push a gravel bike onto the tar. While the pro’s might push a road bike as far as the cobbles of Paris Roubaix, they have that luxury of a team car with spare bikes on the roof.

While real heroes might just carry on with a bone shaker velocipede everywhere and anywhere, I for one prefer to ride a gravel bike on the gravel and a road bike on the tar, or a gravel bike when I am clueless about what I will find 100km from the nearest rural town. Soft, I know.

Enter the road/gravel bike pair: two bikes to cover all the bases, preferably matched to the way you ride, the kind of rider you are and the level of performance you require.

Bikes have a certain character, which is the sum of many parts; from geometry to ride feel, aesthetics, performance focus; you name it. Perhaps, through endless riding, you have become symbiotically adapted to the precise geometry and positioning of your favourite bike. Wouldn’t it be great if we could find a pair of bikes matched by a common design brief and character; where we feel equally at home on one or the other as we shift from the road to the dirt. That’s more like a pair of bike twins than just any old combo we just happen to have in the shed.

To me, this bike twin thing really has become a thing. Some enlightened makers are now building road/gravel bike twins around a common brief. Take the Specialized S-Works Aethos project. The brief is a mix of outrageous light weight, speed, lack of gimmicks, and simply quiet unobtrusive engineering that is simultaneously classic and cutting edge. What happens if that brief is also applied to a gravel bike? That’s what the new S-Works Crux is about.

It’s crazily expensive and very blingy for a gravel bike, but Roderic Gill rates the 2024 S-Works Crux as on of the best all road options available, a ‘dirty Aethos’ if you like,

The Aethos and the Crux are non-identical twins. They both share the aethos of the Aethos! They are aesthetically matched, and share very similar parts, all subtly modified to best suite the road type to which each is separately tuned. The geometry is subtly different, but the ride is genetically linked.

One Or Both?

You certainly don’t need both! But if that single design brief appeals, you would be equally satisfied with either depending on your predilection for road or gravel or a particular road/gravel mix.

Specialized aren’t the only makers playing this game. Colnago has recently released a gravel version of its illustrious C68. Same brief, different use cases. So too for Cervelo: the Aspero 5 and the Caledonia 5 are two variants of the same basic brief.

And then there is the Pinarello Dogma F and Grevil F combo. In every case, the basic premise is that if you fit with the aethos, geometry and character of one, you will be satisfied with either bike or both. There’s a presumption here that there really is no such thing that one bike that can do it all. That’s the point of a pair. The philosophy is that if you want to cover all the bases, you can get the one pair of bikes to do it all. You can kind of see why such a proposition is so attractive to bike makers with an aspiration for greater sales!

A Bike Re-invented

All this is my theory why Peter Denk, the design guru behind the Aethos, re-invented the Crux to be a dirty Aethos rather than remain as the ultra competitive cyclocross weapon it once was (and maybe still is).

The Crux and the Aethos are twins with masterfully considered difference. The S-Works Aethos is pure magic on climbs. There is, in my experience, nothing like an Aethos for fast climbing and sheer joy-of-the-ride on the flats (but the Aethos is still not a Dogma F…) The Crux feels a touch heavier, slightly more constrained in the hills and less sharp on corners than its ultra-light sister. But it’s only by a touch. The Crux is very acceptably close. These bikes really do feel like … two glorious dimensions of the same thing.

With a 50mm fork rake across all sizes the bike is designed for speed and agile handling.

The notion of riding the S-Works Aethos on the gravel induces an anxiety for a broken bike and a painfully broken body. The experience of riding the new Crux on endless smooth tar, in comparison with the Aethos, is kind of like riding in a perpetual light head wind. The Crux feels just a bit more languid. But less so than, I would suggest, most other gravel bikes out there. But on the gravel, the Crux is king. The roots of this difference are in distinctive geometries, a slight weight penalty for the Crux and the realities of fatter more squishy gravel tyres. But together, an Aethos and a Crux will rule the world!

Completely Revised

The new Crux is a comprehensive re-working of the old CX original. For starters, tyres can now go out to 47mm instead of 33mm. The frame geometry is stretched and bent a la endurance rather than cyclocross.

It’s all top-shelf Specialized. The frame is of the same 12R top end carbon as on the Aethos. The bars are Roval Terra carbon, the wheels are Roval Terra CLX, the groupset is SRAM Red AXS EXPLR one-by, the tyres are Pathfinder 38’s, The seat post is a carbon Alpinist. The saddle is an S-Works carbon Power. There’s nothing on the Crux you would want to change as everything is already top of the top end. The Aethos and the Crux cost exactly the same at $18,400!

A high-end build, overall weight is just 7.35kg.

Its in the fine details that the Aethos and the Crux diverge. The Crux’s geometry is more relaxed. There is more frame on the Crux as the top tube drops less. The wheels are a bit deeper on the Crux and they weigh a touch more for increased strength while still being outrageously light and compliant. They are also 25mm internal width which means that, technically, you can’t run tyres less than 29mm (who makes a 29?) Everything is tubeless, of course.

The Crux has considerably more trail (trail is the horizontal distance between your bike’s steering axis and the centre of the front tyre’s contact patch). The Aethos features 55 mm of trail and the Crux, 64 (on my size 56). 64mm is relaxed and aimed at a more stable, rail-like ride. The Aethos’s 55mm trail is fast and furious.

Impressively Light

The size 56 Crux weighs in at 7.35kg. That’s about 1.3kg more than the Aethos. But 7.35kg is pretty much as light as it gets for a gravel bike.

How does the Crux ride? It is superb! Climbing is wondrous. Descents are controlled and thrilling. Compliance is pretty much as good as it gets. And it is fast. Race winning fast. This is one superb hooning machine.

And on the tar? Squishy 38mm tyres aside, no roadie is going to complain. It’s not an Aethos. But it is close enough for government work. Aethos and Crux are, indeed, a perfect pair.