Specialized Aethos 2 First Ride: Fantastic Ride at the Limit of Lightness

Because of UCI rules, the differentiation between the best lightweight bikes and the best aero bikes in our list of bike reviews continues to shrink. It’s just easier to hit the minimum weight these days so brands are hitting the number and then moving on… except for a few.

The Cervelo R5 and the Scott Addict RC are the latest bikes to ignore that weight limit and just go for it with low weight as a target. They weren’t the first though. That distinction goes to Specialized who in 2020 launched a bike unlike the trends of the time. The Aethos has round tubes, ultra low weight, and exposed cables. People love it. Five years later, there’s a new Specialized Aethos 2.

I had a chance to go to the Specialized headquarters and spend some time riding the new bike. Here’s what I found.

Quick hits: 7 stand out details of the Specialized Aethos 2

• A size 56 painted frame in the RTP raw carbon / premium Fjord metallic color hits the scales at 595 grams
• The lightest full build is the S-Works Aethos 2 SRAM RED AXS at 5.98 kg.
• The less expensive 10r frame adds 110 grams compared to the 12r layup.
• Max tire clearance is 35mm with standard ISO 4mm clearance on each side.
• Shimano Ultegra with a 10R frameset is your least expensive build option at $6,599.
• The 12r carbon fork weighs 284g
• Compared to the Tarmac SL8, the new geometry adds 15mm of stack with more BB drop and a longer wheelbase.
• For more information and purchase visit the Specialized Website

Specialized Aethos 2 frame details

When the original Aethos hit the market it was not only the lightweight king but also a bike that spoke to the rejection of bikes like the aero focused Specialized Venge. It was for people that wanted a bike that looked like a classic bike and the aesthetic was a big part of that.

The round tubes were both an engineering solution that allowed more strength with less carbon  while also a very strong aesthetic statement. Then the market moved on. The Venge disappeared and the Tarmac started to look pretty damn classic in comparison to the competition. In 2025, the Aethos doesn’t make sense the way it did in 2020.

To address that, the biggest difference you’ll find is revised geometry. While the old Aethos was an unapologetic race bike with a lightweight focus and classic styling, now you can pretty much get that in the Tarmac. Why choose a Specialized Aethos 2?

Specialized is making the case that if you want the race bike, along with every little advantage it has in speed, pick the Tarmac. If you want a bike that’s more about the ride feel then Specialized Aethos 2 for you.

To get there the geometry looks a whole lot like an actual endurance bike like the Scott Addict, but not quite. If I compare my size 54 frameset to a Tarmac in the same size, the stack increases by 15mm with most of that coming from a 13mm taller headtube. It’s also a slightly slacker 72.5° vs 73° headtube angle, there’s a 3mm bigger bottom bracket drop, and the wheelbase is 14mm longer. Notably that wheelbase isn’t quite as long as an endurance bike and it’s also all coming at the front of the bike as the chainstays are the same.

The other big geometry related change is tire clearance. When we did our best all-road bike field test we ended up testing the Aethos even though it wasn’t really an all-road bike. Next year the Specialized Aethos 2 should definitely be in that test as there’s now room for a 35mm tire and, although I haven’t tested it this way yet, I’d bet this is a very capable all-road option.

Now the other big change is going to be a little more controversial. The original Aethos had exposed cables. A lot of that was likely the technology at the time but it was also something a certain segment loved about the bike. At this point I’d say it’s looking very dated but not everyone will agree. Doesn’t matter where you fall on that spectrum though, the cables are now gone… kind of.

The Specialized Aethos 2 uses internal cable routing. The top models use the Roval Alpinist Cockpit II with Integrated bar and stem while the lower models use the Roval Alpinist Carbon Handlebar. Depending on your point of view though, there’s an upside. The routing isn’t fully internal. The cables exit the bars ahead of the stem, even with the integrated unit, and enter the headtube again at the front of the steerer tube.

This is the same system you’ll find on the Tarmac. It could mean it’s a little easier to pack into a travel case and it might also mean it’s easier to swap handlebars. Specialized says it’s possible to use any standard bar and stem combo using a 1 1/8” steerer clamp and, in case you are curious, the same is true of the seatpost which is a standard round 27.2 design.

And that’s the new.

I mean there’s UDH now but in terms of the big stuff, the rest of Specialized Aethos 2 is going to look very familiar. If you somehow ignore the cables I think you’d actually have a very tough time telling the two generations apart.

There’s still round tubes and all the little details that make the old bike what it is remain. If you look at the seatpost junction the distinctive detailing hasn’t changed at all. The shoulders of the fork look the same too and there’s still a standard BSA bottom bracket.

Specialized also points out that this is still the lightest road disc frame. It’s very close though. Realistically you’ve got choices from Scott and Cervélo that are nearly the same weight.

The other thing to consider is that most people won’t be riding the 12r carbon frame. Cervélo only sells one version of the R5 frame and it’s 650 grams for a size 56 and the Scott Addict in the heavier HMX carbon is 679 grams. Meanwhile the Specialized Aethos 2 in the heavier 10R carbon is 705 grams. So even if the Aethos 2 is technically lighter in the 12r carbon, the model most people have won’t be the lightest option compared to Scott or Cervélo.

Honestly though, none of this matters. I only mention it because it seems worth making it all clear. What’s more interesting is that the three lightweight kings are all coalescing around the same weight. Specialized confirmed that this isn’t an accident. The brand said it was possible to make a lighter bike but not a lighter bike you actually want to ride.

The Specialized Aethos 2 I was able to weigh was a size 56 (my 54 had a stack of spacers) and the scale reported 6.1 kg ready to ride minus pedals, bottle cages, or a computer mount. That’s incredibly light.

Build details

The basic concept is S-Works with the lightest frame and either Dura-Ace or Red groupsets. From there you can step down to the heavier frame and Force or Ultegra with Alipinist wheels and cockpit or step down again to the two piece bar and stem with Roval C38 wheels and no power meter. There’s also a frameset available at either level for $5,499 or $3,499.

S-Works Aethos 2 SRAM RED AXS – $13,999

S-Works Aethos 2 Dura-Ace Di2 – $13,999

Aethos 2 Pro SRAM Force AXS – $8,499

Aethos 2 Pro Ultegra Di2 – $8,499

Aethos 2 Expert SRAM Force AXS – $6,999

Aethos 2 Expert Ultegra Di2 – $8,499

Specialized Aethos 2 geometry

I already talked through these details up above but it’s leaning towards endurance bike and stepping away from the race bike geometry of the old Aethos and the current Tarmac.

Specialized Aethos 2 ride experience

When I rode the first generation Aethos this spring during our field test, I loved it. I immediately gravitated to what I can only describe as a fun riding experience. There’s a snap to it that begs you to push a bit harder. At the same time there’s an element of nervousness to the Aethos. It wasn’t the easiest bike to ride on the white line at the edge of a road and descending in the wind was not a great experience. I still put something like 200 miles on it that week.

When you get on the Specialized Aethos 2, at first it feels like nothing changed. I was riding with a small group and found it positively addictive during the small surges you get in a group. Every little rubber band, only exaggerated by me dropping back to grab video clips, was an opportunity to hammer back on then proceed to the front.

It’s a 13lb bike so, yeah, it climbs just fine. More than that though I wanted to drop to the back at the start of every climb then go all out and try to catch the group again. Climbing prowess is a given but the desire to attack a climb for fun is what really matters.

Of course I can’t actually catch a fast group every time and I wasn’t riding with slow people. I sometimes found myself needing to really commit to the chase and spend time getting back. I also, dutifully, took my turn in the headwind at the front from time to time. In those moments, I normally rely on aero advantage and I did miss it a bit here.

I have narrow shoulders and the ability to get low on a bike. It’s an asset I use regularly when paired with an aero bike and it can be magical.

The Aethos replaces that magic with a different kind. Instead of flinging yourself at the wind, you’ll want to stand on every climb. You’ll also love the feeling of acceleration on this bike. Just make the catches quick.

About that nervousness though. It’s still not completely gone. I just wouldn’t call it nervousness anymore. On the Aethos 2 it reads more as preciseness. If you point the bike, it goes and that means it’s maybe not the most sublime descender. I imagine if you know the roads better, and are willing to commit, you’ll end up appreciating it but be aware of what you are getting.

It does track in a straight line noticeably better though. After too many winters on rollers I sometimes like to ride directly on the white line at the edge of the road. The last version of the bike made that difficult. This time the little extra wheelbase helps a lot.

The Aethos badge is well known as a bike that offers an incredible ride. With the Specialized Aethos 2, you won’t find me saying anything different. It’s the same but better.

It’s also worth some comparison. The obvious bikes are the Cervélo R5 and the Scott Addict RC. I haven’t ridden the Cervélo but the Scott is much more of a race bike. The Scott is a stiffer bike with a lower front end and, although it’s not part of the story, it has a bit of an aero advantage as well. In short, while it might seem a good comparison, it’s actually a much different bike. Instead I find myself comparing it to the Lightspeed Coll dels Reis. Neither is a race bike but they are both for going fast and they both offer a similar ride feel. The Aethos 2 is stiffer and lighter while I’d say the Lightspeed is a bit better on a descent.

Usability

Specialized actually does pretty well in this category. There’s a threaded bottom bracket and it’s BSA which is easier to get a tool on compared to internal T47.

There is internal routing but there’s no funky steerer tube and it’s external under the stem. For the most part I’d call this a half measure that’s not really making it easier but also not fully hiding the cables. On the other hand, it does make it an amazing travel bike since it’s easier to get the bar and stem off and folded even if you’ve got a one piece cockpit.

You’ll also find UDH at the rear. Scott claimed that UDH was too heavy but I appreciate that Specialized created a special version that’s lighter but still uses the design. It lets you swap in a regular piece if you ever need to while also saving a claimed two grams. Even better, it means you can still use RED XPLR if you want to really push the all-road concept.

Conclusion

My negatives with this bike center around the idea that I’d like to see the bike pushed further. Fully internal routing, even lighter, or 38mm of tire clearance. That said, the Specialized Aethos 2 is a gorgeous bike that’s sublime to ride. Specialized has also done a great job differentiating from the Tarmac.

Last time I spent time with the Specialized Aethos I felt it was just a little nervous on windy descents and I didn’t find it the easiest bike to hold steady on a tight straight line. I still loved it though and the Specialized Aethos 2 addresses both of those issues. To be clear it doesn’t completely turn the name into an endurance bike, there’s still an edge, but it does tame those negatives a bit.

At the same time Specialized is also adding a bit of stack. There’s an engineering purpose for this, it helps share the load, but you can think of it as building the spacers into the frame. It does make the headtube look a little visually odd but not as much as 15mm of spacers so I’ll call that a win.

The Specialized Aethos 2 is the perfect bike for the kind of person who wants a fast bike but isn’t racing. It’s noticeably not aero but the way it moves under you makes you want to push harder. It rides a lot like a really good titanium bike but it’s drastically lighter. This is a ti bike built out of carbon.

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