An ultra-light disc-brake option

It seems that the crew at Specialized have been hard at work, they just released an all-new model, the Aethos, a lightweight (sub-700 gram frame) option that replaces the Tarmac as the Morgan Hill-based brand’s lightest road bike. Specialized has famously said aero is everything, just check out their latest iteration of the Tarmac, but from the looks of it they realized that not everyone puts aero on their priority list and the result is the Aethos. This isn’t to say the Aethos is huge steps back aerodynamically, but it moves the priority of aero further down the list. We opted for a frameset instead of a complete build and paired it with some of our favorite components. While this route is rarely less expensive it delivers a more personalized ride.

Weight and Build

The Aethos is maybe the lightest disc frame we have seen and our size 54 frame hit the scales at 622 grams. The fork is 311 grams for a total weight of 933 grams. Specialized continues to remind us that this bike is not up to legal UCI weight even though it has a UCI sticker. Speaking for the vast majority, who cares? We have yet to be restricted in our events by the arbitrary rules that the UCI places on the elite few that race their events.

Our frame is one of the stock painted options and Specialized says there are options that have reduced paint and hit the scales a few grams less. When you add in the 153 grams worth of small parts and the 150-gram Roval seatpost we have a starting weight of 1236 grams or 2.72 pounds.

Our complete bike that includes Hed Vanquish RC4 Pro wheels with 28mm Kenda Valkyrie TLR Pro tires set up tubeless. For the drivetrain, we opted for the 12-speed SRAM Red eTap AXS. The drivetrain is light, and because of its wireless shifting system is aesthetically pleasing with only brake hoses. For the cockpit we went with an alloy Easton EA90 120mm stem matched to an Easton EC90SLX carbon bar. The bars are wrapped with Lizard Skins DSP V2 2.5mm bar tape. To finalize the build we opted for a Fizik Antares 00 Carbon Braided Saddle on top of the Roval Alpinist Carbon Post.

The complete bike hit the scale at an impressive 14.43 pounds. That’s impressive since cutting weight wasn’t our top priority and with a few modifications, we could easily be sub 14. With that said this is a setup that we feel is a great balance of stiffness, durability and performance.

Geometry and Aesthetics 

There seems to be some level of confusion and debate on the choice, but the Aethos has the same fit as the Tarmac, so we consider it to have a  performance/ race geometry. For some, this seems out of line since Specialized is targeting the rider who is less interested in racing. For us, it seems like a perfect fit since we like going fast and performance-oriented geometries but have very little interest in bumping bars for a podium position ourselves.

The biggest changes aesthetic-wise come to the seat stays as they are now back to the good old days where they meet with the top tube. Specialized says this was chosen because of the strength it offers on a bike with minimal structure. Like the SL7 Specialized has opted for a threaded bottom bracket interface and will likely make it easier for the brand to maintain standards in production and minimizing creaking. The frame also uses a 27.2 round seatpost to help keep the weight down. The wedge and aero post used on the Tarmac also require more structure in the frame to work and this was not an option to hit weight goals. Best of all for us is the minimal graphics and name free downtube. The S-Works logo has been moved to the rear of the top tube and the Aethos logo is found on the head tube.


While we have no tools to back any of the Specialized claims, from our riding experience they are likely correct.

The Ride

After having a little over a month on the Aethos it is clear this should have been where the Tarmac went and the SL7 should have maintained the Venge naming in our opinion. Either way, we now have what we think is a more rider-optimized option that still maintains the performance geometry. The comfort level in the saddle is more in line with the Tarmac SL6 and significantly more compliant than the SL7. With exposed cables near the head tube, this bike will be much easier to travel with (when that is an option again) and will fit in a larger variety of bike travel bags and cases.

For some of our testing, we swapped in a power meter to better compare to the Tarmac SL6 and SL7 bikes we have tested in the past.

Performance-wise the Aethos hits all the marks and from our testing feels like it offers almost the same levels of stiffness that the Tarmac does, but obviously in a much lighter package. Out of the saddle efforts transfer have a solid response and stiff bottom bracket. Descending is impressive and unlike many other bikes on the ultra-light list that are in our opinion noodles, the Aethos is solid.  The wheels stay aligned as we pushed through high-speed turns as well as tight technical ones. Overall if we were to have ridden the bike before we knew the weight, we would have never guessed that it might be the lightest disc frameset on the market.


To start Specialized will offer three models and a frameset. Pricing is steep for the S-Works models but for those that want the lightest they will bite. For the rest, a bit of patience usually pays off as the technology trickles down into more affordable options that use the 10r carbon.

Founders Edition: $14,500
S-Works Di2: $12,500
S-Works eTap: $12,500
Frameset: $5,200

Get real time updates directly on you device, subscribe now.

Comments are closed.