Argon 18 unveils new Sum and Sum Pro – aero, light, and stiff race-ready bikes

Another option in the do-it-all road bike category, but don't expect to ride one anytime soon.

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Argon 18 has unveiled its new road bike, the Sum. The Sum is Argon 18’s answer to the modern race machine, combining aero and lightweight details for a one-bike solution. As you might expect from a new bike in this space, there is the almost obligatory internal cable routing, dropped seatstays, aero profiled tubes, and a frame that appears to be leaning heavily on the recently relaxed UCI rules. 

Here at CyclingTips, when reporting on any new product announcements, we typically note the item’s availability towards the end of the article. Unfortunately, I feel I need to mention it right from the start for the new Sum and Sum Pro. You see, despite how fast this bike looks, the new Sum is not officially available until “late 2022”.

Undoubtedly, global supply and shipping issues play some part in the lengthy wait from announcement to availability. Furthermore, with Team Novo Nordisk expected to race on the frame throughout the upcoming season, Argon 18 likely had to make the frame official now. But, for those in the market for a new bike now for the season ahead, I feel it is essential to explain from the off that the Sum is unlikely to be an option. 

The Sum features an entirely new frame said to offer the aero gains of Argon 18’s Nitrogen with the ride quality of the Gallium Pro. Argon 18 is renowned for its aerodynamic prowess with its Electron track frame a favourite on the boards, and the first bike sub-4-minute individual pursuit bike. The Canadian brand has applied that aero expertise to the development of the new Sum, and the results are clear to see.

A tapered head tube is said to reduce drag while maintaining rigidity and low weight. That head tube sweeps back and flows into the down tube to create a huge intersection. Argon 18 claims this increased surface area improves stiffness and smoothes the airflow behind the head tube for improved aerodynamics.

Sticking with the bike’s front end, Argon 18 flared the edges of the profiled fork legs to deflect airflow away from the down tube. The down tube itself is optimised for use with a bottle while still keeping a focus on reduced weight. Out back, the seat stays are just 10 mm thick for aerodynamic efficiency, while a slightly arched shape is said to provide compliance and comfort. 

A new design process is said to “strip away all unnecessary weight within the new aero profile tube shapes.” While Argon 18 doesn’t offer any detail on this new design process, external weight-saving measures such as the slender seat tube and minimal chainstays are clear to see. The end result is a size medium painted (thank you Argon 18) Sum Pro frame that weighs in at a claimed 850 g. The lower-tier Sum frame tips the scales at 890 g. Argon 18 has not provided any complete bike weights. 

Argon 18 is keen to stress that this bike is about more than weight and aero. Ride quality was another key focus for the design team. On the ride quality Argon 18 says “a rider-orientated design approach ensures a frame that is both rooted and responsive, with a ride experience most aero frames can’t match.”

Argon 18 says the new frame sizing is “better tiered” than that of the Gallium Pro, pointing to the size medium, which now measures slightly smaller than the current offering. The new frame also features a D-shaped seatpost, seatpost cutout, dropped seatstays and a slender top tube for increased compliance. Still, Argon 18 says it has maintained the power transfer qualities of the Gallium Pro.

The new Sum also gets Argon 18’s almost signature 3D head tube system. This system offers riders the ability to adjust the head tube length with three options (0 mm, 15 mm, 25 mm) per frame size. In numbers, the 3D system can offer a stack of 540 mm right up to 564 mm, and a reach from 390 mm up to 397 mm in a single size medium frame.

By adjusting head tube length, Argon 18 claims the 3D system provides a stiffer solution than spacers alone and increases the fit window thanks to the increased range the system offers in combination with traditional spacers. One of the major benefits of the 3D system as I see it is the ability to adapt the geometry of an aggressive racing frame to better suit the positional needs of non-World-Tour riders.

As clever as the 3D system is, its appearance is certainly not everybody’s cup of tea. Its partnership with the FSA ACR system on the new Sum is likely to do little to improve the aesthetics of either system. 

Argon 18 has built-in 32 mm of tyre clearance on the new Sum. While certainly much more than we would have dreamed of for a road racing frame just a few years ago, 32 mm does seem on the conservative side for a new frame in 2022.  

When they do go on sale, the Sum and Sum Pro will be available as framesets only. There will be just two complete bike options for both frame levels, with either SRAM Force AXS or Rival AXS builds. Besides the groupsets, the wheels are the only difference in the builds.

The Sum Pro SRAM Force AXS bike gets the pick of the hoops with Hunt’s 48 mm Limitless wheelset, while the Rival build features the Hunt 4 Season All-Road wheels. Meanwhile, the Force AXS build gets those same 4 Season All-Road wheels on the Sum complete bike while the Rival AXS build features Team 30 clincher wheels. 

We haven’t yet had the opportunity to test the new Sum, but we look forward to doing so in future. While do-it-all race machines are now almost commonplace in the pro peloton, this is the first such offering from Argon 18. Argon 18 has made some strong claims about the new Sum and the Sum Pro, and the company’s reputation in the aero space makes these claims all the more exciting. 

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