Behind the Design: The Sum Pro’s Real-World Advantage

The Sum Pro combines aero engineering and lightweight performance to be the ultimate road race machine: fast on the flats, powerful on the climbs. But how do we know we’re delivering real-world results to our riders? Read on to learn about our design process, aero testing, and what sets our bikes apart.

Our testing has found the Sum Pro has comparable aero performance and is significantly lighter than a competitor’s leading World Tour bike. And because we take a holistic approach to our design and consider actual riding conditions, the Sum Pro is designed to perform optimally on all courses—rolling, flat, or serious climbing—and our testing considers the aero effects of real-world riding, such as the rider’s body and water bottle. 

At Argon 18, we optimise our frames from the very first step in the design process: ideation. We begin by looking at specific design features and focusing on the small details that will earn a performance advantage for our riders. 

Let’s look at the Sum Pro downtube, one of the key focus areas in the design of the bike. In the ideation stage, we explore various NACA airfoil shapes and evaluate geometry options—such as tube width, length, and shape—that establish the foundation for stiffness and overall performance. This geometry selection sets the framework for maximizing performance, while the layup process that follows fine-tunes the final details to deliver the best possible ride experience for our riders.

For the Sum Pro, we looked at the traditional narrow tube shapes we see on most aero bikes, the rounder tube shapes seen on most lightweight bikes, and a hybrid shape that optimised aero performance while minimising the bulky aero shape. Often the traditional aero tube shapes need more material to 1) provide sufficient stiffness, and 2) to reinforce the sharper curvatures. Our hybrid shape was able to avoid this additional material and achieve a lower weight. Using finite element analysis (FEA), we can generally benchmark the stiffness of these chosen shapes, before further fine tuning the properties with the layup.

Read more about our carbon engineering process here.

We often use the phrase “optimal balance” at Argon 18, and that’s exactly what we were looking for in this design process: the best combination of aero performance and lightweight advantage. 

After we’ve identified several possible design options to optimise the aero performance of a specific part, we test those possible iterations using CFD, or computational fluid dynamics 

Read more about our CFD process here. 

In the images below you can see the three different approaches for the Sum Pro downtube (the view is cross-section, looking down from above the bike, parallel to the ground, slicing around where the water bottle is. Red represents faster airflow; blue slower). You’ll notice that we’re including the most important factor: real-world conditions such as the effect of the bottle and the rider’s legs on aero performance. You can see that the third option, our optimal balance between aero and lightweight tube shapes, is able to guide the flow of air around a standard cylindrical water bottle in an efficient way.  

CFD, as most simulation methods, does not replace real-world tests. That is why wind tunnel tests are frequently used to validate what we see in CFD. We can also test how the frame performs in a more realistic riding environment by using a mannequin.   

For the wind tunnel testing we did with the Sum Pro, we decided to benchmark against existing data collected from 2021 to 2024 by Tour Magazine, as well as test against a leading competitor’s World Tour bike which we brought with us to the wind tunnel. 

To see the full Tour Magazine results, please click here.

You can see that the Sum Pro achieves aero results comparable to WorldTour competitors and other leading frames, as tested by Tour Magazine. The differences in measured aerodynamic drag fall within the margin of error for wind tunnel testing—meaning the bikes can be considered equal. However, the standout result is that the Sum Pro achieves these numbers while maintaining a significantly lower weight. This further demonstrates that the Sum Pro outperforms some of the most successful WorldTour bikes in both aerodynamics and weight.

“For me the bike is the perfect combination between lightweight and aerodynamics,”

Matyas Kopecky, Team Novo Nordisk rider.

Note: 
These measurements are estimates based on the aerodynamic differences measured 1) by Argon18's tests in the SSEH wind tunnel with Scope Artech 6.A wheels and 2) the results of the stock build wheelsets measured by both Argon18 (in the case of the Scope Artech 4) and by Cycling News and GrandFondo magazines (Bontrager Aeolus RSL 51 TLR). World Tour competition bike and Sum Pro tested with Scope Artech 6.A wheelset at SSEH wind tunnel. The results shown reflect tests performed with mannequin legs. 

We now know the Sum Pro offers comparable aero performance and significant weight savings compared to its competitors. But sometimes it’s still hard to know exactly what that advantage means in the real world. So, in our final performance tests we set out to measure exactly how much time you can save on the Sum Pro. 

This calculation was done using an online tool called Best Bike Split where wind tunnel data can be entered as an aerodynamics input, even accounting for multiple yaw angles.

The Sum Pro was benchmarked against a World Tour competition bike on one of the Tour de France’s most prestigious climbs: Alpe d’Huez. For this simulation, real wind tunnel data and weather conditions were used to calculate a professional rider’s effort on the iconic climb. In our Alpe d’Huez simulation (shown below), we found that a pro rider gains an 11-second lead on the Sum Pro compared to a leading World Tour bike. 

While Alpe d’Huez places a high importance on fighting the forces of gravity, it is important to showcase the Sum Pro’s ability on a less mountainous, rolling terrain. For this, we looked to Liège-Bastogne-Liège, the monument filled with punchy climbs.

Assumptions
1) Calculations made using wind tunnel aerodynamic drag values. 2) Professional rider estimated to have an FTP of 360W, weight of 65kg. 3) Intensity factor varied based on segment and rider type. Alpe d'Huez: 120%; LBL: 100% 4) Constant hood position assumed to be maintained during segments. 5) No effect of drafting, other riders taken into consideration.

The Liège-Bastogne-Liège simulation is focused on the final climb, Côte de la Roche-aux-Faucons, as well as the final stretch to the finish line. While aerodynamics contributes significantly less to a rider shielded in the peloton, the Sum Pro’s balance of aero efficiency and low weight is crucial for attacking uphill and holding an advantage on the flats and descents. In this scenario, it saves 3 seconds for a pro rider in the final 15.6km push to the finish —significant margins in a decisive race moment.

Additionally, the Sum Pro provides a 350-gram weight advantage with the same wheelset (a 5% reduction). Our balanced engineering ensures the same aero performance as the leading WorldTour bike on these iconic courses but with an even lighter frame—potentially delivering the famous marginal gain that can make the difference between taking 1st or 2nd on the podium.

Looking at simulations with each of the bikes’ top-end stock builds, which increase the weight advantage to 640 grams (a 9% reduction), the Sum Pro extends the lead to 18 seconds on Alpe d’Huez.

In short, the advantage you feel on the Sum Pro comes from countless hours of design optimization and testing to ensure performance is engineered into every part of the frame. But don’t just take it from us – our pro riders feel the advantage too. 

“For me the bike is the perfect combination between lightweight and aerodynamics,” say Team Novo Nordisk rider Matyas Kopecky. “I have been riding and racing on the Sum Pro for three seasons now and it has been three years of pure joy on the bike. You can look at the science and understand it, but the experience riding the bike is what makes you appreciate top-level engineering, and that this is truly a race machine.”