Canada's Argon 18 has just unveiled two new road bikes called the Sum and the Sum Pro that are said to combine light weight and aerodynamic efficiency. Merging these two attributes has been a huge theme in high-end launches over the past couple of years, with Argon 18 saying that the new bikes are designed to perform both on the flat and in the mountains. They're going for the 'one bike to rule them all' vibe that Specialized was keen to shout about with the launch of the Tarmac SL7.
Argon 18's introductory spiel goes: "Meet the best of the best: aero to match the Nitrogen, pure road performance to match the Gallium Pro, with race-ready handling and premium ride quality."
The Nitrogen and Gallium Pro are existing models in Argon 18's range, of course. Or, they were. With the addition of the Sum and Sum Pro to the range, the Nitrogen, Gallium Pro, and Gallium are all retired. Thanks for your long service and all, but off you trot.
"The all-new Sum features Argon 18’s most advanced layup and technologies, offering a premium combination of aero and lightweight engineering, while ensuring ride quality," says Argon 18.
Lightweight, aero, comfortable - those claims are pretty much standard when a new road bike is released; how does Argon 18 back up those promises?
The hourglass-shaped head tube is said to provide aero efficiency while retaining stiffness and the profiled fork legs are intended to "deflect air away from the down tube for maximum aero advantage".
"CFD (computational fluid dynamics) analysis shows the Sum's aero performance as equivalent to the all-aero Nitrogen and 9% faster than the Gallium Pro Disc," says Argon 18.
The brand also says that CFD has allowed it to strip away unnecessary weight while maximising the aero performance.
"The down tube, top tube and chainstays are optimised for the perfect ratio of size, material thickness and aerodynamics," it says. "The hourglass-shaped head tube provides low drag while being rigid and lightweight."
Argon 18 says that the dropped seatstays and "indented seat tube" – it's more of a curve than an indentation, if you ask us – improve the ride quality, providing 30-35% more rear compliance than the latest-generation Gallium Pro... and we're fans of a good statistic here at road.cc.
The Argon 18 Sum and Sum Pro are built to the same road race geometry. The medium-sized model, for example, comes with a 50.5cm seat tube, a 55.7cm top tube, and a 12.6cm head tube. That head tube might sound short – and it is – but the two models use Argon 18's existing 3D system https://www.argon18.com/en/argon-18/technologies/3d that allows you to add height without the increased flex associated with headset spacers.
If you don't use the 3D system, the stack is 54.0cm and the reach is 39.7cm on the medium-sized model, giving a stack/reach of just 1.36. That's ultra-aggressive. If you use the 3D system to increase the head tube length by 25mm, the stack/reach becomes a far more back-friendly 1.45.
For those of you taking notes, the head tube angle is 72.7° on this size and the seat tube angle is a pretty steep 73.5°. And while we're talking numbers, Argon 18 reckons that there's space for tyres measuring up to 30mm – which is generous on a bike of this kind.
Argon 18 is keen to point out that the cockpit is non-proprietary. Both the Sum and Sum Pro use BB86 bottom brackets and an internal seatpost clamping system.
With all these similarities, what's the difference between the Sum and the Sum Pro? It's simply down to the carbon layup, the Sum Pro featuring Argon 18's top-level build. No weight details have been given.
The Sum and Sum Pro will be available as framesets and with SRAM Force AXS and SRAM Rival AXS builds but not until late 2022.
We currently only have the frameset prices:
Argon 18 Sum £2,799.99
Argon 18 Sum Pro £3,699.99