Alex Hunt, Merida, Ronan Mc Laughlin
The new Reacto has been a long time coming, and not only because the fourth-generation bike launched back in July 2020, just as a 21-year-old Tadej Pogačar was winning his first Tour de France.
In the six years since, the aero bike category has quietly transformed. The once single-minded aim of drag reduction has broadened into something more complex. Brands are chasing lower weight, finding space for bigger tyres, and adjusting geometry for shorter crankarms and forward-shifted positions.
Cannondale’s new SuperSix is more Evo 4.5 than Evo 5
The more everything changes, the more it stays the same.
Beyond the evolution of the aero bike canvas, the actual public launch of the Reacto 5 feels late to the party because it was already raced discreetly by Bahrain Victorious at last year’s Tour de France and Vuelta a España. Since then, Merida’s presence in the WorldTour has ended, leaving the Reacto, at least for now, aimed squarely at the amateur racer rather than the pro peloton.
With that in mind, the question isn’t simply whether the Reacto is more aerodynamic than before, but whether it reflects what an aero bike is expected to be in 2026. To find out, I headed to Valencia, Spain to ride the latest generation of the Reacto for a few hundred kilometres and meet the engineering team to understand how Merida has navigated development in a constantly changing environment.
What did Merida want to achieve with the Reacto?
While we have grown accustomed to brands presenting the pursuit of outright aero gains as the dominant force in race bike development, the word Merida engineers kept returning to was “balance.”
In practice, that meant navigating a set of tensions that are increasingly present in the aero category. Perhaps unconventionally for an aero bike platform, the brief wasn’t to build the most aerodynamic bike possible, nor the lightest aero bike on the market, something that itself aligns more with the latest breed of do-it-all race bikes. Instead, it was to be competitive across several areas that often pull against one another: aero efficiency, weight, pro-level race performance, usability, and visual distinctiveness without tipping into more radical, polarising aesthetics. (Say, like the Oltre XR from Bianchi, which replaced Merida as Bahrain’s bike sponsor.)
One of the key targets was to retain the comfort and stiffness values of the fourth-generation Reacto while bringing the total system drag down to a level competitive against today’s flagship aero bikes. To quantify that, Merida aligned its targets with Tour Magazin’s aero protocol. That meant a half mannequin pedaling at 85 rpm, 45 km/h wind speed, and ±20° of averaged yaw angles. Under those parameters, the goal was to bring the Reacto 5 in under 200 watts, a figure that the brand identified as the entry point into the top tier of modern aero road bikes. For reference, Specialized’s Tarmac S-Works Tarmac SL8 comes in at 209 watts of total system drag, and Cervelo’s latest S5 measures 202 watts.
But simply hitting a drag target wasn’t all the Reacto had to deliver. Weight was just as important to the project, with the goal for the Reacto 5 to come in at the UCI’s 6.8 kg minimum weight limit, while still achieving Zedler ADV+ safety testing certification for a 120 kg system weight.
The brief was ambitious. Merida didn’t want the Reacto to dominate a single metric; instead, it aimed to be competitive across several. Which raises the question: is this truly an aero bike, or is it a slippery all-rounder?
5% faster than the previous Reacto
Under the Tour Magazin protocol (but as of yet, not verified by Tour Magazine itself), the top spec fourth-generation Reacto recorded a system drag of 210 watts. The figure for the new headline Reacto One (the name given to the most aerodynamic model in the range) is 196 watts, achieved with a UCI-illegal in-house developed integrated cockpit (a first for Merida), 1x drivetrain using the Classified hub system, and DT Swiss ARC 1100 wheels.
While the component choices aren’t the same between the fourth-generation Reacto and the new one, the bikes were both tested as they ship (Tour Magazine sometimes uses reference wheels for tests, but not in all cases). The 14-watt reduction of the Reacto One equates to roughly a 5% improvement in performance, albeit specific to the Tour Magazin testing standard, which doesn’t necessarily reflect real-world riding.
The more conventional top-tier models use 2x groupsets and score a system drag of 202 and 205 watts, depending on the specification. But perhaps more commercially relevant is Merida’s claim that much of the range matches or exceeds the outgoing flagship model’s performance. Even the Reacto 4000, the entry point to the range at £2,400 / €2,800 /AU$4,000, measures 215 watts with its stock aluminium wheels. The brand claims that upgrading to 60 mm wheels drops the figure to a claimed 210 watts, effectively matching the previous generation’s top-tier number.
Visually, the new Reacto looks like a steady evolution of the outgoing model, unmistakably part of the Reacto family. But beneath the paint, development began with a return to first principles. From there, Merida partnered with wheel brand Reynolds for wind tunnel validation, using a bolted aluminium sub-frame that allowed individual 3D-printed tube sections to be swapped out rapidly. Entire tubes and sections of them were iterated in isolation to refine the design.
The results of this process are most visible at the seat tube. Rather than aggressively hugging the rear wheel as we’ve grown used to seeing, Merida chose to slim the tube significantly, below the seat stays. Testing showed that a tight wheel cutout only delivered consistent gains when the tyre-to-frame gap was extremely small. Once that gap increased, the benefit dropped off quickly.
With official clearance for 32 mm tyres, and real-world room for 35 mm rubber at a squeeze, optimising the seat tube for a single narrow tyre range would have compromised the bike’s usability. Instead, Merida accepted what they claim to be a negligible (under one watt) aerodynamic trade-off in favour of weight reduction and flexibility in tyre choice.
The fork has also grown deeper and more angular, with a steep-sloped crown that blends more smoothly into the head tube. Part of that is visual, an aesthetic consideration to give the Reacto a unique look in a sea of increasingly homogenised aero bikes, but there is aerodynamic intent too, and this is the first aero bike the brand has released under the UCI’s newer equipment rules. By reshaping the transition above the fork crown, Merida reduced the bike’s frontal area, shrinking the high-pressure zone created by head-on airflow.
The fork crown has become more angular to improve the airflow over the front of the bike, as well as provide a unique profile.
Like some Merida bikes of the past, the new Reacto sports disc coolers between the brake calipers and the fork and rear triangle. While heat build-up and brake fade aren’t a huge concern with the latest generation of disc brakes, the goal is to maintain consistent power and modulation on long, steep descents. That’s a negligible performance gain, but one that the development team saw as worthwhile.
Merida also looked to further integration for aero gains, becoming the latest brand to jump aboard the aero bottle train. The frame offers two down tube cage mounting positions. Based on internal testing, Merida found that using the aero bottles, rather than traditional round bottles, saved 2.5 watts when a single bottle was used and 3.5 watts when two bottles were used, with the bike testing marginally faster with the bottles in place than a bare frame (the claimed 196-watt drag figure was achieved with regular round bottles fitted, as per the test protocol).
However, at the time of the media camp, these were not yet available and will follow at a later date than the bike, so for the time being, these benefits are off the table, and bottle functionality cannot be commented on.
While changes to the frame and fork are responsible for some of the aero gains, one area disproportionately contributes to the 5% increase in aerodynamic efficiency – the cockpit.
The cockpit conundrum
Roughly half of the Reacto 5’s aerodynamic gain comes from the CW 1P cockpit. That alone makes it central to the story. What makes it more interesting is that the component responsible for that savings also derailed the entire project.
Did we do a good job with this story?