It seems that with every new aero road bike released these days, there is at least some mention of the UCI’s 2020 decision to relax its frame design rules. But what were those changes and why are they so often cited? What follows is a delve into what the landscape before and after those changes and why, despite being broadly considered successful, there may be another update on the cards already.
The rule changes ratified by the UCI at the Imola World Road Championships in 2020 and effective January 1st, 2021, were originally proposed to the UCI by the World Federation of Sporting Goods Industry (WFSGI) on behalf of the cycling industry to address concerns about outdated and overly restrictive regulations that were stifling design innovation in performance bicycles. The UCI’s decision to adopt them now directly influences the bikes we buy.
The proposed changes, although seemingly relatively minor on paper, aimed to create greater design freedom for manufacturers. But change didn’t happen overnight. Adjusting to the UCI’s updated regulations is a lengthy process that requires both time and a deep understanding of how to maximise the new design freedoms without introducing unintended trade offs in stiffness, durability, or handling, not to mention the lengthy design cycles many manufacturers operate to.
Now, as new bikes designed under the new rules roll out, it’s clear these changes present significant opportunities for manufacturers to innovate and optimise frame designs in ways that are only now becoming evident.
The new rules bring road, time trial, track, and cyclocross frame design under one umbrella but, more importantly, ditched many of the restrictions that hampered innovation for the previous two decades. But what exactly changed, what do these changes look like on bikes, and what else might be coming down the road?
No innovation please, we’re Swiss
To answer what changed in 2021 we must first go back to 1996 and the introduction of the Lugano charter.
Named after the Swiss city in which it was conceived ahead of the 1996 World Championships, the Lugano Charter was introduced by the UCI to set boundaries on bike technology and innovation in response to the wave of innovative bikes that had characterised the decade before that.
That wave was kicked off by Moser’s Hour Record bike in the 1980s, and by the mid-90s, when Graeme Obree and Chris Boardman were battling it out for the Hour Record – not to mention Tour de France stages in Boardman’s case – the UCI had had enough of the superbikes it deemed had no place in its version of the sport.
The Lugano Charter, fully implemented by 2000, outlined the new rules UCI hoped would maintain “the primacy of man over machine.” These new regulations, which manufacturers and riders had to follow to ensure their equipment was approved for use in UCI-sanctioned events, effectively defined the UCI’s vision of what a bike should look like and how the rider should look on it. It introduced strict limits on frame and component design and the use of prototypes, a minimum weight limit, regulations on rider position, and restrictions to curb aerodynamic advancements.
Core Principles – The charter’s primary objectives were:
- To ensure cycling is a sport of athletes, not machines.
- To maintain the traditional look of bicycles.
- To make equipment available to all, preventing the advantage of one-off prototypes.
Key Rules – The Lugano Charter established specific regulations, including:
- A 6.8 kg minimum weight limit for bikes.
- The 3:1 aspect ratio (a rule dictating that any tube’s length could not exceed three times its width, limiting aerodynamic designs).
- The horizontal saddle rule (mandated that the saddle had to remain horizontal, with a maximum tilt of 2.5 degrees (later increased to 9 degrees in 2019), ensuring fair positioning and compliance with traditional riding ergonomics).
- The commercialisation rule (mandated that equipment used in UCI-sanctioned events must be accessible to the public via regular retail channels).
- Two wheels of equal size.
- A double diamond frame with a top tube, down tube, seat tube, and chainstays.
- Explicitly banned the use of recumbents.
Then, despite the UCI facing significant criticism over the years – particularly for its conservative approach to innovation, which critics argued stifled innovation and the seemingly inconsistent interpretation of its rules – nothing much changed for the next two decades.
Perhaps most frustrating for many involved, the wording used within the regulations was mostly grey and open to interpretation. Items that the regulations seemingly clearly prohibited were in regular use, e.g., aero-profiled time trial helmets, which, truth be told, are basically fairings and so strictly prohibited under UCI regulations. [Shhh Ronan, don’t tell them! – Ed.]
Meanwhile, manufacturers, engineers, and designers never quite knew how the UCI would view a new design even when that design adhered to the rules as written. With much of the language used so ambiguous, many felt that was the exact intention: A ruleset so open to interpretation that the UCI could pick and choose how and when it applied.
Initially, there wasn’t much of an issue as manufacturers were still getting to grips with the new wonder material, carbon fibre, and the industry’s understanding of aerodynamics was still in its infancy. However, as its understanding of both improved exponentially, the old regulations of that period made it difficult for manufacturers to balance and enhance aerodynamics, stiffness, and compliance in bike frames. For example, the mandate for tubes to be at least 2.5 cm wide posed a significant challenge in achieving the desired compliance levels. At the same time, the 3:1 aspect ratio rule, restricting tube shapes to no more than three times longer than their width, severely hindered aerodynamic advancements.
Come 2020, the industry had effectively hit a ceiling, glass or otherwise, beneath which new bikes brought ever more marginal updates. Above that ceiling and out of reach, the manufacturers argued, lay innovations that made everyone a winner: The industry, the racers, and the consumers.
New possibilities
Fast-forward to the present day, and while the principles of the Lugano Charter still form the backbone of UCI equipment regulations, the 2020 update marked the first significant relaxation of design rules since 1996, paving the way for many of today’s aero bikes.
Although incremental updates over the years allowed minor positional tweaks like negative saddle angles and more aerodynamic fork profiles, the 2020 overhaul dramatically loosened restrictions on frame tube shapes.
Designers were given far more freedom to innovate. The new rules permit significantly narrower and/or more aero-profiled tubing, enabling sleeker, lighter, and more aerodynamic frames.
Here is a list of the main changes and the opportunity they provided designers:
Relaxation of the tube aspect ratio
- Previous Rule: The UCI enforced a 3:1 aspect ratio limit, meaning the length of any tube could not exceed three times its width.
- Updated Rule: The aspect ratio limit was relaxed, with the new 8:1 ratio allowing for more aerodynamic tube shapes.
- Implication: Designers could now create thinner, deeper aero profiles that are more aerodynamic and, thus, potentially make for faster bikes.
New minimum tube dimensions
- Old Rule: Minimum tube widths were 25 mm (excluding fork blades and seat stays), restricting opportunities to improve aerodynamics and/or compliance.
- New Rule: The minimum tube width was reduced to 10 mm, enabling much narrower frame sections.
- Implication: This opened the door to thinner tubing, which could reduce drag or improve comfort/compliance.
Seat post positioning
- Old Rule: Previously, the seat tube and post had to follow a straight line, connecting the saddle to the bottom bracket. This, along with tube angles, enforced traditional double-triangle frame designs.
- New Rule: The new rules allow for the seat post to be attached to the seat tube and/or within a designated area along the top tube.
- Implications: The new seat post positioning rule allows manufacturers to detach the seat post from the seat tube and diverge from the traditional double-triangle designs. Designs like the Colnago Y1Rs are only permitted thanks to this rule change.
Compensation triangles
- Old Rule: Compensation triangles, the bridge-like structure connecting the inner side of connecting frame tubes (e.g. the underside of the top tube to the inner face of the seat tube), were previously only permissible on time trial bikes.
- New Rule: The UCI now permits using compensation triangles in road frames.
- Implication: Compensation triangles offer an aerodynamic gain. These subtle frame additions help guide airflow smoothly across critical areas like the seat tube and head tube junction.
As an added bonus, the pocket these co-called compensation triangles add to the seat tube / top tube cluster offers designers a new location to integrate seat post clamps.
Unified frameset approval procedure:
- Old Rule: Previously frames were approved for use in a single discipline, such as road (RD), time trial (TT) or cyclo-cross (CX)
- New Rule: The new rules delivered a single frameset approval process now applied to road, track and cyclo-cross frames.
- Implication: This unification of the frame approval process was designed to streamline the process for manufacturers. It also means riders may use any approved frameset to participate in any UCI “mass start” road, track or cyclo-cross event and/or “individual” events depending on the handlebar type used and rider position.
New rules, new challenges
The regulation updates were generally well received, with many hopeful that the new opportunities would spur a wave of innovation and allow manufacturers to explore new avenues in frame design. History now shows that was only partly true.
The new regulations did come as a breath of fresh air for designers and engineers, opening up many new opportunities. But anyone who thought bikes would morph overnight into futuristic bike-shaped objects was wrong.
With design cycles usually taking years, many manufacturers were already locked into new designs under the old regulations. Furthermore, having new rules to play with is one thing; understanding how best to use them is an entirely different challenge.
The “it’s hard to find a bad bike these days” adage of modern times is a far cry from the early days of aero bike design. First-gen aero bikes earned a less-than-flattering reputation, many likened them to “gates” due to their heavy, harsh, and unforgiving ride characteristics. Over time, designers balanced aerodynamics with handling and ride quality through new carbon layup technology, new designs, and learned to leave some straight-line aerodynamic potential on the table if it meant a better overall bike. By 2020, manufacturers had mostly cracked the code of creating aero bikes that weren’t just fast in the wind tunnel but also performed well in the real world.
The introduction of new regulations opened up exciting possibilities – thinner, taller, and more aerodynamic tube profiles were now on the table. However, the new regulations introduced an entirely different design landscape that had to be understood. While the freedom to explore thinner, deeper tube profiles couldn’t be ignored, it required relearning how far to push the designs. The challenge wasn’t just about seizing new opportunities, but understanding which aerodynamic gains were low-hanging fruit and which came with potential pitfalls.
Challenge Accepted
What kind of pitfalls are we talking about? While the updated regulations, effective from January 2021, unlocked numerous possibilities, they also introduced fresh stiffness, durability, and – potentially – safety complexities that manufacturers had to understand.
For instance, take the challenge of maintaining or even improving stiffness and structural integrity while simultaneously integrating thinner and deeper tube dimensions. The new 10 mm minimum tube thickness allowed for lighter, more compliant, and more aerodynamic designs, but thinner tubes inherently reduce a frame’s resistance to torsional forces.
Achieving the ideal stiffness profile across key areas such as the head tube, down tube, seat tube, bottom bracket, and chain stays is essential for handling, power transfer, and long-term durability. Without careful balancing, a promising frame in CFD simulations and wind tunnel tests could prove horrible on the road.
Furthermore, these thinner tubes, more complex shapes, and tighter radii present another challenge, as they require even tighter tolerances and precision manufacturing, which in turn drives up production time, complexities, and costs. Even minor imperfections in carbon fibre layup could compromise a frame’s structural integrity. With less room for error than ever, manufacturing frames just got a degree or two more difficult.
In short, while the new regulations provided a thrilling opportunity to rethink bike design, they also demanded a more measured and thoughtful approach to ensure that innovation didn’t come at the expense of ride quality, safety, or practicality.
With the most prominent brands, like oil tankers, taking time to change direction and treading only tried-and-tested courses, it was always going to be years before the new rules were fully utilised. As such, any rule change-inspired frame design revolution remained pretty subtle until “Super Worlds” in August 2023, when nations had to use their track bikes for the 2024 Paris Olympics in competition as part of the approval process.
The 2023 Stromm track frame is one such example, with the American company pointing directly to the rule changes as key in making its new frame possible. On its website, the company claims, “The UCI has lifted the decades-old 3:1 tube shape ratio restriction, giving engineers room to create shapes with 600%+ lower drag sectionally than before, and Stromm is the first bike to take full advantage of this new rule change.”
As narrow and profiled as the Stromm looks, it doesn’t come close to the Look P24, the Japanese national team’s V-Izu TCM-2, or Team GB’s Hope-Lotus HBT Paris in terms of radical divergences from the norm. All three featured some variation of a split or offset seat post, each with a unique twist on multiple other frame elements.
Factor took a slightly less obvious approach with its Hanzo Track, but was no less innovative in leveraging the new regulations. It featured a bayonet steerer and a deep head tube, fully capitalising on the newly aspect ratio allowances.
Factor also adopted a clever interpretation of the new seat post positioning rules. By mounting the seat post at the very rear of the top tube, they effectively positioned it behind the frame. While not as dramatically offset as the Colnago Y1Rs that would come over a year later, this design extended the aerodynamic profile in the seat post area, adding to the already maximised compensation triangle.
In simpler terms, Factor utilised the revised rules to increase the airflow-smoothing surface area, enhancing the aerodynamics of the new bike.
Notwithstanding all that innovation, coming on the track as it did, much of the potential of the new rules had gone unnoticed by the bigger road-riding population. That was until the Colnago Y1Rs landed just before Christmas in 2024 highlighting the unique shapes and seat post positioning now possible under the new regulations.
While the bayonet fork steerer and aero profiles throughout the Y1Rs were nothing new its offset seatpost was new to many and only possible under UCI rules thanks to this 2020 regulation change.
There were, however, plenty of other subtle changes on the road in the years between, if you knew where to look. The Factor Hanzo time trial bike unofficially unveiled at the 2021 Giro was one such bike; with its deep aero profiles and thin stays, it was a clear step change in TT bike design. The original Pinarello Dogma F followed shortly after, giving us a glimpse of things to come by adopting a much narrower seat tube. A year later, Scott followed suit, with its new Foil using both narrower and deeper tube profiles throughout to further optimise its dedicated aero platform.
Some things never change
So are the new rules a success? Mostly, but that doesn’t mean they are here to stay.
Going back to 2020, the WFSGI’s push for these new rules came at a time when the UCI’s Technical Regulations had become overly complex and confusing. The ambiguous wording and frequent amendments made the UCI’s frame approval process both complicated and sometimes costly for manufacturers.
Most had hoped the 2020 rule change would deliver clearer and more consistent regulations that the UCI would implement as written.
However, while it initially seemed the rule would provide this clarity, fast-forward to 2025 and manufacturers often report they find themselves in the exact same position as before: effectively arguing with the UCI over interpretations of rules, with the governing body seemingly ready to flip-flop on said interpretations from one frame to the next.
The result is lengthy back-and-forth discussions on the conformity of new designs that manufacturers argue comply with the rules as written. The €22,000 spent by Wilier on multiple revisions of a time trial bottle for its Supersonica it was originally told complied with the regulations only to be later told it didn’t, last year proves one prime example.
So, do we need a further update? Possibly. While some argue cycling needs a design code of construction, most agree better wording and implementation of the rules as written is what is most needed right now.
Designers and engineers often speak of designing new frames or components within the regulations as written, only for the UCI to reject the drawings without specific reason. Sometimes the UCI will U-turn when provided with examples of similar already-approved designs, and sometimes they won’t. Manufacturers are increasingly frustrated, but fearful of speaking out and risking a backlash from the UCI.
A backlash may be on the cards anyway, though. While the UCI’s prototype and commercialisation rules are far from perfect and manufacturers often turn to ridiculous price tags and long lead times to effectively de-commercialise a new product they want to keep exclusively for their sponsored teams, this practice was previously mostly reserved for track frames. However, it feels like 2025 is the year similar practices might make it to the road.
With the aforementioned Y1Rs and other similar hyper race team-focused – and hyper-expensive – bikes coming to market, there’s a feeling manufacturers are effectively turning to building the equivalent of prototype racing series equipment designed specifically for the pros. While the UCI will still require any new frames be commercially available, any sales are almost an added bonus on such projects rather than the main focus they are in most other product lines.
Furthermore, with the threat of sweeping changes from the UCI in the name of improved safety, many designers and manufacturers don’t know where they stand right now. Press on with the existing regulations only to have any progress scrapped with one sweep of UCI president David Lappartient’s pen, or wait for new rules that may or may not come and find themselves behind the competition if they don’t?
The 2020 UCI rule changes have opened new avenues for innovation. But they also pose significant engineering challenges, and we haven’t yet seen them fully utilised.
Balancing the opportunities and challenges requires a blend of advanced understanding, materials, precise manufacturing techniques, and continuous testing to ensure frames are not only faster but also reliable and enjoyable for riders at every level. In that sense, there is a fair argument that the rules are working as is; all that’s needed now is for the UCI to leave the rules to do that work.
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