It all started with the UCI and a raft of rule changes to the equipment regulations of cycling’s world governing body on 1 January 2023.
Among the key changes we outlined at the time were the banning of super-narrow handlebars, updated time trial handlebar regulations and, crucially, the end of the so-called ‘3:1 rule’.
The 3:1 rule meant the maximum length-to-width ratio of a component could be no greater than three-to-one, much to the disdain of aero enthusiasts and boundary-pushing bike designers, who knew deeper profiles could, in theory, make a bike faster. Following the 2023 rule change, however, bike brands can design bikes with tubes up to 80mm deep and as narrow as 10mm.
Head tubes, though, can now be up to 160mm deep, thanks to updated rules surrounding compensation triangles in that area.
Fast-forward to 2025, and we’ve seen the aero bike make something of a comeback. Dare’s Velocity Ace-AFO, Ridley’s revamped Noah Fast and Tadej Pogačar’s new aero bike, the Colnago Y1Rs, have all been released this winter. All take advantage of the UCI’s relaxed rules, and sport tube changes that simply weren’t possible a few years ago.
“The new 2023 rules allow the use of larger compensation triangles around the head tube area, which made the Noah Fast’s design possible,” Ridley’s product manager, Bert Kenens, tells BikeRadar.
Indeed, what unites the Ridley Noah Fast and Dare Velocity Ace-AFO are the sail-like, extreme head tubes. Now, at the end of a typical product-design cycle, we’re seeing the fruits of the labour of aero innovators such as Ridley, Dare and Colnago.
“We tested different lengths of the head tube within the boxes of the UCI to find the optimal length and profile,” says Kenens, referring to the template of boxes defined by diagrams shown in the UCI’s regulations.
The extreme head tubes of new-age aero bikes may well be 2025’s most divisive tech trend, judging by the reaction to our Instagram post when we spotted the new Noah Fast at the Velofollies trade show in Belgium in January. Comments such as ‘Brilliant and beautiful’ and ‘They ruined the bike. Just saw it. Shame’ provide a flavour of the responses to our video of the bike.
However, Ridley could have taken the design even further, according to Kenens.
“We could have made the head tube even a bit deeper but, according to our analysis, we found the right balance between aero efficiency and side wind conditions (and weight) with the current design,” he says.
Of course, aero innovation is nothing new, and one brand flirting with the limits of aero innovation before the UCI’s updated rules came into force was Ribble, which released the radical Ultra in 2021.
The Ultra features an integrated handlebar design with 'wake-generating' bulges on the tops and tube profiles that tested the 3:1 rule in place at the time of the bike’s release.
“The head tube, fork and handlebars are the first components to encounter and disrupt airflow,” says Jamie Burrow, head of product at Ribble.
“By using a deeper, truncated aerofoil design, the air stays attached to the surface longer, reducing drag. This approach [on the Ultra] pushed the limits of the UCI’s former 3:1 ratio rule.”
Form follows function
For brands such as Ridley and Ribble, aerodynamic efficiency – combined with real-world riding performance – was the number one priority in designing their aero bikes, and both were happy to break from conventional design wisdom in doing so.
Ridley’s goal for the new Noah was simple, Kenens says: “to make the fastest bike we have ever made”. According to the brand’s press material, the new bike saves 8.5 watts compared to its predecessor at the WorldTour pace of 50kph.
“When maximising aerodynamic performance, form truly follows function,” says Kenens. “Aesthetics of a bike are, of course, important, but it is also something very subjective. It will be very difficult to make a bike that everybody likes, or you will get the comment that there is nothing ‘new’ on the bike.”
Kenens says “deeper head tubes are key in making fast bikes” and expects future aero bikes to adopt a similar profile to that of the Noah Fast (and Dare Velocity Ace-AFO).
“We are pretty sure there will be more bikes in the future that will use these deep head tubes,” he adds. “Others will use the same [head tube] shapes if they look to get the best aerodynamics."
Kenens points to the convergence of lightweight-aero bikes when predicting the design trend for aero machines. ‘It just looks like a Specialized Tarmac’ is a comment we at BikeRadar see regularly when a new bike is launched with dropped seatstays and slender, aero-lite tube profiles.
“Just as we have seen that a lot of the all-round performance bikes have similar shapes, this can happen also for the future aero bikes as brands will try to optimise the frames within the [new] rules set by the UCI,” says Kenens.
However, while Dare and Ridley’s new aero bikes share some notable similarities, in terms of the head tube shape, the Colnago Y1Rs bucks the trend elsewhere, with a unique layout centred around an angled seat tube that also takes advantage of the 2023 update to the UCI’s equipment regulations.
In this case, the UCI’s frame regulations update included changes to where the seatpost could join the frame. The resulting layout, according to Colnago, helps a rider stay in their aero position for longer, while the angled design also effectively increases the depth of the tube.
This, Colnago told us, leads to “more probability for the airflow to be linear, in an area already affected by the rider's spinning legs”.
Colnago’s testing suggests the Y1Rs saves 20 watts at 50kph and zero degrees of yaw compared to the Colnago V4Rs, Tadej Pogačar’s bike of choice through the three-time Tour de France champion’s trailblazing 2024 season. However, against an unnamed competitor, the advantage narrows to one watt.
We’re yet to see Pogačar race in 2025, but will watch with interest to see whether the Slovenian, who also won the Giro d’Italia and World Road Race Championships in 2024, will ride the Y1Rs, the V4Rs or switch between the two.
We expect the latter. The aero Y1Rs supposedly weighs 7.45kg with pedals and cages, so Pogačar's V4Rs should be marginally lighter and, therefore, we think he'll still use it for mountain stages.
Time trial inspiration
While the Noah’s head tube will be the first thing to catch the eye of anyone who sets eyes on it, it’s not the only new aero feature at the front end of the bike. The Noah Fast’s cockpit integrates with the top tube, while the handlebar itself follows the trend for narrowing the rider’s position on the bike, measuring 36cm between the shifters.
The Colnago Y1Rs is another new aero bike that sees the stem slip seamlessly in line with the top tube (the bike also features a hinged head tube design reminiscent of the Cervélo S5), while the Dare Velocity Ace-AFO follows a similar design. If you think that aero bikes are starting to look like time trial bikes, you’re not wrong.
“To reduce the drag in this [cockpit / head tube] area, we used our knowledge of the development of the Dean Fast [time trial bike], where the base bar is integrated with the top tube,” says Ridley’s Kenens.
“By integrating the cockpit in the top tube, we significantly reduce the drag created in the area behind a traditional cockpit.”
Kenens acknowledges that this alters the stack height of the Noah, but that this has been “compensated and accounted for” in the cockpit design. “We offer three different stem stacks in our cockpit range and the stock builds will come with a mid-rise cockpit that will match the handlebar height of a more traditional frame design,” he adds.
An aero comeback?
So, is this the return of the aero bike?
Well, it never really went away, despite the lightweight/aero all-rounder taking centre stage in recent years and the industry’s desire to flip-flop between trends, but aero bikes are undoubtedly having something of a renaissance.
Kenens is resolute in Ridley’s ongoing commitment to aerodynamics, though. “At Ridley, the aero bike never disappeared,” he says, pointing to the continuation of the Noah since the original – one of the first aero bikes – was launched in 2007.
In the years since, we’ve seen sprinters such as André Greipel and Caleb Ewan win on Noahs, and aero innovations come and go. Remember the split forks/stays and integrated front and rear brakes of the 2011 Noah?
“We have always believed in the importance of the aerodynamics of a bike,” Kenens adds. “Especially when you’re racing, you only have one goal: go as fast as possible from point A to B. Every watt saved will help you to go faster or save energy for the final of the race.
“At the speed of modern road racing, the aerodynamic performance outweighs weight savings on the bike in practically every race.”
Despite this, we know how pro riders are often drawn to lightweight designs and Ribble’s head of product, Jamie Burrow, doesn’t see a complete aero takeover on the horizon. It’s all about choice, he says.
“Over the past few years, we’ve seen a real mix of bike designs,” says Burrow. “Some brands have moved away from pure aero road bikes and instead introduced all-rounder models – bikes that are lightweight, stiff and optimised for aerodynamics.
“For high-performance, pro-level bikes, it makes sense to have the best tools for the job. That’s why offering both a pure aero bike and an all-rounder/climbing bike seems like the ideal solution.”
Looking to the future
What’s next for aero bikes, then?
Bike designers now have more “freedom to innovate” within the UCI’s new regulations, Burrow says, but he feels there’s much more to the aero equation than the frame and fork.
“It’s about the entire bike and rider working together as one,” he says. “This means focusing on every detail, from handlebar and head unit integration, to seatpost and saddle design, as well as surface textures and airflow optimisation.
“In a sport driven by marginal gains and the fine details of performance, there’s still so much more to achieve.”
For Ridley, the new Noah Fast may have only just been launched, ready for the 2025 campaign with the Uno-X Mobility team (coincidentally, sponsored by Dare up until the end of 2024), but Kenens and his team are already looking ahead. Don’t expect any spoilers here, though.
“We have already started brainstorming the fourth generation of the Noah Fast,” he says. “Unfortunately, we cannot disclose where we will be heading in the design of that bike as this is confidential information.”
