Colnago Y1 RS vs Cervélo S5: Two Cutting-Edge Aero Race Bikes Compared

Introduction

The Colnago Y1 RS and the Cervélo S5 finished first and second on general classification at the 2025 Tour de France, and that alone would be enough to justify putting them side by side. The more interesting story is what the two bikes represent: two different answers to the same question about how a modern race bike should move through the air. Both sit at the front edge of aero design, and both have helped push lighter all-rounders towards the margins in men’s professional racing.

This comparison covers the design thinking behind each frame, the specification each brand builds around it, how the two behave on the road, and where the money goes. One of them comes out ahead on the balance of the package, but there is a great deal to like about both.

The Aero Race Bike Era

Aero road bikes have taken the Tour de France in 2022, 2023 and 2025, and the direction of travel in men’s racing is clear. Frames that once traded weight for drag are now fast enough that teams are willing to give up a little on the scales. What has changed is that the penalty in ride quality has largely disappeared. Neither the Y1 RS nor the S5 carries the old reputation of aero bikes being awkward in crosswinds or nervous on descents. Both sit close to well-sorted all-rounders such as the Enve Melee, and to lightweight platforms such as those from Orbea, in the way they handle.

That matters for anyone buying at this level. A race bike that is only fast in a straight line is a compromise. A race bike that is fast and easy to live with is a genuine upgrade.

Colnago Y1 RS: An Unconventional Aero Platform

The Y1 RS was unveiled in December 2024 and went on to take the 2025 Tour de France title. At launch, Colnago claimed it was the fastest bike in the professional peloton, beating its nearest competitor by one watt at 50 km/h. It is the looks that draw attention first. The offset seat tube is unusual, and Colnago says it contributes to aerodynamics while improving compliance, with the side effect of pitching the rider slightly forward. It also makes the effective seat tube angle steeper at 73.7 degrees on a size large, which opens up the hip angle.

Specification is top tier only. Colnago builds the Y1 RS around two-by groupsets including Campagnolo Super Record 13, SRAM Red AXS and Shimano Dura-Ace Di2. Wheelsets run from mid-level Vision SC45 wheels upwards, with Enve SES 4.5 wheels available as a paid upgrade. There is no power meter at this price, which is a notable omission on a race bike.

Where Colnago does well is customisation. Through its dealer programme you can choose an inline or setback seat post at no extra cost, and adjust chainring size, crank length and cassette. The front end uses a small 19 mm upper bearing and a 1-1/8 inch lower bearing with CeramicSpeed solid lubrication.

Cervélo S5: A Refined Aero Package

The S5 has been the reference point in this category since it carried its team to Tour de France wins in 2022 and 2023, and the current version doubles down on those strengths. The head tube and fork leg cords are deeper, while the head tube, seat tube and seat post have been slimmed down. A new Reserve wheelset was developed alongside the frame and contributes to a claimed 6.3 W saving at 50 km/h. Cervélo also claims a net frameset weight saving of 124 g, even though the fork gained 57 g from its deeper leg profiles. The cockpit abandons the bolt-together design of the previous model.

The seat tube is curved to hug the rear wheel, and a Shimano Di2 battery sits in a port under the bottom bracket. Entry to the range is more accessible than the Colnago, with second-tier groupsets and DT Swiss 240 hubs laced to Reserve wheels. A complete S5 starts at around £9,200.

Frame, Fork, and Cockpit Details

Up front, the two bikes share an approach. Both use bayonet style forks with a free-floating head tube section, which allows a longer head tube structure without disturbing the effective steering position. In theory that preserves the handling of a well-designed all-rounder while improving airflow in a high-pressure area. Both also use one-piece handlebars with a two-prong stem section and a pronounced rise, shaped to sit flush with the frame when slammed. Both are proprietary, but both brands allow a free swap to a different cockpit size at the point of purchase, which matters a great deal.

There are differences too. Cervélo uses a more conventional 1-1/8 inch upper and 1-3/8 inch lower bearing arrangement. Seat post real estate is tight on both frames, to the point that posts need cutting to size. Battery placement differs as well: the S5 tucks its Shimano Di2 battery under the bottom bracket, while the Y1 RS hides it in a port under the down tube bottle cage.

Specification and Value Compared

At the specification compared here, both bikes cost close to £12,000, and the S5 spends that money more convincingly. Its Reserve wheelset is wider at 25.4 mm internal front and 24.4 mm rear, and 34.3 mm and 32.5 mm external, with different front and rear depths to balance aerodynamic efficiency, stability and weight. Despite the extra width it is claimed at 1,554 g, slightly lighter than the 1,590 g Vision SC45 wheelset on the Colnago, which measures 21 mm internally and 31 mm externally. The Reserve wheels also use ceramic bearings against the steel bearings on the Vision set.

The S5 adds a dual-sided power meter, which the Y1 RS does not include. Its 54/40 chainrings suit a strong rider on a flat day but will be too big for many customers. On the other side of the ledger, the S5’s default seat post cannot be changed to an inline or setback version at no cost, while the Colnago lets you swap both and fine-tune the gearing at purchase.

Ride Quality and Handling

Both bikes feel fast, and both are far easier to handle than their tube profiles suggest. Slab-sided aero frames can feel vulnerable in crosswinds and reluctant to change direction, but neither of these suffers from that. They are among the most stable and confidence-inspiring race bikes in this class, close in character to a good all-rounder. The S5 feels slightly more sure-footed in windy conditions, most likely because of its progressive rim depths. The Y1 RS feels a touch more agile, with steering that takes a little less effort to respond.

Under hard pedalling, the S5’s large bottom bracket area delivers a tangible sense of stiffness. The Y1 RS is stiff enough, but arguably not quite as unyielding. Neither is harsh, and the S5 has the edge on comfort: 29 mm Vittoria Corsa Pro tires on the wide Reserve rims offer more volume than the 28 mm Pirelli P Zero tires on the narrower Vision rims, and the difference is noticeable on coarse chip seal surfaces.

Weight, Tires, and Tire Clearance

On the scales, the S5 came in at 7.53 kg in a size 58 frame, with the Y1 RS at 7.66 kg in a size large. The S5 also accepts tires up to 34 mm against 32 mm on the Y1 RS. That extra breathing room is unlikely to be used by most racers, but it is a useful margin to have.

Buying Advice: Which Aero Race Bike Suits You

If you want the most complete race package for the money, the S5 is the simpler recommendation. You get a power meter, a wider and deeper wheelset with ceramic bearings, more comfortable rubber and greater tire clearance, all from a lower entry price and with a claimed aerodynamic benefit built into the wheelset. As configured here, it is the better value and the more rounded ride.

The Y1 RS remains a serious proposition. Its dealer programme allows free changes to seat post style, chainring size, crank length and cassette, which is exactly the kind of flexibility more brands should offer. It also feels marginally more agile. The catch is that reaching a comparable wheel specification costs extra, and the missing power meter is a real gap on a bike at this level. If customisation and a sharper front end matter more to you than an out-of-the-box race package, the Colnago earns its place.

Conclusion

Both of these bikes sit at the leading edge of aero race bike design, and the performance is tangible from the first hard effort. The Cervélo S5 wins on specification, value and all-round polish, with a power meter, better wheels and a more comfortable ride at the same money. The Colnago Y1 RS counters with a fuller customisation programme and a slightly more agile feel, but you will pay more to bring its wheels up to the same standard. For most racers spending this kind of money, the S5 is the more sensible place to start.