Cervelo R5-CX, a cyclocross race bike designed for Vos and Van Aert
Yes, it has a threaded bottom bracket.
Yes, it has a threaded bottom bracket.
What happens when multi-discipline heroes of cyclocross find themselves on a team sponsored by a bike brand that doesn’t offer a cyclocross bike? Well, that brand makes a cyclocross bike.
The new R5-CX is Cervelo’s first-ever production CX bike, and the company isn’t shy that it was built based on the specific requests of Marianne Vos and Wout van Aert, who respectively hold seven and three rainbow jerseys in the cyclocross discipline.
Below is an explainer of this narrowly focussed race bike that is currently only in the hands of pros. Production versions won’t be available until 2022, and while Cervelo has confirmed both complete bikes and framesets will be available, the spec details and pricing are yet to be finalised. For now, they just wanted to release the details of a bike that’s already winning World Cups.
For an even deeper look, we’ve just published a CyclingTips Nerd Alert podcast episode where the designers of this bike chat about all the design decisions (such as the threaded bottom bracket!) that went into making a purpose-built cyclocross race bike.
It’s worth noting that Cervelo did produce a pair of R3 Cross frames back in 2007 for US racer Jonathan Page, and while these frames were there for the first American male to stand on a World Cup podium, they never reached production. Given that the UCI now requires raced products to be available for sale, the R5-CX will exist as something that can be purchased.
The new CX frame offers a similar aesthetic to the R5 road bike with which it shares its name. The truncated tube shapes are similar. The wholly integrated cabling at the handlebars is just about identical. And the D-shaped seatpost remains (more on this below).
The fit and geometry figures are of course unique to this bike and were closely based on the requests of those who own rainbow jerseys. The stack is intentionally low, the bottom bracket is raised, the chainstays are longer, and the standover is higher to give more shouldering room within the front triangle.
Frame stiffness is high – higher than the Aspero 5 and new R5. According to Cervelo’s engineering manager, Scott Roy, the stiffness is most comparable to the previous generation R5 road bike and is well suited to the high-power and short-duration discipline.
Exact frame weights are still being finalised but Cervelo estimates a painted 56 cm will sit around 830-860 grams, while the matching fork should be about 360 g.
Despite cyclocross requiring the use of no larger than 33 mm tyres, the regular racing through thick mud sees some substantial tyre clearance provided here. Cervelo’s director of product management, Maria Benson, mentioned a theoretical tyre clearance figure in excess of 50 mm, and while that hasn’t been tested to the limit, it’s obvious this frameset will have room for gravel-friendly rubber (although you should expect some toe overlap).
That integrated front end with concealed cabling is an interesting choice for a bike that will be pressure-washed more often than its rider showers. As discussed in the upcoming Nerd Alert podcast, the decision to wholly hide the hoses/wires was to make shouldering the bike tangle-free and it also removes the need for any external port or similar opening that can take on mucky water.
Similarly, there are no external modular ports provided to add mechanical shifting or a wired dropper. Cervelo claims it will have extremely good sealing for the headset bearings that are trapped in place by the brake hoses, and of course, there’s no way to dispute such a claim at this time. For a look inside this cabling system check out my review of the Aspero 5.
Pictured up top is Vos’s race bike which shows just one bottle cage mount on the seat tube. Production versions will have mounts for two bottle cages, but no other provisions. Want to run fenders? You’ll need to use clip-on ones, just like the pros.
The RS-CX has a threaded bottom bracket. Now that in itself isn’t normally a feature worth its own sub-heading, but this is Cervelo we’re talking about. Cervelo has long (and stubbornly) stuck with BBright, its asymmetric and wider adaption of the PF30 format. This new bike offers a glimpse of what’s hopefully to come in future models.
Of course, it wouldn’t be Cervelo’s style to offer just any old bottom bracket format, and so the R5-CX features what’s effectively the company’s BBRight system but with T47 threads. And while that may sound like it’s a proprietary thing, in reality, the system should fit all common cranksets and work with a standard ‘inboard’ T47 cup on the left, and a standard ‘outboard’ cup on the right. Yes, it’ll be a bit trickier to buy a bottom bracket for, but you’re at least not locked into any one system.
Currently, Cervelo claims that its BBright press-fit system remains the best option for building a lighter and stiffer frame, but that in this specific use case the compromises are worthwhile for a bike that may have its bottom bracket pulled from the frame after every race.
In the Nerd Alert podcast, Scott Roy goes into great detail about this system and teases what it may mean for future Cervelo bikes.
Cervelo is no stranger to using flexible D-shaped seatposts on its road bikes, but its gravel-going Aspero made the purposeful move to a regular old 27.2 mm round post. And while the engineers of Cervelo suggest that a round seatpost was the initial concept for the RX-CX, it was actually the rainbow jersey winners that requested a non-round one.
Not only does the D-shape seatpost help with isolating the rider from the terrain (and it’s perhaps a little more aero, too), it more importantly will always remain straight in the event of a crash or a botched mount. The seatpost equipped is the same Cervelo carbon model that’s used on the new R5.
And speaking of mounting and dismounting, Cervelo fits the R5-CX with two securing seatpost clamps – one that sits on the frame as expected and a second that bites onto the D-shaped seatpost itself. According to Roy, this design decision isn’t so much for absolute saddle height security (which it does help with), but more for simple replication of exact saddle height after removing the seatpost. Both of these seatpost clamps are external band-style clamps, too.
If you’re keen to know more then I’ll take this chance to yet again plug the Nerd Alert podcast episode. Otherwise, you can expect Cervelo to release more details in 2022 as the bike goes into production.