Updated – EB14: Cervelo Ups the Aero Road Ante Again with a New S5, plus Updated RCA
After almost universal accolades from the cycling media for the previous generation of the S5 as possibly the fastest road bike on the market, including our own, instead of taking it as a compliment, Cervélo took it as a challenge to make the bike even faster. What resulted is a new bike that chops another 21.3 watts off from the last S5 VWD.
At the same time for the RCA, Cervélo went back to the drawing board to see how they could make their handmade super bike an even better all-arounder, and where they could make measurable weight gains.
Read on for full details on the S5 and the lowdown on the new RCA…
Cervélo establishes a set of design priorities as they develop each of their bike lines, and with the S-series it goes: 1. Aerodynamics, 2. Stiffness, 3. Weight, then 4. System Thinking. One of the System Thinking approaches applies to aerodynamics, so through CFD Cervélo studied the impacts of individual bike elements on the total aero drag of a road bike with its rider. The numbers revealed key elements that had major effects, and these were items where they dove into more deeply to minimize drag:
- 1% – seatpost
- 2% – rear brake
- 3% – front brakw
- 5% – rear wheel
- 9% – drivetrain
- 9% – bottle
- 9% – fork
- 16% – frame
- 16% – front wheel
- 30% – handlebar
The primary focus of the S5 being aerodynamics, Cervélo put a lot of work into making sure their off-the-shelf bike remained an aero market leader. The did this by lowering the downtube even more and smoothing the transition as it drops to meet the fork, reshaping the already truncated downtube to accommodate the real world inclusion of water bottles, reworking and smoothing the transitions from the headtube down across the lower headset bearing and down the fork, slightly extending the seat tube cutout, and reshaping the seatstay cluster to better shield the rear brake.
Aerodynamics also improve through the use of new aero components. First, a new single position aero post for the first time will be interchangeable with the S5 and S3. A 2-position post will also be available to push a more forward position (and will be included with the 48cm frame to accommodate the fit of smaller riders.) More of a surprise is the inclusion of a new all carbon Cervélo Aero handlebar. The new bar is the result of a happy medium design between an all out crazy bar and a conventional approach. The end result is a 270g (at 42cm; 80mm reach/128mm drop) shaped bar with double inboard cable routing that saves 4.4Watts over a round bar in the wind tunnel and still includes a standard 31.8 clamp. The bar will come on all three S5 models, and will be available separately for $400 from the beginning of October. (Other market prices and availability are yet to be announced.)
Update: We spoke again with Cervélo about the Aero handlebar, and even though it appears to grossly exceed the 3:1 rule, it has been specifically checked over with the UCI, and has been approved for road use!
The second element was the stiffness, where it was an immediate requirement to maximize stiffness while not compromising on weight. By generally increasing the widths of tubing sections overall and optimizing material application, a major increase of 35% in headtube stiffness and 17% fork lateral stiffness was achieved, bringing the aero road bike into the performance realm of modern round-tube rod bikes. These major improvements were also supported by new manufacturing techniques that led to better put together frames, and upsized constructions like overall bigger BBright bottom bracket shapes and a 1 3/8″ lower headset bearing. The third element come directly from optimizing construction for a marginal weight reduction.
System Thinking gets even bigger into a usability perspective with features like future-proof cable routing, customer feedback leading to a 2cm reduction in stack vs. the last version, and an overall increase in attention to detail. The bike’s fork now allows 360° rotation, internal or external Di2 battery mounting, a simpler and more serviceable rear brake attachment, keyed seatpost binder, and straight shot cable routing. Tire clearance is a place where there is big improvement over previous versions. With the 26mm wide HED wheels spec’d on the Dura-Ace bikes, there is clearance for 25mm and (slightly) bigger tires.
Bikes get spec’d with partner Shimano drivetrains, Rotor cranksets, and HED wheels. The Dura-Ace Di2 version will retail for $10,500, Dura-Ace mechanical for $8500, Ultegra mechanical for $5500, and a frameset for $4500.
With the handmade attention to detail of the RCA, Cervélo won Eurobike Gold last year, and continues to refine their top of the line frameset. New highlights with the newest version are reduced overall weight, improved durability, and slightly more availability. With the RCA as Cervélo’s ultimate road bike, design priorities are Weight, Stiffness, then Ride Quality.
The frame now weighs in at 670g (54cm w/ all aluminum hardware included) for an actual weight gain of ~3g from last year’s model. The added weight comes from boosts in durabilty and ride quality with the addition of the 1 1/8″ – 1 3/8″ headset, future-proof internal cable routing, as well as reinforced tubing throughout in places that were previously susceptible to damage during regular use (read: sitting on the toptube, crashing, leaning/dropping the bike on its side, etc.) It is actually impressive that frame weight didn’t increase when you see the success Cervélo had with independently isolating the longitudinal (front to back) stiffness from lateral (side to side) stiffness. They were able to do this in large part by refining the specific placement and reducing excess overlap of individual carbon layers, with a result of +15% lateral and -7% longitudinal stiffness for an overall more lively yet efficient ride. They were able to increase the performance almost exclusively through the development of new production methods that can only be carried out at the low production, hands-on levels of the CA facility.
The biggest improvement by far though was the redesign of the fork and its move to the RCA production. The fork itslef is now just 277g, for a weight savings of 35g since the last iteration. The fork is one of the first from Cervélo to bring back a slightly curved fork blade to improve ride quality and bump absorption. Two of the main areas where weight was saved were in the inclusion of ultra high modulus fibers that could now run continuously up into the steerer as a result of the tapered bearing seat, and in the application of the much lighter, RCA high paint standard.
The bike will be sold only as a frameset for $10,000. The very time consuming handmade production will still limit overall availability (Cervélo can only produce about 1 frame per day in their California Criterion facility.) But unlike last year it will not be a limited addition, so production will roll ahead as long as cyclists are willing to spend the big bucks. In the words of Cervélo get your order in ‘early and often.’