Cervelo has redesigned its vaunted S5 model for 2015. The original Cervelo S5 was a ground-breaking design, widely hailed as the best aero road bike on the market. While new introductions (like Parlee’s stunning ESX) have upped the level of competition, Cervelo has remained one of the top aero road bike manufacturers as other bike manufacturers have raced to try to catch up. However, as fast as the first generation S5 was, there was still room for improvement. For example, the bottom bracket area and head tube were not as laterally stiff as some claimed to desire. Finally, some complained that the ride on the S5 was firmer than they wanted for long rides. Cervelo heard these complaints and has addressed them in the ’15 Cervelo S5. Many changes were made to the frame and fork, but four of them really stand out as ways that the ’15 Cervelo S5 is different from the previous generation.
New Cervelo S5 Fork
First, the new ’15 Cervelo S5 has a larger diameter head tube and the fork is tapered, from 1 1/8″ at the top to 1 3/8″ at the bottom. This larger diameter head tube, coupled with the larger fork steerer, makes the front end stiffer and more responsive. According to Cervelo, these changes, coupled with a revised carbon lay-up, have increased torsional stiffness in the head tube by 35%, and lateral fork stiffness by 17%. The net result is more immediate handling and even more lateral stability at speed.
New Cervelo S5 Bottom Bracket
Second, Cervelo redesigned the bottom bracket area of the bike. The result is that the BBRight bottom bracket of the ’15 Cervelo S5 is now laterally stiffer, by 6%, as compared to the previous generation Cervelo S5. Our own 6’4” Dean Phillips raced the previous Cervelo S5 to the MA State Road Championship title in ’12 and didn’t find the bike lacking in bottom bracket stiffness. However, 6% is 6%. For those who wanted more drivetrain stiffness out of the Cervelo S5, the ’15 version takes it a step further.
Improved Cervelo S5 Compliance
Third, Cervelo sought to address the comfort concerns. Wind tunnel tests showed Cervelo that the top tube and chain stay shapes had very little effect on the aerodynamics of the bike. So, Cervelo borrowed the top tube and chain stay designs from Cervelo’s most comfortable, and highest level frameset, the R5CA. The R series is known for their smooth ride, part of why they are such great endurance bikes, and the R5CA is the epitome of the R series design. Borrowing the design of the top tube and chain stay, coupled with revisions in the carbon lay-up of the other parts of the frame, has resulted in a tangible change of the ride of the ’15 Cervelo S5 bike. While it may not be quite as comfortable as a Cervelo R5CA, the ’15 Cervelo S5 is a bike that is hard to criticize when it comes to taking a 5 hour ride without feeling like you have taken a beating and maximizing your aero benefit.
Improved Cervelo S5 Tire Clearance
Fourth, with the old Cervelo S5, clearances around the rear wheel and tire were very tight, to the point that a rider could not use a 25mm tire. The redesign has widened the gaps around the rear wheel, so that now you can equip the bike with 25mm tires. Changing to 25mm wide tires lends added comfort to the ride of the bike, as a wider tire rides smoother, absorbing more road imperfections than a 23mm. In addition, somewhat counter intuitively, a 25mm tire can have less rolling resistance than 23mm, because the size of the tire contact patch on a 25mm tire is able to stay more consistent over road imperfections than that of a 23mm.
The ’15 Cervelo S5 retains some of the hallmarks that made the original Cervelo S5 so fast. The seat tube is cut out to allow the rear wheel to be brought forward, tucking into the cut out, thereby improving air flow over the wheel. The seat stays are shaped for maximum aerodynamic efficiency and the design incorporates what Cervelo terms a “drop down” down tube, lowering the down tube towards the front wheel. This smooths the air flow from the front wheel, over the down tube, and reduces air turbulence that would otherwise form behind the front wheel. The seat post is aerodynamically shaped, and can afford two separate positions for attachment of the saddle clamp, thus improving the fit options. The frame is designed to accept both mechanical and electronic cabling, so if you get an Ultegra mechanical group from the factory, you can later upgrade to Di2 easily.
The design of the ’15 Cervelo S5 was not just aimed at quieting critics, Cervelo was also trying to improve the overall aerodynamics of the bike based upon the latest data. Extensive computational fluid dynamics and wind tunnel testing was done during the design of the bike and the tube shapes and relationships were further refined from its predecessor. Cervelo also knows that a bike can’t go very fast without a rider and, a few years ago, they designed a human form they dubbed “Foam Dave”, a full-scale mannequin copy of professional rider Dave Zabriskie formed out of high-density foam, to be used in the wind tunnel. This form was mounted on the frameset so that an accurate picture of the aerodynamics of the bike and rider could be fully analyzed. Many small changes were made to the frame shape as a result of these tests, and Cervelo’s data shows that a ’15 Cervelo S5 can save up to 21.3 watts compared to the previous S5 design. For those with power meters, you know how hard gaining 21.3 watts of power can be; for those already at peak fitness it is impossible to gain 20+ watts through training alone.
In order to save this amount of drag, Cervelo had to really look at some details and items that were previously not the realm of the frame company. For example, Cervelo’s wind tunnel testing led them into the realm of handlebar design. Being on the front of the bike, handlebars can have a fairly large impact on the overall aerodynamics of the bike. So, Cervelo has equipped the ’15 Cervelo S5 with a fairly radical handlebar that pushes the UCI design limits to their maximum (yes, the handlebar on the ’15 Cervelo S5 is UCI legal…). The bar is fairly conventional in overall dimensions to modern standard with a reach of 80 mm and a drop of 128 mm and the design of the curve of the bars places the brake levers in a comfortable and accessible position. The radical part of the ’15 Cervelo S5 handlebar is the shape of the top of the bar. The bar is very wide, as you can see by the photo. Unlike some super-aero bars, the ’15 Cervelo S5 handlebar does not have an integrated stem, but thankfully uses a conventional stem. Cervelo found that the shape of the stem did not add or detract from the overall aerodynamics, so for ease of fitment they thankfully elected to make the bars compatible with convention 31.8mm stems. While some may argue about the aesthetics of these new bars, they do accomplish the goal of improving aerodynamics. According to Cervelo, the new bar design alone gives a 4.4 watt advantage over a standard round handlebar. The only drawback with these bars is that they are not the most comfortable when riding with your hands on the top of the bars, even for riders with large hands, due to their shape.
The placement of the brakes on the ’15 Cervelo S5 deserve kudos, because they buck the trend some manufacturers have followed in placing brakes in positions that are supposed to be more aerodynamic, but that make installation and adjustment very difficult. Cervelo maintained that traditional seatstay mounted brake location on the Cervelo S5, and the work in the wind tunnel resulted in a design that shields the caliper by the overall shape of the seat tube and the seat stays. No aerodynamic efficiency is lost by this very functional location. Curiously, Cervelo also decided not to move the front brake to behind the fork, again making the bike much easier to work on and making the brakes perform better as well. Cervelo has never been a company to compromise aerodynamics. We are confident that there was little to nothing to be gained by placing the brakes in a far less convenient place and brakes placed in more traditional locations almost universally perform better than ones shielded under chainstays and behind forks.
When it comes to components, the ’15 Cervelo S5 comes equipped with a choice of three Shimano drivetrains: Dura Ace 9070 Di2, Dura Ace 9000 with mechanical shifting, and Shimano Ultegra 6800. The bikes equipped with Dura Ace come with HED Jet+ 6 SCT wheels, shod with Continental GP tires. These wheels have an alloy rim with 60 mm deep carbon fiber fairing. These are very good quality wheels that, while not the lightest at 1,737 grams for the set, are very aerodynamic and versatile. The Ultegra equipped bike comes with the same wheels as the previous generation S5, the Mavic Cosmic Elite S aero alloy wheels with Mavic tires. Other components include Rotor BBRight press fit bottom bracket bearings, and a Rotor 3D+ aluminum alloy crankset. The crank is equipped with the increasingly popular 52/36 “mid-compact” chainring combination while the stem and headset bearings are FSA. The saddle is the Fizik Antares.
The price of the all Dura Ace Di2 Cervelo S5 bike is $10,000, while the mechanical Dura Ace bike is $8,000. The Ultegra-equipped bike is the real deal of the group, at $5,500. The Ultegra 6800 mechanical group works great, and only sacrifices small increments of performance to the Dura Ace mechanical group in terms of functionality. If you have to save some money, get the right frame first and upgrade those wheels and parts at a later date!
Why are aerodynamics so important on a bike? On a level surface, at 25 mph, over 80% of your power can be consumed overcoming aerodynamic drag. Of course you, the rider, are the biggest problem, but the bike can make a big difference too. Even at slower speeds aerodynamic drag is the largest power consumer, far more than rolling resistance or drivetrain losses. So, aero bikes can help almost anyone ride faster. With the changes in the design, the new 2015 Cervelo S5 is still at the head of the aero bike class. Want to go fast with the least amount of rider power? A properly fit aero bike is a great way to do it
It is important to note that the ’15 Cervelo S5 does make one significant departure from the rest of Cervelo’s road line. While other Cervelo road models share the same geometry as each other, Cervelo reduced the height of the head tube on the ’15 Cervelo S5. This will of course make it so that the bike has a narrower fit window than their other aero bikes, the Cervelo S3 and S2. A number of riders will need to find out of if the front end height is adequate for their needs and position. This highlights all the more why it is crucial to understand whether a bike actually fits you well before buying it. Make sure you take a Rider Matched approach to bike selection as the ’15 Cervelo S5 is a very fast and well designed machine, but if it does not fit your riding position well, it won’t realize its potential for you and all the changes Cervelo designed to help make the bike faster mentioned above will be for not.
Fit Werx is an authorized dealer of Cervelo Cycles with locations near Boston in Peabody and Lexington, MA, outside of New York City in Ridgefield Park, NJ and near Burlington and Stowe, VT in Waitsfield.