Note: An overview of the 2019 Cervelo S3 can be found here.
Aero road bikes continue to gain interest each year and for good reason. There is no doubt that, all else being equal, bikes designed with aerodynamics in mind are faster. This means that a rider leading out the group on an aero frame bike is using less energy than the riders around them on non-aero tubing. Conversely, if you find you are chasing the group, a well designed aero frame can make that situation take less effort too! Cervelo cites studies that show that up to 88% of a rider’s power is used to overcome aerodynamic drag. While the majority of drag is caused by you, the rider, the bike does make a noticeable contribution and anything that can be done to make the frame slipperier will obviously make the rider faster.

Cervelo was a young company when they first introduced an aero road bike (and created the category) – the aluminum Cervelo Soloist. These Soloist bikes went through a number of different versions and designs through the years, including the Cervelo Soloist Carbon, before arriving at the refinement of the most recent generation of Cervelo “S” line bikes. The Cervelo S line is comprised of three models, the S5, S3 and S2 and, to my mind, the real star of this line is actually not the top of the line Cervelo S5, but rather the S3, for its combination of performance, components, and price.

The Three Basic Aero Bike Challenges

There are three basic challenges with most aero bikes. First of all, aero-shaped tubing has more tubing surface area than traditional tube shapes, so an aero frame bike is almost always heavier. Second, aero bikes with their narrow profile downtubes and stays can be softer in the bottom bracket due to trying to keep the tube profile as narrow and aero as possible.   If it gets too soft, this means some of your pedal effort is lost to frame flex instead of getting to the rear wheel. Third, aero bikes often ride firm and some are just plain harsh. Personally, I do not ascribe to the advertising adage that “aero is everything”, at least not when it means I am going to get beaten up by my bike. So how does Cervelo address the three problems mentioned above?

’15 Cervelo S3 Weight

First, Cervelo pays careful attention to the layup of the carbon fiber in the Cervelo S3 to help keep weight down. So, while some weight gain compared to a non-aero shaped bike is unavoidable, the difference is negligible. A factory equipped Cervelo 54cm R3 Ultegra that we have here in the shop weighs 16 pounds 4 ounces on our scale while the 54cm Cervelo S3 Ultegra we have in the shop weighs 16 pounds 7 ounces. As I said, negligible.

’15 Cervelo S3 Bottom Bracket Stiffness

Second, several years ago Cervelo attacked the bottom bracket flex issue with its proprietary BBright design. We have written about BBRight before, so I will not take long – Cervelo uses asymetrical chainstays (larger on the non-driveside) in combination with an oversized bottom bracket shell to help increase the stiffness of the drivetrain. The bottom bracket shell is 20% stiffer than the previous generation Cervelo Soloist Carbon frame. So, the S3 is quite adept at controlling flex in this critical area for almost any rider, resulting in improved power transfer to the wheel.

’15 Cervelo S3 Compliance & Comfort

Third, the last generation of aero road bikes, while often very fast, were not the most comfortable bikes ever made. Cervelo heard these concerns and aggressively attacked this concern with the new Cervelo S3 design. The rear triangle of the Cervelo S3 no longer has aero shaped seatstays, as the aero shaped seatstays did little from an aero perspective, but they did make the ride a fair amount stiffer; the Cervelo S3 seatstays now resembles the lithe stays on the R3 that help make it so comfortable. The previous generation of Cervelo S bikes had massive chainstays, which were quite responsive, but were not particularly forgiving. Like the seatstays, the new Cervelo S3 has chainstays that resemble those on Cervelo’s R line of bikes. Improved comfort without harming aerodynamics – win:win.

’15 Cervelo S3 Aerodynamics

Finally, Cervelo’s wind tunnel studies have shown that the shape of the top tube was not of importance to the road bike aerodynamics. So, Cervelo incorporated a top tube on the latest Cervelo S3 that is rounder, sort of like the Squoval tubing found on the R series, than the previous design to improve ride comfort here as well. While not completely accurate, it isn’t too far off the mark to say that Cervelo took the best aspects of its aero frames, and combined them with many of the elements that make the Cervelo R line so comfortable. The result is a bike that is aero without making comfort compromises in the process.

Cervelo Aerodynamic Innovations

Cervelo pioneered the use of many design elements that are now common on other makers’ aero road bikes years ago. These innovations include the cut-out seat tube, airfoil shaped down tube, designing the bike to limit turbulence between the front wheel and down tube, with a variable shaped down tube that widens as it approaches the bottom bracket. In addition to stiffening the bottom bracket, this design allows the frame to channel air over the water bottle mounted on the down tube, which otherwise can be a large impediment to smooth, laminar airflow. All of the cables, except for the front brake of course, are routed internally and the Cervelo S3 frame is equipped to handle both cable and electronic shifting systems. There are aero bikes available from other manufacturers that may appear to be more aggressive aerodynamically than Cervelo’s. However, looks can be deceiving. In the wind tunnel, and on the road, the new Cervelo S3 and Cervelo S5 bikes test as some of the most aero bikes on the market. In fact, when our resident TT National Champion’s (Dean Phillips) Cervelo S5 (close kin to the S3’s shape) was tested against his Cervelo P5, there was virtually no difference between them. In fact, in some scenarios the Cervelo S5 he rode at Nationals tested better than his venerable Cervelo P5! While many “aero” shapes on bikes seem to be driven more by marketing than actual performance results, Cervelo has put the actual performance and ride quality front and center on the latest Cervelo S3. When the aerodynamics of the Cervelo S3 is coupled with the comfort it offers, the Cervelo S3 is not a “one hit wonder” – it is a good choice for day-in and day out fast riding for most anyone that if fits well.

’15 Cervelo S3 Component Specifications

The Cervelo S3 comes well equipped from the factory with either Shimano 6800 Ultegra mechanical or Shimano 6870 Ultegra Di2 kit. The shifters, derailleurs and brake calipers are 11 speed Shimano Ultegra 6800 and there is little to complain about in the performance of these components. Shifting is firm and precise, with the improved shifter feel of Shimano’s new 11 speed shifter design adding precision to the lever’s feel while preserving the light action Shimano is known. The newly redesigned Shimano 6800 Ultegra brake calipers have even better feel than before, and are very powerful. The handlebars on the ’15 Cervelo S3 are the aluminum 3T Ergonova Pro, and the stem is the 3T ARX Pro. Again, no complaints – these are name brand components from a reputable company. The crankset is a Rotor 3DF, designed specifically for use in Cervelo BBright frames, and come equipped with the semi-compact combination of 52/36 round chainrings. The crank spider can also accept a 50/34 combination if you want a lower low gear. The Rotor crank shifts fine, albeit not quite as nice as an Ultegra crank in my opinion.

The wheels on the ’15 Cervelo S3 are a set of Mavic Cosmic Elite S. If I had to pick a weak spot on this entire bike, it would be the wheels – the place that is the weakest point on most factory spec bicycles. Mind you there is absolutely nothing wrong with the Mavic Cosmic Elite S that comes on the Cervelo S3. They are strong, durable, relatively stiff, relatively aero at 30 mm deep, and roll nicely on quality bearings and hubs. The Mavic Cosmic Elite S is actually a really nice step forward from the base level Shimano wheels that many bikes (including Cervelo) have spec’d through the years. The reason I say they may be the weak spot is their weight of 1,770 grams. It is amazing how perspectives change quickly; not all that long ago 1770 grams would have been considered fairly light for wheels. Not anymore. The wheels are the one component I would consider upgrading if finances permit on almost all factory equipped bikes. This all being said, in the $4000 range for the mechanical Ultegra equipped bike and just a little over $5000 with Di2 electronic shifting, the Mavic Cosmic Elite S wheels on the Cervelo S3 are competitive with what comes from other manufacturers, and they should perform well for a long time. Besides, if the whole bike weighs under 16.5 lbs with 1770 gram wheels, it is pretty easy to make it weigh about 15.5 lbs with just a wheel upgrade!

All in all, if it fits you well, the Cervelo S3 is a really nice riding and fast bike – arguably the best riding truly aero road bikes available. Velo Magazine recently tested a variety of aero road bikes, and the Cervelo S3 came out on top, due to its combination of speed, aerodynamics, smooth ride, and simply excellent all around performance. I couldn’t agree more. I have enjoyed test-riding each Cervelo S3 on the roads of Vermont each time I have built or worked on one. Our clients in VT, MA, NH, NY, NJ, CT, Quebec and beyond who have purchased them have universally echoed this opinion. Available as a built bike or as a frameset ($2,300) that can be built up however you would like, the Cervelo S3 continues the Cervelo engineering tradition.

For those looking to go another notch up in aerodynamics, lower weight and drivetrain stiffness, Cervelo also offers the newly redesigned S5 for 2015 and for those looking to go a pricepoint down, they offer the Cervelo S2. The Cervelo S2 shares the same frame as the S3, but with a lower spec fork and a combination of Shimano 105 and FSA components with Shimano RS010 wheels at $2,600. The Cervelo S2, like the S3, makes for a package at its price point that is hard to beat both in speed or comfort.  If you are considering an aero road bike, and a Cervelo fits you well (the best way to find out is to get a Rider First Fitting at Fit Werx before choosing your bike or have us use your fit data from your previous fitting to find out what fits well), the Cervelo S3 should be very high on your list. It is a benchmark bike for good reason and most riders would be hard pressed to find a more aero and better riding road bike.

Fit Werx is an authorized dealer of Cervelo and other quality bike brands.  Contact a Fit Werx location Lexington or Peabody, MA, outside of NYC in Ridgefield Park, NJ or near Stowe and Burlington, VT in Waitsfield for more information on the Cervelo S3 and/or to schedule a New Bike Fitting.

Article By Jim Weaver
Service Manager
Fit Werx, Waitsfield, VT