First Ride: Cervelo’s New S5

When Cervelo launched the S5 back in 2011, it was widely considered the most aerodynamic road bike on the market. Engineering parameters placed aerodynamics on top of the list then, but that has shifted slightly this time around. Even though the second-generation S5 still holds true to its engineering roots, a heavy emphasis was placed on increasing lateral and torsional stiffness to give the aero-road bike less of an aero-road-bike feel.

A MIX OF NEW AND OLD
“Improving stiffness was goal number one,” Cervelo engineer Graham Shrive told us. Basically, Cervelo wanted their aero bike to have similar handling characteristics as the R5 and R3 that use more traditional tube shapes. To accomplish their goal, Cervelo utilized some of the very features that have been applied to the R-series line, such as a tapered steerer tube (1 1/8 inches to 1 3/8 inches) over the straight (1 1/8 inches) steerer of the previous design. Chainstays also took on the configuration of the R-series, while the width of the cutaway seat tube increased by 5mm. In all, Cervelo claims the changes equate to a 35-percent increase in head tube stiffness and 6-percent in bottom bracket stiffness. Refinements in the layup process help keep frame weight the same as the old S5 VWD (1065-gram), even with the increased size of the head tube and seat tube.

Since the S5 is in fact an aero-road bike, minimizing drag numbers is still a critical element to its design. A claimed 21-watt savings is what Cervelo found for a stock S5 with Dura-Ace Di2, HED Jet 6 Plus wheels and a new Cervelo handlebar compared an older S5 with a stock build of Dura-Ace Di2, Mavic Cosmic wheels and a 3T handlebar. Since we’re told that the new frame has identical drag numbers as the older one, it’s the new parts spec that accounts for the entire 21-watt savings.

Cervelo_S5-front

AND THE CHANGES ARE…
Even though the overall look of the new frame hasn’t significantly changed, there are many notable updated features. An often-heard complaint was the lengthy head tubes Cervelo has opted to use. So, between the frame and redesigned fork, the new S5 has reduced the stack height by 13mm for a size 54 and 15mm for a size 56cm.

As far as brakes go, there is not an S5 disc version, nor is there an underchainstay- mounted brake design, either. Cervelo found that tucking the brakes away in hard-to-access places didn’t necessarily equate to lower drag numbers. Rather, they were able to orient the seatstays in a way that helps shield the rear brake from the wind while keeping it in an easily accessible location and free from any proprietary design elements.

 

Cervelo_S5-Side

A personal favorite for us is the fact that there’s now adequate tire clearance to easily allow a 25c tire (even with HED’s 25mm-wide rims)—splendid! Also on the to-do list was finding a hiding place for an internal Di2 battery. Cervelo ultimately found a home for it in the downtube, where it’s accessed through the cable guide underneath the bottom bracket. Since charging is done from the junction box located under the stem, there is little need to ever access the battery.

AERO BAR AND NEW BUILDS
Cervelo broke down how much drag each part of the bike accounted for in the wind tunnel. What they found was that the handlebar was responsible for 30 percent of drag, nearly double the amount from the frame! Although there are already a handful of flat-topped, thin-profile handlebars already on the market, Cervelo engineered their own that pushes the UCI’s 3:1 ratio right to the limit. In wanting to maximize the number of hand positions possible, the handlebar maintains its wing shape all the way across the top rather than tapering at the stem. Unfortunately, for those running a computer, you’re on your own for mounting solutions on the handlebar itself. SRM and Pioneer users will have to get creative, since the head units from those brands can’t be stem-mounted. The all-carbon aero handlebar comes on all three S5 builds and is also available as an aftermarket item for $400.

Cervelo_S5-handlebar

The flagship S5 sells for $10,000 and includes a full Dura-Ace Di2 build, in addition to HED Jet 6 Plus wheels. A mechanical Dura-Ace version is $8000 that uses the same HED wheels, while a mechanical Ultegra model is $5500 and uses Mavic Cosmic wheels. Cervelo has typically delivered their complete bikes with wheels that are under-spec compared to the rest of the build, but this has now changed. With the two top S5 models coming with HED’s Jet 6 Plus wheels, it’s a spec that gives the bike out-of-the-box performance. The S5 is also available as a frameset for $4500.

UNDER THE TUCSON SUN
Even though Cervelo unveiled the S5 at Eurobike in late August, our first opportunity to get a test ride didn’t come until we were brought out to Tucson, Arizona, in November for two days of riding in the desert on the Dura-Ace Di2 model. We were put up at Team Garmin rider Tom Danielson’s Tucson Cycling Escape camp, which is situated just one mile from the Saguaro National Park and less than nine miles from the infamous 21-mile climb of Mount Lemmon.

When it came time to get our fit dialed, there was one vivid memory of doing the very same thing on the old S5, and it wasn’t a good one. At that time, when we pulled out the seatpost to examine it, the internal clamping mechanism fell into the seat tube, and only after a silly roadside acrobatics routine were we able to retrieve it. Cervelo listened to our (and many others’) cries and fixed this flaw.

Once out on the bike, we headed over to the eight-mile Saguaro National Park loop. The single-lane-wide, one-way road was a nonstop, up/down, left/right roller-coaster ride. A few punchy hills littered the route and provided the opportunity for some efforts. After a couple of laps on the course, we knew the road well enough to push the speeds into each corner and get a feel for the bike’s ride qualities. In and out of the corners and up the puncher climbs, the S5 didn’t have the lumbering feel that is oftentimes associated with aero-road bikes.

Cervelo_S5-Outdoor

The following day was the biggie—the 21-mile, 5500-foot climb up Mount Lemmon. Unlike the day before where there was a lot of sprinting and high-wattage efforts, there were few shenanigans on the two-hour climb, as we were content to just let the relentless mountain take its bite, especially after some strong wind gusts made our going even slower. Since aero frames and 60mm-deep wheels go together with gusty winds like oil and water, the descent was a rather hair-raising one. Coming out of a turn and having a crosswind blow you clear across the road kept us on our toes, and remembering that regardless of how many refinements are done to an aero-profile tube, it’s never going to handle with the same ease as a round tube in windy conditions.

After two days of riding in Tucson, we are happy with the direction Cervelo decided to take for the new S5. Rather than sacrificing all else for achieving marginal gains in wind-tunnel numbers, Cervelo chose to target its weak links in order to make the S5 much more of a real-world performer. As for Cervelo’s carbon handlebar, the 128mm drops were a nice depth, and finding a relaxed hand position on the tops was easy to do with so much real estate, but we missed the comfort of bar wrap and computer-mount solutions.

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