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BANYOLES, Spain (VN) — It seemed strange that in the year of the aero bike, Cervelo didn’t have anything to show as Trek, Specialized, Ridley, Cannondale, and others unveiled new speed machines. While Cervelo didn’t get to party with the big boys at the Tour de France, its new S5 was worth the wait. This thing flies. And that’s not even what makes it so cool.
The most noticeable update to the platform comes in the form of the spaceship-esque stem. The two-pronged stem looks a lot like early mountain bike stems, and it’s part of a more complex system. All cables get routed through the handlebar, into the stem, and then directly into the head tube, which is completely hollow. An external steer tube that extends off the front of the head tube contains a tensioning rod to keep everything pressed down in place.
The stem is slightly adjustable by using 2.5mm spacers. The angle adjusts from 0 degrees to 2.5 or 5 degrees, and you can add up to 30mm of spacers to adjust the height. Various stem lengths are available in 10mm increments. If that’s not to your liking, you can also get a standard stem adapter to go back to your more traditional stem.
Other goals for the redesign included changing the geometry (lowering the stack height in particular, and lowering the bottom bracket), and of course, making it faster.
On that tip, Cervelo claims a whopping 42 grams of drag savings from the previous S5. That’s a massive margin. In order to ensure it was indeed faster than its predecessor, Cervelo engineers did what everyone else does: they sent the bike to the wind tunnel. But unlike its competition, Cervelo decided to base its aero claims on the combination of both the bike and the rider, since, according to Cervelo, it doesn’t really matter if a bike on its own is faster than another bike on its own. Bikes don’t move by themselves, after all. So Cervelo tested the S5 with a dummy in the wind tunnel, and concluded that its new bike is the fastest one on the market.
That’s because the new stem design allows unimpeded air flow where once a round tube shape (the enemy of aero) protruded and created drag. According to Cervelo, the air flow attaches to the top tube, thereby reducing low pressure behind the rider. Also, by considering where high pressure is created as it comes off the rider’s body — behind the rider’s legs, for example — Cervelo was then able to create tube shapes that would reduce that drag.
Aside from aero gains, Cervelo focused on enhancing torsional stiffness, which translates into the ability to keep your wheels in plane. Essentially, that means your steering should tighten up and your bike shouldn’t fight your pedaling force in sprints. Cervelo touts a 14 percent increase in torsional stiffness and a 25 percent increase in bottom bracket stiffness.
In keeping with modern trends, the S5 now has clearance for 28mm tires. It ships with a 25mm tire, and while Cervelo wouldn’t say so, the 38.1mm of clearance between the chain stays would likely accommodate a 30mm tire.
If a superbike sounds cool but isn’t on the menu for you, Cervelo’s S3 shares many of the same aerodynamic advantages, minus the fancy redesigned stem. You’ll get a more traditional cockpit setup — though the stem still has a trick up its sleeve: it’s essentially an inverted quill stem, secured in place with a wedge — and it will be available in both rim brake and disc brake versions. Cervelo says the new S3 is 102 grams of drag faster than the previous version.
This bike keeps going. And going. And going. I was astounded at how well the S5 holds its speed; it seemed like it was willing to go much faster than I was down descents. In sprints, I was able to sustain my wattage goals for a longer period of time. It’s hard to say whether that’s a true testament to the funky stem or redesigned tube shapes, but it’s also hard to argue against it. Something about this bike makes it incredibly fast.
Transitions from downhill to uphill felt nearly effortless, since it doesn’t seem to carry much in the way of excess weight. While it’s not a climbing bike, it doesn’t seem to be much of a burden on climbs either. I’ll reserve final judgment of its climbing abilities once I get some miles on it back home in Colorado.
The handling too was superb. No longer do aero bikes have to be burdened by sluggish steering that you have to fight in switchbacks. The S5 tracks well, follows a line without an overdue amount of rider input, and tracks almost flawlessly in a straight line without your hands on the bar. Carving high-speed turns was a joy on this thing. It’s not ultra-responsive like a climbing bike, but I don’t want it to be. This notion was reinforced during a sustained sprint: wrenching on the bars didn’t seem to throw the bike off its line at all. I could think about other things, like going fast, rather than keeping the front end under control.
In that vein, the unique cockpit seems to increase lateral stability substantially. Wrenching on the front end felt like pure force, not pure fight. Everything about this bike seems to want to shoot forward in almost all situations. I’m curious what it will feel like on a sustained climb at home like Lookout Mountain, but I’m pretty confident here. This bike is toe to toe with Trek’s Madone for favorite bike of the year honors.
Despite some harsh-looking tube shapes, the bike is actually fairly comfortable. By the end of 75 miles I was feeling it in my neck and shoulders, and the front end felt a bit chattery by the time my upper body was tired, but otherwise, there was a surprising amount of compliance. That said, it doesn’t come close to the comfort of Trek’s Madone, though it’s fair to say that wasn’t Cervelo’s aim with this bike. It’s all about speed, and on that goal the S5 exceeds expectations. You’re largely left to tire pressure for compliance, and that’s fine for a bike like this.
The stem takes some getting used to aesthetically, but it’s not a noticeable feature once you start riding. In fact, the only time I remembered I was riding a goofy stem was when it offered a new hand position that I liked: thumbs tucked in between the tops and the arms of the stem.
This is, of course, a first ride review, and while I got over 100 miles on the S5, I still have questions about its comfort over rough roads and sustained climbing. If it can exceed expectations in those realms, Cervelo has certainly created an aero bike that expands the definition of the category.