While Cervélo claim to have created the aero road bike category, and won last year’s world championships with their S3, other, larger manufacturers have since made inroads into the Canadian firm’s dominance. Their new S5 aims to put a stop to that.
Scott were the first to show their hand at last year’s Tour de France, with a prototype that would became the Foil. Specialized flexed their aero muscles earlier this year with the Venge, taking Milan San Remo on the weekend of its release. And just last week Ridley showed a very strong second edition of their Noah Fast with proprietary aero brakes.
Cervélo unveiled their new bike earlier this week but announced it wouldn't be formally launched to the media until Friday, 1 July. However, we had a chance to throw a leg over the new S5 thanks to Boulder Cycle Sport, who bought one back from the distributor launch. Anyone in the area is welcome to visit their shop in Boulder, Colorado and put their own hands on the bike.
Boulder Cycle Sport co-owner, Taro Smith, with Cervelo's new S5
Ride & handling
We had a limited time on the bike and were forced to make a decision: climb and descend, or take it to our local time trial route. We chose the latter. The S5 is said to be more aero (92g less drag, for an equivalent of 9w savings; wattage savings jump to up to 32w when compared to a non-aero-tubed bike), lighter (by 80g; claimed weight 990g) and stiffer than the S3 — itself a market-leading bike — and it's the latter property that makes itself felt first.
We found the bike surprisingly stiff — much more so than we were expecting, especially through the front end. Cervélo claim it's 12 percent stiffer than the S3 and stiff enough for Thor Hushovd — hard to argue with that. It was certainly well mannered enough on our rolling test route, where top speeds approached 70kph, but we've yet to negotiate steep hairpins and challenging descents that call for dynamic, aggressive riding.
Front-end stiffness isn't as good as on a top-level non-aero road bike – if that's an issue, look to Cervélo’s own R5 instead – and neither is overall comfort; this is a bike that's been built for speed. The tall, vertically oriented seatstays, massive chainstays, enormous shaped seat tube and aero seatpost combine to offer a rather jarring ride. A firm ride from the rear end is a sort of trademark of Cervélo’s, however, it does make the bike feel fast.
The rear end offers a somewhat bumpy ride
While we weren't able to take the S5 to the wind tunnel, it felt very fast on our test route. On the flats 35kph was easy to maintain and we were able to sustain 45kph for five-minute intervals, which we consider an accomplishment. We encountered gusty crosswinds which produced some buffeting of the frame and wheels. This was noticeable and gave the bike a nervous feel, but easier to manage than that normally associated with deep rims.
The S5’s geometry mirrors the R5 and S3 in most areas, save for head tube length — the S5 is 14mm taller than the S3. This means fewer spacers are needed below the stem, allowing the rider to capitalize on the frame’s aerodynamic benefit. We’re not sure what the pros will think, though, Cervélo claims that all of the current team riders can achieve their desired position with a -17-degree stem.
The head tube is 14mm taller than the S3 and houses a standard 1-1/8in steerer
Frame & equipment
BikeRadar's technical editor, James Huang, covered the salient features of the new bike in his introduction of the S5 yesterday. However, Boulder Cycle Sport co-owner Brandon Dwight further explained a few areas of the frame that Cervélo called attention to at the dealer launch.
Name: The bike is called S5 because of the five key aero features incorporated in the design of the frame: the dropped down tube, integration and airflow around regular bottles, extended seat tube cutout, shielding seat stays, and the aerodynamic shape of the BBright bottom bracket.
Dropped down tube: Cervélo say that front wheel, fork and specially shaped down tube create smooth airflow from the front of the crown and head tube that transfers immediately to the down tube. The S3’s larger gaps created turbulence and drag. However, tire size looks to be limited to 23mm on the S5.
The S5's dropped down tube
Bottle integration: The S5 down tube is teardrop shaped until about two-thirds of the way down where it flattens for bottle bosses. This flattened mount is said to throw the trailing edge of the airflow to the bottle for smoother flow. There are also three bottle bosses on the down tube, which allow for a high mounting position for two bottles and a low mounting position for one. The low mount prevents a seat tube bottle from being mounted but reduces drag by a claimed 14g/1.4w. Arundel’s Chrono aero bottle is said to offer no measureable drag in Cervélo’s testing, making it the fastest option.
Seat tube cutout: Cervélo say their seat tube cutout offers the most rear wheel coverage of any aero road bike on the market and the width of the cutout is matched to the tire to offer uninterrupted airflow. “By designing the seat tube’s trailing edge to act as a shield in front of the rear tire, the seat tube smoothes the airflow onto the rear wheel, reducing the high pressure a rear tire typically experiences at its leading edge, thus reducing the aerodynamic drag.” Additionally, the S5’s seatstays are built to ‘shield’ the rear brake and cleanly direct air past.
The S5's seat tube cutout
BBright: While the BBright bottom bracket design is said to increase pedaling stiffness on the R5 and R5ca, it has a dual purpose on the S5. Cervélo claim it offers more surface area for aerodynamic shaping and hides bearings that would increase drag if they were housed in conventional aerodynamic cups. The company say BBright has a ‘net zero’ effect on aerodynamic drag.
Boulder Cycle Sport’s S5 came equipped with a 3T Ergonova cockpit, SRAM Red (S900 BBright compatible crank) groupset and Mavic’s Cosmic Carbon SLR wheelset, all of which worked without flaw during our first ride. As outfitted, without pedals, the 54cm package weighed 15lb 13oz (7.17kg).
15lb 13oz on Boulder Cycle Sport's scale