Aero Revisited by Nick Legan and Caley Fretz Photographs by Brad Kaminski
A
decade ago the aero road bike segment didn’t exist; today it is redefining how race bikes are made. Ten years after Cervélo led the way with its aluminum Soloist, Specialized, Felt, Scott, Litespeed, Ridley, Blue and others are fighting to make race bikes that best their round-tubed competitors. In the past, significant aerodynamic gains came at the cost of frame stiffness, which explains why many racers preferred round-tube bikes. But what do the aero bikes of 2012 have to offer?
In our second round of aero road bike testing (For our first test, see Velo April 2011) we once again made use of the independent test facilities at the A2 Wind Tunnel and Microbac Laboratories, Inc., ensuring objective testing of aerodynamics and torsional stiffness. For the wind tunnel, we prepped each bike by setting a standardized bar height and cutting off the excess steerer tube. We ran cables as short as possible on each of the bikes while remaining operable for daily use. We removed the saddles (something the wind rarely sees) and made sure the same amount of seatpost was left exposed on each bike (measured saddle rail clamp to bottom bracket center). Gear selection and crankarm position were also carefully set and locked in place. Lastly, we used the same set of wheels for each test, a pair of Enve Smart 6.7s with 23mm Vittoria Corsa CX tubulars inflated to 100 psi. No water bottle cages were installed, nor were pedals or any other accessories. To test torsional stiffness, Microbac replicated our earlier tests, which measure frame deflection at three locations under load. For more detailed information on that test, see page 84. Numbers, however, only tell part of the story for VeloLab, so wooly hardman Nick Legan and racer wunderkind Caley Fretz undertook the majority of on-road testing, which
totaled more than 150 hours of saddle time. We also solicited input from a number of Velo editors; together we put the bikes through their paces across varied conditions (though mostly cold ones). After last year’s round of testing, we were excited to see how the latest aero road models stacked up against each other and their predecessors. Cervélo’s S3 took victory last year and the new S5 already has an impressive palmarés. But Specialized has entered the fray with its world championshipwinning Venge, Litespeed’s C1 was our Buyer’s
Guide Editor’s Pick in 2011, and the Scott Foil had impressed us enough last summer to put it on the cover of this year’s Buyer’s Guide. Cervélo’s competition is stronger than ever. The first thing that struck us was how much stiffer all the bikes felt compared to last year’s steeds. The stiffest frame in our 2011 test, the Ridley Noah, would have placed 4th in this test, only beating the S5. Clearly manufacturers have worked hard to make their go-fast aero machines more well-rounded. In addition to measuring our test bikes against one another, we explored what sort of advantage these aero machines give a rider over a traditional, round-tubed road bike. The answer: quite a bit. Riding at 30 mph, these bikes save a rider between 9.8 and 20.5 watts. When you’re on the rivet, digging for another 10 watts is a big task. Read on for more specifics on which bike might be right for you. They’re all great machines, but each has a unique personality. While we did rank the bikes first through fourth, be sure to look at the points in the categories that matter most to you. By reading carefully, you’ll find a bike that best caters to your needs.
A2 Wind Tunnel in Mooresville, NC
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TECH & TRAINING » aero bike test different carbon layup to make a small concession in the name of comfort. But that doesn’t mean the Foil is suddenly a Cadillac. Hardly, in fact. Boneshaker is what came to mind for this skinny fella. The Foil is a pure race bike. Sniveling, whiny, easily-broken riders need not apply. The Foil’s super rigid frame and fork assured that each and every ounce of effort made was translated into forward motion. Coming off a steel bike with classics-style wheels meant that stomping on the pedals on the Foil was almost alarming. The Mavic Cosmic wheels are great for general riding, but their heft kept the Foil from a perfect score in the Acceleration category. The Foil doesn’t enjoy the same inspired handling that the S5 and Venge offer. Part of that may be due to the super stiff frame. A bit of bounce and snap seem to help a bike’s handling. The Foil is more a point and shoot bike. You know exactly where the wheels are on the bike. But if you mess up a corner, don’t expect any forgiveness. The Foil requires a talented rider to bring out its full potential.
Scott Foil 10 by Nick Legan
$7,500 15.2 lbs 56cm
User Friendliness: 13/15 points
2012 editors’
pick
BY THE NUMBERS user friendliness
15
13
VALUE
total score
20
16
SUBJECTIVE RIDE QUALITY: 23.5 OUT OF 30 6
COMFORT
10
SCIENTIFIC TESTING: 25 OUT OF 30 TORSIONAL STIFFNESS
weight
4
5
9.5
ACCELERATION
10
81.5 /100 8
HANDLING
15
15
10
10
wind tunnel
15
“A weapon, made to parry and thrust its way to the finish line”
T
he Scott Foil is one of Velo’s favorite race bikes and, despite being beaten in the wind tunnel, it has won this round of testing with its extremely stiff chassis, a user-friendly frameset and highvalue spec. It’s a weapon, made to parry and thrust its way to the finish line. The Foil is the least aero looking of our test, but its subdued tube shapes are quite effective both in the lab and on the road. With a set of lively wheels, the Foil is pure racer.
scientific Testing: 25/30 points torsional stiffness: 15/15 points wind tunnel: 10/15 points
In torsional stiffness, the Foil handily beat the other three bikes in the test. Interestingly, the 2012 model wasn’t as rigid as the 2011 bike we had previously tested at Microbac. More on why later. At the wind tunnel, the Foil came in behind the S5 and the Venge and ahead of the C1. While that meant the Scott only received 10 points for third,
82
the truth is that the Litespeed, Specialized and Scott machines were only separated by an average of 43 grams of drag (over our full sweep of yaw). That’s only a 4.3 watts difference between them.
Subjective Ride Quality: 23.5/30 points Comfort: 6/10 points Acceleration: 9.5/10 points Handling: 8/10 points
For 2012, Scott engineers used a slightly
The seatpost, though Scott-specific in shape, worked well. Tolerances were reasonable, but remember the carbon friction paste when installing it. The Ritchey one-bolt head makes for easy adjustments and Scott offers two setback options. Like the Venge, Scott includes a chain catcher on the Foil. Unlike most front derailleur-mounted catchers, Scott’s design mounts to a boss on the seat tube below the front derailleur. It’s simple, clean and very effective. There is one thing to note for those considering electronic drivetrains. Routing Di2 or EPS wires internally is impossible without drilling the frame, if you buy a bike with a mechanical group. Conversely, the electronic-specific frame won’t accept a mechanical group. Poor tolerances on the fork dropout spacing made installing a wheel difficult. The dropouts were too widely spaced. Nothing was structurally wrong, but this was annoying nonetheless.
Value: 16/20 points
Scott offers the Foil with a less expensive HMF layup that is a phenomenal value. If you’re tearing up the local road-racing scene, you might consider buying yourself a cheaper version. Shimano’s mechanical Dura-Ace is expensive, but compared to Di2 or Super Record, it’s fast becoming a value. For $7,500 the Foil 10 also includes Mavic’s excellent Cosmic Carbon wheels. They are a robust set of aluminum-rimmed clincher wheels, ready for action.
Weight: 4/5 points
The second lightest weight in the test kept up the Foil’s consistent accumulation of points.
VELO may 2012 velonews.com
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TECH & TRAINING » aero bike test
overall deflection (lower values are stiffer) 6.05mm 6.28mm 6.75mm 7.07mm
.66
4.48 4.50
For these illustrations, we compared the four test bikes with ENVE Smart 6.7 wheels to a standard road bike with the same wheels. We calculated a weighted average for drag in the wind tunnel across all yaw angles to produce an overall representation of each bike. 1150
STANDARD ROAD BIKE
1100 1050 1000 950 900 850
.71 .86 .89
-25
4.74 5.40
WIND TUNNEL RESULTS Drag (grams normalized to 30mph)
TORSIONAL STIFFNESS RESULTS
-20
-15
-10
-5
5
0
10
15
20
25
YAW ANGLE
100lbs pushing down
4 WAYS TO CHEAT THE WIND* *down tube cross sections provided by manufacturers, all to scale
1.35 0.96 0.89 0.71
33mm Deflection in mm
52mm
30mm
The torsional stiffness test we co-developed with Microbac Laboratories, Inc. measures how a bike moves at three different points while subjected to a simulated pedaling force. Here’s how it works. The front fork is fixed. The rear dropouts are mounted to a dummy axle that pivots on an eyebolt, allowing the rear of the bicycle to twist and move laterally. A chain is connected from the large chainring to the dummy rear axle to transfer the pedaling force through the rear triangle. Dial indicators contact the bike at the center of the drive-side crankarm’s face, at the top of the head tube and at the top of the seat tube. Two 50-pound dumbbell weights are hung on a spindle screwed into the left crank positioned horizontally forward and the values are recorded on the three dial indicators. — LENNARD ZINN
84
36mm
TIME SAVED OVER 40KM
Watts saved Time saved (sec)* CERVÉLO S5 20.5 - 82.0 SPECIALIZED Venge 14.1 - 56.4 SCOTT Foil 11.7 - 46.8 LITESPEED C1 9.8 - 39.2 * Versus a round-tubed bike with ENVE wheels, over 40km at 30 mph (50 minutes) Power to overcome aerodynamic drag is drag force times velocity, but the equation is not linear, because as the drag force decreases, the speed increases, which then causes an increase in the drag force, etc. As long as the changes are small, relative to the total drag force of the bike and rider, however, we can use a simple linear relationship: that 50g of drag force = 5w power savings = .5s/km at 30mph. — LENNARD ZINN
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TECH & TRAINING » aero bike test
Results » Aero: not always narrow T
he Scott Foil’s victory here proves that the aero road segment continues to evolve and, in a way, fragment. A new breed has arrived, with versatility across riding styles deemed more important than absolute speed against the wind. We now see an influx of wider tube shapes with innovative aero profiles that provide most of the wind-cheating benefits, particularly in crosswinds, without hurting ride quality. These new frames strive to remove the compromise in ride quality that we’ve always had to accept in our quest to shed drag. The top two performers in this roundup are of the new school, coming within spitting distance of the best in the wind tunnel while maintaining superior stiffness and ride quality. They are, in other words, better allaround bikes. Are they quicker on a solo attack? Probably not. But they are far better to ride and race every day. The victorious Foil placed only third in the wind tunnel, tightly packed with the Venge and C1, but walloped the rest in the stiffness lab and blew us away with its race-worthy ride quality. It rides exactly like a quality, non-aero race frame should: ultra stiff with impeccable handling, if a somewhat harsh ride. When a bike rides this well, the aerodynamic benefit is just the icing on the cake. The Specialized Venge also takes a step away from traditional thin airfoils in favor of more rounded tube profiles. The result is a frame that was thoroughly consistent, testing well, but not at the very top of the heap in both the wind tunnel and the stiffness lab. A close second behind the S5 in the wind tunnel proved it can be quick against the wind, and its third place at Microbac turned out to be a blessing in disguise, as the Venge proved more comfortable than its nearest competitor. Against the wind, the more traditional shapes of Cervélo’s S5 still reign supreme. It is unquestionably the fastest road frame available today, very nearly a time trial bike with drop bars. But the narrow front end, teardrop down tube and ultra thin seat stays that make it so slippery hurt it in the stiffness lab and on the road. The venerable S5, which can trace its lineage back a decade, may not have taken the same steps towards versatility as some of its competitors, but it is still wider and stiffer in crucial places than any of the lower branches on its family tree. That means that even though it placed last in our torsional stiffness test, it’s still 16% stiffer than its predecessor, the S3. For the speed freak and the solo breakaway artist, it still cannot be beaten. Wind-cheating frames are getting cheaper, too, as our fourth-place bike proves. For $5,600, you can land Litespeed’s C1 Dura-Ace, which may have been slowest in the wind tunnel here, but is still considerably faster than any round-tubed frame. It did well in the stiffness lab, placing second, and can be had as low as $3,000 with a cheaper group. At that price, why not take the free speed? Last year, we called aero road frames “the new frontier.” Now the wagons have arrived. With the introduction of new-school frames like the Foil and Venge, the settlement process has begun, and the downsides of going aero have slipped from slim to none.
Aero Partners
Velo has turned to the fine folks at the A2 Wind Tunnel for years when pitting wheels and bikes against the wind. The repeatability of the tunnel and the constant drive for perfection from the A2 staff assures quality results. And we’re not alone in visiting the tunnel. Many manufacturers are regular visitors; Lance Armstrong has spent time there refining his time trial position. A culture of speed permeates the small town of Mooresville, North Carolina, home to A2. Many top NASCAR teams are based there. The tunnel used to test bicycles is the little brother to the neighboring AeroDyn Wind Tunnel, a larger, higher-speed facility for racecars and trucks. At $1,770 an hour, the AeroDyn tunnel is not cheap, but that doesn’t stop teams from booking the tunnel year-round. Dave Salazar is the general manager at A2 and he personally ran all of our tests. Only a week before we arrived, Salazar and his crew finished testing a new automated yaw system that halves the time necessary to test a full sweep of yaw angles. That’s good news for A2 clients, as it makes time in the tunnel more cost effective. Electronic actuators, controlled remotely, rotate the deck of the test rig. The calibration process was intense and is much more precise than the previous manual system. The automated system borrows technology and programming used on the NASCAR side of testing and took two years of on-and-off work to finish. Salazar said that the system was probably ready to go earlier, but the A2 crew tested for months to assure repeatability. Velo was only the third client to use the system and it cut the time needed for testing dramatically. Manufacturers are the clients most likely to use the new system, to help in designing/refining new products. At $490/hour, A2 also captures video of each run, as well as still images from the top, side and front. The ability to go back and check a run after an anomaly is vitally important to assure valid aerodynamic testing. When athletes come to the tunnel, they primarily focus on a zero yaw angle. That’s due to the time involved in position changes. Going this route also decreases the hourly rate to $420/hour. The Velo tech crew would like to extend many thanks to Dave Salazar and the A2 Wind Tunnel for their time and careful testing. For more info, visit www.a2wt.com. — NICK LEGAN
THE FINAL TALLY LITESPEED C1
SUBJECTive RIDE QUALITY: 52
CERVÉLO S5
SUBJECTive RIDE QUALITY: 52
SPECIALIZED VENGE
SUBJECTive RIDE QUALITY: 55
SCOTT FOIL
SUBJECTive RIDE QUALITY: 56.5
86
SCIENTIFIC TESTING: 20
72 75 77
100
SCIENTIFIC TESTING: 23
100
SCIENTIFIC TESTING: 22
SCIENTIFIC TESTING: 25
100
81.5
100
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