From the pages of Velo: VeloLab’s Aero Revisited
Editor’s Note: In April 2011, we unveiled VeloLab, our in-depth bike and component testing program that combines objective, lab-based metrics with on-the-road evaluation. In the 18 months since, we’ve tested more than 25 bikes, from sub-$1500 budget road racers to the bikes of the WorldTour. We’ve even given four commuter rigs a spin and tested a run of seatposts for vibration. In our November issue, Lennard Zinn puts five different tubular tires through the paces in Finland to determine the effects of tire size and air pressure on rolling resistance. The following cover story first appeared in our May 2012 issue and pits four aero road bikes against each other: the Cervélo S5, the Scott Foil, the Specialized Venge and the Litespeed C1.
Aero revisited: One year on, how far have aero road bikes come?
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).
The latest models
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 championship winning 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.
Torsional Stiffness Results
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.
Wind Tunnel Results
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.
Time Saved Over 40km
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
by Caley Fretz
Strong in the lab, but weak in the wind tunnel and slightly off expectations on the road, the C1 narrowly slots into the final spot in this roundup. But, as is so often the case, that one figure doesn’t tell the whole story: the Litespeed strikes the best balance between aerodynamics and stiffness, between speed and cash outlay.
The C1 will roll off the show floor for a few thousand dollars less than anything else in this test, despite its comparable component group. Its frame sits just a few watts away from the most aerodynamic available, and is torsionally stiffer than two of the bikes that beat it overall. It is very nearly as good as the best here and is still faster than any traditionally shaped frame, making it the undisputable winner for your wallet.
Scientific Testing: 20 of 30 points
The C1 tested well in the lab, slotting into second behind the Scott Foil in our torsional stiffness test. It may have been 4% less stiff than the Foil, but it was a significant 11% stiffer than the similarly-shaped S5, with most of that difference coming at the seat tube.
It was the slowest in the wind tunnel, but was still packed closely with the other aero frames and was well ahead of our round-tubed control bike. In fact, it was faster at 0˚ and 5˚ yaw than the Foil, ending up with only 19 extra grams of drag (using our weighted average), or about 1.9 watts at 30 mph, compared to the Scott.
Subjective Ride Quality: 18 of 30 points
The C1 is quite comfortable for an aero frame, likely thanks to the tapered seat stays, which are pencil-thin near the seat tube. The front end feels much harsher than the rear, though only because the back end is so buttery smooth.
Both acceleration and handling suffer from a muted feel, lacking the crisp response we expect from high-end carbon bikes. The C1 is plenty stiff, and laying into it mid-sprint is rewarded with an equivalent surge, but overall ride quality feels a bit wooden.
The short chainstays, 12mm shorter than the Specialized Venge and a full 2cm shorter than the Foil, combined with a stable 58mm of trail were likely intended to provide a balance between agility and stability, but the result is a frame that doesn’t seem to want to provide either. Twitching around in a group doesn’t feel natural, and the bike is hesitant to commit to hard corners. However, once you get it on edge it does hold a lean very well. As a result, it was most at home on long, swooping descents rather than tight switchbacks or right-angle crit corners — most definitely a long solo breakaway kind of ride.
User Friendliness: 13 of 15 points
The C1 garners the most User Friendliness points of any bike in this test, and for good reason. It’s the easiest to work on, easily swapped between mechanical and electronic systems, with no real stinker components. It does have internal routing, but came out of the box with nice, long sleeves for easy installation — sleeves that can be used again next time you need to swap cables.
The saddle clamp is a bit odd, though, with a lateral, two-bolt design requiring quite a bit of force to keep the saddle from twisting sideways.
Value: 18 of 20 points
Is the C1 the best bike in this test? No. But at $5,600, it isn’t just the best value; it blows every other bike out of the water. Cheaper than the Foil by $1,900, the Venge by $3,200, and the S5 by $3,400, and yet just a tiny bit slower in the tunnel and stiffer than all but the Foil in the lab, the C1 is untouchable for the money. Use the thousands saved and pick up a set of aero race wheels and you’ll have a quicker ride than just about everyone else on the start line.
Weight: 3 of 5 points
The C1 was third lightest in this test at 16.12 pounds.
Cervélo S5 VWD
by Caley Fretz
With a lineage tracing back a decade to the original Cervélo Soloist, the S5 is the undisputed aristocrat of aero road frames. The question, now, is whether it can stave off the influx of new, well-rounded competitors. The S5 is Cervélo’s fastest aero road frame ever, better across the board in our labs than its predecessor, the S3. It remains unmatched in the wind tunnel, holding on to its crown across all wind angles, and is unquestionably the fastest option for a solo attack up the road. But road racing isn’t all about the breakaway, and the S5 isn’t the best multi-tasker. The narrow tube shapes that send it to the fore in the tunnel hurt it elsewhere, and ultimately kept Cervélo from coming out on top again.
Scientific Testing: 23 of 30 points
The S5 was the fastest in the wind tunnel, quicker than second place by about 5 watts at 30 mph and faster than our control bike by 82 seconds over 40km.
In the lab, the S5 fell behind in our torsional stiffness test, proving to be a full 14% less stiff than the Scott Foil. The S5 is, however, 16% stiffer than the S3 we tested last year.
Subjective Ride Quality: 23 of 30 points
Gone are the spindly stays and traditional tube junctions of the S3, and with them goes the old model’s comfort. A lounge chair the S5 is not, with every bump distinctly felt through the hands and backside. But the level of comfort is perfectly average for a race bike, and we were not unduly beat up as we have been with aero road frames in the past.
The S5 is still stiffer than its predecessor and, like the S3, springs back nicely when power is thrown into it.
The S5’s handling is the shining star of the bike’s ride quality. Quick to turn and stable once in a lean, it swoops through descents unlike any other bike in this test. Cervélo seems to have found the geometry sweet spot, as the S5 has the same mind-meld handling
as its predecessor.
My only gripe, and it is a rather large one, is the obscenely tall 179mm head tube on our 56cm frame, which made it impossible for me to obtain my regular position, even with a -17˚ stem. I could size down and use an equally obscene 150mm stem and tons of seatpost, but I shouldn’t have to: this is a race bike, used by people who want low positions. Cervélo should design it as such.
User Friendliness: 12 of 15 points
The S5 can be easily retrofitted for electronic or mechanical groups, a feature that is becoming critical as Di2 and EPS continue to gain market share.
The two-position seatpost allows the rider to move the clamp between zero and 40mm offset positions. This is a great feature for anyone planning on using the S5 for triathlons, too.
Cable routing is internal and installation is only mildly frustrating when first building the bike, before the bottom bracket is installed. Feeding the Di2 wiring harness through the frame becomes a bit more difficult with the BB pressed in, though. The rear brake mount is a bit funky, and we took another point off for the monster head tube, which makes sizing difficult.
Value: 15 of 20 points
The S5 VWD (Vroomen White Design) we tested takes a big hit on value, largely due to its Dura-Ace Di2 group and the fact that much cheaper versions of the same frame are available. The VWD frameset alone goes for $5,900, which is $2,900 more than the regular S5 and $2,100 more than the Team version used by Garmin-Barracuda. Paying the premium for the VWD version will lighten the frame by about 270 grams over the regular S5 — whether that’s worth lightening your wallet by $2,900 is a question we can’t answer for you. But it certainly doesn’t pay in the performance-per-dollar ratio we use to calculate the Value score.
Weight: 2 of 5 points
The S5 was the heaviest in this test by a smidge.
by Nick Legan
This bullet of a bike was used to great effect by Mark Cavendish and Matt Goss last season and Tom Boonen has already notched a few wins on one in 2012.
Specialized markets the Venge as “more bike than aero.” Normally, I’m not a fan of ad-speak, but it sums up the bike well. The Venge is a great bike that happens to be aerodynamic. Because it’s stiff enough for sprinters, but comfortable enough for long days in the saddle (especially solo ones where aerodynamics play a larger role), the Venge is the high-performance jack-of-all-trades in this round-up.
Scientific Testing: 22 of 30 points
Second fastest in the tunnel and third stiffest in the lab meant the Venge was lagging behind both the S5 and the Foil after the scientific testing portion.
Cable routing can have big aerodynamic impacts and we feel that this is where the Specialized was left behind by the Cervélo in the A2 Wind Tunnel.
While some have complained that the Venge is too stiff, it ranked third in our torsional stiffness test, ahead of only the S5. Because we test the bikes as a system (including cranks, bb, etc.), it may be the superlight Specialized cranks that are giving the Venge a higher deflection number. Front derailleur rub under hard acceleration led us to believe that The rings may allow some flex, though we have not isolated this in a test — and they shifted just fine.
Subjective Ride Quality: 24.5 of 30 points
It is always tough to rate a race bike on comfort. After all, that’s not what they’re about, but I rode the Venge with deep carbon wheels on dirt roads, chip seal pavement and everything in-between and was very pleased with the ride. It’s no endurance bike, but if I were in the market for a new race bike, I’d want one that smoothes out the road just a little.
While the Venge’s number may have lagged behind the others in stiffness, it didn’t feel that way on the road. A bit of snap or spring can be a good thing and the Venge is a lively bike. The stock Roval wheels are nothing to write home about, but like the Mavic Cosmic Carbons on the Foil, they’re good, reliable wheels that won’t hold you back. Carbon tubulars (or wide clinchers) for race day offer a noticeable improvement, though.
Handling is where the Venge earned back some Ride Quality points. Simply put, it’s brilliant. Two things are at play: the excellent race geometry and a frame that handles crosswinds well. Even with deep wheels, the Venge didn’t buffet in blustery conditions. Because it felt so predictably flickable, the Venge encourages you to attack corners.
User Friendliness: 10.5 of 15 points
All of these aero road bikes have internal cable routing, something we’re very picky about in the Velo tech room. Thankfully, the Specialized routing is straightforward. The derailleur cables entering the down tube may have slowed the bike a bit in the tunnel, but the Venge is easier to work on than the S5.
One item that shows some clever thought is the seatpost. It is reversible for more or less setback. The shape is symmetrical front to back. Having a perfect airfoil shape doesn’t mean much, however, if you can’t achieve your position. The saddle rail clamp mechanism is a good one too, but adjusting seat height was a huge pain. Tight tolerances are a good thing, but they were so tight on our test bike that it took ages (and a mallet) to dial in seat height. Big thumbs down there.
We loved seeing the inclusion of a chain catcher. Chapeau.
Value: 15 of 20 points
It’s always difficult to justify any bike that costs north of $8,000 and the Venge is no exception. We like SRAM Red, but if we were spending our own money, we’d look at the Vengo Pro Ui2. It’s $2,200 cheaper and offers Ultegra Di2. The downside is a heavier frame. Then again, the $18,000 McLaren version makes the S-Works we tested look like a bargain.
Weight: 5 of 5 points
The lightest in the test by over half a pound.
by Nick Legan
The 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 high-value 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 of 30 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, 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 of 30 points
For 2012, Scott engineers used a slightly 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.
User Friendliness: 13 of 15 points
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 of 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 of 5 points
The second lightest weight in the test kept up the Foil’s consistent accumulation of points.
Aero: Not Always Narrow
The 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.