Cycling Aerodynamics: Going Aero Without Going Broke

By Kevin Kolodziejski

Whether you race or not, whether you ride 10,000 miles a year or four-tenths of that in two, one thing’s for sure.  It’s part of your cycling DNA.  It’s the continual craving (except on recovery rides) to go just that little bit faster.

What’s not so certain is how you cater to the craving.  While I can only assume it doesn’t include hypodermic needles and unmarked packages from foreign countries, I can’t assume much else.  But I can tell you there are ways increase your average mph without risking jail time.  Some, just like PEDs, cost a ton of money.  Others are not nearly as expensive.  And some are even free.

With cycling aerodynamics, there’s a big range of how much money you can spend and how much time it will save you. Let’s take a look at where you can get the biggest aerodynamic savings for the least amount of money.

Recognize the Extreme Importance of Body Position in Cycling Aerodynamics

“It won’t cost you a dollar to reduce your [aerodynamic] drag,” says Dr. Len Brownlie, an aerodynamicist who has advised both Canadian and United States Olympic cyclists; Easton Wheels; HED Wheels; Giro Helmets; and Smith Optics, runs Aerosport Research, and agreed to be interviewed for this article.  In fact, Brownlie sees improving your body position as ”the single most effective thing you can do” to increase cycling speed.  Makes sense, considering it’s not your bike but your body that creates 75 percent of the aerodynamic drag as you pedal.

Improving flexibility — particularly in your hips and lower back, areas that tend to tighten from cycling — is crucial to bettering your on-bike positioning.  Taking a yoga or pilates class works wonders, but so does an alternative that’s free: creating your own stretching routine.  Simply search the internet for ideas, experiment with different movements, and go by feel to determine which ones work best for you.  For me, nothing reduces the tightness and intermittent pain in my hips (from titanium rods being screwed into both of my once-fractured femurs) like the Happy Baby, a yoga stretch I discovered this way.  For you, stretches such as the Happy Baby done regularly will allow you to ride in the drops comfortably for a greater portion of your ride — which increases your overall speed more than you might expect.

When compared to placing your hands on the stem or the hoods, wind tunnel data has determined that riding in the drops reduces drag between 15 and 20 percent.  So if you rarely ride in the drops during your typical solo and spirited two-hour ride and now do so for half or two-thirds of that time, you simply have to go farther in that time.  In other words, free speed.  And while you’re in the drops, there’s more you can do to further reduce drag: roll your neck to lower your chin (it better fills the open space created by your arms and shoulders); keep your elbows tight (it reduces frontal surface area); and do what you can to keep your back flat.

“Do what you can” is the appropriate phrase here because when you rotate your pelvis forward to reduce the rounding of the back and lower your shoulders, you invariably forfeit power, so you must strike a compromise.  Keep in mind that keeping a flat back on a road bike doesn’t mean your shoulders need to be as low as your hips — the holy grail of hardcore time trialists everywhere. 

A study published in the June 2014 issue of Journal of Biomechanics, in fact, determined “a fully horizontal position [on a time trial bike] is not always optimal” and being more upright when your speed goes below about 18 mph is better.  An ideal road bike position drops your shoulders so that they’re no more than four to six inches higher than your hips, according to Fred Matheny, author Fred Matheny’s Complete Book of Road Bike Training, 13 other bicycling books, and co-founder of RoadBikeRider.com.  If going that low just doesn’t feel right, Matheny suggests raising your seat a millimeter or so.

Test Your Aero Bike Position for Speed, Without a Wind Tunnel

To know exactly how much improvement your stretching routine and position changes are creating, you could spend time in a wind tunnel, but that takes the sort of cash only a few cycling psychos are willing to spend.  If you go to the A2 Wind Tunnel in Mooresville, North Carolina, for instance, be prepared to drop a grand for the two-hour time minimum.  But there is another way to gauge your improvement that requires no legal tender, only a flat road on a windless day.  I first read about it many years ago in an article by Matheny.

Reach 20 mph with your body in your former position and then coast.  When your speed drops to 5 mph, note a landmark and begin back pedaling in your old style.  Mark how far you go.  Turn around, use the same stretch of road, and repeat the process five or six times.  Establish an average distance of how far you go during the back pedaling from the 5-mph point on.  Then do it all again using your new, more aero body position.  The bigger the difference between the two, the more aero you’ve become.

If your area lacks flat roads and windless days, Brownlie suggests an alternative. Come to a complete stop on a lightly traveled, steep-at the-top hill, assume your old body position, and coast down it.  Check your speed at the bottom.  Do this five or six times to get an average speed and then repeat the process using your new body position.  You’re sure to be faster the second time around; how much faster is a matter of the steepness and length of the chosen hill.

Aero Cycling Apparel for Speed — and Not Just on Race Day

In the same way I can’t picture you doing the sorts of stuff that leads to a two-year ban from USA Cycling if you get called upon to pee in a cup, you may not see yourself squeezing into a skintight skin suit so aero that when compared to standard bibs and a jersey reduces a pro’s 40 km TT time by more than two minutes.  But if you can and you’re willing to spend up to $600 — an amount that would get you something similar to what Alex Dowsett wore when he broke the UCI Hour Record in 2015 — you’re probably keeping it in a closet until race day.  Yet there are ways to make what you wear on a typical ride more aero.

Brownlie says, “Everything that flaps has to go,” which means you mothball that rain jacket with the sleeves that flutter like hummingbird’s wings when the wind whips up.  And when you no longer need the warmth of the wind vest, don’t unzip it.  Take it off.   Sounds too obvious to mention, right?  Except I’ve been on more than one fast-paced ride littered with local legends and a couple of up-and-coming pros and witnessed guys grimacing as if they were giving birth falling off the back of the group with their unzipped vests billowing like boat sails.

The next time you need to purchase cycling clothing, buy from a company that offers more than one cut of jersey and select the snuggest-fitting option.  Some companies offer as many as three different cuts, but the terms are inconsistent.  Pactimo uses “Relaxed,” “Traditional,” and “Aero,” whereas Voler opts for “Comfort,” “Athletic/Club,” and “Fitted/Race.”

Don’t think your choice of bibs makes much of a difference?  You’re probably right.  But shaving your legs does.  It reduces drag by seven percent.  A pro triathlete stumbled upon that discovery, Brownlie explains, when he forgot to shave before a wind tunnel session and tested himself both ways.  Because they never expected such a result, the researchers at hand eventually tested five more cyclists in the same manner.  All recorded a similar aero edge from the razor’s edge.

Replace your low-cut socks with ones that go at least to mid-calf and have a slightly raised texture.  Brownlie calls it “an anomaly of evolution,” but human skin is “slow,” so covering up as much as you can helps.  Use shoe covers in fair as well as foul weather.  Besides keeping your feet dry, they make the enclosure system on your shoes, something that agitates air flow sometimes 100 times a minute or more, more streamlined and thereby more aero.  Wearing them, according to Brownlie saves a pro going all out about 30 seconds over 40 km.

Better still, the time savings at speeds slower than an all-out pro’s pace are even higher.  Nathan Barry, Cannonade Design Engineer with a Ph.D in applied aerodynamics, told Selena Yeager for a July 2020 Bicycling magazine article “the slower you go, the more time [any improvement in] aerodynamics will save you, because you’re spending more time on the road.”

Consider Replacing Your Helmet for Something Faster to Get Big Aerodynamic Benefits

The U.S. Consumer Product Safety Commission recommends replacing your helmet every five to 10 crash-free years; the folks at Giro and Bell suggest three.  But based on the difference in speed that a more aero helmet makes, you may want to buy ahead of schedule.  In a test he conducted in 2016, Brownlie found the fastest time trial helmet to be the POC Cerebral, saving a pro going all-out for 40 km up to 34 seconds.  Though you probably don’t want to wear a TT lid on daily rides, one road-aero helmet tested, the Smith Ignite saved more than 21 seconds at the same pace over the same distance.

Brownlie has continued his work with these new road-aero helmets, and in the aforementioned Bicycling article explains that the Giro Vanquish, Smith Ignite, and Specialized S-Works Evade II “are very close in terms of aerodynamics to the traditional full aero lid, but they’re more comfortable and don’t turn into a sail if you look down.”  If you’re going to pick just one helmet for all-around performance, he suggests one of those.  You’ll pay, however, between $250 and $300.  Yet even for the most frugal cyclist who also yearns to go faster, doing so is an absolute bargain.  Interpret the data compiled during a 2007 study performed at MIT, and you’ll see that making such a helmet swap saves as many watts as replacing slow wheels with faster ones — at a fraction of the cost.

Upgrade Your Wheels, Downgrade Your Wallet

“Slow” wheels on moderately priced, better-than-entry-level road bikes, like the DT Swiss R470 road disc wheels found on the Specialized Roubaix Sport, cost a couple hundred dollars when purchased separately.  “Faster ones,” upgrades like Zipp 404’s, cost a couple thousand.  In Brownlie’s research, he has found replacing a 24-spoke box-section rim with an aero one using 5 spokes saves 23 seconds for that frequently mentioned pro-doing-a-40km-TT — about the same as the helmet change and at a far greater cost.  And we all know that the higher-quality tires you’d want on aero wheels aren’t exactly cheap, either.

What you may not know is how significantly your choice of rubber factors into a wheel’s aerodynamics.  When Bownlie tested the same aero front wheel with tires manufactured by five different manufacturers, the difference in drag varied as much as nine percent.  And the rear wheel?  You might need to plunk down two grand to pick up what’s de rigueur for a TT, a disk wheel, yet numerous studies show the rear wheel doesn’t affect aerodynamics to the extent the front wheel does.  In fact, Brownlie believes that if you’re building up a TT rig piece by piece, the rear wheel should be the second-to-last item you purchase — the last being a TT frame.

“[An aero frame] and bars all help to some degree, but for a keen amateur road cyclist they are not going to make that much of a difference compared to changing body position.”  That’s good to know if you want to shave seconds off your old PR without securing a home equity loan.  Top-of-the-line TT bikes cost five figures.

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Feel the Need for Cycling Speed? This Chart Will Help You Ride Faster

UPGRADE	COMPARED TO	TIME SAVED	ESTIMATED POWER SAVINGS1
Skin Suit	Typical road kit	134 seconds	23 watts
Improved Body Position to Full Tuck on Aerobars	Upright  position	56 – 122 seconds	10 to 21 watts
Deep-rim (65 mm) 12-spoke Front Wheel and 3-spoke Back Wheel	Standard road wheels	71 seconds	14 watts
Time Trial Helmet	Standard road helmet	67 seconds	11.5 watts
Shaved Legs	Unshaved legs	50+ seconds	10 watts
3-Spoke Wheel (back wheel, 0 yaw)	Disk wheel (back wheel, 0 yaw)	29 seconds	5 watts
Road Aero Helmet	Standard road helmet	21 seconds	3.5 watts
Time Trial Frame with Aero Tubing	Time trial frame with standard tubing	17 seconds	3 watts

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Test subjects’ bodies, the cause of 75 percent of the drag created in wind tunnel testing, can be quite different, especially when compared to yours.  So can testing protocols.  For instance, the initial test that found shaving your legs creates only a negligible saving of time used a mannequin leg with or without human hair glued to it.  Moreover, it’s hard to make direct comparisons between different studies. 

All this and more make it hard to know precisely how much faster aerodynamic improvements will make you. The following chart, however, based on a professional rider going-all out in a 40km time trial, should help you decide how you want to feed your insatiable need for a bit more speed.  This fact bears repeating: keep in mind what Barry told Bicycling: At slower speeds than the pros TT, you benefit even more from aerodynamics because of the increased time need to cover the distance.

Except for the information about shaved legs, all else in the chart comes from research done by Brownlie, whose  is so highly regarded that his findings have been frequently cited.  The shaved-legs info comes from “The curious case of the cyclist’s unshaven legs” by Alex Hutchinson and published by The Globe and Mail in 2014.

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Kevin Kolodziejski began his writing career in earnest in 1989. Since then he’s written a weekly health and fitness column and his articles have appeared in magazines such as “MuscleMag,” “Ironman,” “Vegetarian Times,” and “Bicycle Guide.” He has Bachelor and Masters degrees in English from DeSales and Kutztown Universities.

A competitive cyclist for more than 30 years, Kevin won two Pennsylvania State Time Trial championships in his 30’s, the aptly named Pain Mountain Time Trial 4 out of 5 times in his 40s, two more state TT’s in his 50’s, and the season-long Pennsylvania 40+ BAR championship at 43. 

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Special thanks to Len Brownlie, Ph.D, who is President of Aerosports Research (www.aerosportsresearch.com), a Sports Consultancy that offers a full range of aerodynamic design and testing capabilities to elite athletes, national sports organizations and leading sporting good manufacturers.  With over 30 years of wind tunnel testing experience and a lengthy client list of World Championship, Tour de France and Olympic medalists, Aerosports Research can help your organization reach the podium.