Every triathlete wants to throw down a jaw-dropping bike split. To ride to your potential, it is imperative to optimize aerodynamics and minimize rolling resistance.
In this article, I will document Working Triathlete’s current recommendations for reducing drag and rolling resistance. The science is always evolving as equipment improves and we discover new ways to reduce drag (who would’ve guessed five years ago that shoving a bottle down the front of your jersey would be more aerodynamic?). These principles will evolve over time, but they represent our best understanding as of this article’s publication.
HOW TO IMPROVE CYCLING AERODYNAMICS
Body position
Your body position impacts aerodynamics more than anything else, accounting for 70-80%+ of total drag. Ultimately, you want to reduce frontal surface area by getting low and narrow, while still being able to generate power efficiently.
Recently, we’ve seen a shift from an emphasis on getting super-low to getting narrower. Many athletes are adopting slightly higher positions — their backs are not perfectly flat — but they are paying attention to what their shoulders are doing. You want your shoulders to be narrow and not “splay out.” This can be achieved by playing with aero pad width and the tilt of your extensions.
As you modify your position to get low and narrow, ensure your hip angle (pedal to greater trochanter to clavicle) at the top of your pedal stroke is no less than 40 degrees. 45 degrees is better. Shorter cranks can help open your hip angle, enabling you to get lower up front without being too scrunched at the top of the pedal stroke.
It is important to strike a balance between aerodynamics and the ability to put out power. Mitch’s position is a good compromise between the two.
Higher hands in cycling
Recently in the TT/triathlon world, we have seen a trend of higher hands. Ten years ago, almost everyone was riding with their aero bars parallel to the ground, with only a few outliers riding a “high hands” or “praying mantis” position. Now, most high-level athletes are opting for a 5–25 degree tilt, raising their hands to the level of their chin or eyes. Increasing the upward tilt of your extensions may benefit you in the following two ways:
1. You will likely be more comfortable with a correct high-hands position, making it easier to stay aero for a higher percentage of the race.
2. Closing the air cavity between your chin and hands may improve aerodynamics, especially if it leads to narrower shoulders.
Nonetheless, it's essential to approach the adjustment of your aero bars with caution. Pay close attention to the impact on your shoulder positioning. Generally, a narrower shoulder profile is more advantageous assuming you can maintain that position. Some athletes may benefit from a more aggressive tilt (15-25 degrees), while others will perform better with a milder tilt (5 degrees or even 0 degrees).
Jersey/Tri Suit/Calf Guards to optimize aerodynamics
Fabric can play a major role in reducing drag. Certainly, tight apparel is better than loose clothing flapping in the wind, so strive for a tight, wrinkle-free fit. But there has also been a lot of research and testing into how different fabric types and textures reduce drag. Compared to bare skin hitting the wind, a rougher textile surface will create a small, turbulent layer that can reduce pressure drag by enabling the air to remain attached to your body for longer, which can reduce the drag caused by a differential in air pressure between your front/leading edge and back half. Airfoil shapes like a teardrop can have a similar effect.
To leverage the aerodynamic benefits of textiles, wear a short-sleeved tri suit with minimal wrinkles rather than a sleeveless one. And wear aero calf guards, which can save a few to over 15 watts (Link to Ero’s testing). Aero socks can also save a few watts, though the full calf sleeves will likely be faster as they cover more surface area.
Helmet
Aero helmets are a worthy upgrade, delivering one of the best dollars-per-watt-saved bang for your buck. The airfoil shape will help the air flow over your body better, potentially saving around 15 watts (Silca). Although the best helmet for you will vary depending on your position and anatomy, if you’re not going to test, then you can’t go wrong with a Giro Aerohead or Rudy Project Wing. These are among the fastest helmets for most people.
Deep Wheels
Deeper wheels in the 60-90 mm range will be faster than shallower stock wheels. Flo claims their 60mm carbon wheel-set is 23 watts faster at 25mph compared to Mavic Open Pros (Source).
In nearly all situations, a rear disc wheel will be faster than an open rear wheel. Unless you’re everesting, the benefits of a rear disc outweigh the extra weight. And it’s a myth that running a disc is less stable in windy conditions. By moving the center of lateral force/pressure farther back and more underneath your center of gravity, it actually has a stabilizing effect in the wind.
Water Bottle Placement
The drag penalty of a poorly placed water bottle can be substantial. As a rule, do not put anything between your legs. Between the aero bars and behind the saddle are the best places to store them.
When positioning bottles behind the saddle, the closer to the seat and the more horizontally you can place the bottle, the more favorable it is for minimizing aerodynamic drag.
Aero bottles between the legs may be OK depending on how your frame+aero bottle interacts with airflow. In some cases, a bottle between the legs (aero or round) reduces drag, but most reports from wind tunnels show a drag penalty larger than when you put one between the aero bars or tight and horizontal against the seat.
Below, you'll find data from Aerocoach's water bottle testing, which illustrates the drag penalties incurred at a speed of 40 kilometers per hour.
o Downtube 900 ml bottle = 8.2 watt penalty, 3:20 in Ironman
o Seat tube 900 ml bottle = 5.7 watt penalty, 2:30 in Ironman
o Saddle 900 ml bottle = 2.5 watt penalty, 1:05 in Ironman
o BTA =1.2 watt penalty with 500 ml, 30 sec in Ironman
As mentioned earlier, there has been excellent data recently showing how placing a bottle down your jersey to act as a faring can reduce drag to a magnitude of 5-10+ watts (Source). It seems like the higher the bottle sits, the better. And larger bottles are more effective than smaller ones. Camelback bladders and 1.5-liter bottles seem to be most effective.
Shoes
Few people think of shoes as a way of reducing drag, however they matter. Having straps and boas hanging off your shoes can cause drag to the order of 5-8 watts. I’m a fan of Giro Empire SLX or ACC shoes, removing the tongue, and putting on flat elastic laces (Link). Notably, Bradley Wiggins wore the SLXs when he broke the hour record, presumably because they test faster than clunkier shoes. Other aerodynamic shoes include Bont Zero+ and the recently released VeloVetta shoes.
HOW TO IMPROVE ROLLING RESISTANCE
Apart from reducing drag, the next most important consideration is reducing the rolling resistance where the tires meet the road. Among the most impactful and cost-effective upgrades you can make to increase speed is to select faster tires. The difference between a fast set of tires and tubes (if applicable) and slower ones can exceed 20 watts.
Aerocoach and Bicycle Rolling Resistance are two great sources for assessing rolling resistance. As you can see on Aerocoach’s website, running Vittoria Corsa Speeds over ENVE SES tires can save nearly 15 watts.
As a rule, the fastest tubeless tires have rolling resistance as low as the fastest clincher tires run with latex tubes. Latex saves 2-4 watts per tire over butyl. For example, the Continental GP5000 TR will be as fast as the normal GP5000s, but only if you run the normal GP5000s with a latex tube. You can’t go wrong with running Corsa Speeds, Michelin TTs, or GP5000s.
Drivetrain
While not directly related to aerodynamics or rolling resistance, every wise triathlete should pay attention to their drivetrain. A clean and well-lubricated drivetrain can save 10+ watts over a dirty one. Waxing your chain (best) or using a product like Rock and Roll Gold (2nd best) is wise. Waxing is a bit more labor-intensive, so we often recommend athletes use Rock and Roll Gold as it tests well and cleans the chain as it lubricates it, making it very easy to keep the chain clean and lubed with one single product. If you are a bit more mechanically savvy, waxing your chain and/or running a polished chain will save a few additional watts.
Cliff Notes:
-Minimize frontal surface area by getting low and narrow (narrow shoulders). But don’t get too low. Your hip angle should be 45 degrees at the top of your pedal stroke.
-A small upward tilt of the aero bars can help if it makes you more comfortable, narrows your shoulders, and closes the air cavity between your hands and chin.
-Wear an aero helmet. Probably the Giro Aerohead or Rudy Project Wing.
-Aero calf guards will probably be faster than bare legs
-A tight-fitting sleeved tri suit will be faster than a loose or sleeveless one
-Only put bottles between the arms and behind the saddle. Maybe an aero bottle between the saddle is OK. But it depends on your frame.
-Run deeper wheels. And always run a full disc rear wheel
-Select your tires carefully
-Maintain a clean drivetrain
Conrad Goeringer is an Ironman Certified Coach based out of Nashville, TN. He is the founder of Working Triathlete and author of the book The Working Triathlete. His passion is helping athletes of all levels and with all schedules achieve their endurance goals. Reach out to learn more about coaching packages and for a free consultation.