The Aero Hierarchy: How to Go Faster Without Spending a Lot of Money

posted Jun 4, 2012, 5:06 PM by Donald Vescio
It’s easy to spend a lot of money on cycling, especially as today’s newest and greatest is replaced in six months by an even better model.  To go fast on the bike, one needs to factor three connected variables: training (preparing your body to race); strategy (determining optimal pace, etc.); equipment (maximizing performance gain through appropriate equipment selection).  What is especially interesting about cycling is that you can focus on any one or all of these factors.  The most successful competitors will strive to maximize gains in all three.

What follows is a basic hierarchy of aerodynamic return on investment.  The following recommendations will help you realize significant performance gain, while also providing you with a rough guideline on the best value for your money.  Note that the hierarchy below is organized in descending order of importance--that is, the greatest gain is listed first.

  1. Your body will contribute over 70% to your overall aerodynamic drag deficit.  The fastest time trial or triathlon bike and the most expensive aero wheels will not offset the penalties associated with a poor position on the bike.  Your first, and most important aerodynamic investment should be a proper fit on your race bike.  A good fitter will help you balance aerodynamic gains with biomechanical efficiency; a fit will help you maximize your application of power over time, which will result in significantly greater performance. (Approximate Cost: $250 and up)

  2. The next step would be to work with your fitter to properly place you on aerobars.  The importance of aerobars cannot be overstated.  This past spring, I did a series of wind tunnel tests in which I compared two equally fast aerodynamic bikes, with the only difference between the two was the handlebars used.  Paying close attention to detail to minimize controllable variables, I found that I realized a 40 watt advantage when using aerobars as opposed to traditional drop road bars.  40 watts is a huge difference--at my race speeds, it factors out to be an approximately 1.5 minute advantage for ten miles.  Aerobars also provide mechanical advantage for the rider, too: rather than using your musculature to support your upper body when in race position, properly fitted aerobars will enable you to transfer your body weight to your handlebars via the bony structure of your arms.  For most riders, this will yield significant savings in energy and economy of the course of a long ride. (Approximate Cost: $100 and up)

  3. You’ve been fitted and you now have aerobars; it’s time to take a look at helmets.  There are many different makes and models of aero helmets on the market today, and most have relatively distinct design philosophies.  One feature that the best aero helmets share is that they have smooth and continuous surfaces, that their shells are not interrupted by sharp shapes or vent holes.  The basic principle is sound and replicable: the more vent holes in a helmet, the slower the helmet will test aerodynamically.  What about heat build-up on hot days?  Research suggests that a significant amount of cooling will take place via the exposed face and neck and that full-shell aero helmets do not appreciably add to a racer’s overall heat load in most conditions.  Don’t have money for a full aero helmet?  Consider covering the front vent holes of your standard road helmet with clear packing tape, which will provide you with surprising aerodynamic gain. (Approximate Cost: $125 and up)

  4. Hydration is critical for all endurance athletes, and there has been a lot of research into different ways to carry liquid while on the bike.  In most instances, carrying a standard round water bottle will offer little penalty over the more expensive and sometimes harder to use aero water bottles.  For most riders, it is advantageous to place a water bottle on the seat tube to help direct air flow around the rear wheel.  Also note that behind the seat bottle mounts work best when the bottles are closely tucked underneath the seat; bottle that extend backward from the seat tend to fall into the air flow that is directed over the rider’s back, which can be a considerable source of aerodynamic drag.  Need a second bottle?  Consider mounting one horizontally between your aerobars.  Carefully position, a bottle placed in this location actually can act as a fairing for some riders.  Vertical hydration systems that fit between the aerobars also can work well for some riders--just keep the drinking straw short. (Approximate Cost: $50 and up)

  5. The rear wheel of your bike sits in a complex aerodynamic location--it is partially faired by the seat tube on some frames, but it also forms part of the bike’s trailing edge that can experience relatively choppy air flow.  The front wheel, on the other hand, forms the leading edge of your bike and enters relatively clean air.  In relative terms, then, greater aerodynamic gains can be made by focusing on the front wheel first.  A good aerodynamic front wheel will have a low spoke count (<20), and spokes will be bladed (good) or oval (best) in shape.  Rim depth will be in the range of 50 millimeters or deeper, with the ideal depth determined by rider speed and wind conditions. (This is a complex topic that deserves its own separate article.)  In addition to selecting a front wheel that has few spokes and a deep rim, care also should be placed on the width of the tire in relationship to the rim.  In general, strive to keep the width of the tire equal to or less than the width of the time. (Approximate Cost: $400 and up)

The five recommendations above focus on how to manage airflow around the front of your bike.  Additional gains can be made by managing airflow around the trailing edge (the rear) of your bike, but your financial cost for performance will be relatively high for your aerodynamic return.  Next month’s article will take a look at finer, more granular strategies to optimize aerodynamic investment.    For now, the take-away is relatively simple:

  1. Get a good fit

  2. Use aerobars

  3. Wear a smooth helmet

  4. Pay attention to where you place your hydration

  5. Find a low spoke count, deep rim front wheel