How Do I Choose an Aerobar (Part One)?

posted May 25, 2010, 8:33 AM by Donald Vescio   [ updated Sep 12, 2011, 8:11 AM ]


A well-designed aerobar is important for those who want to be competitive in time trials or multisport events, but choosing a set can be complicated.   There are many different styles of aerobars on the market and it can be difficult to determine what make and model might be best for you.
There are two considerations that you need to evaluate when selecting an aerobar: the aerodynamic characteristics of the aerobar’s design; its ability to match your fit coordinates.  The focus of this article is on aerodynamic considerations.  Aerobar fit selection will be the topic of the next article.

Aerobars come in a variety of materials and price ranges. One can spend under $150 for solid aerobar system, or over $1,500 for aerobars that are custom made to user specifications.   But is there a significant performance difference between lower priced and higher priced aerobars?  A lot depends upon the design of their construction.

The Simpler Version

Basic aerodynamic principles are pretty straightforward.   Thin objects tend to test faster than thick objects, and flat objects tend to be faster than round objects.  When examining an aerobar for its aerodynamic properties, take a close look at its base bar’s profile from a head-on perspective: the thinner the aerobar is, the more that it disappears from view, the faster it most likely will be.  So, for instance, an aerobar that’s flat and thin like Vision’s should test more aerodynamic than a more traditional base bar made out of round or ovalized tubing.  In most instances, aerobar extensions will have negligible impact on an aerobars’ overall aerodynamic performance.

Note how this base bar is made out of flat, thin stock





Note how the base bar is made out of round tubing; there will be more drag associated with this base bar than the base bar in the example above.



This example is the slowest configuration yet; note the significant amount of surface presented to the wind.


The Slightly More Technical Version

When evaluating an aerobar’s aerodynamic characteristics, one generally can discount the aerobar extensions, as they face parallel to the wind and are largely shadowed by the rider’s hands and arms--if the primary criteria for selecting aero extensions is comfort.  Base bars, on the other hand, do impact a rider’s aerodynamic equations.

The key concept to understand is aspect ratio—the ratio between the thickness of the bar (think: height) and its depth.  In most cases, large aspect ratios tend to be good; the original Hed aerbar was very flat and deep, and it had an aspect ratio of approximately 6:1 (it was six times deeper than its thickness).   A base bar made out of round stock has an aspect ratio of 1:1—its height is the same as its depth.   In terms of base bars available for the consumer, then, a 6:1 base bar  should be more aerodynamic than a base bar that has a 1:1 ratio.

Now, the UCI has begun enforcing aerodynamic restrictions on component design that have long been in its rule book.  Basically, most of the rules and regulations boil down to a single premise: you cannot have an aspect greater than 3:1.  As most manufacturers will follow UCI equipment regulations, even though they don’t come into play for most competitors, the most aggressive aerobars today do not exceed a 3:1 aspect ratio.  What this does is greatly simplify the selection process for most riders.   As a 3:1 ratio is about as fast as you can get under UCI criteria, riders should select base bars that have minimum protuberances and smooth transitions.  All things being equal, a well-designed sub-$100 aluminum base bar that has a good 3:1 aspect ratio will perform just as well as a $1000+ specialty carbon version.  Vision’s aluminum base bar, in other words, is a great value for its cost, as it normally performs at least as well as the high end carbon Heds, Zipps, and Ovals. As for aerobar extensions, there is absolutely no performance difference between carbon and aluminum offerings.  Provided that you find a set of extensions that are comfortable for you, there will be no performance gain of carbon over aluminum.

What’s the take-away?  Buy an aero base bar with the deepest aspect ratio possible and which can be adjusted for your position.  Take the money that you save by purchasing a good aluminum aerobar setup and apply it to the purchase of a good aero helmet or front wheel—your return (and your performance) will be the better for it.