In road cycling, the draft effect is so huge that other concerns (maneuverability, handling, comfort) can, in certain instances, supersede aerodynamics. When a rider is in a paceline and getting a 30% draft benefit most of the time, she should be more concerned about her ability to maneuver her bike, shift and brake easily, and get into a moderately aero position when it’s her turn to pull. Most road bike manufacturers place primary emphasis on handling, control and stiffness. Aerodynamics is second fiddle to these criterion.

Wheels, helmets and clothing fall in line here as well. A good road racing wheel is generally aerodynamic, but not so much that it hampers maneuverability and weight. Helmets are of the normal variety, for comfort and ventilation. Clothing is generally form-fitting, but a bit on the loose side, for comfort and to support pockets.

In triathlon cycling, the rider rides all alone, with no draft benefit. Consequently, the bike and rider must be much more streamlined, as the rider is constantly exposed to the wind. Handling is not as great a concern, as there are no other bikes near the rider. Manufacturers consequently design bikes primarily for aerodynamics, with handling, stiffness and sometimes comfort taking a backseat.

Wheels and helmets get the same treatment. On the vast majority of triathlon courses, a very deep front and a disc rear wheel is the best choice. An aero helmet is almost always the best choice for the same reason–though ventilation is compromised, the aero benefit of a pointy helmet is huge. Clothing is generally tighter than cycling clothing, for maximum aerodynamics. Long-course triathletes can get away with pockets, but short-course athletes should go with a tri-suit or skinsuit.

In summary, road cyclists are not as concerned with aerodynamics because of the need to be nimble, and the huge benefit of drafting. Triathletes should choose equipment based almost entirely on aerodynamics. The moral of the story for triathletes is: if it won’t make you more aero, you had better have a very good reason to race with it!

Caveat: I am aware that many of the equipment choices triathletes make can be, and often are, applied to road cycling, especially in shorter races such as criteriums. Even if a rider is getting a 30% benefit from drafting, the small benefit from the skinsuit or the deep dish wheel counts for something, regardless of the draft. However, the road cyclist isn’t as unilaterally concerned with aerodynamics as the triathlete (for example, one wouldn’t run 1080s during a 5 hour hilly road race), so the point still has some merit I think.

The big three differences between a road bike are:

• Tube shapes.  Road bikes tend to have round tubes designed for stiffness and handling.  Triathlon bikes tend to have airfoil shaped tubes designed for aerodynamics.
• The handlebars.  Road bikes have traditional “drop” handlebars, with integrated shifters and brake levers.  Triathlon bikes have “aerobars” and “pursuit bars,” with shifters on the ends of the aerobars and brakes on the end of the pursuit bars.
• The angle of the seat tube.  This is the tube that runs from the crankset toward the saddle.  In the top of the seat tube sits the seat post.  On road bikes, this tube is positioned at approximately 73-74 degrees from horizontal (90 degrees would be perpendicular to the ground).  This gives a comfortable, powerful pedaling position while in a road position.  On triathlon bikes, this tube is positioned anywhere from 76-79 degrees from horizontal.  This helps the cyclist to rotate his or her hips forward.  The cyclist’s back can then get “flatter” and thus become more aerodynamic.  There is also some research that says that it’s easier to run following a cycle with a steep seat tube angle compared to a shallow angle.

There are a few other small differences, such as saddle choice, wheel positioning/choice and crank arm length.  However, the above three reasons are the biggest differences between road bikes and triathlon bikes.

If you’re thinking about buying a tri bike, but already have a road bike, use the road bike for a while.  You’ll be just fine.  You can even buy “clip-on aerobars” for your road bike and get the benefits of aerobars without spending $1500+ on a tri bike!  In fact, if you go to any local sprint triathlon, you no doubt will see more road bikes than tri bikes!

However, if you’re serious about triathlon, a tri bike is the way to go.  These differences really do make a difference in your speed and comfort during the cycling leg of a triathlon.

1. Comfort.  You won’t want to be chafing a few miles into the bike or run.
2. Aerodynamics.  Any clothing choice should be tight-fitting, to minimize drag on the swim and bike.
3. Pockets.  In longer races, you’ll probably want pockets to hold the miscellaneous stuff you’ll need to carry.
4. Color.  This is usually personal preference, but lighter colors tend to be cooler than darker colors (and may be more “revealing,” if you know what I mean).

Once you’ve thought about these factors, you can start to look at your specific options:

1. Tri shorts and a tri top.  This is the most common option for triathletes.  It’s comfortable in all three disciplines, aerodynamic on the bike, and often come with pockets for the run.  The shorts have a minimalist pad for some comfort on the bike without getting in the way on the run.  Most triathlon clubs sell their tri kit in this form, and often it’s a cheap and simple option for new racers.  Remember to leave your tri top in transition before the swim, and put it on in T1.
2. Trisuit.  This garment is similar to the above, except it has a one-piece construction.  These have the advantage of slimming your midsection if you’re carrying a little extra in that region (who isn’t).  Check the neckline if you’re buying one–a high neckline will be more hydrodynamic while a low neckline will “scoop” in the water.  Many of these suits do not have pockets, which can be an advantage or disadvantage, depending on the race distance.  I do all of my races in trisuits, mostly because I have one that makes me look kinda like Superman.
3. Sport-specific attire for each sport.  Especially in longer races, you may find that wearing a swimsuit for the swim, bike clothes on the bike, and run clothes on the run is more comfortable and efficient.  You lose time in transition performing a complete clothes change (and in some races, nudity regulations prohibit this), but you may gain time in the end because you won’t be chafing or adjusting your clothes at all.
4. Miscellaneous combinations.  Some wear tri shorts and a looser-fitting bike jersey with sleeves.  Some can tolerate bike shorts on the run.  Some wear just a speedo for the whole race (you had better be good looking to pull that one off)!!

Your best bet is to leave yourself with several options on race day.  Conditions may dictate your choice of attire–for example, a wetsuit swim means you can leave your tri-top on under your wetsuit, while a non-wetsuit swim means you couldn’t wear your bike jersey on the swim.

Most importantly–when you’re done, wash your clothes as soon as you can.  Your domestic partner or roomate(s) will thank you.  Trust me.