June 16, 2006 -- We would all like to have the top-of-the-line, custom-built, super-sleek, super-fast, full-on-aero bike for our triathlon racing. Modern tri bikes are the fastest, lightest, most technologically advanced bikes ever built. However, all that science didn’t come free, and top-of-the-line rigs can cost you. Yet, if you can’t (or don’t want to) take out a second mortgage on the house to gain a bit of speed there is another option. In response to numerous e-mails asking how to make a standard road bike more aero, here is the basic recipe to do just that.
Drive-train position
The first thing most people notice when they see an aero/TT bike are the aerobars. The aerobar is the most obvious detail that grabs you and says, “This rig is built for pure speed.” However, to get the most out of your machine you must first address your drive train: in other words, your feet, legs and hips.
First, let’s get the geometry out of the way. Your standard road bike will have a 73-degree seat-tube angle -- compared to the more aggressive 75- to 78-degree seat-tube angles found on most tri bikes. Also, the top tube on a road bike will be a bit longer than on a tri bike. These differences are because a road frame is designed for multi-purpose riding: climbing, descending, cornering, etc. A road frame will be more stable, due to rider weight distribution, whereas aero bikes put more weight over the front axel giving the bike a dart-like feel, particularly on downhills.
Also, a road frame can be more efficient because it puts the rider in a position to use the larger muscles of the legs more evenly. An aero bike puts you in a more powerful position, placing more demand on the quadriceps, as compared to the hamstrings and glutes. This allows for more power but less efficiency when not on flatter roads. Thus, aero bikes tend not to climb quite as well. However, for a triathlete this forward position is good, because running will place more demand on the hamstrings and glutes, and generally courses are relatively flat. Therefore, throughout a triathlon the muscular demand is equalized, leaving you more prepared to run.
To properly mimic the steeper seat-tube angle of a tri bike on your road bike, you will need to move your saddle forward. Find a point where (while seated on the bike with the crank arms at 3 and 6 o’clock) the knee cap of the forward leg will be directly over the toe of your shoe when a plumb line is dropped from the knee cap. This is quite far forward - -expect your saddle to be nearly all the way forward on the rails. In some cases you may need to turn your seat post around from its normal position in order to access the correct position. However, this is not possible with all seat posts, so try to get the position you need with your post as is. Remember to mark where the seat originally was, so you can get back to your road position easily.
Keep in mind that for every centimeter your seat comes forward you will have to raise it half a centimeter in order to maintain your original seat height. You should place about a 30-degree bend in your knee at the bottom of the pedal stroke. This means your seat should not be so high that you reach at the bottom of the pedal stroke, causing your hips to rock from side to side. Someone riding directly behind you can let you know if this is happening. If you keep your seat height the same when you move the seat forward, you will be just a bit lower than your road position. This is often a good thing. A slightly lower saddle offers a bit more power. I would suggest trying the forward position with the same saddle height first. If this feels awkward, raise the seat by half the distance the saddle was moved forward.
Aerobars
Now we can get to aerobars. For easy transformation of your road bike to a tri bike you will want to use clip-on aerobars, which will allow you to quickly change your set up without having to re-route cables, change shifters and get different brake levers. Before purchasing clip-on aero bars check the diameter of your handlebar; 26mm used to be the standard clamp diameter, but larger stem clamps are becoming more common, requiring a 31.8mm stem and bar. This is an important factor because you may want to use a shorter stem but the same bars (more on that later). If you are using a 31.8, you will need to buy the proper size aerobar. Most bike shops should be able to help you find what you need.
Once you have your aerobars you will need to position yourself on them. You have already adjusted your drive train, so you are halfway there since your saddle position will determine where you arms and shoulders should be. There are four factors to consider when positioning aerobars:
1 Your ear should be directly over your elbow. More specifically, the leading edge of your shoulder (deltoid) should be in line vertically with the back side of you elbow, creating slightly less than a 90-degree angle in your elbow. This is where you may want to consider a shorter stem. If you have a shorter torso, the bars of a standard road bike will usually be a bit too far forward for you to be able to get your elbow angle where you want it. By shortening the stem, you bring the bars back, allowing for the proper elbow angle.
2 Ideally, your forearm should rest on the pad of your aerobar just ahead of your elbow on the wider, more muscular section of your forearm. The closer to your wrist you rest the more uncomfortable you will be.
3 The handle area of your aerobar should settle into the palm of your hand when you elbows and forearms are in the correct position. Thus you will have two solid areas of contact with the bars: elbow and hand.
4 Lastly, your elbows should be in line with the width of your hips. Any narrower will make your position unstable and constrict your breathing. Any wider and you become a huge air scoop and lose aerodynamics. However, if you are new to aerobars you may use a wider position for a few rides in order to be more stable until you get used to the position.
Roughly 75 percent of a rider’s power is used to overcome aerodynamic drag. The above suggestions won’t give you all the benefits of a true triathlon bike but will offer a huge improvement over your standard road position. These improvements will help you to drop a few minutes off you bike split and most likely help you to drop your buddies as well.
Good luck, see you at the races.
If you have a triathlon-training question for Jimmy Archer, please e-mail Triathlete Magazine Interactive.
Jimmy Archer is a six-year professional triathlete and coach with a degree in exercise physiology and 10 years coaching experience. Jimmy coaches through NYC Triathlon Consulting and can be reached at jimmy@jimmyarcher.com.