You’re Not as “Fit” As You Think: A Crash Course on Triathlon-Specific Bike Fit

Featured image photo credit: Kaori Photo

Over the past decade, Tri bikes have come a long way. They are drastically more aerodynamic, lighter, and many of them fit a larger variety of riders. With these advancements, it’s easy to see why a new bike is so enticing. Rather than guessing about the time savings available on a new bike, wind tunnel data can now show you that “Bike A will save me 40 seconds over Bike B”. While many triathletes will spend thousands of dollars to save these seconds, they often forget that without a proper fit, you’re missing out on far more time saving opportunities that cost a whole lot less.

If you are attempting a fit at home, you’ll need a few tools. If you are a user of iOS; you’re in luck. The easiest DIY fit is done with the use of an app called Bike Fast Fit. For a mere $4.99, you can give yourself a complete fit with video analysis and aerodynamic drag calculation, and save it to iCloud straight from your device. The app itself is very self-explanatory, but here are a few tips to make sure you get accurate data:

1) Make sure to correctly align your wheels into the guidelines of the app. This will allow for a correct video analysis.

2) Make Sure that your bio-markers are in the correct location. If you are not in the right spot, the angles will not be accurate. Luckily the app lays out these points in a easy to understand manner so you don’t need a doctorate in anatomy to identify the markers.

For example, to measure knee angle correctly, center the middle dot at the lateral femoral condyle (bony protrusion behind the knee cap on the outside), and point the ends toward the greater trochanter at the hip (the top of the femur, felt also as a bony protrusion on the outside of the thigh) and the lateral malleolus at the ankle (your ankle bone).

If you’re not so tech-savvy and/or don’t use Apple’s iOS, you can also buy a measuring tool known as a goniometer to help you with your fit. While the name sounds confusing, it’s simply a device that measures different angles (i.e. hip, knee, shoulder, etc.). With this tool, you can fit yourself by following some basic angle guidelines. These guidelines are:

Tri Fit Knee Angle Knee angle (picture shown above): Knee angle is used to find the correct saddle height. Center the goniometer at the lateral femoral condyle (bony protrusion behind the knee cap on the outside), point one end towards the greater trochanter at the hip (the top of the femur, felt also as a bony protrusion on the outside of the thigh) and the other to the lateral malleolus at the ankle (your ankle bone). Depending upon your flexibility and past riding preferences, this angle should be between 145 and 155 degrees.

Tri Fit Hip AngleHip Angle: Hip angle is used to determine how much saddle to aerobar drop a rider can handle. With too much drop the rider might be very aerodynamic, but you slowly loose the ability to produce power. Too little drop and you give up free speed to poor aerodynamics. To measure hip angle, place the center of the goniometer on the greater trochanter at the hip, stretch one end through to the clavicle, and the other through the bottom bracket. Again, depending upon the your flexibility and past riding preferences, this angle should be between 100 and 115 degrees. You may need to experiment with a few different aerobar setups to get the fit you need.

Tri Fit Shoulder AngleShoulder Angle: Shoulder angle is measured after hip and knee angles, and is used to determine how much reach the rider needs while in the aerobars. Too big of an angle and you will likely experience unwanted shoulder pain. The shoulder angle is measured by placing the center of the goniometer at the elbow, one end through the clavicle, and the other parallel with the ground. Some riders will like this angle to be a perfect 90 degrees while others will like it to be closer to 110 degrees. As long as you fit in this range (90-110), choose whatever is most comfortable for you.

Many different factors influence how to achieve a proper TT/Tri bike fit, but the three main factors are; flexibility/biological factors, the distance of the race, and the bike itself.

1) Flexibility | A primary aim of Tri-specific fits is to limit the negative influence of biological factors on your speed. Genetically, some people are just more flexible than others, and those who are more flexible can achieve a lower, more aerodynamic position. Previous injuries also play a factor in flexibility. On paper you may be flexible enough to achieve a very low position, but if you’ve had back pain in the past, this may not be the case. In general, if you’ve had injuries in the past that limit your position, err on the side of caution and stick to the more comfortable set-up.

2) Race Distance | Ironman: Unless you’re like pro triathlete Jordan Rapp who has spent decades adjusting to such an aggressive position, chances are you are going to want to have a bit more upright setup. For such a long distance race, the ability to make power and stay comfortable is much more important than being as aero as possible. Choosing the right saddle for you will play a big role in how comfortable you’ll be in an aggressive position, so keep that in mind as you dial in your fit. Don’t forget that when you jump off that bike after 112 miles, you have still have a marathon to run.

Half Ironman: For the majority of riders, the same rules that apply to ironman also apply to the 70.3 distance. Many will want to have comfort as their number one priority. For those who are looking to get on the podium though, an aggressive position may be exactly what you need. Depending upon how flexible you are, a lower position may be the best way to set a new PR.

Sprint/Olympic: Due to the bike portion of the race being much shorter, many athletes can get by with a not-so-optimal position just to get them through the race. Those looking to do their first triathlon may not want to get into a low-aerodynamic position, but should still be properly fitted to their bike to help with injury prevention.

3) The Bike | Another limiting fit factor is the bike itself. Some bikes are considered “long and low” while others are “short and tall”. “Long and low” bikes have long top tubes and short headtubes while “short and tall” bikes are at the other end of the spectrum with short top tubes and long headtubes. In general, those with a short torso and long legs will want to look for a short and tall bike (Specialized Shiv, Cannondale Slice), while those with a longer torso and short legs will want to look at long and low style bikes (Kestrel 4000) The best way to avoid the issue of the wrong style bike is to simply perform your fit prior to making a big bike purchase. Then you can compare the measurements you need to the manufacturer’s published frame geometry.

Why go to all this trouble you ask? A proper fit will not only make you a faster rider, but will also help prevent injuries. Getting your body to fit into all of the above-mentioned angles allows each muscle to properly fire, allowing it to operate at full capacity. This not only allows you to produce more power, but because your body is now in a position that uses the correct muscles for the task at hand, the opportunity for injury greatly decreases. So before you go and purchase your new bike, do a bit of research to make sure it not only looks good, but also fits well.