Why a Proper Triathlon Bike Fit Improves Efficiency

Why a Proper Triathlon Bike Fit Improves Efficiency

I’ll never forget the sight I saw at my first IRONMAN 70.3 as I rode along the coast of Lake Michigan (yes, I’m talking about Steelhead). However, the spectacle before me had nothing to do with the race venue.

It was the proficiency of my competition that had me baffled.

As a novice triathlete at the time, I’ll fully admit I knew next to nothing about the intricacies of cycling. Especially on a time trial bike. But even then I had a hunch something was wrong as I whipped by athlete after athlete upright and un-aerodynamically atop my cheap aluminum frame road bike.

What were my fellow age group athletes riding? Full carbon fiber time trial machines ranging in brand from Trek, Felt, and Cervelo – all thousands of dollars more expensive than my puny proxy of a two-wheeled racer.

Yes, there’s something to be said about “the engine” on top of the bike but these people shouldn’t have been THAT slow.

I saw numerous triathletes spinning their legs at 120 rpm going nowhere. Some bounced up and down on their saddles. Some were so stretched out and hunched over I’m surprised they were even able to balance on the bike.

There was obviously an issue. Here everyone had expensive, state-of-the-art speed demons, but they might as well have spent their money on a mountain bike. The problem wasn’t their bike or their fitness. It was their position—which was being hindered by an improper triathlon bike fit.

Make no mistake, the best bike fit will improve efficiency. There are three key considerations in achieving a proper fit:

1. What’s Your Angle?

Your hip angle on a bike is paramount in achieving the best fit.

Efficiency means completing your race in the least amount of time with the least amount of effort. On a Tri Bike, this means you need to balance power and aerodynamics. Power will equate to a faster time and aerodynamics will reduce effort. However, depending on your body, you may have to sacrifice one for the other.

But what you don’t want to sacrifice any measurement in is the calculation of your hip angle.

Hip angle is measured by three points of contact: collarbone, hip, and bottom bracket. This, of course, is determined primarily by saddle height and distance to the aerobars, as well as the height of the aero bars. Those measurements will determine where these points of contact are suspended in space while riding.

Whether on a road bike or TT bike, the hip angle SHOULD BE THE SAME, ideally between 95-105°. The difference being the geometry of a Tri Bike’s seat post is at a steeper angle so you want to be able to comfortably achieve the ideal hip angle while still being aero.

This is the biggest mistake most riders make in their triathlon bike fit. If you don’t aim for the correct hip angle, you’re going to either lose power or aerodynamics or both when you don’t necessarily need to. It’s the key to comfort and cycling efficiency.

It should be noted the steeper your seat angle is (the farther forward you’re placed), the lower you might be able to place your aero pad height. The lower your aero bars, the more aerodynamic you will be positioned.

Hip angle must be preserved while recognizing not everyone will be able to “rotate” forward in order to be more aerodynamic. It depends on the rider’s body type, flexibility, strength, and biomechanics.

2. What’s the Saddle Height?

Saddle height is the second piece of the puzzle. This consideration impacts power. Proper saddle height should put your knee angle between 140-150° when at the bottom of your down stroke.    

If the saddle is too low and the angle too acute, you’ll be spinning and bouncing without producing any power. Saddle too high and angle too obtuse and you’ll have to rock your body side to side to reach through the entire down stroke. Not only is this very uncomfortable, but it also lacks power.

As you might have assumed, incorrect saddle height affects hip angle. Again, use hip angle as your litmus test. Get both this and the saddle height right and you’re well on your way to a successful triathlon bike fit.

3. What’s the Cockpit Length?

The cockpit length is the distance your body needs to work within the saddle and the aero bar pads. This is where comfort and aerodynamics come into play.

Taking a cue from Dan Empfield’s article of this subject on SlowTwitch.com, “Your aero bars should be placed such that your forearms represent a column perpendicular to the weight they’re supporting.”

As most in the business agree, the ideal angle between your torso and your upper arm should be somewhere around 90°. Too under or too over this angle and supporting your torso becomes unsustainable. 

When an athlete has trouble staying in the aero position due to lack of comfort and rises out of it to relieve the discomfort, he’s lost the entire aero advantage. At that point, you’re better off on a road bike.

Not to sound like a broken record, but proper hip angle solves this problem. This is why it’s critical to take measurements on your hip angle BEFORE purchasing a Tri Bike.

By doing this, you’ll know at what point within the cockpit length your elbows need to be placed in order to achieve the 90°. With that knowledge, you should be able to single out which Tri Bikes have the correct top tube length.

Answer these three questions effectively and when you test your bike fit and efficiency, you’ll be very pleased. In other words, you’ll pass.

But hopefully you’ll rarely be passed.


TRIDOT TAKEAWAY:

A Tri Bike wants to make you aero. Its geometry is designed for this very purpose. With the proper angles and measurements, you don’t have to sacrifice power to achieve efficiency and comfort.


TRIDOT TALK:

So much more can be said on this subject. For example, the importance of comfort cannot be overstated. Saddle choice and other measurement variations can help in this department. But what else about triathlon bike fit contributes to cycling efficiency? Are there other topics you’d like to add? Let me know in the comments!


Source:

Cockpit Length - Dan Empfield - Sep 13th, 2007

http://www.slowtwitch.com/Bike_Fit/F.I.S.T._Tri_bike_fit_system/Cockpit_length_22.html


JARED MILAM is a professional triathlete, TriDot coach, and member of the Tri4Him Pro Team. He has 16 years of competitive running experience and 11 years of competitive triathlon experience with a half Iron PR of 3:59 and a full Iron PR of 8:30. Coaching under the TriDot system since 2011, Jared loves working with aspiring triathletes of all ages and performance levels.