Bike Fit triangle

Bike fitting is a topic that evokes strong feelings amongst cyclists. Some think it is absolutely essential to have the perfect fit. They tend to think of that perfect fit as the one and only optimal solution. It exists somewhere in Plato's cave and it takes a real expert to discover it. Once discovered untold magical benefits will befall the fitted.

I am quite skeptical when it comes to fitting. I believe that humans are very adaptable and that they can get "used to" and perform well using a wide range of possible fittings. I know from personal experience that I did well on frames as small as 51 cm and as large as 61. I am 6'1'' or 182 cms tall and when I plug my measurements into a fit calculator the recommended frame size is always 58 cms (the old fashioned c-to-c seat tube or equivalent length). Currently I ride a 56 cm frame because I feel better in a slightly more upright position.

There is a way to bring some order to the chaos of fitting. Basically I view fitting as a compromise represented by a triangle of power, comfort, and aerodynamics. The optimal fit, or the range of optimal fits is somewhere in the inside of the triangle. Even though it is customary to think of the triangle as equilateral, the "exact shape" really depends on the person. In some people optimal power and optimal aero are close together, whereas in others optimal power is closer to optimal comfort. In most individuals however, we have a real triangle and serious compromises need to be made.

Furthermore, not the whole inside of the triangle is accessible to all. There are limits to how far an individual can go along the major axes. The range represents how adaptable a person is. Some people may never be able to get close to optimal power while in aero while others may never be aero while comfortable.

Boonen, road bike

Even in the textbook case of an equilateral triangle where the whole internal area is accessible, the optimal fit is not defined. It depends. It depends on the type of riding a person does and there are optimal fits for every riding experience. Many competitive cyclists will have two fits, one for regular racing and one for time trialing. They will use different bikes for these activities too.

Cancellara: road position

Cancellara TT position

If you predominantly race in packs, you probably want to bias your fit towards optimal power. Although aero is important, it is far less important in pack riding where you can draft. Comfort too can be compromised if the usual races are short 1-3 hour events. If this is your typical ride you will do best with a power fit.

If you predominantly ride alone and compete in long time trials or triathlon you will prefer a good aero position. You can give up some power to get there as the overall result will still be favorable. Experience has shown that nearly everyone has to give up power to get good aero. How much you should give up depends on how adaptable you are.

Finally, if you are an endurance cyclist and often ride in excess of 100 miles, you will value comfort more. Even ironman athletes will want to give up some aero and some power for comfort, especially when comfort means keeping the legs fresh for the run.

It also matters whether you prefer to climb or sprint on the flats, and whether you mainly ride on the track or on the road. Once again, you need not find a globally optimal solution and you can easily train two or three optimal but different positions. The only thing to keep in mind, is to do your race training using the position (and bike) you will ride in the race. Otherwise you may be in for a nasty surprise.

Today I rode 30 miles.

Shaving off seconds

Quite a bit of work has been done on the 40 kilometer (roughly 25 mile) time-trial. Although I would not consider 25 miles on a bicycle an endurance event, something can be learned from these studies. Twenty five miles is long enough so most power generation is done aerobically and therefore the findings are to some extent applicable to longer distances.

Time trials (TT) are easier to study than mass start races, where team tactics, skill, experience, drafting benefits, and other hard to measure variables easily cloud the picture. TT studies can be found in many publications and I won't repeat them here except to highlight a few rather self-evident facts. You may wonder why someone would care about things that are self-evident, but in this day and age there is so much information (read advertising) out there that many people forget the basics.

Not surprisingly, training provides the biggest gains, exceeding those of lighter bikes, aerodynamic frames, and other gadgets. Furthermore, the less "base" you have, the bigger the effects of training will be. If you are an experienced cat 1 cyclist, training will help but not nearly as much as when you are a novice or rookie. Still, elite riders can expect as much as 3% gain from a good program. That is certainly significant enough to make a difference. One would expect the gains of training to be even bigger for longer distances. Clearly, a 100+ mile ride requires training. You cannot "buy" your way into such an event.

Weight matters but only when you climb. You need to do a fair amount of climbing before you can see the benefits. For a short 25 mile time-trial, that means you need a pretty steep average grade, well in excess of 5%, but over a distance of 112 miles, things add up rather quickly. When it comes to weight, every little elevation change matters. Those numerous 15 ft "bumps" on the road may not show on the map, but when you add them all up, they can easily become a serious climb by the time you are done.

The best way to reduce bicycle weight in a race is not to buy a lighter frame, but to watch what you lug around. First take a look at your saddle bag. There is no need to carry a laptop computer with you in a race. There is also no need to carry enough supplies to cross the Kalahari in summer.

Two large full water bottles will add 3 pounds (1.3 kg), more than many frame fork combinations. While that may make sense on a long training ride in the hot sun, it is rather silly in a race or event, where you can get fresh, cold water every 10 miles or so. Grabbing a bottle will not slow you down significantly once you learn how to do it properly. But carrying extra weight will not just slow you down, it will also tire you out.

On the flats, aerodynamics matter the most. In mass start events, that means drafting. While most people can draft in a headwind, few seem to understand that you need to ride in a echelon to draft in a crosswind. This obvious fact seems common knowledge in Europe, but it is rare to see American riders ride that way. For time-trails and triathlons you need to resort to aero equipment as drafting is not allowed.

The gains from a proper aero position and frame can be quite significant. Some estimates for a 40K TT are as high as 2.5 minutes. Furthermore, these gains tend to be the same irrespective of your level of training. First and foremost, good aero means nothing flaps around in the wind. Watch that race-number. You can easily waste 10-20 W! That is a huge drag, even for an elite cyclist. The second thing to watch out for is items stuck to your frame. That $5 pump can easily nullify the gains from a $3,000 frame. If you "need" the pump, then be sensible enough to save the money on the frame.

Lastly, it may surprise some, but caffeine, the only legal performance enhancing drug saves anywhere from 1 to 1.5 minutes over a 40K distance. That is more than half as much as your aero-frame, at a much better price point. 

Sugary drinks help too, but much less so. When it comes to sugary drinks (or carbohydrates), there is no significant difference between the various brands. Just as long as you supply the calories. In general, you should not exceed 300-400 calories per hour as that is the limit of what people can absorb in a race. There is little benefit from "long-acting" or "slowly digesting" carbs during a race. You need the energy right then and there. During a race is not the time to start storing energy or digesting food.