Another way to look at it is a little more mathematical. For this one, we'll use Mott's average improvement of 8.3 minutes. First, we need to address the large difference in the time reductions. Mott originally calculated that the average times had decreased by 14 minutes, but then realized that bike splits before 1998 included the time the athletes spent in the transition area. There's no way to know exactly how much time that took, so Mott estimated that everyone spent 4 minutes in T2 before starting the run. While 8.3 minutes is a great advantage, we have to remember that the athletes gained it over a span of 112 miles. As a general rule of thumb for bike aerodynamics, you need to "save" about 10 watts of power to gain 40 to 60 seconds of time over a distance of 25 miles. Let's give the Kona bikes the benefit of the doubt and say that 10 watts gives them a full 60 seconds. A little back-of-the-envelope math gives us an idea of just how much better today's bikes need to be to save the athletes 8.3 minutes. First we calculate how many 25-mile "segments" there are in a 112-mile course.
112 ? 25 = 4.48
So there are about four and-a-half 25-mile segments over which to save time. Now to calculate how much time we need to save per segment:
8.3 ? 4.48 = 1.852
We need to save 1.852 minutes per each 25 miles. How many watts is that? If 10 watts gives you 1 minute, then
1.852 x 10 = 18.52
Today's bikes therefore need to save more than 18.52 watts over the frames of yesteryear to decrease your time by 8.3 minutes. That's completely achievable. In fact, we've probably seen those gains in triathlon bikes in the last five years alone. So let's run the same calculation for a 14-minute improvement. Without belaboring the math, it comes to a savings of about 30 watts. Can bikes improve that much? Yes, they can. And they have, for the most part.
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The bike itself accounts for about 30 percent of your total aerodynamic drag while cycling. The athlete, his clothes and helmet make up a bigger, more complex shape. You don't have to look at too many old photos from past Ironman races to see that we've come a long way in figuring out how to position a triathlete on his bike, not to mention how to optimize the shape of his helmet. So really it's not all about the bike. Athlete position and equipment improvements probably take the lion's share of the credit for lower bike splits between 1988 and 2005. As the Austin group noted, improvements in the average bike time of the top 10 cyclists in Kona since 2006 have been very small. This is probably more indicative of improvements in the bikes themselves. All the equipment manufacturers have caught up to one another in terms of making bikes that best fit athletes for aerodynamics and accessories to enhance their performance.
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