Saturday, February 17, 2007

Why do little guys suck at time trials?

OK, so maybe they don’t suck, but they certainly aren’t particularly good. (We’re talking generalities here people...)

If you look at cross-section of cyclists, it seems that smaller riders can climb, larger riders can time trial, and sprinters are sort of a mixed-bag. Why does this seem to be the case? I had a monumental thought this morning - actually, a number of thoughts - and actually liked some of them.

Let’s address big rider flatland performance. We’ll start by pointing out that flat time trial performance is enhanced with more power and less drag. The force to overcome any particular amount of drag is directly related to the coefficient of drag multiplied by the frontal area. Of course there are other factors, but we’re dealing in generalities here, so let’s keep the problem bound to the major factors. (However, if you insist on precision, then go to a wind tunnel. You’ll come up with the same conclusion. Of course, if you’re that anal, then you’ll probably feel better about it only after dumping a whole lot of money anyway. Or you can use the equation here for calculating drag.)

Where was I? Oh yeh. Remember from Geometry class that Area is squared, while Volume is cubed. Consequently, given two equal riders, as one gets larger, his increase in mass (volume) will go up much faster than his increase in area. Even more so when you consider that frontal area in a TT position does not increase as fast as the body’s area. Assuming that the mass of the rider is directly related to the power (i.e. he is not just getting fat), then our answer is apparent. In short, as the rider’s mass and power increases, the drag he must overcome increases, but much more slowly. Hence, given two equivalent riders, the bigger one will have an easier time overcoming drag.

Before you start thinking, “Why is so-n-so a fast time trialer? He is not big.”  Remember, we’re dealing with equivalent riders, and NOT considering training, bike set up, or genetic freakdom.  There is a lot more to being a fast time-trialer than size. I am simply pointing out that in cycling size does matter.