One thing disturbs me. Actually, many things disturb me. You could just say that I'm disturbed and leave it at that. On the issues of tri bike fit and the way tri bikes are manufactured, though, one thing has been standing out: the way both bike manufacturers and their customers think that a 78-degree seat angle and an oblong-shaped down tube make any bike a tri bike.

I thought I'd tell you the tale of my own personal bikes—and the differences between them—that might illustrate why a great many bikes categorized today as tri bikes are really curiously made, if in fact one is supposed to use the bike for its intended purpose.

Head tubes are what I'm going to whine about today, and let's get right to it. A graphic at left shows a head-tube view of two of my bikes side by side. On the left is my tri bike, and my road bike is to the right. The two tubes shown are more or less of equivalent scale. You can see how much taller the head tube is on my road race bike.

I am 6'2" tall, and my bikes are always right around 60cm, plus or minus depending on frame material and whether you're measuring center to center or center to top. (I won't go into that here.) The head tube -- the tube on the front of the bike the fork goes into -- on my road bike measures 17cm tall. This is the one tube in the bike that is usually measured end to end, instead of from the theoretical axis, or "center," of the junction between two tubes.

The head tube on my tri bike (left in the photo) is much shorter, only 12cm in total length. Why is this? It is best explained by looking at the graphic just below that shows both my road and my tri bike from the nose of the saddles forward. This is a small graphic, and now that I'm 43 and half-blind (I had 20/20 vision five years ago, and for you young whippersnappers who think you'll live forever, the eyes are the first things to go, and they go right at 40—you can set your watch to it), I recognize the need for larger resolution graphics. So if you click on this graphic you'll pass through to a more legible view of it, and all the same text you see below will appear below the larger graphic as well.

The lime-green horizontal line over each bike is roughly drawn from the top of my saddle forward. The green vertical line closest to the saddle represents the elevation between the top of the top tube and the top of my saddle. My tri bike, at bottom, has two green lines almost next to each other, with the shorter one representing the elevation distance on my road bike. The longer green line represents the extra distance on my tri bike. In other words, the top tube sits a lot closer to the ground on my tri bike than on my road bike.

The reason is this: The head tube on my tri bike must be short or I won't be able to get my aero bars low enough. My top tube connects to the head tube, ergo my top tube cannot be any higher off the ground than the top of my head tube.

I must stop here just to ward off the inevitable emails I'll get without adding this caveat: My top tube could theoretically slope upward as it travels back toward the saddle. If it did so it wouldn't be as low along its entire distance as the graphic displays. In the old days time trial bikes were made with these sloping top tubes. They were called funny bikes. Nowadays, though, it has become apparent that there is no real benefit to having the seat stays, seat tube, and top tube meet up higher, closer to the saddle. Top tubes and seat stays do not come up as high as they used to, and we all just ride longer seat posts now. (And not only on our tri bikes, but also on some road bikes, like some made by Giant and Specialized, which, because they're road race bikes, do have taller head tubes—but the top tubes on these bikes actually slope downward toward the rear of the tube).

My head tube must be as short as it is because most of today's popular tri bars—such as those made by Syntace and Profile—are made so your forearms meet the armrests some several centimeters above the top of the handlebar. Unless you have a pretty short head tube you won't be able to get the handlebars and armrests low enough.

Take the case of my tri bike. I have a threadless (Aheadset style) stem on my bike, and you can flip this stem upside down if you like. Either way, you're going to have the stem rise or fall 6 degrees from the reference point of a right angle to the steer column. (Whoa, what did I just say?) It's pretty simple, actually. Imagine a 90-degree stem, one that—when you affix it to the steer column of the fork—sticks out at a right angle from the steerer (the part of the fork that you clamp a threadless stem onto). The sort of stem I prefer isn't at a right angle to the steerer—it rises 6 degrees, i.e., sticks at an angle 96 degrees from the steerer. Or, if you flip it upside down, it falls 6 degrees (and is 84 degrees relative to the fork's steer column). Yes, you could have a much taller head tube and compensate by putting a stem on the bike that has a steeply downward drop, but what is the sense of that? Besides a lot of extra metal for no good reason, you'd lose the adjustability a stem such as the one described above gives you.

If I flip my stem so that it falls 6 degrees and take out all the spacers that would raise the stem height except for one teensy 5mm spacer, I'll end up with about 13.5cm of armrest drop. What I mean is that my armrests—where I lay my forearms—are 13.5cm closer to the ground than is the top of my saddle. The greater the drop, the more aggressive your aero position is. How aggressive is my position? We have an equation for this on our tri bike fit section. The top of my saddle is 80cm from the center of my bottom bracket axle. That means my armrests, based on our equation, should be between 13cm to 16cm below the top of my saddle (if I'm an in-shape, flexible, top pro). I'm in the less-aggressive end of the range. Scott Tinley, at about my height (we can ride each other’s bikes interchangeably) has an armrest drop of 15cm. So my drop is relatively aggressive, but not overly so.

There are a few other things about my bikes that I'd like to point out. My road race bike and my tri bike have identical 135mm stems. My road bike has a 60cm top tube, my tri bike a 56cm top tube. You might think this is an overly large difference in top tube lengths. Yet even with my short top and head tubes, and using a Syntace Stratos Zero (which is what is on my tri bike, but you could use pretty much any flat pursuit bar), my climbing position on my tri bike and the hoods position on my road bike are exactly the same distances and upward angles from my bottom bracket. Which is to say that when climbing out of the saddle, I feel exactly the same on the two bikes, at least from a fit perspective, and this is precisely what is supposed to be the case.

My road bike dimensions offer me a quite standard road riding position. My tri bike dimensions—including the short top and head tubes—do not yield an out-of-the-ordinary tri bike fit. My armrest drop is about normal, my upper arms and torso form roughly a right angle, and my climbing position is spot-on.

Here is the curious thing. As we at Slowtwitch compare tri bikes made by all the various companies, there are obvious examples of companies that "get it" (according to us), such as Cervelo, Yaqui, QR, Kestrel and Trek. Yet there are others—some quite well known—that persist in using (again, according to us) gawdawful geometries that make no sense. Using my tri bike size (59cm) as an example, three well-known companies have tri-bike head tube lengths of 17cm, 18cm, and 19cm. Not only is my tri bike built with a 12cm head tube, even my road bike has only a 17cm head tube, and I consider it probably a centimeter too tall!

In fact, comparing the top and head tubes of various bike companies, one will notice that their head tubes are often the same height on their tri and road bikes. Likewise, the same can be said for their top tube lengths.

The moral is this. In an article elsewhere on Slowtwitch, we compared "aero" tube sections. The idea was to present the huge span between various companies purporting to make "aero" bikes. The same line of reasoning may be utilized when looking at how a bike should fit and handle, and that is what I'm aiming at here. Of course there is the argument that certain bikes might be more appropriate for riders who don't want to have a particularly aero position, and so the head tubes should be taller. That is a perfectly acceptable position. Our response to this is that there are perfectly acceptable bikes for such riders: road race bikes.

I don't mean to be flippant with that statement. There is nothing wrong with using a standard road race bike for triathlons. Unless one is prepared to ride an authentic tri bike with authentic tri geometry—and adopt an authentic tri position—a road race bike would probably be the faster machine.