This is the big time. The story of Zipp isn't one about copycat products, or "as good as" mentality. Zipp Speed Weaponry is something of a gold standard for both aerodynamics and construction quality. Everything about these hoops is simply exquisite. My feelings about Zipp are perhaps best expressed by Samuel L. Jackson's line about the AK-47 machine gun: "when you absolutely, positively got to kill every mother*** in the room, accept no substitutes." Of course, like all premium products, Zipp comes at a premium price. The wheels are choice, and you'll pay for the privilege of riding them.
For 2012, the biggest changes in Zipp's lineup are the introduction of the 303 Firecrest, the arrival of the ultra-stealthy Beyond Black colorway, and finally the expansion of the accessory lineup. I wanted to take a really deep look at the whole set of wheels, and try to point out how a triathlete might make sense of it. At first blush the plethora of wheel options can seem confusing, but once you separate the forest from the trees, the Zipp lineup becomes my favorite collection of wheels anywhere. If you're looking at getting some expensive hoops, you'll want to consider their purpose, your athletic goals, and your particular riding ability and physical characteristics. It's a complex equation, but I'm going to break it down into some very simple terms.
Before going into the merits of each wheel, however, I want to take a moment to talk about wind. You've likely heard about crosswind handling over and over, and how the new generation of wheels, particularly the Firecrest series, handles so much better than the last generation. But typically missing from these discussions is a nuanced look at how the wind actually affects the cyclist, and it does so in two distinct ways. The first element is steering torque - that is, the force that's actually acting to change the direction your front wheel is turned. This is by far the more potent of the two components of force in terms of handling, and is also the component that can be improved by more advanced rim shaping. This is one thing that Zipp has worked so hard to optimize in the Firecrest series.
The other element is overall side force, which is the one that basically feels like you're being pushed to one side. It effectively operates at your bike's overall pressure center, which will be somewhere near your center of mass, but can be moved forward or backward depending on the wheels you choose. Moving this force rearward is generally helpful from a steering perspective on account of the so-called sail effect, meaning that a deeper wheel in back is generally desirable. When the side forces get high enough, your yaw angle will get well beyond the stall angle of the wheels, and you start to really feel the force of the wind. For example, if you're traveling at 20mph, and get a gust of wind at 40mph, your yaw angle is 45-degrees, which is well beyond the stall angle of even the slickest hoops. In those cases, your deep hoops give the wind more to push against, and you feel a greater force moving you to the side. In those kinds of harsh winds, shallower wheels can be your friend.
But in any event, it's always better to have a rear wheel deeper than your front. Why? A deeper rear improves handling by acting as a sail: when the wind pushes your rear wheel aside, the rear half of your bike wants to turn out, pointing your bike into the wind, which in turn reduces the component of the wind vector that's pushing you to the side. In short, it is a self-correcting move. It takes really harsh winds before that sail becomes a liability rather than a benefit. On the other hand, wind catching on your front wheel directly affects your handling by trying to turn your front wheel, forcing you to constantly fight to maintain control. So a shallower front helps reduce steering trouble in the wind. That's why you rarely see pros racing with a matched set of wheels - even when they aren't using discs, the rear wheel is almost always deeper than the front.
With all that in mind, I'm going to start by going over each wheel individually, and then describe what I think are the optimal wheelsets for different kinds of athletes. I'll start with the new 303, and go deeper from there.