I’d never considered the 303 a wheelset for triathletes. The rim depth stepped down so much from the 404, there didn’t seem enough to make it worth much aerodynamically. It was just a beefed-up version of the hillclimber’s 202. As I turned the new wheel over in my hand at a press launch, I could see my mind changing.
The new 303 is a totally different beast than it once was. It looked a little deeper, which made me think this wheelset suddenly had a bit more allure for triathletes. But again, inspecting the wheel revealed much more. And test-riding it, which Zipp invited us to do during a morning ride up 17-Mile Drive, revealed even more.
To be clear, it is a deeper aero wheelset, going from 44.1mm of rim depth to 45 mm. For a guy who is fairly attuned to rim depths, I picked up on the cue. But it’s the rim’s girth, that tells a new story. And looking at a cutaway cross-section illustrated it.
Instead of a semi-toroidal cross section (where the carbon bows out from the bridge, then bows in at the brake track, where it then travels up to the rim’s edge dead vertically. Now it joins the rest of the Zipp wheel line as being fully toroidal, curving evenly from the top to bottom of the rim.
That curvature does a few things. First, it makes for a more comfortable wheel; the carbon’s bowing acts as a leaf spring, Zipp says. Spring classics guys and cross racers will appreciate the forgiving flex the rim inherently delivers.
It also makes for a wheel that, in the wind tunnel, performed better than the previous 303 iteration across a wide range of yaw angles. That curve makes the wheel look “fatter,” which looks better to the wind at off yaw wind angles.
Finally, it made for a perfect mate of a wider rim—this was our biggest notice. The old rim width was 20.3mm. The 2009 iteration? A massive 25.4mm. It’s geared for cyclo-cross and roadies that are looking for that leafspring shape to make it a more comfy wheel, while that wider width will hold a 27mm tubular cross tire much better.
But in a tri world where leading edge aerodynamics of the tire is an increasingly-studied and considered factor, the wider rim has another benefit: it hide a 23mm race wheel from the wind with greater ease. The wider track means the wind will hit the tire and transfer more smoothly onto the rim, instead of eddying behind the tire before moving rearward onto the rim. Zipp’s Sub 9 and 808 have quietly already gone to a much wide rim track, but incorporated into the shallower 303, the width is more pronounced. It’s a great advancement in the Zipp line.
When’s it available? How about today? These new 303s shipping as we speak. If you’re either a hilly race fan (Monaco, Wildflower, Alpe d’Huez tri or the like), or a smaller rider who is often blustered around by deeper wheelsets, even 404s, the new 303 is the ticket. While ITU pros like Emma Snowsill have this wheel as their mainstay, I won’t be surprised to see more age group triathletes taking a second look at the 303.