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To choose is to live. We have to admit that we find ourselves splitting hairs when choosing between the Zipp 303 and the 404 as the ideal racing wheelset. They're both feathery light and extremely aero, with the 303 being a bit lighter and the 404 being a bit more aero. What should be the tipping point? 50 less grams of weight or 14mm more of rim depth? The lighter wheel will accelerate better, but the deeper rim will slice through the air better.

Lighter riders, snappy riders, those who fear getting buffeted by crosswinds, will be happier on the 303s. Their 44mm rims are still pretty deep and the dimpling pattern is the same as previous versions of this wheelset. The toroidal shape allows the rim to act as if it's much deeper than it really is. And the new 303 is actually lighter than the old.

Buyers of the 303 in the tubular rim version will benefit from Zipp's new way of building carbon fiber rims. Zipp calls this method Carbon Bridge construction, and it is more than just laying up piles of carbon fiber. It employs Kevlar thread stitched in a co-axial helix (think round) to bind the layers of carbon fiber at the top of each rim's sidewall. What the stitched segment does is better spread out the compressing load that the rim experiences as it nears and passes the ground. They call it a "capstone." The result is a rim that is 28% more impact resistant than earlier iterations and allows Zipp to remove material from under the tire bed (hence the lighter weight).

And while we love the ride and weight of tubulars, there are plenty of days when we want the reliability of a clincher wheelset. You know what we mean. Changing a flat is painless, quick, and you can go 100% on the repaired tube or tire immediately. And in many cases, the weight disadvantage of clinchers is negligible. Zipp has shaved over 40g from the 303 clincher wheelset weight.

The Zipp 303 clincher is more than a superb all-around wheel. It's also a supremely comfortable wheel, easy in crosswinds but fast, and shock-absorbent. The story behind the wheel is the toroidal shape. There is a carbon bulge beneath the aluminum rim. The dimpled carbon section helps slice and smooth the airflow over the rim and tire and since the carbon is structural, it is also shock absorbing. The rim itself weighs a mere 200g, which needs the bonded carbon lower section to work. The spokes are affixed to the carbon. Between the spoke track and the rim, the curved carbon functions as a leaf spring, compressing every so slightly to take the edge off rough and imperfect roads. If you've ever felt that deep-section wheels have a harsh ride, we recommend you try clincher Zipps; you'll come away with a different opinion.

The joining of carbon to aluminum, known in Zipp-speak as M2CM, is also stronger than all get out. When tested alongside other rims for impact, the 303 clincher set a record for durability. In terms of aerodynamics, the structural carbon fiber and aluminum hybrid is much more aero than any aluminum clincher rim with a carbon fiber fairing. The 44mm 303 tested faster than a 65mm faired rim.

The Zipp 303 has 20 radial spokes in the front wheel. The rear has 24 spokes, with the 12 drive side arranged in a cross-two pattern and the 12 non-drive spokes in a radial pattern. All spokes are straight-pull Sapim X-Ray with aluminum nipples. The tubular rim width is 22.35mm, and the clincher rim width is 21.5mm. The depth is 44mm. The cassette body can come with Campagnolo splines or Shimano/SRAM splines for the appropriate cassettes. The hub bearings can be upgraded to ceramic. The front tubular wheel weighs 498g, the rear tubular 608g for a total wheel weight of 1106g. The front clincher wheel weighs, 736g the rear clincher 844g for a total wheel weight of 1580g. One note of interest to Zipp clincher owners: The maximum recommended tire pressure on the clinchers is 125psi.