Because cyclocross tires have to accommodate a particularly wide array of conditions -- from pavement to pure mud -- in a single race, their tread pattern has to be especially capable. Having been refined over many years, and on its way to countless podiums and numerous world championships, the Challenge Grifo 33 Clincher Tire delivers that capability, and then some. The Grifo owes its success to a host of seemingly singular contributions, but ultimately, it all comes down the tread pattern. Challenge bestowed a pattern, that, at first glance, appears low in profile -- and that's because it is. The pattern design doesn't require the extra weight of bulky, tall knobs. Instead, the evident knob shape provides ample grip in terrible conditions while minimizing the associated rolling-resistance over harder stuff. The highest point of the pattern lies in the middle of the tire, while moving outward, the knobbies gradually take on a svelte shape to provide traction in corners. However, the Grifo's tread pattern is intended to be mounted in either direction. Should you require heavy traction, say in hearty mud conditions, Challenge recommends that you mount the tire with the tread orientation facing backward. For "normal" race conditions, mount with the tread rolling forward. Regardless, you'll be rolling fast. For durability, the Grifo is constructed from a highly puncture-resistant and lightweight Super Poly casing. The bead of the tire uses an open tubular design. We know that it sounds like an oxymoron -- a clincher tubular. However, the benefits of Challenge open tubulars are astounding. They use the same hand-made construction techniques and materials as Challenge's tubulars. The only difference is that instead of being sewn, beads are actually formed by folding the casing around Aramid fibers. What's Aramid? Aramid is used for the tire beads for the same reason that it's used for bullet-proof vests -- its lightweight, compact strength.