So, you can go ahead and start working away at that, or you can read my answer here: Generally speaking, tires with fewer, bigger knobs work better in mud than those with many small knobs. The reason is fairly simple: Mud packs into the gaps between the more numerous knobs, and then you don't have a treaded tire, you have a mud tire. Less clear is the benefit of long knobs that run across the tire, from side to side, like "paddles." The theory is that they dig into the soft earth and give the bike some grip. But I think they also cause mud to build up, and reduce traction rather than aiding it. Mind you, the current tires on both my mountain bikeswhich shall remain namelesshave the paddle-style design and I think they work fairly well. But next winter I'll probably ride on tires with knobs.
Tires with lots of knobs run more smoothly, so are faster on hard surfaces. It's also trueor at least obvious to methat big, widely spaced knobs reduce grip on some surfaces because they break up and soften the top soil layer. But, every tire maker has its own design, and its own rationale for using it. So trial and error, to take into account your own riding style and the trails you visit, has to be taken into account.
Need more than scientific musings? Get totally inspired by 2006's best new bikes in the April 2006 issue of Outside, on newsstands now, where science and technology meet sleek, irrefutable style.
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