Tires - tread types
Cutaway Cutaway tread gets its name because it appears that
the low sections have been "cut away" from thicker areas. There are
channels between wide flat areas of tread. In general, cutaway treads roll very
smoothly on pavement or smooth rock, because the surface "sees" a
continuous flat surface. The tread becomes active when the tire encounters loose
or wet trail. Cutaways are often bi-directional -- the tread is the same either
direction. The tire above, if placed on a rear wheel, wound be mounted so the
"pointy" part of the tread aims in the direction of travel (when
viewed from the bottom of the bike). The flat ends would "push off" as
the tire drives the bike.
Knobby Knobby tires have bumps that stick up from the
surface. These tires are excellent in loose or damp terrain. Knobbies make more
noise, and have a rougher ride, but the payoff is better hold on the trail. This
tire is mounted on the front. Because the front tire's job is to STOP the bike,
the wide (higher) side of the center knobs aims towards the front of the bike,
when viewed from below. This gives the tread better holding power. If this tire
were mounted on the rear, it would be reversed -- the wide
"trail-grabbing" side of the knobs would face the rear of the bike as
the tire meets the trail. Widely spaced knobs are better in mud and snow. Most
racing tires are knobby tires with smaller knobs. The UMB
on-line store sells high-performance and XC race tires.
Bar Bar tires are used only on the rear wheel. The transverse
bars "scoop" loose dirt, mud, and snow to drive the bike forward. A
bar tire is very rough and noisy on pavement. Because the tread is uninterrupted
through the center of the tire, this tire has less lateral (side-to-side) hold
than a knobby -- the wheel will be more likely to side-slip when traversing a
rock slope or when turning on a loose trail.
Semislick The semislick tire has a band of smooth tread in
the center of the tire. This makes the tire roll very smoothly on pavement or
stone. On the sides of the tire, aggressive knobs hold when the bike leans.
Semislick tires can be good on hard-pack trail or sandstone. Because there's
less rolling resistance, and the weight of the tread is reduced, these can be
good racing tires if the course doesn't include much loose stuff
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