It didn't take me very long to learn how to tell a brown trout from a rainbow or a brookie. And I easily mastered the differences between a pumpkinseed and a bluegill. But when confronted with the redear, redbreast, or longear sunfish, things got a good deal more complicated. Even now, I usually consult a field guide to be sure.

So it is with tires for a 4x4. With so many designs available, how can you identify the correct tire for your pickup or sport utility? Consulting the simplified ``field guide'' below can make things easier. Use it to narrow the choice to a particular type of tire. Then go to a tire dealer or mail-order specialist for information on specific models within the tire type.

Essentially, there are four types of tires of concern to outdoorsmen: 1) highway rib; 2) highway/all-season; 3) offroad/all terrain; and 4) maximum traction offroad. 1 For the most part, unless you specified an offroad tire option, highway rib tires probably were original equipment on your 4x4. Their design provides good, even wear, low noise levels, and a smooth ride. These tires often have low rolling resistance that helps increase fuel economy.

Highway rib tires usually have a four- or five-rib design. Each rib is siped, which means the ribs have little slashes that help provide biting edges for dirt, slush, and snow traction. The grooves between the ribs can be jagged to provide even more of a bite. The shoulders (the inner and outer ribs) are wider to help cornering and braking performance. These tires are designed primarily for highway use, but will perform adequately in light to moderate snow and on level gravel and dirt roads.

2 The highway/all-season tire maintains the rib-type look, but the ``ribs'' now consist of small, independent blocks positioned circumferentially around the tire, which help it deliver greater performance in dirt and rain. The zigzag sipes in the blocks also help traction on snow and ice. This type of tire is an evolutionary step up from the tire profiled above. The more aggressive tread design helps it better deal with dirt and snow, so that as loose dirt and snow are compressed into the openings, you actually end up with more traction. At the same time, the rib-type design helps the tire maintain on-road performance very close to a highway rib tire. The highway/all-season tire works well on dirt roads, gravel roads, sand, and in moderate snow.

3 The offroad/all-terrain tire has as much capability off the road as it does on the road. The tire features an interlocking tread design, which means that before the ``leading tread block'' leaves the ground, the ``following tread block'' has already come into contact with it. This allows the individual blocks to work together to help maintain ride quality and promote even wear. In addition, the multi-faceted tread blocks help deliver traction from any direction on dirt, sand, and gravel; provide handling, acceleration, and stopping ability in order to avoid a rock or a stump; and help the vehicle negotiate other obstacles. The lugs on the shoulder of the tire and the pockets between each lug foster good offroad steering response and traction. This is a tire for dirt trails, rocky trails, shallow mud, and moderate to heavy snow, yet it remains fairly civilized for highway use.

4 As the designation suggests, the maximum traction offroad tire is focused mainly on offroad travel. Nonetheless, the newest designs are acceptably refined for highway travel. Notice that the interlocking tread design now features large, free-standing blocks. Also, the siping has been replaced by large gaps. The goal of this tire is to bite into loose or muddy surface areas for maximum traction and propel the vehicle forward. The very large opening between the lugs helps make the tire self-cleaning: the mud is compressed as the tire gets a grip and then expelled as the tire rolls on. (Smaller grooves allow the mud to pack in between the lugs and not be expelled.) The wide grooves also help the tire perform well on loose shale and rocks. (Grooves that are too close together can't get a grip, sort of like a rock climber who can't spread his fingers.)

The tire's shoulder area has two designs to further enhance traction on loose or muddy surfaces. The varying shoulder width offers different biting edges for traction, which makes the tire the only choice when you are likely to encounter deep ruts. To take advantage of this feature, deliberately alternate right and left turns of the steering wheel; this will gently pinch the tire against the edges of deep ruts, which allows the shoulder lugs to claw at the sides of the rut and pull the vehicle forward. In effect, the tactic provides the feeling of an additional lower gear. Though it's probably too aggressive for deep sand, this tire is the best on loose surfaces, mud, and extremely deep snow.