Tallying the Trade-Offs
--Bob Nagy
Choosing the right tire is a pivotal decision for any SUV or light-truck owner, regardless of whether you're spending time locked onto the tarmac or bounding around in the boonies. Here are a few key points to remember when selecting sensible shoes for your vehicle.
Three main elements central to the design of any tire--P-Metric or LT-spec, radial or bias-ply--determine its primary characteristics: basic construction, tread design, and tread depth. As a rule, the more plies in a tire's carcass, the stronger and stiffer its sidewall. The additional structure in most serious off-road rubber makes it more resistant to trail damage, but the price is usually a marked reduction in on-road ride comfort.
Tread depth and tread design can be viewed as two sides of the same coin. Tires optimized for pavement work generally have shallower tread depth and less open void area, features that contribute to lower noise levels, reduced rolling resistance, lower wear, enhanced steering feel with less squirm, and better overall fuel efficiency when used as intended. They often incorporate circumferential grooving--to better evacuate water and prevent aquaplaning--as well as more internal siping to improve bite in packed-snow conditions.
Off-road tires, on the other hand, tend to display exactly the opposite characteristics, visually and functionally. Both A/T (All-Terrain) and M/T (Mud-Terrain) spec have deeper tread and a far more open pattern with less integral siping and grooving, traits that ensure clear superiority when negotiating dirt or mud trails and better gripping surfaces for walking across rocks or logs. On the downside, those features have a corresponding negative impact on NVH, fuel economy, precision control, and longevity when driven on paved surfaces.