Get A Grip

I can't remember where or when I first saw it (as is usually the case), but I recall a tire company's television ad stating something to the effect of how tires are the only parts of the car that actually make contact with the road. Such an obvious statement, but one that should be considered nonetheless: Simplified, Newton's first law of motion states that an object will maintain a constant velocity (either in motion or at rest) until acted on by an unbalanced force. In the case of a car, energy produced from any of its components remains balanced until imparted through contact with the road. In this equation, the only media for transfer of energy-and literally the gateway to performance-are the tires. All those thousands you've spent building your engine, solidifying your chassis or increasing braking performance mean nothing without good tires.

A quick look into the construction of tires will reveal there's a lot more to them than just reinforced rubber and a couple of steel belts. What makes a "good" tire is often the accumulation of expensive materials, and an involved design and construction process. Think the No-Name Xtreems that came with your $400 wheel-and-tire package are living up to the potential of your $2K suspension or $7K engine build? Think again.

Aside from holding air, providing maximum traction is the first and foremost job of a performance tire. Acceleration, braking and handling are all limited by how well your tires grip the driving surface. According to Yokohama's Paul Algarin, there's more to traction than what's apparent at first-finger poke.

Tread

"Tread composition is a good indication of how a tire could grip the surface, but there are more factors to consider in how well it will provide traction overall," Paul cautioned. "A faulty tread compound may feel soft and effective to the touch, yet become brittle under load or soften under duress of heat, which will decrease traction." Just as broth, for example, is only one ingredient in a good soup (I'm writing this before lunch), rubber is only part of a good tread compound. The compound of an average passenger car tire contains silica, silane and vinyl-based polymers-generally speaking, expensive ingredients that manufacturers will skimp on to keep costs down. "It's the proportion of these additives that gives a tire compound its characteristic-grip, heat resistance, durability-and makes one different from another," he offers.

All DOT-approved tires have a tread pattern; maximizing traction means maximizing the amount of area of a tire's tread pattern that makes contact with the driving surface, called its contact patch. But even a quality tire with a smaller contact patch can handle better than a poorly-constructed tire with a larger one. "Tires with larger amounts of tread void tend to flex more under load," explained Paul. "Whereas a racing tire with a properly-engineered tread lug can minimize tread void, and feature a less flexible pattern." A good example can be found in the ADVAN AO48's single-block tread lug that reduces flex with its one-piece design and tread voids that narrow from the tire's surface, giving the lug a "firmer stance".

Tread Life

Mr. Lincoln comes in handyWith so many tires with varying tread depths in production, how can you tell if your aging stickies have enough tread life to still be considered legal for road use? While the state inspection mechanic will measure your tread's depth with a complex piece of equipment called a "ruler", you can always get a good idea of how your treads stand by inserting a penny, heads-down, into their grooves and seeing how much of Abe's head is still visible. If part or all of his head is visible, you're in good shape. If you can see his entire head, see that you order up some replacements fast. And if your tread completely covers the penny, you've picked up the wrong magazine; the off-road section is over by Playgirl. Now saddle up and head back to the mountains, Heep driver.

Bead

By nature, rubber is a very elastic substance. Without reinforcing help from other materials, a tire's rubber would expand, causing the tire to lose its shape when put to use. A long, single length of steel wire wrapped several times over is molded into the tires bead, ensuring the tire doesn't stretch at high speed and lose its contact with the wheel. Don't expect a cheaper tire's bead to be reinforced as well as this Advan Sport's.