Performance Tires - Tire Anatomy 101

The Inside Story On Performance Tires

Shane Reichardt Jun 1, 2000 0 Comment(s)
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This cutaway of a Yokohama A520 shows how the tire is constructed. Though various tire manufacturers use special features in their products, the basics are usually similar.

Tires--they're round and made of rubber. What else is there to know about them? Plenty! Save for a few die-hard restorations, most performance enthusiasts will change the tires on their classic to something other than what was standard equipment. Choosing the right tires for your performance driving habits and conditions can be a confusing process, to say the least. Walk into any tire retailer and you're sure to be overwhelmed with a wide array of options. Which is right for you? Well, many enthusiasts will go with a popular tire because their friends are using them, or they'll stick with a particular brand because it's always worked well for them in the past. The reality is that there are probably a dozen or more tires that will suit your needs, but finding them isn't easy.

Knowing the size is the easy part. Determining your needs and the environment you will be driving in will help reduce the number of tire choices. If you live in (and will do most of your driving in) a wet environment, tires designed for rain will be a big help in keeping the rubber side down. Someone living in the deserts of Arizona may not care about the wet handling capabilities of their tires. In some areas it might be a good idea to have a set of tires for summer and another set for the wet winter months.

If you only drive your car short distances and most of that is to and from the drag strip, you should consider one of the DOT-legal drag tires that are currently available. A number of high-performance tire companies like BFGoodrich and Mickey Thompson have begun to offer these, and they are a great alternative to changing wheels and tires when you arrive for a race.

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The Toyo RA1 is a DOT-legal racing tire. It is designed for grip in the corners as well as on the straightaways. Tires intended for racing but legal for the street will often have limited treadwear, as is the case with this tire, which shows a 40 in the UTQG treadwear listing. It's a great tire, but don't expect a long life driving it on the streets.

One thing we found while researching this story is that almost every tire manufacturer has a website with enough information to boggle nearly any mind. With an Internet connection, you can do a great deal of research on various tire designs, compounds and, hopefully, find the perfect tire for your driving needs. If surfing the Internet isn't an option, try finding a local tire retailer with a large selection and a knowledgeable staff.

Basics
We all know that tires are made of rubber, but did you know that different tires use different rubber composition? From harder compounds built for high mileage to softer materials designed to "stick" to the road, there is a lot of technology that goes into creating a specific tire.

This information can be read in the tire ratings or the UTQG (Uniform Tire Quality Grade). These letters and numbers tell you the wear, traction, and temperature characteristics of a tire. Usually, achieving high performance in one area means a trade off in another area. For instance, a high-traction tire with a softer compound will typically has a shorter life span (poor wear). The wear charistics of a tire are listed as a numerical value, with 400 being the highest. Toyo's Proxes T1-S has the highest traction and temperature ratings and a wear rating of 280. The Toyo Proxes RA1 have a wear rating of only 40, mainly because they are hard-core road racing tires. BFGoodrich's drag radials, on the other hand, list an extremely high traction number but have no listed durability because their ultra-soft (sticky) compound isn't intended for use as an every day driving tire.

Temperature grades range form A to C, with A being the highest. Temperature grades represent a properly maintained tire's ability to dissipate heat under controlled indoor test wheel conditions.

Tire pressure is another important factor in tire performance and longevity. Proper air pressure should always be read while the tire is cold (preferably after it has been sitting for eight hours). Proper tire pressure will ensure the tire makes the best contact with the road-better contact, better traction. Under- and over-inflation are also big causes of wear on tires. To find the correct tire pressure, consult the tire manufacturer and/or vehicle manufacturer recommendations. One thing to remember, though, is that the best pressure isn't what is listed on the sidewall of the tire. This is simply the maximum tire pressure. Tire pressure should be set for your vehicle's weight or load.

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BFGoodrich also offers a DOT-legal ultra-high- performance tire in their g-Force T/A KD. The treadwear is right in the middle of the scale with a 200.

Performance Street Tires
You want a number of different things from a set of street tires. For instance, too stiff a sidewall may translate into a harsh ride. Conversely, a soft sidewall will cause the car to be less responsive and soft. A hard tire compound may last a long time but may also be louder. Too soft a compound will cause the tire to wear quickly (and it may collect rocks and debris and toss them at your nice paint job).

The "series" tire you run can have nearly the same effect as a soft sidewall. A low-profile tire has less of a sidewall to cushion the ride. This is great for most high-performance machines, but may leave your wheels open to damage should you hit a rock or pothole (little sidewall to absorb the impact).

One of the new features incorporated into many tires is a sidewall stiffener, which is a hard filler placed above the bead. By filling this void the sidewall is stiffened, making for a more responsive ride.

Another feature found on some tires is a rim protector. This ingenious feature is little more than an extra rubber shoulder near the edge of the wheel. Its purpose is to protect the wheel from damage should you accidentally get a bit too close to a curb. It's a simple feature that's not found on all tires, but one you should consider the next time you purchase tires.

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Drag Tires
One of the biggest differences between a performance street tire and a tire intended for the strip is the sidewall. On the street, a performance tire should have a fairly stiff sidewall. This allows the tire to be more responsive. Less sidewall flex will allow the car to respond faster when you crank the wheel.

With most drag tires, you will want at least a small amount of sidewall softness. This allows the tires to wrinkle. Wrinkling allows the shock of acceleration to be taken up by the tires rather than by the suspension (though ideally your suspension should be doing most of the work). The goal is to find a tire with just the right amount of sidewall softness to work with your suspension combination.

Some drag racers with a well-setup suspension may not want too soft a sidewall. The advantage of a stiff sidewall is less tire wrap or sidewall distortion, thus better reaction at launch. This is good for heavy cars, or cars with a suspension, that can absorb the initial launch. If you were running a fixed suspension car like a dragster or an altered, you would need a softer-sidewall tire to absorb the launch.

There are two ways to stiffen the sidewall. One is to run tubes to help support the sidewall. Another is to match the tread width with the wheel width. Going 1 inch wider on the wheel width will help stiffen thesidewall. One thing to remember is that too stiff a sidewall will cause the tires to lose traction on launch, because all of the torque is immediately transferred to the contact patch which, responds to the shock by unleashing cool clouds of tire smoke.

DOT legal drag tires are a godsend. Now those with streetable vehicles can drive their car to the track and not need to change to sticky tires when they get there. We wouldn't recommend driving to and from work on them, but to and from the track is no problem. One important thing to remember with these tires is that each manufacturer has specific instructions on the proper burnout. Though a John Force long, smoky display might get the crowd on their feet, it probably won't do much for your performance.

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This photo shows the BFGoodrich g-Force T/A KDW--a performance tire intended for wet and dry driving conditions.

Glossary
Aspect Ratio: The relationship of a tire's height to its width, expressed as a number that represents the nominal percent the tire's height is of its width.

Bead: A round hoop of steel wires that is shaped to fit the rim around which the tire's body plies are wrapped and holds the tire onto the rim.

Belt: A rubber-coated layer of cords that is located between the body plies and the tread rubber. Cords may be made from steel, fiberglass, rayon, nylon, polyester, or other fabrics.

Bias-Ply Tire: A pneumatic tire in which the plies are laid at alternate angles less than 90 degrees to the center line of the tread. Plies usually run at angles of about 30-40 degrees relative to the tire center line in a criss-cross fashion.

Carcass: The tire body beneath the tread and sidewalls; also called the casing.

Cold Inflation Pressure: The amount of air pressure in a tire, measured at ambient temperature before a tire has built up heat from driving.

Compound: The hardness or softness of the rubber used in tire construction.

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As you can see, water is pushed aside to allow the tread to make maximum contact with the pavement.

Cord: The strands of material forming the body plies or belt plies of the tire. Cords may be made from aramid, fiberglass, rayon, nylon, polyester or steel.

DOT Markings: A code molded into the sidewall of a tire signifying that the tire complies with U.S. Department of Transportation safety standards. The DOT code includes an alphanumeric designator that can also identify the tire's manufacturer, production plant, date of production, and brand.

Footprint: That portion of the tread in contact with the road.

High-Performance Tire: In the tire industry, those tires with speed ratings of S or greater and aspect ratios of 70 or less.

Highway Tires: Also called summer tires; designed for wet-and-dry weather driving, but not for use on snow and ice.

Hydroplaning: A skimming effect caused by tires losing contact with a surface covered with water when traveling at speed.

Innerliner: The innermost layer of a tubeless tire. The innerliner prevents air from permeating through the tire.

Overall Diameter: The outside diameter of the inflated tire, without any load.

Overall Width: The distance between the outside of the two sidewalls, including lettering and designs.

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Mickey Thompson ET Street /BFG Comp T/A Drag Radial and BFGoodrich's Comp T/A Drag Radial.

Plus-Sizing: An option allowing drivers to customize their vehicle by mounting low-profile tires on wider rims of greater diameter, usually enhancing vehicle appearance, handling and performance.

Radial Tire: A tire built with casing plies that cross the crown at an angle of 90 degrees.

Rotation: The changing of tires from front to rear or from side-to-side on a vehicle according to a set pattern; provides even treadwear.

Shimmy: Wobbling of wheels from side-to-side on a vehicle. Shimmying can be caused by a variety of factors, including improperly balanced tires, poor alignment and bent wheels.

Shoulder: The area of a tire where the tread and sidewall meet.

Sidewall: That portion of a tire between the tread and the bead.

Sipes: Special slits within a tread block that increase wet and snow traction. Sipes provide more biting edges and allow for the dispersion of water from under the tread surface.

Speed Rating: An alphabetical code (A-Z) assigned to a tire indicating the range of speeds at which the tire can carry a load under specified service conditions.

Tread: The area of a tire where the tread and sidewall meet.

Tread Rib: The tread section, usually composed of many tread blocks that run around the circumference of the tire, separated by the circumferential tread grooves.

Treadwear Indicator (Wear Bars): Narrow bands, sometimes called "wear bars," that appear across the tread surface of the tire when only 2/32 inch of tread remains.

Tread Width: The width of a tire's tread.

Traction: The friction between the tires and the road surface; the amount of grip provided.

UTQG: Uniform Tire Quality Grade. A government-mandated tire rating system based on a tire's performance in treadwear durability, traction, and temperature resistance. UTQG ratings are branded on a tire's sidewall.

Sources

Toyo Tires
800-442-8696
www.toyotires.com
Bridgestone/Firestone
Chicago, IL 60680
800-367-3872
www.bridgestone-firestone.com
Yokohama Tires
Fullerton, CA 92631-5106
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