Tires 101: An Introduction: Difference between revisions
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==Radials== | ==Radials== | ||
And that brings us to an important matter for tire buyers | And that brings us to an important matter for tire buyers: Should I buy a radial tire? The answer is a firm "maybe". (The answer for EX 250 owners is a firm "uhh, forget it.") To understand the difference between a radial and a bias ply tire, it helps to know a little bit about tire construction. | ||
A tire is nothing more than a bladder for air. It is made of rubber reinforced with some sort of fiber ( | A tire is nothing more than a bladder for air. It is made of rubber reinforced with some sort of fiber. (Once they were reinforced with canvas; now they're reinforced with kevlar. Times have changed). The rubber keeps the air in, and the fiber keeps the tire together, in addition to imparting shape characteristics to the tire. Tires are constructed in layers, each layer consisting of fibers laid in parallel, then impregnated with rubber. The final element is the bead, which is simply a wire put around the edge of the tire to help it clamp to the rim. | ||
The way these layers are placed on the tire is what determines whether the tire is a bias-ply or radial tire. In short, a radial is a tire where the threads in the ply are | The way these layers are placed on the tire is what determines whether the tire is a bias-ply or radial tire. In short, a radial is a tire where the threads in the ply are perpendicular to the bead. This gives them the appearance of radiating from the center of the tire, thus the term radial. Bias ply tires are a little different, because the angle of the fibers is at a bias to the bead, usually at an angle of about 70 degrees. For reference, a "zero degree" layer would be a belt around the circumference of the tire. | ||
Okay, so what does it mean? Well, a bias-ply tire requires a minimum of two layers to support the sidewall and the tread. The layers are fairly stiff, and essentially must scissor against each other to flex. This makes the tire run hotter. A radial tire needs only one ply, and thus is not only softer | Okay, so what does it mean? Well, a bias-ply tire requires a minimum of two layers to support the sidewall and the tread. The layers are fairly stiff, and essentially must scissor against each other to flex. This makes the tire run hotter. A radial tire needs only one ply, and thus is not only softer but runs much cooler, and weighs less to boot. Advantages all around: lighter, cooler, more compliant. This means that not only can you run a softer compound for radials, but it will provide better grip since it can conform to the road better. Great! | ||
But wait! There's a catch -- radial tires require wider rims to support the same tire width. That means that a 120/80 bias ply tire would work on a 2.5 inch rim, but a 120/80 radial would need a 3.0 inch rim to support it properly. Why does a radial need a wider rim? In simplest terms, a radial tends to have a softer sidewall, and a wider rim with a similar aspect radial puts less load on the sidewall, causing it to distort less under load. Most radials are designed for wider wheels, and putting them on a narrower rim will distort the cross-section of the tire and affect the handling of the bike -- almost always negatively. | But wait! There's a catch -- radial tires require wider rims to support the same tire width. That means that a 120/80 bias ply tire would work on a 2.5 inch rim, but a 120/80 radial would need a 3.0 inch rim to support it properly. Why does a radial need a wider rim? In simplest terms, a radial tends to have a softer sidewall, and a wider rim with a similar aspect radial puts less load on the sidewall, causing it to distort less under load. Most radials are designed for wider wheels, and putting them on a narrower rim will distort the cross-section of the tire and affect the handling of the bike -- almost always negatively. | ||