If your tire is damaged, then often one of the most cost-effective options is a repair. Repairs can be an especially good idea if the other tires on your car are already somewhat worn. Having two tires on the same axle with wear that differs significantly can cause several problems, especially on newer vehicles. The uneven amounts of wear can create issues with your anti-lock braking, traction control, and other systems that depend on your wheels spinning at an even, predictable pace. By having the tire repaired, you save yourself the cost of replacing both tires when only one is damaged.
There is, however, one situation where a repair is not an option: sidewall damage. This can come as a surprise to many customers. After all, the sidewall doesn't even contact the ground, so what makes it so important?
The Anatomy of a Tire
Before explaining why your sidewall is such a vital part of your tire's construction, it is first essential to get some terminology out of the way. The sidewall, unsurprisingly, is the portion of the tire that you see when looking at it from the side. The area that makes contact with the ground is known as the tread. Contrary to popular belief, "tread" does not explicitly refer to the pattern of raised areas and grooves. Instead, it is the whole contact surface of the tire. The raised areas and slots (the "tread pattern") on street tires is what pushes rain and snow away from the tire's tread.
Internally, your tire consists of an inner liner that forms the air seal. Although it is completely hidden from sight once the tire is mounted on a wheel, this liner is what keeps the air inside of your tire. Above this is a framework of fabric which helps to reinforce the tire. Above the frame is the belt, which adds stability and rigidity. Finally, the tread and sidewall are the parts of the tire that are visible from the outside.
The Importance of the Sidewall
With so many internal and external parts, it can be challenging to understand what makes the sidewall so special. A puncture anywhere can potentially damage the inner liner and cause the tire to lose air, so why can't a sidewall puncture be repaired? The answer lies both with the role of the sidewall and with the forces that act on it.
Tire punctures are usually repaired using an external plug. As your tire moves across the ground, the forces acting on a tread plug will help it to stay in place. With a sidewall plug, the forces acting on your tire can potentially cause the puncture to deform, allowing the plug to loosen and break free. Your sidewall also provides lateral rigidity to the tire and damage to the sidewall can compromise the overall structure of the tire. Since tire repairs are only intended to seal leaks, they will do nothing to prevent this structural damage from causing the tire to fail.
Know When to Repair and When to Replace
Although repairing sidewall damage is impossible, most minor punctures to the tread can be sealed or plugged. In these cases, repair almost always makes more sense than replacement unless the tire is very old and already in need of replacement. If the damage is located on the sidewall or the areas close to the edge of the tread (known as the shoulders), then replacement with a new tire is almost always the better option. In these cases, it is essential to replace both tires on the same axle so that they can wear evenly.
For more information on car tires, contact a tire service.
