What Causes Unevenness When Touching the Sidewall of a Tire?

[StevenRose]

When touching the sidewall of a tire, the unevenness felt can be either indentations or bulges. These two types of irregularities on the tire sidewall stem from different causes. Indentations: These are caused by the joints of the tire carcass cords. Since the joint areas consist of two layers of cords while other areas have only one layer, the joint areas are actually stronger than the rest. During the initial use of the tire, slight expansion occurs under air pressure. The joint areas expand less, making them appear slightly indented. Bulges: These are caused by the joints of the inner liner or sidewall rubber. Due to the increased thickness at the joint areas, they appear slightly raised when the tire is inflated. From the causes mentioned above, whether it's indentations or bulges, these irregularities do not affect the tire's performance or safety. Moreover, due to the tire manufacturing process, such unevenness is fundamentally unavoidable. Every tire has it, though the degree of visibility may vary slightly. You can continue using the tire with confidence, and there is no need for replacement.