What Causes a Black Ring Around the Edge of a Tire?
2 Answers
Tire wear with a black ring on one side indicates that the tire surface has a certain tilt angle, commonly referred to as tire cupping. A wheel alignment is required, as this is a common issue with new cars. If not adjusted, the black-ringed area will wear flat in about a year. The causes of tire cupping are as follows: Inaccurate wheel alignment: This results in the four tires not being aligned on the standard required horizontal and vertical lines, causing the two wheels on the same side to experience cupping when driving. Whether it's the front or rear wheels, the main issue is that they don't run straight, leading the vehicle to self-correct, which increases friction on a specific part of a tire and accelerates wear. Incorrect toe adjustment: Toe refers to a slight inward tilt of the front wheels, similar to pigeon-toed feet. This is the optimal angle for stable high-speed driving. Every vehicle has its own toe angle, and if this angle is not properly adjusted, it can also cause tire cupping. Steering gear failure: This can also lead to tire cupping and deviation. Uneven or deformed frame: For example, some accident vehicles experience tire cupping due to frame or body deformation. Significant differences in tire pressure among tires: Mixing tires of different specifications can also cause cupping. Solutions for tire cupping: Frame deformation requires correction; most other cases of tire cupping can be resolved by adjusting the toe and performing a wheel alignment.
With years of experience in auto repair, I often encounter car owners asking about the black ring around the tire edge. Simply put, it's mainly caused by insufficient tire pressure. When the tire pressure is low, the tire deforms during rolling, causing the outer sidewall to rub directly against the wheel rim edge, leaving black marks over time, like accumulated rubber debris. Sometimes, accidentally hitting the curb while parking can scratch the tire with the rim, also causing this black ring. Occasionally, it can be due to the accumulation of brake pad dust. This issue may seem minor, but it's actually quite dangerous: if left unaddressed, the inner edge of the tire will wear thin, leading to air leaks or even blowouts. I recommend checking the tire pressure immediately. If it's below the manufacturer's standard (like the value on the sticker on the door pillar), inflate it right away. Also, park further away from the curb and have a mechanic inspect the suspension system during regular maintenance to avoid uneven wear. Developing good inspection habits, such as using a simple tire pressure gauge monthly, can save a lot of trouble.
