There can be three main reasons why the sidewall separation/bubble can appear.

The first reason can be caused by structural failure of the tire which is attributed from poor bonding during the manufacturing process and is likely to appear within the first six months of the tire’s usage.

The second reason for the bubble or bulge in the sidewall is the tire’s inner liner is damaged from impact with curbs, potholes, debris or railroads which are the most common reasons.

The third reason is often caused by driving with a flat tire and part of the sidewall will slip under the edge of the wheel. This creates significant wear and tear on the tire.

Either way, when the bubble/bulge does appear, they are usually very small and overtime compromises the strength of the tires. One way to think about this is that a typical tire can roll about 900 times every mile or so and the air pressure builds up inside and the tire bubble will continue to expand and further reducing the strength of the tire’s wall/bond.

With a combination of miles, noise and vibration the tire is will eventually blow out . It may take weeks or months after an impact before the bubble is visible. At this point, the driver may not even know when or what impact might have caused or worsen the condition.

Bubbles or bulges in the sidewall are normally the result of the tire’s inner liner being damaged from an impact that creates a small hole or tear and compromises the strength of the sidewall plies. In most cases, the impact that caused the damage was not severe enough to be noticed by the driver, yet it was strong enough to damage the tire. Impacts with curbs, potholes, railroad crossings or debris in the road are the most common culprits. On occasion, a sidewall bubble can be caused not by an impact, but a structural failure of the tire.