Sidewall cracks: pressure vs. aging

Sidewalls often fail before the tread wears out, and the cause usually falls into one of two categories that can look similar but come from different problems.

Fatigue cracks come from riding at too low a pressure for too long. You'll typically see a few larger cracks concentrated in the upper part of the sidewall. Underinflated tires have to flex more to support the same load, and that repeated flexing eventually tears the rubber. Other telltale signs of chronic underinflation include abnormal wear on the left and right shoulders of the tread rather than the center, and visible "walk marks" on the tire and tube from the tube shifting inside an underinflated tire.

Aging cracks come from the rubber compound simply getting old, whether from UV exposure, ozone, or just time. These tend to be smaller and spread evenly across the whole sidewall rather than concentrated in one area.

In practice the two often overlap, so it's not always possible to point to a single cause. Either way, once cracking is visible, the tire's structural integrity is compromised and it should be replaced rather than pushed further.

Updated on: 08/12/2026