A tire indentation is normal, a tire bulge isn’t — Learn the difference

A tire indentation in the sidewall is a perfectly normal part of the manufacturing process

Tire indentation in the sidewall, or “undulation,” is a normal result of radial tire construction. The undulation is formed during the manufacturing process as tire plies are wrapped around a mold. The plies start at one tire bead, go up the sidewall, across the tread area, down the opposite sidewall, and finally to the opposite tire bead area. The plies are wrapped side-by-side and as the wrapping is finished, the final wrap overlaps the first ply. It’s this overlap you’re seeing that looks like an indentation. But it’s a perfectly normal visual result of tire manufacturing and is NOT a defect. It does not impact the performance of the tire.

The undulations are more noticeable on larger sidewalls

The indentation will be more noticeable on tires with larger sidewalls than on low profile tires. The tire sidwall indentation may also be more noticeable on tires with higher inflation pressures.

There’s a big difference between an undulation and a tire bulge

While a tire indentation is perfectly

A bulge is much different than an indentation. A bulge is dangerous and the tire must be replaced ASAP

normal, a tire bulge is not. The tire in this image is unsafe and must be replaced. See this post for what causes a tire bulge.

©, 2020 Rick Muscoplat