A car tire typically has a sidewall that is between 1/4" to 5/8" (5 to 15 mm) thick. However, this can vary depending on the specific tires that are being used. Some tires may have thicker or thinner sidewalls, depending on their design and intended purpose. For example, race car tires often have very thin sidewalls to help improve grip and handling. Likewise, some off-road tires may have thicker sidewalls to help protect against punctures from rocks or other debris.