Wear Indicator
WARNING: This page is about a different car, the 2004 Suzuki XL-7, 2004 Suzuki Grand Vitara, 2003 Suzuki XL-7, and 2003 Suzuki Grand Vitara. However, it is still accessible from the selected car via links, so may be relevant.
The original equipment tires have built-in tread wear indicators to show when tires need replacement. These indicators will appear as 12 mm (0.47 inch) wide bands when the tire tread depth becomes 1.6 mm (0.063 inch). When the indicators appear in 3 or more grooves at 6 locations, tire replacement is recommended.