4.2.2. Condition of tires
To ensure safety, tires should be replaced with a height of the drawing of a protector 2–3 mm. Height of the drawing of a protector, minimum admissible on the law (1,6 mm) is reached when the protector wears out to the index of wear. Several indexes of wear are put at identical distance from each other in deepenings of a running surface. Their situation is noted also by indexes on a tire sidewall.
All cars manufactured by Opel/GM are equipped with indexes of wear of tires. Concerning use of chains of antisliding see hl. 1 "Operation manual".
In case of tires with the drawing of a protector connected with the direction of rotation when replacing tires pay attention to designation of the direction of rotation. Replace tires only coaxially.