Do you know when to replace your summer tires with winter tires? Changing tires is required by law. Winter equipment is mandatory here from November 15th until March 15th. The law stipulates that the minimum tread depth for a summer tire is 1.6 millimeters, while for a winter tire it is 3 millimeters. Therefore, all of you who do not have summer-winter tires and they are too worn, you must report to a vulcanizer by the legally prescribed deadline and have your car retreaded.