The groove where the wear indicator is located is 1/16 inch (1.6 mm) shallower than elsewhere on the tire. If the tread has worn so that the indicator is exposed, replace the tire.
Worn out tires have poor traction on wet roads.
Honda Civic Owners Manual. Inspection and Maintenance
For your safety, perform all listed inspections and maintenance to keep your
vehicle
in good condition. If you become aware of any abnormality (noise, smell,
insufficient
brake fluid, oil residue on the ground, etc.), have your vehicle inspected by a
dealer.
(Note, however, that service a ...