you should buy a new tire.
Built-in
treadwear indicators, or "wear bars," which look like
narrow strips of smooth rubber across the tread will appear
on the tire when the tread is worn down to one-sixteenth of
an inch. When you see these "wear bars," the tire
is worn out and should be replaced.
Visually
check your tires for signs of uneven wear. You may have irregular
tread wear if there are high and low areas or unusually smooth
areas. Consult us as soon as possible.