Tires often give their owners signs of problems in plenty of time to have them corrected. Learn to "read" these early warning signs and you can prevent many wear problems that shorten tire Many tires have tread wear indicator bars molded into the tread. When the tread is worn down to where you can see a solid bar of rubber across the width of the tread, it is time to replace the tire. Here is another simple test you can perform to measure tread depth on your tires. Place a penny into a tread groove with Lincoln's head upside down and facing you. If you can see the top of Lincoln's head, it is time to put a new tire.ife by thousands of miles. Consult your tire sales associate for further information.