In our November issue of Consumer Reports, we recommended using a quarter to determine when it’s good time to start shopping for new tires. (See “Tire Maintenance.”)

Since the story was published, some have mistakenly interpreted our recommendation as being that when tires have worn to 1/8” of tread depth that it’s time to replace tires. The measurement is about the distance between George Washington’s head on a quarter to the edge of the coin if you are using the quarter as a tread depth gauge. Let’s be clear: That’s a good time to start thinking about tire replacement, and begin researching and shopping.

At this depth, most tires still have some all-weather grip left, which gives you time to shop around for the best price and tire model that suits your car’s needs. Tires worn to the tread wear indicator bars (set at 1/16” and indicated by the use of a penny) in any or all of the grooves should be replaced immediately, leaving little time to shop for new tires.

In reality, consumers don’t often think about replacing tires based on tread depth alone.  Some wait until the steel belt edges show—that alarms us. We suggest changing tires earlier if your tires are losing grip in the wet or during winter driving conditions.   

If you’re in the market for car or truck tires, refer to our Ratings and all-new tire finder that can help identify the best tires for your ride. (Available to online subscribers.) 

—Gene Petersen