Tread wear bars are visible: These bars of hard rubber are designed to be visible when your tire’s tread has become worn. If these tread wear bars show up, it’s time to buy a new set of tires. If you’re not sure where they are, you’ll see a mark on the sidewall that indicates where to look.
Your tire depth gauge indicates worn treads: Under European law, your treads must be at least 1.6mm deep around the tire’s circumference. For winter tires, Goodyear recommends a minimum tread depth of 4mm. It’s a good idea to purchase an inexpensive tread depth gauge to check that your tires meet the legal minimum. Make sure you take measurements on both the inside and outside of your treads.
Small objects are lodged in the tread: It’s not uncommon for small objects to get stuck in your treads. If they’re stuck in the groove, take them out carefully, being sure not to damage the tire. If you spot something that looks as if it’s gone through the rubber, like a nail, leave it in until you can get to a garage. Otherwise you’re likely to end up with a flat tire.
Tires are worn on the outside: If you notice that your tires are worn on both of their edges, you might need to inflate them or check for leaks. Tires lose air naturally, but driving on underinflated tires uses more fuel and puts you at greater risk of accidents. Make sure you check pressure regularly. If you notice that only the front tires have worn edges, you might be taking curves and corners too quickly.