Tires do not last forever. Some tires wear out faster than others, but how can you tell when it is time to make a tire change? Using a tread depth guage is certainly one way to determine if your tires are ready for the recycle bin. You can even use a coin as a guide for how much tread remains on your tires.
All of that aside, the best way to determine if your tires are toast would be if they are still providing a safe level of traction in the worst conditions you face. Dry traction is seldom the problem, but being prepared for wet conditions or even winter weather means your tires need a few 32nds of tread depth to keep you safely on the road.
Most tires worth their weight in salt lose the bulk of their hydroplaning resistance once the tread depth reaches 4/32. For snow traction the 6/32 tread depth is when snow and ice traction starts to slip away.
Knowing when to replace your tires based on your driving conditions and the part of the country where you drive most frequently will help your vehicle get a grip. A quick call to one of our sales specialists just before the rainy or snowy weather comes to your area will give you a good idea if it is time to replace your tires.