Between 300 and 500 miles. Why the range? Because how quickly a shoe wears depends on you. If you land hard on your heels with each stride, for example, you're going to wear through shoes more quickly than more efficient runners. Go by feel. If after a normal run your legs feel as if the shoes aren't providing you adequate protection, they probably aren't. Give your legs a week to make sure it's really the shoes and you're not just tired. If the shoes still feel dead, replace them. We can tell you that the vast majority of runners replace their shoes too late. When you can see white midsole material poking through the outsole or when the sole under the heel looks crushed, the shoes are long past their prime.

• Shoes Information