Did you know that running shoes have an expiration date? Now before you go checking the label, I don't mean literally. Every shoe has a limited number of miles in them before they become a liability. As you've porbably guessed, higher quality shoes tend to get more miles, around 450 miles total. Cheap bargain shoes rarely make it to 300. But there are exceptions. Just because its spendy, doesn't mean its made well.
When your shoes have given up the ghost so to speak, you are more prone to get injured. Knee problems, ankle problems. etc. This stems from the wear patterns and decreased shock absorption.
So how do you know when your shoes should be laid to rest? Do you wait until the rubber is falling off? Here's the easiest ways to tell:
Do your legs feel a little more beat up then normal?
If you grab the top and bootom of your shoe, does it twist easily? (meaning the center of the sole has broken down. )
Is the tread really worn on one side, making the shoe tilt?
Is it just not comfy anymore?
Yep, you are the best barometer. If it doesn't feel good, get a new shoe. Otherwise, you might be at risk for overuse injuries. A heavier person will need to replace their shoes more often. I know, its not fair. Tell me about it. Light little waifs can get away with every 450 miles or so.
Keep track of your miles, and really start to pay attention around mile 300.
Another good tip is to find a shoe you like, then buy a spare set. Rotate. Makes them last longer.
And never wear new shoes to a race. Just saying.