It’s not always obvious that it’s time to trade in your running shoes for a new pair. Even when they’re falling apart at the seams, it can be painful to part with your kicks after shelling out $100 or more for them. But remaining fiercely loyal to your favorite pair of aqua-orange Saucony sneakers can cause problems and pain down the road.

“If you keep a pair of shoes for too long, you open yourself up to injury and damage to your joints,” said Sarah Bowen Shea, co-founder of the runners’ site Another Mother Runner and co-author Tales of Another Mother Runner (March 2015, Andrews McMeel). Research shows that when a shoe is overused and the cushioning sole has collapsed, the lack of shock absorption can contribute to running injuries.To take the guesswork out of when it’s time to spring for a new pair of sneakers, follow these expert-recommended tips:

* Track your miles:
In general, you want to replace your running shoes after you’ve logged 300 to 500 miles. Along with how often your run, your weight influences where you land on that scale. “A 5’ 2” 110-pound runner is easier on her shoes and can get more like 500 miles out of them than a 5’ 11” woman who weighs 165 pounds,” explained Shea. To make it easier to keep track of your miles, download a training app like Strava and Training Peaks, which allow you to log what shoe you’re training in and track how many miles you’ve run in them. Or simply keep a journal and note your weekly mileage and what shoe you wore. Another option: Do some basic math. If you know you run 15 miles in a week, then in five months, you’ll have logged 300 miles.

* Pay attention to your body:
Consistent runners are usually attuned to their bodies and know when things feel “off,” which might signal that your running shoes aren’t giving you the support your joints and tendons need anymore. “If you tend to have knee issues or an Achilles tendon problem and your knee or tendon feels funny, you might realize, ‘Oh right, I’ve had those shoes for eight months,” said Shea.

* Look at the treads:
“If they’re noticeably worn down, it’s time to get new shoes,” said Shea. “The materials they’re using these days are very resilient so if the shoe is showing wear, you are due for new ones.”

* Check the mid-sole cushioning:
If your feet roll in, aka overpronate, try this test: put your running shoes on a flat surface. If the shoes lean in toward each other, that means the mid-sole cushioning is starting to compress, which can set you up for injury, noted Shea. In other words, it’s time for a new pair.