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I’m an avid runner but mostly stick to shorter distances. This year I’m shooting for my first 50K. How will I know when it’s time to replace my trail-running shoes, since I’ll be tackling lengthy, high-volume training? FYI, I’m also on a budget. —Ultra Newbie

Dear Ultra Newbie: Trail-running shoes can be expensive—upward of $200 a pop. So I tend to run mine down to their last lugs before I commit to new kicks. 

Last year I trained for my first ultramarathon, and over nine months, I bagged trails coast to coast, from Washington’s Columbia River Gorge to North Carolina’s Appalachia. The terrain varied from rough limestone-shale fields to swampy singletrack to slick red sandstone. About 700 miles in, on the same pair of , I noticed worn spots developing on the tread. I also felt soreness in my ankle joints not akin to the usual fatigue I’d feel after 20-milers. So I bought a new pair and broke them in before race day.

As I’ve learned since, putting down major mileage on the same pair of shoes may increase the risk of injury. Essentially, there’s a sweet spot between squeezing the bang for your buck and pushing your trainers too far—and it’s different for every athlete. Several variables play into how often runners should update their trail shoes, including stride habits, terrain type, training goals, body composition, and even weather conditions. While there’s no straight answer, I chatted with a few running experts to get more clarity for you, Ultra Newbie.

Maximum Mileage for Your Trail Shoes

According to Eli White, a trail-running coach and manager at in Salt Lake City who has set course records at five U.S. ultras, any runner who gets 700 miles out of one pair of shoes is an outlier. “Just like road shoes, most trail shoes will last around 300 to 500 miles,” he says. “There are always exceptions to this rule of thumb, based on the person, the shoe, and the terrain, but 700 miles is well above average.”

The life of your shoes also depends on how well you take care of them. I wear mine exclusively in the backcountry and pull the insoles to dry them out after each run—likely the main reason I maxed out that pair at 700 miles.

Signs That Your Shoes Are Breaking Down

General wear and tear in trail-running shoes corresponds to the three main parts: the upper, the midsole, and the outsole. The thing is: it’s easy to see if your shoes are falling apart on the outside, but it’s easy to forget what fresh cushioning feels like on the inside as you gradually wear them down.

The upper and outsole show the most obvious signs of wear, like seam- and heat-seal separation, thin or bald tread, holes and small tears, stretched-out material, and other visible deformities. Notice any of these? Replace your shoes.

But it’s the breakdown of the inner midsole that’s often overlooked, hard to identify, and can be most dangerous in propagating injury potential. Philip Snyder, general manager of in Wheat Ridge, Colorado, and a running-industry specialist for more than a decade, says midsole breakdown was the likely culprit for my ankle soreness. 

Tiny air pockets throughout the midsole’s EVA foam compress as your foot lands with each stride. In a shoe with life left, the cushion rebounds to its original shape. “A shoe that has started to flatten out at best makes the running experience less enjoyable and at worst leads to overuse injuries,” says Snyder, who runs on trails 45 miles per week himself. In other words, it’s safe to say you shouldn’t push your shoes as far as I did. Lesson learned.

The type of terrain you frequent can also determine how quickly and where a shoe breaks down. “Running on rough, rocky surfaces will wear down the tread on the outsole faster. And harder, packed surfaces will cause the midsole cushion to compress quicker,” says White. If there are rips in the material, your foot may slide around, causing blisters or poor balance. If the inner cushion gets compressed, you’re less protected underfoot. 

Tips to Increase the Life of Your Trail Shoes

Clean the Upper Regularly

“Periodically, rinse off sweat and debris from the upper, which can expedite the breakdown of the materials,” says Snyder. He recommends removing the insoles, soaking the shoes with a mild dishwashing detergent, and using a scrub brush to knock loose larger particles. Then air-dry them with newspaper stuffed inside. “Don’t put running shoes in the dryer,” he warns. “The heat will break down the adhesives and potentially damage the midsole.”

Use Your Trail Shoes Exclusively for Trail Runs

Slip on a pair of recovery shoes or sandals before and after your runs, as well as to and from the trailheads. “Not only will this extend the life of your shoe, it will also ensure that your shoe is performing to its greatest potential,” Synder says. “Walking and running put different forces on your shoe, and the materials in your shoe will adapt to your running gait. If you also use your shoe casually, the materials won’t fine-tune to your gait.”

Similarly, he says, taking off your shoes after runs allows the midsole foam a chance to refresh and reset before your next outing. 

Stock Up on More than One Pair

Make the most of the inventory at a specialty running store by trying on a variety of shoes there. “If your budget allows, consider having multiple shoes in your trail-shoe quiver, as the proper amount of trail running shoes is n plus one,” says Snyder.

Erik Dube, a 15-year veteran of the running-shoe industry at in San Luis Obispo, California, says it’s important to have at least two pairs of shoes in your arsenal and to rotate using them. “While there are a lot of good all-around trail shoes in the market that will cover your needs, I enjoy getting shoes that fit a certain aspect of my weekly trail life,” says Dube, who has completed 80-plus ultras over his 24-year trail-running career. He recommends “something that has more cushion for the weekend long run, something with a little more grip for the rocks, roots, or mud, or something a little more low profile and nimble for the up-tempo runs.” 

After learning the hard way last year, I now have three pairs of running shoes: two for trails, one for roads.

Keep Track of Your Mileage

It’s especially important to log your shoes’ mileage and stick to that 300-to-500-mile range when it comes to gauging midsole vitality. Dube says that while most well-made shoes can last for 300 miles, this can vary greatly depending on the type of shoe you use and your running stride. “I know some people who will go through a pair of shoes in 200 miles, while others can get over 500 miles on the same pair,” he says. The bottom line? Chart your mileage so you don’t push yourself to injury like I almost did.