When to replace running shoes: the 600 km rule

Where the 600 km rule comes from.

The number is not from a single laboratory. It is the median output of thirty years of footwear engineering studies and manufacturer guidance. Most major brands publish lifespan ranges between five hundred and eight hundred kilometres. Asics tests at five hundred to seven hundred. Brooks publishes four hundred to six hundred. Salomon trail shoes hold up to eight hundred because they are built denser.

Six hundred is the safe centre point. If you weigh more, drop to five hundred. If you run light and on softer surfaces, you can push past seven hundred. The rule is a guide, not a calendar.

What “dead foam” actually means.

Most running shoes use one of two foam families: EVA (ethylene-vinyl acetate) or PEBA (polyether block amide). EVA is older, cheaper, and degrades faster. PEBA is newer, found in modern super-shoes, and lasts longer per kilometre but starts more expensive.

Both foams degrade by the same mechanism: the air pockets inside the foam permanently collapse under repeated load. A fresh shoe rebounds back to ninety-five percent of its shape within milliseconds of impact. A dead shoe rebounds to seventy percent and slowly. The energy you used to push off, you now spend compressing dead foam.

Five signs your shoes are gone.

1. Uneven outsole wear. The rubber on the outsole tells you which part of the shoe is doing the most work. Patches worn smooth past the rubber layer mean the shoe is past its halfway point.
2. Visible midsole creasing. Press the midsole with your thumb. If it stays compressed for a second instead of bouncing back, the foam is fatigued.
3. Sole flat patches. Place the shoe on a flat table. If it rocks or sits unevenly, the midsole has collapsed asymmetrically.
4. Bounce loss. The shoe feels heavy and dead in the first kilometre. New shoes feel quick.
5. Post-run knee or shin soreness. The most important signal. Your body knows before the visual cues catch up.

Mileage matters more than time.

A two-year-old pair with two hundred kilometres on it is fine. A six-month-old pair with eight hundred kilometres on it is not. Time degrades foam slowly through oxidation; load degrades foam quickly through compression. Compression always wins.

This is why manufacturers publish kilometre ranges, not date ranges. Your training volume sets your replacement cycle, not your purchase date.

How to actually track mileage.

Three ways. From most fragile to most reliable:

1. Memory. You will lose track within ten runs. Do not use this method.
2. Paper log. A small notebook by the door, you write the kilometres after each run, you tally weekly. Works if you are disciplined. Most are not.
3. Per-shoe logging in an app. You assign a pair to each run, the app tallies automatically and alerts you when you cross a threshold. Strava supports this. AltCrew Shoe Locker does too.

AltCrew Shoe Locker pings you at five hundred kilometres and again at six hundred. You see retirement coming and budget for a new pair before the foam quits. Read more about Shoe Locker.

Indian context: weather, terrain, surface.

Three factors shorten shoe lifespan in India:

• Monsoon water absorption.Repeated soaking and drying breaks down EVA foam structure. If you run in heavy monsoon, deduct ten percent from the shoe’s expected lifespan.
• Asphalt vs trail. Indian asphalt is harsher than European or Japanese asphalt due to aggregate composition. Road shoes wear faster here than in temperate-climate testing labs.
• Dust and grit. Fine particulate from Indian roads embeds in mesh uppers and outsole grooves, accelerating mechanical wear without affecting the midsole. Looks tired before it is tired.

What rotating two pairs does.

A pair of running shoes recovers between thirty and forty eight percent of its compressed structure if you give it twenty-four to forty-eight hours of rest between runs. This is why rotating two pairs extends the lifespan of each pair by roughly thirty percent.

Practical translation: if you run four to five times per week, two pairs is the right number. Three pairs is optimal for high-mileage runners. One pair is the worst case, the foam never gets a recovery cycle.

When NOT to replace.

The shoe looks scuffed but feels fine and the midsole press test passes. The outsole has surface scrapes but no rubber-through patches. You ran in mud and the shoe is cosmetically rough.

None of these are structural. Cosmetic ageing is normal. Replace when the foam dies, not when the upper looks tired.

The bottom line.

Track every kilometre on every pair. Plan for retirement at six hundred. Rotate two pairs to push each toward seven hundred. Listen to your knees before your stopwatch.

AltCrew tracks all of that for you, free for members. Join the waitlist and we email you when the app drops on May 31, 2026.