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On Running Shoe Wear and Outsole Durability

Shoe wear patterns fascinate me. At the end of each run, I have the habit of taking my shoes off and scrutinizing my sole wear patterns to see if anything interesting pops up. I may look a bit odd walking down my street barefoot while staring at the soles of my shoes, but at this point I think my neighbors know me well enough to not question my sanity.

Saucony Fastwitch SoleI used to absolutely destroy the heels of my running shoes. In fact, I once burst the air pocket in the sole of a pair of Nike’s by grinding down the heel so badly. Those days seem to be long gone. Since going minimal and working on my stride, outsole wear on my shoes has decreased dramatically. I do still get some wear on the heels, but after 70+ miles of running in the Saucony Grid Type A5 flat, for example, I can still clearly read the “GET SOME!” mantra found under the lateral heel (see stock photo above and to the left) – and it’s still completely green. In the old days I would have done some serious damage to that region by now.

This brings me to an issue that I hear about a lot – excessive shoe wear and “poor durability.” The reality is that when people have excessive wear on a shoe, it is more likely that the issue is with their running form rather than the shoe construction (unless the shoe construction is causing them to run in an inefficient way, which is entirely possible).

Shoe outsole wear is the result of friction between the sole and the ground, not impact (the latter has a bigger effect on midsole compression). People often tend to think that wear patterns are an indicator of foot strike type, and they can be, but not all wear occurs at initial contact. For example, wear under the big toe typically occurs at toe-off, probably due to twisting of the foot relative to the ground.

I have videos of people whose feet glide into ground contact like an airplane approaching a runway. They skid forward on their heel before the forefoot comes down, just as the back wheels of an airplane make contact prior to the front. This is what destroys heels, and is why I still wear down the heels on shoes when I walk in them – I tend to be a scuffer when I walk. I also suspect that some forefoot strikers reach out and skid with the forefoot, causing excessive wear on the lateral forefoot (aka Kinvara-Killer Syndrome).

When you run, excessive friction can be a sign of inefficiency since it isn’t helping you move forward, particularly if you are plowing forward into the ground. Rather than landing like an airplane, picture your foot contacting like a helicopter touching down. When you watch experienced barefoot runners in slow motion, it’s as if their foot pauses for a moment in the air prior to touching down gently (see video below). Why? Because if they plowed forward they’d tear the skin off of their feet. I’m convinced that a big part of why barefoot running is different is not just that it requires you to absorb impact differently, but that it also requires you to minimize friction to protect the plantar skin. Putting on any kind of shoe alleviates the need for the latter, which is why I think even the most minimal shoe is not a perfect mimic of barefoot running.

So, if you have a tendency to destroy shoe soles rapidly, whether on the heel or forefoot, I’d encourage you to take a video of your gait and see if you’re a scuffer. It might explain your shoe-durability issues. I know of people who can get a thousand miles on a pair of shoes, when the same pair on another person might last a few hundred. In a case like this it’s probably due to a combination of surfaces run on and/or their form.

So how do you correct scuffing? Tough question, but I suspect it’s in many/most cases a symptom of overstriding. When you reach out too far in front of the body with the foot the chances of scuffing are greater than if you touch down gently like a barefoot runner. Think about propelling a scooter – you want the foot to contact the ground quickly and pull backward, not plow forward first then pull. The latter would destroy your shoes really fast! This explanation would apply to both heel and forefoot strikers, the location of max wear is what would differ. To correct this, avoiding reaching out would be the key. Mental cues like “vertical shin on contact” or “put the foot down behind you” can be helpful, as can a video of yourself that may give you an idea of what you actually are doing when you run.

I’m tempted to do a study on this – scan shoe wear patterns and correlate with form videos. Add it to the queue!

Curious, for those who have worked on form change and/or moved to minimal shoes, have you found that your wear patterns have changed? Have you increased the mileage you get out of your shoes? Leave a comment!

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Recent Posts By Category: Running Shoe Reviews | Running Gear Reviews | Running Science
About Peter Larson

This post was authored by Peter Larson. Pete is a biology teacher, track/soccer coach, and dad (x3) with a passion for running, soccer, and science. If you'd like to learn a little bit more about who I am and what I do, click here, or visit petermlarson.com.

Comments

  1. Greg Barnett says:

    I don’t think that’s the right video….

  2. “I think my neighbors know me well enough to not question my sanity.”
    Yeah, they’ve figured out you’re nuts for shoes… Keep up the good work!

  3. I started minimalist running in June of this year. I went with Leming because I wanted a lifestyle shoe that I could also run in as an introduction to minimalism. Not sure what my wear patterns were before because I was not a frequent runner, but I have two solid wear marks in the forefoot; the nubs are gone. The heel look brand new.

  4. I was actually thinking about posting a question on the forum related to my issue with minimal shoe wear. I have been making the transition for the past couple of years and now run exclusively in zero drop shoes. Though I have gradually adopted a forefoot strike and a shorter stride, I find that I am landing on the outside of my “forefeet.” A friend made a comment on it during a half marathon, and when I looked at my shoes afterwards (Altra Instincts at the time), the outside, front edges were chewed up. I guessed that the cushioning in the Altras were allowing my foot to land like that, so I switched to a pair non-cushioned shoes (Inov-8 BareX 180s) and literally ran a hole through the sole where the outside portion of the ball of my feet came into contact with the shoe (i.e. about an inch “down” from my smallest toe) after 150 miles. Not sure if anyone has any thoughts on that type of wear pattern, but I would be happy to donate my shoes to science.

    • Pete Larson says:

      That’s the normal contact point for a forefoot striker. My guess is your foot is moving forward into the ground and creating friction on contact – have you filmed yourself?

      —-
      Pete Larson’s Web Links:
      My book: Tread Lightly – http://ow.ly/bdUO0
      Blog: https://runblogger.com
      Twitter: http://twitter.com/oblinkin
      Facebook: https://www.facebook.com/Runbl

      • I’ve been meaning to get my wife to film me running for a while. That will move up the to do list. It was actually another forefoot striker who told me that I was running on the outside of my feet when I was running in the Instincts (i.e., my feet were angled like the classic supination diagrams), but you may be right about the contact point.

        By the way, I’m reading Tread Lightly now. You might address this completely there, but today’s blog post on wear got me curious.

      • I wouldn’t necessarily draw this conclusion. I’m a natural fore/midfoot striker (just recently helped cleaning up my mom’s house and found some very old running shoes … despite high heels, same wear lateral) and my shoes show a similar wear pattern.
        However, this wear stems from rotation around the lateral edge of the shoe after inital contact. of the foot. Especially with Merrell’s Bare Access you can see this from the scuffing pattern clearly. Like if someone filed off this section perpendicular to the shoe axis.
        This is not a matter of right or wrong running form but some manufacturers forgetting to add a simple rubber pad there. Shoes with such a pad last many more miles for me than bare acess, k-swiss blade foot or kinvara style shoes.

        • Pete Larson says:

          Would be interesting to compare wear patterns to form on a force or pressure plate and et an idea of what is going on. Wonder if excessive supination might also be a factor for some people due to spreading of the sole under pressure. Interesting stuff to think about, not sure how much this has been studied. Time to hit Google scholar!

  5. Any thoughts on asymmetrical wear patterns? Is it possible to over stride with one foot? Plus, how prevalent is midfoot/forefoot overstriding?
    I tear up the far edge of the lateral midfoot in my right foot significantly faster than the left.

  6. I have around a thousand miles on my homemade sandals with no noticeable wear. Ditch the shoes–solve the problem of shoe wear!

  7. Steven Sashen says:

    Pete,

    Now that I’m in the business of making shoes that are nothing BUT an outsole, I have to 1/2 disagree with you.

    That is, I do agree that form is a major factor in sole wear.

    But, we spent a LOT of money to develop an outsole that lasts a long time (we have a 5,000 mile warranty on Xero Shoes — formerly Invisible Shoes — and, so far, none of our 22,000+ customers has worn out a pair).

    When we asked for the material specifications we wanted, our outsole company fought with us. “That’s not what major shoe manufacturers do!” they assured us.

    And when you look at the abrasion resistance numbers that we have, compared to “normal”, we are through the roof.

    Now, granted, there’s more to outsole wear than abrasion resistance. Seemingly paradoxically, a softer sole might wear longer, depending in part on the tread pattern, because it “flexes” more. And, similarly, a harder sole might wear faster because it doesn’t “give” at all.

    All that said, from what I can see now that I’m on the inside is that most shoe companies deliberately use a rubber formulation that wears MUCH faster than necessary, and the cost to improve outsole performance is nominal.

    If you extrapolate from that the idea that most shoe companies build planned obsolescence into their products, let’s just say that from what I’ve seen, I won’t disagree.

  8. My wear has changed dramatically – I used to run in some trad Asics and would wear down the outsie of the heel very quickly. Then I ran for a year & half in just VFFs, and now use NikeFree – in the latter I just logged 800km – a little wear on the heel, but mostly on the forefoot, however I can still clearly see all the sole pattern. I should get many more kms out of them. (There is midsole compression, but I dont mind it. )

  9. I used to run in the Brooks Trance, a typical pronation control shoe. After a couple hundred miles, I would see heavy wear on the back/outside of the heel, and maybe half as much wear on the front/inside sole beside the big toe. My shoes ‘lasted’ 400 miles, though that was more of a midsole compression issue than a sole wear issue.

    I adjusted my form and switched to minimal shoes about 4 years ago and I now see little or no wear on the heel, except maybe a bit on the ones I do walking in. I do see a fair amount of wear in an oval at the center of my forefoot, and a little bit under the big toe. I tend towards the forefoot end of midfoot striking, and think I have a little bit of a twist on lift-off (possibly pronation related – more wear on my right side which pronates more), which may increase wear. I wore through a pair of Vibram KSO’s after ~1000+ miles (small hole right under base of 2nd metatarsal), and recently tossed a pair of Merrell Trail Gloves after 1200 miles. The Trail Gloves were still quite runnable as a road shoe (the trail nubs under forefoot were worn flat), but the stink had reached a critical level.

  10. TYPE A4 – 2500km and still using, very durable shoe, very responsive, just love it. Only setback is the heel-counter – doesn’t disturb, but the INOV-8 no-heel-counter solution is preferable for me.

    Hyperspeed 4 – 2000km and still using, but the red foam is sort of gone till the mid-eva. It is a very soft and mushy shoe, every small road items penetrate through the sole.
    I am not really a shuffler, but when the surface is wet, I tend to have slippage forward. So for me the best time for posture practice is on wet roads, or at winter time on snowy and icy roads. I think the “running in place with high knees” exercise can help a lot to understand what should happen during real running. They call it sometimes 100 knee-ups or sg. I am doing a lot for warming up, to imprint it to my mind. Land softly under my body on for/midfoot, when heel touches the ground relax the calves, then use the hip-flexors to lo drive up the knee, quads, glutes and hammies are relaxed.

  11. Some years ago I was a heavy heel striker. My wear patern was the outside of the heel. After a long transition I’m a midfoot striker. Now my wear patern is te outside of the midfoot. I’m still using shoes with 4-8mm offset.

  12. wanderlust262 says:

    I switched to Kinvaras about 2 years ago and have gone through at least 5 pair by now. Every time I get new ones, I look back at my wear patterns over time. Not only do I have significantly less wear on the heal (I also once popped some Nike Airs due to a hard heel strike), but my small toe has also stopped breaking through the upper.

    My old gait was so off, that the fronts of my shoes were off kilter due to how I was lifting my foot.

    After two years of running the minimalist way, it is all significantly better.

  13. Thanks! I enjoyed learning more about running! Always do!

  14. Robert Osfield says:

    When I started back into running four years ago the wear I got on my shoes was predominately at the on the outside/back of heel, but what wore my shoes out most was the EVA midsoles collapsing after about 200-300 miles in the Nike Pegasus that I wore back at the start.

    Over the last three years I’ve moved to from a mild heel strike to a mid foot stride. The wear pattern has changed, now it tends to be evenly across the outside of the sole from midfoot to the heel. Even though I don’t land of my heel almost all of the time there is still some where there, and I think it’s down to times when I descend down steep technical stony trails. In these situations my landing is mixed up much more, some footfalls the heel might come down first, the next on the midfoot, the next on the forefoot, but common to all will probably be the fact that I’m breaking throughout stance. This breaking force means that often my foot will still be moving forward on landing – a great recipe for ripping the sole of shoe to shreds on the sharp stony trails.

    I’ve worked on trying to get my landing such my foot comes stops moving forward and lands close to vertical while my body glides over the top. Running without socks sure helps in getting the feedback of whether you are getting the landing right and I believe that I do a pretty good job when running on roads and gentle trails. However, for all my efforts if the trail is steep enough I just can’t not avoid skiding a little and I don’t think one can probably expect to have a “perfect” landing. Here shoe durability is king, form will sure help but if you have aggressive enough trails you need a shoe that can handle it.

    In terms of durability I’ve found that my Vivobarefoot Neo Trails lugs are not up to some the steep hard trails that I run on regularly, in fact I think I may have tore off a couple of the lugs on one single landing quite early in my use of the shoes, I did a running jump a couple foot down on to rocks. On the same trails my Inov-8 Roclite 295’s and 314’s shoes have all held up without noticeable damage. The main problem with the Roclite in terms of wear since moving to a midfoot stride has been the EVA mid-sole breakdown at around 600 to 800miles.

    I now have 85 miles on my Trailroc 245’s and the sole doesn’t appear to have much wear anywhere. My Neo Trails now have 368 miles on them and my left shoe is very worn on the outside of the sole where the original lugs got shear off, enough localised wear for me to notice it when standing. When running I don’t seem to notice this problem in the lug wear too much though. The mid sole on the Neol Trails is just a good today as the day when I got them so none of the problems I had with wear of the midsole of the Roclite’s and Nike’s, yep the solution to mid sole breakdown is to get rid of it completely :-)

    • Pete Larson says:

      Your wear patter sounds a lot like mine – I get it along the length of the lateral margin, then across the forefoot and up under the big toe. Ran on an instrumented treadmill last night and I get a small, intermittent impact peak on flat ground maybe in a third of my foot strikes which suggests that I fluctuate a bit to either side of the midfoot with each landing.

      Also agree on socks, much better feedback without them!

  15. Good morning, I was working in my blog this am, (has nothing to do with running), and I happened to find your blog. While I was in the Marine Corp, we would run three miles on a daily basis. I was running the three miles with an average time of 19 minutes without issues. Of course, I was younger then, now in my early to mid 30’s I am getting back into running on a daily basis. However, I seem to have all kinds of troubles with shin splints these days. Despite the pain, I will continue to struggle through the run. Has anyone had issues with shin splints anytime during a run, or after? I have a 5K to compete in this weekend and I’m looking for any suggestions to minimize or get rid of shin splints. Any suggestions would be great. I think I’m just getting old. Thanks everyone.

    • Pete Larson says:

      What type of shin splints do you have? Pain on the front of the shin, or on the inner side above the ankle?

      —-
      Pete Larson’s Web Links:
      My book: Tread Lightly – http://ow.ly/bdUO0
      Blog: https://runblogger.com
      Twitter: http://twitter.com/oblinkin
      Facebook: https://www.facebook.com/Runbl

    • Hi B Davis,

      I had a rather traumatic return to running at 30 as well, having not run regularly since high school. I started for about a month on an elliptical to strengthen and lengthen muscles and tendons in preparation for running, then hit the streets in my brand new Asics 2160’s (12mm drop, highly supportive) for a four mile jaunt. Two runs later I was sidelined for two months with lateral knee pain.

      I biked for those two months to stay in shape and decided my form and TMTS was to blame for my running injury. I then took a six week Chi running class to learn about proper form and decided I needed more minimal shoes to alleviate stress on my knees and land with a midfoot strike. Enter Altra Instinct (0mm drop, no support) and another bout of TMTS, this time resulting in achilles tendonitis.

      More biking and thinking, and it was on to a transitional shoe, the Inov8 Road-X 233 (6mm drop, no support). Things went well here. My soleus was sore, I got “the stick”, stretched and massaged, wore calf compression sleeves, and was able to keep running, if a bit painfully. Completed my first 10k 6 months after returning to running in 50 minutes.

      I then took a hiatus over the cold winter and returned to the road this spring. My soleus was still sore but I thought I could deal with it as before. This time the soreness in the soleus moved medially, as Pete describes below, on the inner side above the ankle. I didn’t pay it enough heed and developed shin splints in both legs. Tried to run through it like an idiot and ended up walking home 2 miles before another three week break.

      The past two weeks I finally gave in and tried a couple of “support” shoes, the Brooks PureCadence first (6mm drop, mild support), and the Asics DS Racer 9 second (10mm drop, medium support). The PureCadence made a big difference in my shin splints. I wasn’t over pronating as much, which triggered the shin pain, but my calves were still sore and being careful, I was stopping about every mile to do heel drops and stretch. Once I ran in the Asics, I realized just how stubborn I’d been avoiding heel rise and support. Gone was any calf pain and shin splints. I finally felt like I could relax my lower legs while running and rely on my hips for the heavy lifting.

      I’d learned to run “properly” but had given up about 1.5 years of time when I could have been running much more often without breaks had I just listened to my body and provided it a platform that stabilized my ankles. I still run with a short stride and land with a flat foot under a bent knee, even with a 10mm heel, so I expect no knee problems.

      Pete’s question about “where is the pain” is important. What are you currently wearing on your feet? If it’s in the front, you are probably over extending your stride and slapping your foot down from heel to toe. The correction for this is pretty simple, take smaller steps, land more forward on your foot, and slow down. If instead you are experiencing pain on the inner side of your shin, and have a tight lower calf, explore some light weight supportive shoes such as the Asics DS Racer 9, Adidas Adizero Tempo 5, Saucony Guide 5, or New Balance 870 V2. I’d say try them all on and just buy the one that fits your feet the best.

      Best of luck to you and remember, don’t run through the pain, STOP and fix it before you sideline yourself.

  16. Dr. Nathan Hinkeldey, D.C. says:

    This is a great blog. I enjoy following the content. I have had many patients with similar issue that have benefited from many of the recommendations on this blog. We are currently doing a series on hamstring strains and then working my way to the knee and foot and would love to include you in a feature. Any interest??
    http://teamchirodm.com/hamstri

  17. Hi again Pete,
    My wear moved from the lateral heel to forefoot when I switched to minimal shoes then dissappeared when my podiatrist brother-in-law (awkward I know ) suggested it can also happen because of calf inflexibilty. This is due to the foot laterally twisting ever so slightly to avoid over stretching just before lifting off the ground (think of a grinding motion). I had never thought of this as I thought I was quite flexible but worked on my calf and the wear stopped occuring. Apparently we are only talking a fraction of an inch in shortness and your body takes over to protect itself by doing this in a subconcious manner.
    Just another take but it worked for me, who knew podiatrists knew so much!
    Steve

    • Wow – interesting perspective on the calf issue. I’ve had a few issues with my feet that were supposedly because of tight calves with my transition into more minimal shoes (Posterior tibial tendinitis in my right foot and a bit of tendinitis on the top of my left foot which I know can be caused by too-tight shoes and/or tight calves, so I’m trying to fix both). I also tend to wear out the bottom of my shoes, though it’s in the forefoot and not the heel (good), but it’s pretty concentrated in a few spots, which shows me that my stride is not right.

  18. I have a high asymmetry to my feet: My right foot is perfectly stable on impact, while my left has low arches and severe pronation. This meant that, as a clueless runner, I started off in the heavy support category, and slowly moved towards neutral, then zero-drop running. Needless to say, injuries have declined, and stopped completely since the transition was completed.

    I looked at my old Brooks Adrenalines (support shoes), which were my first shoes: the upper is scuffed, the midsole has wear – but the outsole looks brand-new, save for where the exposed EVA was damaged by rough surfaces. Interestingly, the most wear is on the front of my left (pronating) shoe. To be fair, the outsole is mostly durable carbon rubber, but I’m impressed – I ran & worked in these for nearly two years and several hundred kilometers.Then at my Nike Pegasus, which were a step forward – neutral cushioned. The small “bricks” at the sole had nubs that are, by now, all worn away – but I clearly remember the forefoot ones wearing first. Overall, very even wear and very little, at that – though I spared that shoe from wet-weather and rough-surface running (it’s white!).
    My currents, New Balance’s MR00, show little signs of wear at the front, significant wear (probably from walking) at the very heel – but the exposed EVA in the midfoot looks undamaged.

    However, I tend to slip a bit in the MR00 when they get wet (the rubber on that shoe has ZERO grip on moist surfaces) – I’ve been wondering if over time, that will affect wear, as I tend to slide my feet backwards at toe-off when grip is insufficient.

  19. Andrew Ward says:

    I’ve done about 900km now and don’t have any signs of wear, all the little lines and ridges are still there. The uppers are in great conditions as well. Just washed every day. I’m not planning on ever replacing this pair for the rest of my life. True barefoot now even my Zero shoes feel odd.
    PS, I enjoyed you book. Great work.

  20. I too used to destroy the heel of my shoes. Now that I’ve changed to good form running, I’ve put 400 miles on my Kinvara 3’s without much noticeable wear.

  21. Hi Pete, I also am into studying my shoes on the sole regularly after I run. When I switched to the Bikila VFF I noticed that I wore through the big toe very quickly on my right foot. I love wearing the Bikila, but I just can’t get enough miles out of a pair before toe wear becomes a problem. I’ve tried to correct it, but haven’t had any luck. On other shoes I’ve noticed a similar trend at varying levels.
    Right now I’m predominately wearing the Altra Samson and after a couple hundred miles can see no extra wear on that area. I’m not sure if the shoe is changing my stride or if the sole is just that much more durable.
    I wonder if others have noticed increased friction on one of their big toes. Any suggestions?

  22. How do you change strikes? from a heel to a forefoot strike?

  23. I have assessed the wear on my running shoes since I changed my running technique and it is quite clearly reflected on my shoes that the wear has changed substantially (I posted the results on my blog http://www.runchaser.com/2012/… ).

    However it seems as if I am still heel striking a little on one foot. I like your analogy of the way a helicopter lands, meaning that the foot should be landing pretty much flat on the ground.

    • Pete Larson says:

      Nice post on your shoe wear – just shared it in Twitter and FB. Asymmetries are not uncommon, I myself tend to wear the heel a bit more on the left side, very similar to your pattern.
      Sent from my iPad

      • Thanks Pete, I think a lot of people think that they land the same on both feet – which is not always the case due to leg length discrepancies and other reasons. It just make it a little more difficult to change technique.

  24. Interesting post. I have actually noticed that the outside of my forefoot takes a LOT of wear, though the heel is not touched at all (I also analyze my shoes). I’ve been learning the Pose running method and my coach noted that I tend to reach forward with my forefoot (instead of heel), which as I was reading tends to cause a lot of wear on the outside of the shoe. I have worked on fixing that and two things happened: 1) the wear was more in the center, and 2) my IT band pain was gone within a week (I’ve been struggling with this since APRIL).

    I think I still scuff though, as I wear out that part of my shoes a lot. Actually, I have the Grid Type A4s, and the bottom center is pretty much destroyed after about 70 miles (just ordered the A5s after your review, by the way – on sale for 62 bucks – had to do it!) I’ll need to fix that. I really wasn’t sure if they should be wearing out so quickly. I should do more barefoot running, but I’ve been struggling a bit with tendinitis in my right foot since I ran too far in my NB MR00s a month or so ago (mostly gone now, but it’s still there).

  25. Greg Strosaker says:

    I had just commented on dailymile the other day that I noticed far less heel wear in my Kinvara 3’s than my Lunarfly 3’s (to be expected due to the lower heel-to-toe drop), but also versus my prior pair of Kinvara 2’s – and also less wear at the toe. I do take this as a good sign that my form is evolving a bit. When I combine this with the fact that I now feel more comfortable in Kinvara’s than Lunarfly’s (calf tightness is less than the hip issues I get with the latter), it seems clear that one’s form can evolve over time – this was strictly through focusing on cadence and some minor form elements, and more experience – nothing all that radical.

  26. Steve Carleton says:

    I know this is probably a late comment to this post, but I was scrolling through my saved RSS Feeds and came across it again.

    I changed up my stride and noticed a radical change in my wear patterns, particularly on the outer edge of the forefoot. I will grind it down in to the cushioning on the outer edge, and only get about 275 – 300 miles on a pair of shoes before the cushioning is completely gone.

    I was thinking that it had everything to do with the pushoff on the outer edges of my feet. I noticed that when I first start my runs, I land/pushoff on the outer edge, but once I get warmed up and moving, I shift more to the center forefoot. Occasionally, I will hear a scuffing sound when I plant my foot, but I don’t seem to be overstriding.

    If you decide to study this more, I would be interested in being a test subject, since I would like to improve my form for better running efficiency.

  27. One factor in lack of running shoe sole durability is that many outsoles are made of polyurethane.

    While you might believe that a material used for automobile tire construction would have to be durable, polyurethane deteriorates faster than latex (natural) rubber. PU (great abbreviation) quickly spontaneously deteriorates without exposure to UV, moisture or heat. Latex rubber does not. Since converting to using polyurethane, most tire manufacturers have changed their warranties to 5 years, and recommend replacing tires older than that, and “obsolete” tire models every 4-5 years to assure that tires are sold before they can show signs of obvious deterioration.

    When a new tire/sole is used on a daily basis, the wear isn’t as noticeable, but if the product is used infrequently, the PU actually breaks down faster. In tires this manifests as cracking along the bottoms of the grooves and spies. In shoes it manifests as rapid tread wear and outsole separation.

    To get maximum tread life from a shoe with a PU sole, buy a new model shoe from a major manufacturer and wear it until it starts to show uneven treadwear. When it does, recoat the worn areas with a thin layer of Freesole. A thin coating of newly cured PU will be more durable than the older uncoated area.

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