Is it time for new shoes?
August 8, 2019
by Nick whitbread
We all come to love our favorite pair of trail runners. Opinions on when it's time to retire them vary. Lets dig in and see if the old faithfuls have a few more miles in them.
When you purchase a pair of running shoes you are looking to find the right pair for your feet and for your individual gait. If you have a wide fore foot you want a shoe that will accommodate that. If you are a heavy heel striker who tends to pronate you might need a medially posted shoe that will offer you some pronation control. There’s many different ways to run and many different shapes of feet. Finding the right shoe for your foot and gait can be a challenging process.
Although you can often find great deals online as there is not the added cost of having a bricks and mortar store, we would always recommend going to a local run shop. Talk to someone who has hopefully run in all the shoes on the wall and if not at least tried them all on and who is familiar with their fit and features. Add to this if you do take the shoes home and run in them and it turns out they aren’t for you, sometimes local run shops will let you return them for a re-stocking fee and you can try another pair.
We at UpRiver stay true to Trail Running, for the sake of explaining shoe wear, lets compare and contrast the difference between road and trail shoes.
Lets begin with cushion and the running surface. Roads are hard. Trails can range from hard packed dirt to softer spongier surfaces. How does that affect the cushion of the shoe? On a hard road surface you are looking for shock absorption. The cushioning material in the shoe (The EVA, Ethyl Vinyl Acetate) is considerably softer in a road shoe compared to a trail shoe. Your gait seldom changes on the road and for that reason you need a shoe that is going to forgive your gait in the areas where you are landing with the most force. In a trail shoe the trail itself offers some cushioning from the foot strike. Additionally with constantly changing terrain the runners strides tend to be shorter and subsequently landing with less force. To best suit this, the cushioning in a trail shoe tends to be firmer than that of a road shoe. This still gives you the cushion you need but offers better reactivity on the changing terrain. If you have ever taken a super well cushioned road shoe into the trails you may have noticed that you lose some efficiency, ie. you have too much cushioning and subsequently your transition from landing to take off is sluggish.
The next difference we notice is the traction. Roads, unless wet, tend to be pretty sticky and uniform. Road running usually involves running in an uninterrupted straight line, so the need for lugs to improve traction and cornering on the shoe is incredibly minimal. To the point where in an effort to lighten road shoes, companies have removed the rubber sole in areas where strike pressure is minimal and replaced it with “contact” EVA, which is designed to wear and grip a little better than the regular EVA used for cushioning the midsole. On a trail shoe the reverse is true. Trails are constantly changing terrain. They can be soft and wet, soft and sandy, they can contain small or large rocks, inclines, descents, off camber sections. They are ever changing and seldom uniformly flat, for that reason there is an essential need for traction. Trail shoes have much deeper and wider lugs than road shoes. The deeper the lugs the better the traction on soft surfaces, the wider the gaps between the lugs on the shoes the better the shoes will clear debris like mud or snow. Trail shoes also sometimes have breaking lugs facing in the opposite directing toward the rear of the shoe for use in descending ( it’s way more fun not to break :). Sometimes the shape of the lugs also offers this ability.
The sole compound itself is also different between road shoes and trail shoes. The road tends to wear shoes quicker so the compound used in the sole of a road shoe is harder (it has more carbon if you want to get nerdy) and is more resistant to wear. Trails are generally less abrasive on the soles of shoes and so making the compound softer allows for better grip in varying conditions. You may have noticed that on the rare occasion when someone had a gun to your head and forced you go for a road run (joke) in your trail shoes, it doesn’t take long to notice some aggressive wear. This is especially true if you tend to be a heavy striker or a foot dragger.
How about the terrain? Roads are flat and smooth, no real obstacles, very minimal risk of landing off kilter and twisting an ankle. The exact opposite is true of the trails. It’s rough, full of obstacles and can be slippery at times. If you hold the fore foot of a shoe in one hand and the heel in your other hand and twist them away from each other, you are testing a shoe’s lateral stability. Lateral stability comes into play when you land on a rock or some other obstacle which inhibits a flat landing. Rather than the shoe totally collapsing it remains somewhat stiff for a moment and allows your brain to catch up with whats happening and correct the situation. There’s no need for this on the road which is why there's little to no resistance when you try this test on a road shoe (unless it's a posted shoe).
What affects the lateral stability of a shoe? If the shoe is posted, meaning it has some sort of mechanical structure or different density of foam on the inside of the shoe to help control the pronation (rolling in) of the heel upon landing. This usually has an effect on the shoes' lateral stability. The stiffness of the heel counter (the part of the shoe that wraps the back of your heel) also has an effect on the lateral stability of the shoe. The stiffer the heel counter the more lateral stability (usually). The other factor in this equation is the rock guard. Roads don’t tent to have rocks to poke you in the foot through the bottom of the shoe, hence road shoes don’t have rock guards. Some trail shoes do, some don’t. A rock guard can be a piece of flexible plastic or a tightly woven mesh that is usually placed between the sole and the midsole of the shoe. Its' job is not to stop you feeling the rocks under foot but to disperse the sharp pressure of landing on a rock across a larger surface area so as to avoid discomfort and to protect you feet. This is one thing to always find out when buying trail shoes. If you are a heavy striker or aggressive descender its a good idea to go for a shoe with a rock guard. It will help protect your feet from bruising and also push through from a sharp rock that might cause a trauma. If you have a lighter gate the cushioning of the shoe itself might be enough protection for your feet.
Debris? The road is usually clean and free from dirt and sand. It’s also hotter and due to the liner direction of travel the mesh used in road shoes tends to be lighter and thinner than trails shoes. In a trail shoe you might be running downhill, stepping down something and cornering all at once in lose dirt. You firstly want to keep any debris out of your shoe, its uncomfortable and will no doubt assist in forming a blister. You also want to keep your foot inside the shoe and not have the mesh upper tear away from the midsole. It’s for this reason that the mesh on trail shoes is usually more tightly woven and thicker. There may be multiple layers and also overlays to help the upper maintain its shape under stress.
We won’t get into stack height and drop today as that could be an entire post on its own. they are also a factor though when choosing a shoe and they do affect how it wears.
So now that we have talked all about the ins and outs of our shoes, how do we know when it's time to replace them? This is where it’s not as simple as you might think. Road shoes are much simpler. For road shoes most authorities recommend replacing a shoe after 6 months of consistent training or three to five hundred miles. Usually the most important feature of a road shoe to a runner is the cushion. The EVA midsole is made from a closed cell foam. It is blown with thousands of tiny air bubbles that help to create the cushion upon landing. Over time and repeated impact these bubbles in the midsole tear and collapse along with the foam itself losing its memory (its ability to return to its original shape). Statistically after a year of consistent wear EVA retains 10% of its original cushion. Shocking right?
When it comes to trail shoes the value equation is very different and somewhat personal. There is so much more to trail shoes that can be valued differently to each runner. So I’ll speak for me and you can take from it what you will. Personally I have never retired a pair of trail shoes because the life of the cushioning in the shoe was over. The trail is so much more forgiving that even in an older pair of shoes, there is plenty of cushion. One of my hips angles in slightly and subsequently my shoes rub together when I run. This along with my running and descending style tends to be incredibly hard on the uppers of trail shoes. Even with re-enforcement prior to running in my trail shoes I inevitably tear through the uppers long before the rest of the shoe is showing much wear at all. When choosing a trail shoe I value forefoot volume, traction, foot protection (rock guard), lateral stability, upper durability in that order. I know that I’m going to destroy the upper no matter what. I want the shoe to accommodate my larger forefoot, have great traction, protect my feet, feel somewhat stiff under foot and have a tightly woven strong upper.
If you look at the pictures attached to this post you can see that these shoes are in rough shape. The inner cuffs of the shoes are ripped open from rubbing together, each fore foot upper is ripped in multiple places through both layers of mesh exposing the inner sock liner. The sole itself is showing moderate wear. To most, these would be in the trash or for lawn mowing only. I still run long distances in these shoes. My biggest concern is that my little toes don’t have great protection as each shoe is ripped on the outside (and the inside). The day my little toe pokes out or the upper rips so far that there is no holding power in the upper to keep my foot from sliding laterally, I’ll replace them. So you can see how individual gauging wear can be.
I probably wear trail shoes long beyond maybe what I should. A good rule I also use is to compare the pair I’m running in to a brand new pair. We all usually have our favorite trail shoes. When you find that favourite shoe it’s helpful if you can afford it to own multiple pairs. I ran in the pictured shoes on Monday, I also have a brand new pair of the exact same shoes that I have run in once and will begin to transition into. As the older pair breaks down I am comparing it to how it feels to run in the brand new pair. Eventually the old pair will either catastrophically fail or I will no longer be able to run in them after feeling how good it feels to run in a new pair of the same shoe. Sometimes it's helpful to have the comparison of new to old. The shoe is breaking down slowly and sometimes you don’t notice how bad they have become until you run in a new pair.
This is the most helpful piece of advice I can offer on when to replace your shoes. If the shoe still feels good and is still doing what you bought it for, keep on running in it. There is no sense wasting money or resources because “someone” told you to replace your shoes at certain intervals.
This is a tangent but I thought it was worth mentioning. I learned this from a very knowledgable and informative Rep that I used to deal with. For Women when you replace your shoes, you should also be replacing your sports bra. The lycra and elastic in the bra break down just like the cushioning in shoes. The bra loses its ability to control and support the way it did at purchase. He also informed me that the best way to wash your sports bra is to wash it separately, in a garment bag with white vinegar rather than soap. This will keep it smelling fresh and make it perform better, for longer.
We hope that helped Bra? (I can see Antonio shaking his head disapprovingly)