Sole Searching: What is the Ideal Tread Thickness in a Minimalist Running Shoe?

by Steven Sashen.

To answer this question, let’s begin with a simple Pop Quiz:

Which of the following fictitious shoes gives you more of a barefoot feel:

a.) ASICs  Nuttin’-2C with a 10mm thick sole
b.) Brooks Zilch-City with a 1mm thick sole

If you answered B, you’re mistaken. But if you answered A, you’re also wrong.Yes, my apologies, but this was a trick question.

In the barefoot/minimalist footwear world, there are several  concepts buzzing around, ideas upon which runners  make buying decisions, that are potentially red herrings. In other words, these concepts can be used to inform or mislead, depending on how they’re used and how much other information comes along for the ride.

And “sole thickness” is a biggie.

If you look at ads for various minimalist footwear products, sole thickness is highlighted.  Sometimes bragged about. Thinner soles, some believe, are inherently better than thicker. Unless you’re a trail runner, then slightly thicker is better. Right?

Well, no. Again, it’s not that simple.

Let’s go back to my trick question.. The reason neither answer is correct is that I didn’t tell you what the soles are made of.

If the 10mm sole was made of cotton candy, you may as well be running on the ground. The sweet, sticky, ground.   But if the 1mm sole was made stainless steel or carbon nanotubes, you wouldn’t be able to tell if you were on the ground at all.

I’m exaggerating for effect — both comic and practical. But looking out in the market, you’ll see sole thickness used as a seeming shorthand for “barefootedness.” In other words,  “thinner” means closer to barefoot.

I recently had an Invisible Shoes customer call me and tell me about his particular brand of minimalist shoe and how it advertised a 3mm sole. He wanted to know whether I thought his shoe was “more barefoot” than our 4mm Connect sandal.

“Great,” I said, knowing the shoe in question. “It’s only 3mm thick. But is it flexible? Can you roll it into a tube?”

“Well, no,” he said, clearly trying. “It’s pretty rigid.”

“And if put on that shoe and you stepped on a nail, how similar would  that feel to stepping on it barefoot? “Wait,” I added, “you better not,” narrowly avoiding a legal nightmare.

I continued, “If you look inside that shoe, can you see the extra 2-3mm of insole padding they added to the 3mm outer sole?”


I could hear in his voice the first stages of someone starting to see through the fog of marketing hype.

Many shoe marketers suggest, and many minimalist shoe buyers believe, that sole thickness is equivalent to “barefoot feel.” It’s not. It’s more complicated than that.

When it comes to minimalist shoes, I feel compelled to paraphrase a line than no man wants to hear from a woman, “Honey, thickness isn’t everything.”

Steven Sashen is the CEO of Invisible Shoes.

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