"There’s a lot of truth in what you see on the bottom of shoes" says Chris Wawrousek,
and he — of all people — is in a pretty good position to know. Seated in a back corner on the 5th floor of the New Balance Design Center in Lawrence, Massachusetts, Chris is literally surrounded by this truth in the form of the hundreds of prototyped, well-worn and yet-to-be-tried shoes that line the halls. Today, though, he’s focused on four pair of shoes in particular: a pair of MT100’s well-loved and hand-carved by ultramarathoner Anton Krupicka, a hybrid pair of MT100’s fixed with a prototype sole from what would become NB Minimus, a pair of NB Minimus Trail shoes, and the shoes that brought us to the Design Center — the forthcoming NB Minimus ZeroTrail.
As we’ve covered before, it’s impossible to discuss the sole design of any NB Minimus shoe without acknowledging the influence of Tony Krupicka’s original MT100’s. Both the worn rubber and the parts Tony carefully carved away played a role in informing the areas in which the sole should be providing additional support — and areas in which minimizing material will lead to enhanced ground feel.
Chris and his team then examined trail-tested NB Minimus soles from Tony to compare expected wear patterns with actual wear. The pods exhibiting the most wear are marked here with yellow stickers for easy reference.
To capture and compare the wear patterns of a range of runners — not just ultramarathoners with a midfoot strike — Chris’ team examined more than 40 ‘wear-tested’ pair of NB Minimus Trail in a similar fashion, noting the pods on the sole that were most worn. The video above shows a composite of those wear samples, with the most-worn pods on each shoe marked in green. As more shoes are introduced, a clear pattern of consistent wear is revealed.
The wear pattern tests informed not only the location of the pods on the sole of the upcoming NB Minimus Zero Trail, but also the size of each. The diameter of each pod is scaled to match the need for ground contact in that region of the foot, while still allowing the foot to flex and bend naturally. The more independent pods allow for increased ground feel. “Anytime you’re breaking up the rubber”, says Chris, “you’re opening up a more-flexible area.”
When you compare the soles of (from top to bottom) the NB Minimus Trail prototypes, NB Minimus Trail, and the NB Minimus Zero Trail, the ways in which the wear patterns informed the design of the sole become unmistakeable.
To remove additional weight while maximizing ground feel, the designers carved away as much material as possible from the rubber outsole — going so far as to cut visible holes in-between the pods.
Fellow designer Andrew Nyssen led the evolution of the sole design for sleek new NB Minimus Zero Road — footwear that has clearly been infused with some of the hard core elements that attracted people to the NB Minimus Trail shoes. To supplement ‘wear-test’ data for the NB Minimus Road shoes, Chris spray-painted the soles of his own shoes a bright red. The durability of the paint allowed him to notice and measure his own wear (he acknowledges his own difficulties in adopting a midfoot strike, witness the black marks on the heel, although Chris has found that the NB Minimus Zeros and ‘lots of practice’ have helped him make the transition).
The findings informed a new design for the sole of NB Minimus Zero Road, with both a reconfigured layout of the pods, and Vibram rubber components that add durability and traction without adding unwanted weight. NB Minimus Zero Road will be the first pair of shoes to use this particular grade of Vibram rubber, which Chris describes (anecdotally, not scientifically) as a “sticker compound”. Careful attention was paid to the balance of light weight and the need for ground contact. As Chris reminded us: “it gets more challenging to have good traction when you have less rubber touching the road.”