New Balance FuelCell Summit Unknown v4 Review

An in-depth review of the New Balance FuelCell Summit Unknown v4 trail running shoe, along with a bit of a shoe history lesson.

By on March 26, 2024 | Comments

[Editor’s Note: With this review, we’re making a rare exception and publishing a review of a product that will only be on the market for a few more weeks. A few of our testers liked this shoe enough that we still wanted to get word out about it, as the Summit Unknown line will be discontinued in the U.S. in the coming weeks. The successor to this line, the New Balance FuelCell Venym, has recently launched in Europe.]

How about a history lesson for all the shoe geeks out there, especially those under 35 who may not remember a little fad called “minimalism” and the roots of the New Balance FuelCell Summit Unknown v4 ($130) featured in this review.

The inception of this shoe, with its 32-millimeter and 26-millimeter heel and forefoot stack height, 8-millimeter drop, and 9.5 ounces (268 grams) actual weight for a U.S. men’s 9 dates all the way back to 2010 when iRunFar’s Travis Liles first reviewed the New Balance MT100. That shoe was based on the last of the little-known New Balance 790, popularized by Anton Krupicka and Kyle Skaggs tearing it up in the late 2000s. Bryon Powell covers the creation of the New Balance MT101 and cult favorite MT110 in this gem of an interview from 2012 with Krupicka and Eric Skaggs about how the shoes were developed. It is difficult to overestimate the impact that these models had on the burgeoning trail running and ultrarunning world, as well as spawning the release of other minimalist fetishized shoes like the Salomon S/Lab Sense and the La Sportiva Helios and La Sportiva Vertical K models.

Having aesthetically peaked in 2011 with trail shoe design (in my opinion), New Balance went in a different direction as “maximalism” took hold of shoe design fads. After several releases of the decent New Balance Vazee Summit starting in 2015, the brand released the New Balance Summit Unknown in 2018. For those of you still with me, this model incorporated some of the cushioning and last features of the New Balance RC1400 racing flat and was a nimble and responsive trail shoe. This most recent version, the New Balance Summit Unknown v4, really flew under the radar as a well-cushioned, lightweight, all-around trail shoe, so we’ve chosen to give this shoe some love.

Shop the Men's New Balance FuelCell Summit Unknown v4Shop the Women's New Balance FuelCell Summit Unknown v4

New Balance Summit Unknown v4

The New Balance Summit Unknown v4. All photos: iRunFar/Bryon Powell

New Balance Summit Unknown v4 Upper

Unassuming is an excellent way of describing the New Balance FuelCell Summit Unknown v4, and the upper is just that. A dual-density mesh and a protective welded overlay protect the upper on a fairly narrow last. It was just wide enough for me to wear, but certainly more narrow in the toebox than past versions. A decently well-cushioned gusseted tongue wraps around the foot and stays secure without wrinkling or moving around. I was unable to test this shoe in truly wet and rainy conditions, but it did provide adequate warmth and protection in wintery weather conditions in slushy snow, and the shoe dried out quickly.

Some runners will find the fit and last too narrow, both in the toebox and midfoot area. If you are a runner who enjoys the more snug feel of a racing flat, this shoe will likely work for you.

New Balance Summit Unknown v4 - lateral view

A lateral view of the New Balance Summit Unknown v4.

New Balance Summit Unknown v4 Midsole

With a fairly modest stack height of 32 millimeters in the heel and 26 millimeters in the forefoot, the New Balance FuelCell Summit Unknown v4 features the brand’s FuelCell midsole foam. This foam is a blend of nitrogen-injected TPU and EVA foams, and its resiliency and durability stand up for many miles. A rock plate provides additional protection and really helps the shoe remain responsive over rocky terrain.

After spending more time in higher stack height shoes this fall and winter, the nimble and lightweight feel of the Summit Unknown v4 felt positively quick over terrain. Additionally, the 6-millimeter drop was a welcome reprieve for this old man’s calves and Achilles.

New Balance Summit Unknown v4 - medial view

A medial view of the New Balance Summit Unknown v4.

New Balance Summit Unknown v4 Outsole

The New Balance FuelCell Summit Unknown v4 uses fairly unobtrusive and low lugs that employ the brand’s proprietary Hydrohesion rubber which is surprisingly grippy. I would compare the stick of this rubber to Salomon’s Contagrip, and it inspires a lot of confidence in sticky mud and clay, on wet rock, through snow, and while negotiating icy trails. It seems durable as well.

New Balance Summit Unknown v4 - outsole

The outsole of the New Balance Summit Unknown v4.

New Balance Summit Unknown v4 Overall Impressions

The New Balance FuelCell Summit Unknown v4 remains a shoe for trail runners looking for that lightweight and agile road-racing-flat feel with some added cushion, rock plate protection, and traction thrown in. I think this model maintains somewhat of a sleeper reputation until some form of quasi-minimalism fad returns to the forefront of trail shoe marketing. I’m only halfway joking about that idea since it’s not runners buying the bulk of high-end running shoes in the United States, but rather healthcare professionals and hipsters latching on to the latest gorpcore trend.

The New Balance Summit Unknown v4 is a trail running shoe free of gimmickry and this is refreshingly reflected in the price as well. Slip on a pair with some two-inch split shorts, strap on your handheld bottle, and experience simpler times.

Shop the Men's New Balance FuelCell Summit Unknown v4Shop the Women's New Balance FuelCell Summit Unknown v4

Our Favorite Trail Running Shoes

Check out our Best Trail Running Shoes article to learn about our current favorite trail running shoes!

New Balance Summit Unknown v4 - upper

A top view of the New Balance FuelCell Summit Unknown v4.

Tom Caughlan

Tom Caughlan is a part of the iRunFar gear review team. Tom has been testing and reviewing trail running shoes and gear for over 10 years. Based in Colorado Springs, Colorado, Tom has been running since middle school and enjoyed competing in college for the University of Michigan. Tom is a psychotherapist by trade and works for the University of Colorado, Colorado Springs.