New Balance Sonic Fuel Core Review


The NB Sonic Fuel Core combines a firm riding and flexible Revlite midsole with a sock upper cinched down by a Boa retention system. It is ideal for those who like quick and fine-tuned adjustability across the top of the foot. The stretchy toebox should accommodate wider feet. It should also appeal to triathletes looking for time savings in their transition. The shoe will be available in July 2017.


I don’t get bow knots. Specifically, I don’t get why we use bow knots to secure our shoes. It’s hard to dial in the tension perfectly, since there is always some slip as the knot is being tied. So, you end up overtightening and hoping everything slips back to the correct tension. They are prone to being tied as a granny knot, which then becomes undone easily. This can be prevented by double tying or using the double loop technique, but it results in a knot that is time consuming or fiddly to undo.

Conventional shoe laces do allow for a variety of tension to be dialed in, particularly if non-standard lacing patterns are used. They are also inexpensive. All that being said, I’m still shocked that this is what we are left with after a few hundred years of shoe development.

Other sports like cycling, skiing and speed skating have developed alternative closure systems for their footwear. Despite having a much larger market and user base, we haven’t really seen these types of technological advancements commonly available in running shoes.

Shoe Parts

Which brings to1-_DSC7872 the New Balance Sonic Fuel Core which uses a Boa retention system. The Boa dial reels in a small line that cinches a large overlay strap across the instep of the foot. The rest of the shoe is a sock-type strecthy mesh upper. There is a reflective NB logo across the top front of the shoe, but it is the same colour as the upper, making for steathy branding most of the time.


Midsole / Outsole

The midsole is made of RevLite, a foam used in many other New Balance shoes. The Sonic is equipped with a 3mm insole and . The specs are very similar to the Vazee Pace, and it was no surprise to me that it rides very similarly. Quite firm throughout, with moderate 5-_DSC7879flexibility. The transition is very uniform with similar cushioning feel in the heel to forefoot. Definitely made for faster runs, I would recommend this for half marathons and under distances.

There is a decent amount of high-abrasion rubber in the forefoot and lateral edge. There are curved flex grooves through the sole, for flexibility. This is definitely a neutral shoe, with no medial post or other stability features in the sole.


The upper is where this shoe sets itself apart from the competition and other NB shoes. As mentioned, the focus is on the Boa retention system. However, the other upper components are interrelated and this influences the overall design.

The forefoot upper is completely unstructured, lacking any welded or stitched overlays. This results in a relaxed fit and should allow for some upper stretch to accommodate wider feet. Those looking for a snug or tight fitting toe box may want to look elsewhere.

The pattern extends to the midfoot and instep. There is no discrete tongue; just a sock upper. The loose overlay cinched by the Boa is the only form of structure. When closed tight, the sock upper slightly pleats were needed to take up the slack. The lack of any discrete tongue removes a key irritation point and avoids the tongue lateral slide problem.

Moving to the rear foot, there is minimal padding around the throat of the shoe. I really like this setup, as I find overstuffed heel collars get in the way of good lacing and contribute to heel slip, for me. The heel cup is very rounded, allowing for a deep seating of the heel within the rear of the shoe. I found it is important to get the fit correct, before tightening the BOA6-_DSC7894. The retention moves and presses downward only and not rearward, so if there is any space behind the foot, it will show up as heel slip. The heel counter is reasonably stiff, giving some lateral stability and support.

There is a small pull loop on the back of the heel, which helps in pulling the shoe on. Despite the one-piece sock upper, I found that the shoe was very easy to pull on; ingress was well thought out. The will appeal to triathletes, where lack of drama here will aid their transition time.

Run Experience

From the midsole downward, the Sonic runs like the Vazee Pace. You will either like the stiff ride, or need something with more cushion. As I mentioned before, this tends to position the shoe as more of a fast tempo shoe, rather than a high mileage trainer.

The real story is the upper fit. The Boa closure allows for a wide variety of fits, from super loose, to cinched medium-tight. I tested the shoe under a variety of tensions. The key point is the tension is easy to dial in and adjust in micro-fine amounts that would be impossible with lacing. All this can be done on mid-run within a 5 second stop. It’s great for dealing with expanding feet on hot days, or just tweaking the fit as you run. It also works with gloves on, which is very handy in the winter.

The main disadvantage is the there is one fit setting for the entire length of the shoe. It is not possible to adjust the fit of forefoot, instep and heel lock independently. The overall fit is linked to the dial setting. So, if you need a looser instep lock, it may trigger some heel slip. All of this will vary, depending on your foot shape and fit preferences.
There is no lockdown for the forefoot at all, since the strap starts at the midfoot.

The strap and lines have a bit of give, so it’s not possible to really crank down hard on the system. At least, I wasn’t willing to reef on it, for fear of breaking something. The large straps over the navicular area spread the pressure over the top of the foot. It prevents the thin laces from digging into the top of the foot, as with other Boa-based systems that wrap the bare lacing over and around the foot.

The overly strap does guarantee that the tension is evenly distributed, whereas an overly tight lacing across a single eyelet can create a hotspot and pain point.


The shoe has a very innovative fit system that is particularly well suited to triathletes and those who like to adjust their shoe fit on the fly. It doesn’t suit runners looking for a very independent tightness over the length of the shoe, although the overall tightness is very finely adjustable via the Boa dial. It’s not going to work for everyone, but for those who do, it works very well.

New Balance is to be commended for releasing shoes with alternative retention system. I hope that New Balance provides a Boa option in a variety of other shoes in different categories, to appeal to a wider audience. The Sonic Fuel Core is available in July 2017.


4 thoughts on “New Balance Sonic Fuel Core Review

  1. Pingback: A Pair of New Balance | Go Faster.

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