New Balance FuelCell Summit Unknown SG Review

This week I’ve been racking up some off-road miles for a New Balance Summit Unknown Fuel Cell SG review (SG stands for Soft Ground). New Balance now makes two versions of the Summit Unknown trail running shoe. The regular version is designed for hard packed trails and has 4mm long lugs. This length of lug will give some traction on wet, muddy surfaces so if you come across short sections of this in your trail run then these are likely to do the job for you. However, if your trail includes longer sections of wet muddy ground then a longer, more pointed stud gives more traction. The Summit Unknow SG has lugs that are more pointed and 6.5mm long, designed to bite in.

The phrase “soft ground” is subjective. If you are a British runner, it might mean ankle deep mud, freshly ploughed farmers fields or sections of calf-deep muddy water. The shoes that perform well in these extreme conditions have studs that are typically 8-10mm in length and the shoes are flexible enough to mould to the contours of the ground to give as much traction as possible. These extreme conditions are not the type of conditions that the New Balance Summit Unknown SG has been designed to tackle.

That being said, if you think that New Balance’s interpretation of soft ground makes the Summit Unknown SG a poor shoe for UK conditions, that’s not the case in my opinion. The Summit Unknown SG is a much more versatile trail shoe than the name might suggest. It offers a good level of grip for all but the most extreme of soft ground whilst offering enough cushioning and underfoot protection for use on harder packed trails and even some tarmac.


The toe box offers a straight big toe line, which improves toe-off and allows your toes to spread. The volume in the toe box is low but it doesn’t feel restrictive to my regular width feet. During my review miles it made the shoes feel comfortable even when running up hill for a long period of time. I tend to wear shoes with a more rounded toe box and have got used to having plenty of space for my toes to spread. The fact that the toe box space is enough for the Summit Unknown to feel comfortable would suggest that it is wider and a more rounded shape than the classic pointed toe box shape that New Balance has produced in the past. There is an overlay that runs around the upper to protect it from abrasion. This is thicker at the toe and extended to give ample of toe protection.

The tongue is fully gusseted to prevent debris from getting into the shoes. This helps pull the upper in around the foot to give a nice snug fit. The tongue is lightly padded and moulds to your foot shape nicely. This meant that even on uneven trails I didn’t feel like my foot was turning or twisting inside the shoes. The heel cup is semi stiffened so it holds you in the shoe when the terrain is throwing your foot around a bit. The padding is light so that it doesn’t absorb any moisture.

Your foot sits slightly inside the FuelCell midsole, which increases the level of stability. There is a nylon rockplate under the forefoot between the midsole and the outsole. This is designed to stop rocks from bruising your feet or thorns putting holes in your feet. The rockplate does stiffen up the shoes. This means that you have a good platform to push off against whilst running up hill and makes the Summit Unknown SG feel a bit like it has a carbon propulsion plate in the midsole. The rockplate also makes the FuelCell midsole feel firm and responsive, which gives the Summit Unknown a nimble feel.

The 6mm heel to forefoot drop makes it easy to land midfoot so I could dance across tree routes or boulders.

The outsole is made of New Balances Hydrohesion Rubber. This is a soft rubber designed to give good grip on wet surfaces. This does work well. However, the low surface area of the more pointed lugs on the Soft Ground version of the Summit Unknown do slide a little bit on really smooth slippery surfaces. An example of this would be moss covered steps that are wet or stepping stones. Don’t get me wrong, they weren’t like ice skates. There was just a little bit of slide at toe off, which is something that I didn’t experience with the flatter studded version. It will only affect those running regularly on wet wood & stone, which most don’t.

The lugs do bite quite well into wet farmers fields and are spread out enough to not easily clog.

I often do hill loops, where I run an uphill section on a tarmac road or hard packed track and do a downhill section on a wet muddy track or muddy field. I found the Summit Unknown SG ideal for this session. I could run quickly on the uphill and then just allow myself to trot down the hill, trusting the shoes to ‘do the job’ for me. Other shoes I have used don’t have enough cushioning for the road section or they don’t have the grip for the descent.

In summary the New Balance Summit Unknown SG is a surprisingly versatile trail running shoe ideal for muddier UK conditions, just not the very worst deep mud. That probably appeals to a lot of Northern Runner trail customers.

Other Considerations
Icebug Capra: A rounded toe box and good level of grip. Traction is better on wet surfaces. Here is our review for more information:

Scott Supertrac 3: A bit more heavy duty and a bit more traction but, designed for the same versatile trail use in wet conditions. Here is a link to our review:

Saucony Peregrine 13: These are a very similar shoe. The toe box is more pointed but, the cushioning and lug depth is very similar:

Inov-8 Roclite G 275 v2: Inov-8’s grippy trail shoe. More flexible than the Summit Unknown which makes it ride really broken ground better but, not as quick on the harder packed surfaces. Oringal version review:

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