Aku Tengu GTX Boot Review

25th Nov 2017

aku boot

I have had the privilege of testing a range of Aku footwear over the last few years and have, without exception, loved them all.  It is partly their great styling (they are Italian after all!), a big part to do with their exceptional quality and then massively, of course, to do with their fit and performance.  I was, therefore, delighted to be recently asked to review their Tengu GTX boot…..


Aku are a brand that prides itself on innovation - using new materials and developing technologies to create state of the art footwear has always been their passion.  Well, they have done it again as the Tengu GTX is a feature rich shoe with a lot to shout about.

If we work from bottom up then the first thing to mention is Aku’s use of Vibram’s new Curcuma outsole which is combined with a PU exoskeleton midsole designed to offer stability and lateral support. There is a carbon fibre and EVA lasting sheet which offers stiffness while also being lightweight.  Finally, to top of the sole and liner specs there is a custom fit insole and a Goretex performance comfort liner.  The Tengu’s outer is made from nylon with suede reinforcements and additional protection comes from a durable PU rand.

In Use

The first thing you will notice about the Tengu is their appearance.  I would challenge anyone to claim these aren't a really handsome looking boot.  I did say Aku nail it with their design skills and I think this is a great example of their flair for style.  The Tengu is available in turquoise and orange or the black with orange that I tested. They both look great.

The second thing to mention is apparent when you pick them up - the Tengu’s are very light.  Aku give a weight of 725 grams and the ones I tested in UK size 8 came in at a little under that.  For a technical mountaineering boot that is very impressive.  This leads us on to what they are actually suitable for.  They will have caught your eye when you saw them on the webpage or shop shelf, but will they do the job for your activity range?

Aku say the Tengu is a technical boot designed for mountaineering activities and go on to say they are ‘ideal for use in dynamic situations on mixed terrain’. In reality, I would say these are ideal for scrambling and Alpine terrain and will also perform well for winter activities where it isn't too cold.

For scrambling and Alpine terrain I say this because the sole unit, with its blocky Vibram sole, is a great choice for climbing rocky ground.  There isn't a specific climbing zone built into the front edge of the sole but the defined front edge and low profile toe box give them precise climbing performance.  Their climbing capability is further enhanced by the Tengu’s stiff midsole.  There is a degree of flex but plenty of stiffness when edging.  Finally, I will talk about fit later but the high ankle also helps climbing performance by offering plenty of support. 

They aren't overly insulated which could be a factor depending on your aspirations, but if the temperature isn't a problem then the Tengu will also tick all the boxes for moderate to mid grade winter use. Again I say this based on the boots blocky sole, its excellent lateral support and edging ability, the high ankle and its compatability with a semi automatic crampon.  It also, of course, also offers plenty of weatherproofness due to the Goretex lining sock.

After all this, it mainly comes down to fit.  As always, I would add a caveat that no boot is of use to the user if the fit is wrong and different boots suit different feet.  I have always found the Aku lasts to be perfect for my normal to wide feet but do ensure to get them professionally fitted to make sure that's the same for you.

From my experience, the Tengu is a superb fit.  The foot is held snugly even before the laces are tightened.  The toe box is snug enough for precise climbing performance but also roomy enough to allow a bit of wriggle room.  They form around the sides of the foot and the heel cup keeps things in place at the heel back.  

The lacing system has a series of tape loops at the bottom (these are great as sit flat to minimise snag risk) and then higher up around the ankle are some durable metal loops. There is a recessed eyelet at ankle height that enables users to pull the ankle firmly into the heel cup.  It is an efficient system that allows plenty of fine tuning and, once it is all tied up properly, the Tengu offers a very comfortable and yet responsive fit.

This isn't a long term test and yet I have tried to use the boots as much as I can.  They have accompanied me on a mountain leader assessment course (I wouldn’t normally wear boots of this type for purely hill walking activities but I wanted to get plenty of miles into them) and I have had several days scrambling in them on terrain up to grade 3.  I also, in the interests of testing, gave them a run for their money on some esoteric gritstone scrambles on the side of Kinder.  I haven't used them on snow yet but have fitted crampons to ensure compatibility. 

In all uses so far I have found the Tengu to be very comfortable and a superb performer.  You'll really notice their light weight and the boot feels trim and efficient on the foot.  On some very wet mountain leader course days they kept my feet completely dry and the blocky sole unit grippy tenaciously on steep grassy slopes and rock.  They did slip somewhat on wet lichen covered rock but then again everything I have ever tried does too).  The carbon fibre lasting plate offers plenty of stiffness but also allows enough flex so the boots don't feel clumpy when walking.

The edging capability is superb and I put this down to that lasting board, the solid edge to the sole unit and the supportive exoskeltelon which Aku use to such good effect.  I really had no problem standing on some tiny features in these boots.

It is hard to comment yet on longer term durability but it is evident they are superbly made and the material combination should ensure they will stand up to lots of abuse and offer a good lifespan.  I can also vouch for how well my other Aku boots are holding up and see no reason these won't be the same.

Oh yes, and just let me shout out again about how cool they look.  Maybe the cat walks of Milan would be pushing it, but these babies really will look very cool on any wearer!  Another hit from Aku.

Posted by Paul

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