Aku Tengu GTX Boot Review


Paul’s Aku Tengu GTX boot review details a semi-automatic crampon compatible technical mountaineering boot from a highly regarded Italian manufacturer.  We hope you find it useful.

I have developed a long history of testing and using Aku footwear and so far they have never failed to impress.  From approach shoes to more leisure styled footwear like the Bellamont Plus which I reviewed here. I have also reviewed their most technical models such as the Montagnard boots here.  I certainly feel I know my way around their range.  With that in mind,  I was keen to try the Tengu GTX and so please read on to find out more.


The Tengu GTX is marketed as a crampon compatible mountaineering boot.  The boots have a nylon and suede upper with Gore-Tex performance comfort lining.  The outsole is an exclusive Vibram Curcuma unit.  This combines with Aku’s double density PU  ‘exoskeleton’ midsole.  The exoskeleton is designed to offer stability and precision for vertical and technical terrain.  A carbon fibre and die cut EVA lasting board adds the stiffness needed for a mountaineering boot and a custom fit pro alum footbed finishes the internal fit package.

A Liba Smart PU rand also wraps around the boots for protection.  The closure system is a combination of low profile tape eyelets on the lower foot and hooks on the upper section.  Mid way through the lacing system there is a locking hook closure for fine tuned adjustment.  Aku quote a weight of 725 grams per half pair but don’t specify which size this relates too.

Aku Tengu GTX Boot Review

In Use

The first thing to comment on is how these boots look.  Like all footwear buyers, I always find looks important in the purchasing decision.  As I’ve experienced with the various Aku footwear I’ve tested,  the Tengu GTX’s are a great looking boot.  They aren’t flashy, but subtly good looking.  The pair I received are mainly a black colour with contrasting orange detailing around the lacing reinforcements.  This orange detailing also follows in the midsole block.  They are delivered with two pairs of laces in different colours, although my preference is the orange pair that complete the colour theme! 

The other detailing is white stitching that criss crosses the boot.  This is there to reinforce the lacing points. It also adds a nice design flair to the boots.  The Tengu’s are also available in a version with blue detailing and a women’s version is available.  

Aku Tengu GTX Boot Review


So,  the next element of my Aku Tengu GTX Boot review will focus on fit and performance.  Commenting on fit is always very subjective as every person’s foot is a slightly different shape.  Add in how big an impact foot width has and you have quite a variety.  All I can say is that I’ve always found Aku footwear a great fit foy my medium width feet.  The Tengu is snug in the toe box without being over restrictive.  It is actually a perfect fit for a mountaineering boot which needs precision on challenging ground.  I found the size 42’s I was sent were very much true to size.

Aku Tengu GTX Boot Review


The lacing system of a boot of this type is key.  The laces thread through flat tape in the lower section and extend low down the toe.  The tape allows the laces to sit very flush to the boot which is ideal for use on steep terrain.  The way they extend down into the toe ensures you can fine tune the fit for climbing.  Then, mid way up the boot there is a locking lace hook.  This allows the lower foot adjustment to be separate to the upper foot.  Above the locking hook is a cord loop designed to pull the foot into the heel cup.  Finally,  there are a couple more hooks at the ankle.  This carefully considered combination really allows the boot fit to be fine tuned and I’ve found it extremely efficient.  

The ankle cuff sits quite high which is important for a mountaineering boot where ankle stiffness is required on steep ground.  It works really well for this.  However,  for walking I prefer to just fasten the laces up to the second to last row.  This allows a little more ankle flex without overly compromising support.

Aku Tengu GTX Boot Review

Walking Performance

So,  the fit is great.  How do they cope on various terrain types?  Over the winter I’ve used the Tengu GTX’s for a variety of days enjoying some mountaineering adventures (local adventures due to lockdown restrictions).  These have typically involved a significant walk in and then scrambling or winter climbing at lower grades.  The boots have also been used a number of times with semi-automatic crampons.

Firstly,  I have found the Tengu’s very comfortable to walk in.  Infact, very comfortable.  As they are designed to work with semi-automatic crampons they are fairly stiff, but there is enough of a rocker in the sole to make walking comfortable.  As mentioned above, I have found them more comfortable for walking when the top lace is left undone.  That’s very much a personal preference though. When walking on steeper or looser ground the Vibram Curcoma sole unit works very well.  The blocky tread pattern provides the grip needed on wet or muddy ground. It has also performed well on wet rock and loose ground.

Technical Ground Performance 

Once on steeper ground,  these boots excel. The stiff edges of the Vibram Curcoma sole unit offers great edging qualities and they grip really well on rock. The solid sole platform also allows efficient use of small edges.  Steep ground performance is also aided by the supportive fit.  The Tengu’s have a high ankle and the heel is held firmly in the heel box.  Again, a great performer. In use with a semi-automatic crampon the Tengu’s have also performed effortlessly.  I have used them with Grivel and Salewa models and both have fitted well and felt extremely secure.

Aku Tengu GTX Boot Review


What else?  Well, although I am early into the life of these boots,  So far they are coping with wear and tear with no issues at all.  Although a reasonable weight, they certainly aren’t the lightest boots out there.  The upside of this is that they are built for longevity. The durable materials and burly build will ensure the Tengu’s are long term companions.  Of particular note is the beefy PU rand which will fight off even the most cheese grater of rock types.

The Tengu’s feature a Gore Tex liner combined with a suede upper (which I proof with Nikwax Fabric & Leather Proof).  This has easily fought off any weather I’ve thrown at the boots this winter.  The addition of a bellows tongue also helps seal out water or snow.  They may be designed and made in Italy, but the Tengu’s will stand up to the wetter and wilder climates like the UK.  


Of final note, and very important to mention, is Aku’s high sustainability values.  On their website Aku have detailed information about where their materials are sourced and also the reason for their material choices.  The Aku’s, as one example, feature zero impact Dani leather.  This is produced using a process that replaces chrome and heavy metals in tanning and therefore lowers the carbon dioxide emissions.  They then reduce the remaining part to zero thanks to certified reforestation.  It is great that the company are focussed on reducing the environmental impact of their production.  It is also great that they are leading the direction of the industry by seeking out solutions.  


If I was asked to finish my Aku Tengu GTX boot review with a summary sentence, what would I say?  I’d say the Tengu’s are a great looking, high performance, sustainably produced and durably built boot suitable for summer and winter mountaineering.  I think they are a great option produced by a family business with a trusted heritage.  As you can see, I highly recommend these boots. The Aku Tengu GTX costs £299.90 and full details are available on the Aku website here.