November 12, 2013

On Shoulder Straps

Tom on the design of the Guide's Pack

Tom on the design of the Guide's Pack

In the über-cush world we find ourselves in, we may sometimes like to imagine that a heavy backpack can be worn over many hours and many trail miles with no discomfort. As some of the techies and engineers who design this stuff (not to mention that we test our packs out in the wild, often with quite heavy loads, and like comfort as much as the next guy) we often hold that up as our Holy Grail: a pack that carries as comfortably as nothing at all. In the not-too-distant past the world had porters (some places still do) and the future may offer anti-gravitation technology (other planets may have this already), but for now we just try to make the shoulder straps on our backpacks as comfortable as possible.

We've been using die-cut, thermo-formed shoulder straps made of closed-cell EVA foam for a very long time. We've refined and further refined the shape of the curve, the width of the pad and thickness and type of foam. Over decades of theorizing, field testing and actual production, we've come to the conclusion that the shape of a shoulder strap is far more important than the thickness of the foam padding. In fact, in our humble opinion, a heavily padded strap can sometimes mask what is essentially an ill-fitting strap, the thickness of the padding essentially making up for a lack of nuance in the shape.

Here's some of the hard-won trail wisdom from us life-long pack builders and users:
Adjust your straps to fit you, but also adjust them during the course of the day. You'll want to distribute the weight of the pack over different muscles/soft tissue over time. Do this, of course, by small adjustments to the length of the lower strap. But use the sternum strap to fine tune and modify the fit over the course of the day as well: tightening the sternum strap will bring the shoulder straps closer together; loosen or unclip the sternum strap for a while so the shoulder straps can ride a bit further apart. Use the waist strap for a while, then loosen or unclip it for a different ride. If you watch closely, most experienced hikers are constantly performing these micro-adjustments as they walk -- after a while the adjustments become as unconscious as shifting weight to one foot or another when standing for long periods or alternating reclining with sitting up straight while sitting for long periods.


Avinash - November 19, 2019

What is the density of your EVA foam for better comfort?

jules - November 19, 2019

hi tom, i am looking for a pack i can use for urban and country travel… long flights when i have to, but more train and public transport and long walks. i will be away for about two months this time, longer next time. my travels almost always include some city and country adventures. i tend towards 25 – 32 litre bags size at the most.

i used to go on long hiking backpack trips in the Sierras and found ‘load lifters’ on shoulder straps the best adjustment for shifting the weight off my shoulders and onto my hips keeping the pack close to my body.
you appear not to use them on your packs. please explain. what am i missing? your bags are very well made. i am looking at the alpine rucksack as it looks to be the most comfortable.
i look forward to hearing from you.
kind regards,

TB Crew - November 19, 2019

@Avinash Hi there!

It is 50kg/m3 or about ~3lb/ft3. Hence the name EV"50".

TB Crew - November 19, 2019

@jules jules,
This is an excellent question, and one we’ve actually just answered in the FAQ for our Synik backpack. Load lifters are somewhat ubiquitous on large internal frame and external frame packs and, on those packs, can be very useful; their application or utility on smaller packs is, in our opinion, of dubious merit.

From a guide to backpacks:
“Load Lifters – Part of the shoulder strap and is used to lift the pack’s weight off the shoulders.”

There’s something akin to a “sky hook” in this concept of how load lifter straps function: how, exactly, does the load get “lifted”? Where’s that weight going? Who, if not the wearer, is lifting this weight? Who, if not the doer, is performing the action? Does free will exist? We digress.

With a large capacity external or internal frame pack, there can be some advantage gained by cinching the top of the load closer in, towards the user’s shoulders, and thus closer to your center of gravity, and some folks swear by load lifters on the big packs they carry.

With an entirely frameless pack, there’s nothing rigid for the top end of the “load lifter” to pull against, and when you tighten these straps you end up simply distorting the soft, unstructured top portion of the pack, distending it over your shoulders to no avail. That applies to packs like the Synik, Guide’s Pack, and Synapse as well, where the internal frame ends roughly where the padded shoulder straps attach and does not continue any higher up (as a frame/frame sheet typically would in a larger pack intended primarily for extended backcountry use).

Our backpacks have a shorter internal frame because they’re fairly small daypacks: if we added “load lifter” straps to our daypacks, they wouldn’t really help “lift” any weight – it’d just distort the soft top of the pack and would do little or nothing to keep the pack’s weight closer to your center of gravity. On the other hand, if we made the internal frames used with our packs longer (taller), extending it higher than the top of the shoulder strap attachment point, it would, in our opinion, start it down a path of becoming a backpacking pack, rather than the travel, EDC, and day-hiking packs we intend them to be.

Hope this helps a bit and we welcome any follow-up questions, observations, or feedback.

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