Home / Gear Reviews / How to Choose / Internal Frame Backpacks vs Frame Stays: Which is Better?

Internal Frame Backpacks vs Frame Stays: Which is Better?

When choosing between lightweight multi-day backpacks, which is better: a backpack with an internal frame or one with frame stays? It’s a question that confuses many backpackers who want to lighten their backpack weight but want to retain the comfort and load-carrying abilities that an internal frame backpack provides.

In many cases, backpacks with frame stays will be as good as those with full backpack frames, provided you’re carrying loads under 30 pounds. But there are so many different types of backpack frames available today, that it’s difficult to make a blanket comparison like this without understanding how internal backpack frames work and the strengths and weaknesses of different frame types. That way you can decided for yourself.

Backpack Frames 101

There are a wide variety of frames used in internal frame backpacks. Some are simple sheets of plastic or wood, some are 360-degree wire loops, U-shaped loops, wishbone-shaped, or strips of vertical and horizontal metal that have been welded together into a reinforced cage.

Despite these form factor differences, all internal backpack frames serve a common set of functions:

  1. Protect your back from the contents of the pack’s bag (back protection).
  2. Prevent the pack bag from collapsing on itself when it’s loaded (backpack shape)
  3. Help transfer load to a hip belt, if your pack has one (load transfer)
  4. Provide an anchor for load lifters, if your pack has them (load lifters)

1. Back Protection

The contents of your backpack can cause discomfort if they poke you in the back or “barrel” into it. For example, if you carry a hard bear canister inside your backpack, a good frame will prevent its edges from poking into your back. The same holds for barreling, where an overstuffed pack bag forms a curved and hard barrel shape that can press down on your spine, making it uncomfortable to carry. A backpack frame can protect your back by forming a hard barrier against these objects or by creating a gap between your back and the pack bag to prevent any discomfort.

2. Backpack Shape

A backpack frame helps maintain the shape of your backpack and its height when you load it up. If you didn’t have a frame, your pack bag would just be a shapeless cloth sack that would fall over on itself when you fill it up. But having a frame helps preserve its shape and makes it easier to pack or find stuff in the pack. A backpack frame also helps preserve the torso length of a backpack, which is one of the key determinants of a well-fitting backpack. Without a frame, the torso length of a backpack shortens when it collapses on itself.

3. Load Transfer

A backpack frame will help transfer the weight of your backpack onto a hip belt if the frame is connected to it. Most internal frames slot into a hip belt or the hip belt is attached to the sides of the frame, which is common on many ventilated backpacks. Either way, gravity forces the load down onto your hips, which is what you want if you’re carrying more than 20 pounds because your legs are the strongest muscles in your body.

4. Load Lifters

Load lifters are designed to tilt a backpack frame forward slightly to transfer more of a pack’s weight onto your hips and off your shoulders. Load lifters have to be anchored to the top of a backpack frame, preferably a horizontal anchor, to accomplish this and not the pack bag itself.

Internal Backpack Frame Examples

Here are some different types of backpack frames to give you a better feel for how they work and their strengths and weaknesses vis-a-vis these four functions.

Framesheets

Examples for framesheets
The Mountainsmith Zerk 40 (left) has a soft foam frame sheet, while the Granite Gear Crown2 38 (right) has a thin and flexible plastic framesheet

Some manufacturers use lightweight and flexible foam, plastic, composites, or even wooden sheets as frames. These provide varying degrees of backpack protection depending on how stiff they are. Foam framesheets and thin plastic framesheets can be pretty ineffective on that score, although they can help create a backpack shape that’s easier to pack and doesn’t collapse on itself. Their load transfer abilities and load lifter effectiveness depend on how stiff they are, which is why you typically find them used for backpacks designed to carry lighter loads. Stiffer framesheets are better for carrying more weight, but they’re usually much heavier.

Wire Perimeter Frames

The Osprey Exos (left) and Osprey Levity (right) have wire perimeter frames that enable ventilation cavities

Wire perimeter frames are commonly found on ventilated backpacks like the Osprey Exos, Osprey Atmos AG, or the Gregory Zulu. They’re metal rods that have been bent into a curved 360-degree shape, making it possible to create a cavity behind your back so air can flow through. They’re very rigid and have horizontal anchor points on the top and bottom of the frame, with a cross-bar for anchoring the shoulder straps. They provide excellent back protection since your back has an air cavity behind it and doesn’t touch the pack bag, and they provide great load transfer since hip belts and load lifters are can be attached to the side or top of the frame. But these ventilation cavities can intrude into the pack bag, reducing their volume, and making it hard to find items packed in them.

Tubular frames

The Gossamer Gear Gorilla 40 (left) and Sierra Designs Flex Capacitor 40-60 (right) have tubular frames that are held firmly in place inside their pack bags.

Tubular frames can be quite lightweight and rigid, particularly if they’re fitted very tightly into a pack and slot down into the hip belt.  While tubular frames are similar to wire perimeter frames in appearance, they don’t form a complete 360-degree loop. Tubular frames vary widely, however, as you can see from these examples. Comfort-wise, they’re good at preventing barreling but are usually augmented with padding sewn into the pack bag or inserted into a pocket to prevent sharp objects from poking users in the back. Otherwise, they’re good at preventing the backpack from collapsing on itself, they make it easier to pack and find stuff inside, they transfer weight to a hip belt if they’re connected directly to it, and can provide an anchor point for load lifters depending on how they’re oriented.

The 3400 has two aluminium frame stays that slot into stay pockets behind the shoulders
Most Hyperlite Mountain Gear backpacks have two aluminum frame stays that slot into stay pockets behind the shoulders. Their larger volume 4400 and 5400 cubic inch backpacks also include a sewn-in foam pad for added comfort and protection.

Frame Stays

Frame stays are vertical strips of aluminum or carbon fiber that are inserted into long pockets inside a backpack and behind your back. Most backpacks that use frame stays will use one central stay or two side by side stays. They’re usually pre-shaped to match the curve of your back although they can be bent further to fit your body shape.

Frame stays are often used by ultralight or lightweight backpack manufacturers that focus on selling backpacks to users who are carrying 30 pounds of weight or less. The argument has always been that you don’t need a heavy and rigid frame for carrying a 20-30 pound load and there is some truth to that, although it varies by backpack and what you have to carry inside of it.

While frame stays provide your back with some protection from a pack’s contents, that’s not their greatest strength. Their primary function is to maintain a backpack’s shape and prevent the torso length from collapsing when you load it up. They will also help with load transfer if they slot into a pack’s hipbelt, preferably a hip belt that’s sewn onto the pack bag. Many backpacks that use frame stays don’t have load lifter straps because they’re not deemed necessary on a lightweight backpack or there’s no solid place to anchor them on the pack.

The Catalyst has two pre-bent aluminum stays that terminate in the packs lumbar pad. They're accessible inside the main compartment so you can shape them further if you need a more personalized fit.
The Catalyst has two pre-bent aluminum stays that terminate in the pack’s lumbar pad fitted to a foam panel for increased comfort and back protection. They’re accessible inside the main compartment so you can shape them further if you need a more personalized fit.

Some pack makers will combine a foam or plastic framesheet and a frame stay together to complement each other. That’s a good way to combine the benefits of both in a backpack. For example, the ULA Catalyst which can carry 40 pounds loads, has a frame consisting of two frame stays for added stiffness and load transfer, combined with a foam pad for improved comfort.

Summary

Frame stays can provide many of the same functions as an internal frame backpack for lighter loads between 20 and 30 pounds, and in some cases even higher. For example, they can provide protection for your back from sharp-angled objects like the sides of a bear canister or cookpot, although this ability is enhanced when they’re combined with a framesheet made with foam or hard plastic. Frame stays also help stiffen a backpack so it maintains its length and shape when loaded. They can also assist in load transfer to a hip belt if they connect directly to it and the hip belt is rigid enough to handle the weight, but may have limited utility as load lifter anchors depending on how they’re positioned on a backpack.

Editor's note: Help support this site by making your next gear purchase through one of the links above. Click a link, buy what you need, and the seller will contribute a portion of the purchase price to support SectionHiker's unsponsored gear reviews, articles, and hiking guides.

Most Popular Searches

  • news for you
  • section hiker
  • backpacking gear reviews

24 comments

  1. Great article…..I guess it is one more reason to buy your pack last. I found this out the hard way.
    Thumbs up!

  2. Great info. I love the Exped Lightning frame design…a single alloy stay in the center with a small “tee” bar on top. Very elegant and functional design.

  3. I need to get a bag with bigger volume than my HMG 2400 and I’m torn between an Ohm 2.0 and a Seek Outside. I love the idea of an external frame and don’t mind the slight extra weight but I’m concerned that the width of the frame is just too big. Conversely I’ve heard that the Ohm needs to be packed very specifically to not have things poke into your back because of its (innovative) inside carbon loop. Any thoughts on this Phil?

    • That’s quite a divergence of options. I just measured by SO Unaweep frame and it’s 14″, which isn’t really that wide although it is about 2″ wider than your HMG 2400. The SO backpacks are definitely less fussy to pack than an Ohm 2.0.

      • Yes, it is a divergence, I agree. I am just narrowing down from many evaluations of different packs, prices, etc. The HMG 2400 is actually about 10 (more like 10.5), not 14″, unless I’m totally mismeasuring the pack.

        Do you find a SO Gila or Divide comfortable and low-proflie when they’re underpacked as well as fully packed? Thanks again.

      • Nope. They’re pretty annoying when under-packed. Lots of extra fabric.

    • If you’re moving from an HMG2400 then an OHM isn’t going to be too much increase in volume if that’s what you need. A ULA Circuit would make more sense if you’re looking for a greater volume pack with better load carrying abilities. In my experience, the circuit carries any load better than an ohm even though it weighs ~8oz more. I have a stripped down Circuit weighing in at 32oz and it’s a great volume for winter gear up to 40lbs max. It swallows gear. My experience at least.

      • I’ve thought about the Circuit but I like the Ohm pocket and side bungee more, especially if you get the Y-strap. I recognize its not that much more than the HMG2400 but the outside pockets are substantially bigger. The Circuit looks like it would sag a lot more if underpacked as your food grows smaller, or depending on different seasons… My issue is really that every trip has such a different combination of *volume*, even if baseweight and total pack weight stay relatively constant.

    • Im curious why you aren’t looking at the HMG 3400?

      • I’ve thought about it, but its one of those things.. if I’m already buying a new pack, maybe I should go more different than just the same bag with 10L more of volume.

  4. Excellent essay & illustrative photos on the various internal frame styles. Your “frame sheet” description is perfect.
    I have that green Osprey EXOS 58 and love its comfort.
    ->My Thermarest sit pad (only half of one) sits in that space behind the trampoline back mesh. Perfect location for it.

    -> I added two 1″ wide aluminum contoured stays to a 3,500 cu. in. Camelbak Commander hunting pack AND an REI padded hip belt so I could carry up to 40 pounds of emergency overnight gear mostly on my hips for backcountry skiing. I bolted these stays through the wimpy plastic frame sheet with stainless steel bolts, washers and Nylock nuts. It has held up to constant training hikes for the past 6 years showing no signs of wear!

    • Good evening Phillip, thank you for all the work you put into this site.
      I have a granite gear crown 2 60 that I love. You reveiw really helped me deside on this pack.thank you ! It fits me perfectly. So well in fact that I’m going to buy a crown 2 38 liter for summer loads. Just waiting for them to go on sale before Christmas.
      I read somewhere on the internet that the frame sheet for the granite gear blaze 60 ac. Would fit the crown 2. Allowing the crown 2 to handle 40-45 pound loads.

      Is this true ?

      • I doubt that will work, but if it does you should tell me.
        The blaze frame pocket has to be open for the shoulder straps to come out. There’s no provision for that on the Crown2 series packs.
        I love my Crown2 38. I use it a lot for shorter hikes and in winter, since it’s so easy to attach snowshoes to it.

  5. This is a nice overview of pack support systems. Not sure i’ve seen such a comprehensive comparison before.

    For multi-night outings, i’m still waiting for my yet-to-be-realized, ideal pack with a perimeter frame, ample outside pockets, and a total weight of 2–2.5 pounds.

    I’m continually evaluating my pack contents, and while the trend of overall weight is downward, i still seem to always have more weight than i’d like. And, coming from a background that includes a lot of trail miles with an old-style, external-frame pack, there’s just a certain comfort/familiariy level that makes me reluctant to give up that structure.

    I’m liking my current North Face Banchee 65, which has an aluminum perimeter frame and ample pocketed storage. At about 3.5 pounds, it’s not *that* heavy for the comfort and features it offers. It’s very comfortable for me, even loaded up with 42 pounds or so.

  6. Canadian Trail Captain / Hike Leader

    Nice article indeed . My experience is not to discount some military packs that are available out there . These packs have come along way from the Alice frame days . If you are carrying heavy weights long distances you might want to capitalize on the experience these packs have proven over the decades . I routinely carry 30kg ( 66lbs ) 10 – 20 km in my TacGear from Deuter . I use a karrimor and a USMC Propper of larger capacity for longer trips . All these packs have made carrying loads on the hips an art . I have never had a malfunction , something you would expect from military kit . They also have enough attachment points to tackle any load like first aid kits to skis and snow shoes . These points are also on practical balance points and all have openings for water bladder lines . Happy trails !

  7. In reply to Corbin (if it helps): I have a Mariposa for lightweight trips and a Seek Outside Divide for heavy haul trips (eg: camping and climbing gear). Both are (for me) outstanding packs. I did the JMT with the Mariposa and a Klymit airbeam which was very good at keeping the bear cannister off my back. The Divide (purchased after reading the guru Werner’s review) has been superb at load hauling, and being in the UK, I rather like the waterproof fabric. It is very adjustable.
    In terms of the inflatable stays – I think the manufacturers are missing a trick. A couple of times I have turned a load carrying pack into a very flexible climbing pack by simply deflating the airbeam.
    By the way, thank you, neighbours across the pond, for producing such good gear.

    • I thought the Mariposa was going to be the next step in my evolution toward lighter packs. I was excited to see it go on sale a few months ago, so ordered one up. (And it has pockets! Did i say i like pockets?)

      But, i was disappointed that the padding on the waist belt did not extend far enough forward to cover the pointy part of the pelvis bone that is covered by the padding on every other waist belt i’ve ever worn. Fell about two inches short. Dang.

      I asked GG if they could do any kind of a custom waist belt with extended padded, and they said no. I’ve read, but haven’t corroborated, that some of their stuff, including the packs, is now assembled in Vietnam, so, if true, that might explain their inability or at least unwillingness to provide a customized solution. So much for cottage-industry service.

      • Before Vietnam, it was Mexico. They haven’t made their own gear for years and years. They’re also too big, in terms of revenue, to really be considered a cottage company.

  8. Another great article Philip!

  9. Very good article and explanation of frame types. Wire perimeter frame packs are to me external frame packs 2.0 (or a hybridized version of an external frame). I have an external frame pack that weighs in at 75 oz or roughly 2 oz more than the Osprey Atmos 65. I also have a couple of internal frame packs, each has advantages.

  10. great article
    thanks

Leave a Reply

Your email address will not be published. Required fields are marked *