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 decide 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

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

Wire perimeter frames are commonly found on ventilated backpacks like the Osprey Exos, Osprey Atmos AG, or the Zpacks Ultra Arc Haul. 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 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

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.

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.

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.

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