External frame packs are easy to spot. They have aluminum tubes on the outside of the pack’s compartments. Internal frame backpacks look like duffel bags that hug the hiker’s back. The “frame,” which is usually some sort of metal stay, is sewn into the backpack.
In both cases, the purpose of the frame (the stiff part) is to distribute weight vertically so that all the weight doesn’t sag to the bottom of the pack.
The external frame pack is the historical standard. Internal frame packs came to backpackers via the mountaineering world, and became popular in the 1990s with backpackers, as well. By the late 1990s, the internal frame packs completely dominated the market for higher-end and long-distance backpacks. But the humble external frame pack still has some advantages.
Advantages of an Internal Frame Backpack
- Most hikers find internal frame packs more comfortable because they hug the body and keep the center of gravity closer to the hiker’s natural center of gravity. This is especially true for women, who have a lower center of gravity than men.
- The suspension system of most good quality internal-frame packs is highly adjustable, making it possible to shift different proportion of the weight to the hips or shoulders.
- Internal frame packs have pockets and compartments, and room for all, or almost all, equipment to go inside, where it stays dry and protected. This means that gear strapped to the outside won’t bang against bushes, rocks, and other obstacles when traveling through rough terrain, hiking cross country, glissading, or rock scrambling.
- Internal frames often have extra pockets and pouches which can be affixed to the pack, or not, making it expandable for larger loads.
- Multiple compartments keep gear organizied and findable.
Advantages of an External Frame Backpack
- External frame packs are a better choice for young hikers and growing teens. The frames can be adjusted, meaning that as a child grows, the pack can grow, too.
- External frame packs are less expensive, making them a better choice for families on shorter outings.
- External frame packs have all kinds of places to lash extra stuff, making them a good choice for a family that needs flexibility; Mom or Dad can take extra weight when Junior gets tired and cranky.
- External frame packs compete favorably in terms of weight with external frame packs designed to carry the same amount of weight. This is because the suspension system of the internal frame packs is heavier than a couple of hollow aluminum poles, which is what external frames use.
- External frame packs are preferred by some hikers in hot and/or humid weather because they offer better ventilation between the back and the pack.
There is a third choice, although it’s much less common. The frameless pack is basically a duffle bag with a waist belt and shoulder straps. This choice is best used by ultralight hikers who are carrying very little weight, and have learned how to distribute it properly. Some manufacturers of hiking gear also make packs with minimal frames (little more than a couple of light plastic stays sewn into the pack). Again, these are best suited for light loads. A hiker who carries too heavy a load with a frameless pack or a light-frame pack is asking for a pain in the neck.
There’s no single right answer to the external versus internal debate. Most high-end manufacturers and hard-core hiker-mountaineers have gravitated to internal frame packs. But external frame packs can offer good value, especially to families and hikers on a tight budget.