What Are Climbing Cams? | Crack Protection Explained

Climbing cams, technically called spring-loaded camming devices (SLCDs), are the workhorse protection for trad climbers tackling crack systems. Unlike nuts and hexes that wedge passively, cams use opposing lobes that expand against the crack walls, converting downward pull into outward grip. This design lets them hold securely in parallel-sided cracks where passive gear simply won’t stay put.

How Does a Cam Work?

A cam works by converting the downward force of a fall into outward pressure against the rock. The unit has 3 or 4 aluminum lobes mounted on one or two axles, attached to a stem with a trigger mechanism. You pull the trigger to retract the lobes, slide the unit into a crack, then release — the springs push the lobes outward to grip the rock.

When weighted, the lobes rotate slightly and press harder into the crack walls. The key to this design is the logarithmic spiral shape of the lobes, which keeps the camming angle constant whether the cam is nearly closed or fully expanded. This consistent angle means the cam holds the same relative security at any point in its range.

Ray Jardine invented the SLCD in the late 1970s, and the design has remained fundamentally unchanged since — a testament to how well the physics works.

How to Place a Cam Properly

Placement quality determines whether a cam saves a fall or rips out. The process sounds simple, but the details matter.

1. Pull the trigger to retract the lobes fully.
2. Insert the cam into a crack segment that matches its expansion range.
3. Release the trigger so the lobes spring outward and contact the rock.
4. Set the cam by giving the stem a firm tug or tap, confirming the lobes bite.
5. Test for movement — a good placement holds solid without shifting when you pull on it.

This gives the cam room to tighten if the placement shifts under load while keeping enough expansion to maintain grip. The crack walls must be solid, sound rock — soft, crumbly, or hollow rock can crumble regardless of how well the cam is sized.

Cams excel in parallel-sided or gently flared cracks. They work less well where a crack narrows sharply or widens dramatically; in those spots, passive gear like nuts often provides more stable protection. For very wide cracks beyond standard cam sizes, specialized active protection such as a Big Bro may be required.

Common Cam Mistakes to Avoid

Even experienced climbers make placement errors. Watch for these:

• Over-camming: forcing a cam into a crack too small for it leaves the lobes barely open, reducing holding power and making removal difficult.
• Under-camming: placing a cam at the top of its range in a crack too wide leaves too little expansion room to stay secure.
• Poor rock quality: a perfectly placed cam fails if the surrounding rock is rotten or flaky.
• Bad crack geometry: cam lobes need parallel bearing surfaces; a wildly flared or pinching crack compromises security.
• Ignoring the extension: a cam placed behind a flake or edge can walk deeper or shift sideways under load. Clip the stem extension to minimize leverage.

Training and practice matter enormously. Wild Country, maker of the original “Friends,” treats its cams as essential safety equipment — a reminder that proficiency comes from deliberate learning, not just owning the gear.

Cams vs. Passive Protection

The distinction matters: cams are active protection because they spring into place, while nuts and hexes are passive — they rely purely on wedging. The best trad racks carry both, using each where it fits best.

Choosing Your First Set of Cams

If you are building a rack, start with a set covering the most common crack sizes you’ll encounter on local routes. A typical beginner rack includes cams from about 0.5 to 3 inches, often from the same family so the trigger mechanisms feel consistent. For a tested roundup of the best options on the market, check out our roundup of the best climbing cams — it compares the top models side by side.

Remember that cams are active protection, not a substitute for sound judgment, partner checks, or proper instruction. Compatibility depends entirely on crack size, shape, and rock quality. Take a course, practice placing cams on the ground, and get feedback from experienced trad climbers before you rely on them leads.