Instructor Tutorial: How to Choose Cam Sizes for Trad Climbing
In this tutorial from Mountain Skills Academy and Adventures, the instructor demonstrates a practical way to estimate cam sizes using your fingers, hands and familiar crack-climbing jams.
The technique connects the width of each cam with a personal reference point on your hand. With practice, recognizing the hand position that fits a crack can help you select a likely cam size more quickly and reduce repeated attempts with different pieces of gear.
Step 1: Get Familiar with Your Cams’ Placement Ranges
Start by handling the cams on your rack and learning their recommended placement ranges.
Pull back the trigger to bring each cam into an appropriate placement position, following the manufacturer’s instructions. Compare its width in that position with your fingers and hand.
This gives you a reference for the space the cam needs when placed appropriately.
Step 2: Match Cam Sizes to Your Hand
Compare each cam with different parts of your hand, such as your fingertips, knuckles, flat hand or cupped hand.
Some of the instructor’s personal examples are:
| Cam size | Instructor’s hand reference |
|---|---|
| 0.5 | Just before the third knuckle |
| 0.75 | The third knuckle and fleshy part of the hand |
| 1 | A flat hand |
| 2 | The hand in a hand-jamming position |
| 3 | A large cupped hand |
These examples reflect the instructor’s hands and equipment. Build your own comparisons using your hands and the specific cams on your rack.
Step 3: Connect Cam Sizes with Familiar Jams
The instructor also suggests linking each cam size with a crack-climbing jam you recognize.
For example, if a crack accommodates a familiar hand jam, you can use your personal size reference to narrow down which cam to try. This connects the feel of the crack with your gear selection.
Step 4: Practise Selecting and Checking the Cam
Practise the technique at ground level. Estimate the crack size using your hand reference, select a cam and assess how it actually fits.
Repeat the process with different crack widths and hand positions. Use each attempt to refine your comparisons and become more familiar with your equipment.
Final Check
After choosing a likely cam size, assess the actual placement:
- The cam sits within its manufacturer’s recommended operating range.
- The lobes make appropriate contact with the rock.
- The rock and crack conditions are suitable for the placement.
- The cam is positioned appropriately for the expected direction of load.
Hand measurements help you estimate which cam to select. A sound placement also depends on these additional checks.
Safety Note
Practise cam selection and placement under the supervision of a qualified climbing professional. Follow the instructions for your specific cam models and learn how to assess the complete placement.
Use the hand-sizing technique to improve your gear selection while continuing to inspect every placement carefully.