Cam timing: how to check a compound bow
Cam timing describes whether a compound bow's cams are in the positions specified for its draw cycle. Synchronization describes how the cams work together, often checked by comparing draw-stop contact at full draw. The correct check depends on the cam system. Use the model's manual and have a qualified shop handle cable or press adjustments.
Recognize symptoms without assuming the cause
| What you notice | Why timing may be checked | Other possible causes |
|---|---|---|
| One stop contacts before the other | The specified full-draw relationship may be wrong | Mismatched modules or incorrect stop positions |
| The full-draw wall feels different | Stop contact or cam rotation may have changed | Draw-length setting or technique |
| A repeatable vertical paper tear | Nock travel can be affected by the cam system | Rest contact, nocking height or arrow mismatch |
| Vertical groups change after cable work | The setup may differ from its previous state | Changed anchor, peep position or rest setting |
The wall is the limit you feel at full draw. A different wall can make you alter how hard you pull against it, which adds another variable to the shot. Record what changed and when, especially after new strings or cables, or a change to the cam modules that set draw length.
A poor score alone is weak evidence. Inspect obvious loose parts and damaged components first, then compare the setup with the last known record. If you see cable damage, abnormal cam tracking or a component coming loose, stop shooting and have the bow inspected.
Start with the model-specific reference marks
Some cams have marks, holes or cable reference positions that help assess rotational position. Read the manual to learn where the bow should be in the draw cycle for that check. A mark observed at brace, when the bow is undrawn, does not automatically confirm the relationship at full draw.
Compare the correct reference for your installed module and draw length. If the system uses paired modules, verify that their settings and stop locations match the manufacturer's intended arrangement. Do not assume that similar-looking holes on two different cam models have the same purpose.
Take clear photos of visible reference marks while the bow is safely at rest. Keep the camera and your hands away from loaded mechanisms. Those photos can help a technician compare the setup, but they cannot replace a full-draw check when the maker requires one.
What a draw-board check involves
A draw board holds and draws the bow under controlled conditions so a trained technician can inspect the cams and stops. The board, attachment points and retaining system must be suitable for the bow. Follow both the board instructions and the bow maker's procedure, including any arrow and containment requirements.
- The technician confirms the bow model, modules, stop arrangement and condition before loading it.
- They secure the bow with the approved retention method and keep people clear of the string, limbs and arrow path.
- They draw slowly toward the specified full-draw position and observe the relevant stop contacts or reference marks.
- They lower the load under control before touching or adjusting any component.
On many two-cam systems, the specified stops should contact together. Some systems use a different reference or an intentional relationship set by the manufacturer. Do not pull harder against the first stop to force another one into contact. That can conceal the mismatch you are trying to measure.
A person standing close to a hand-drawn bow to peer at the cams is a poor substitute for proper equipment. If you do not have a suitable board and the training to use it, ask a shop for the check. Never dry fire a bow to test its behavior.
Why cable corrections belong to a specific system
A technician may correct the relationship by adjusting the effective length of a cable or another manufacturer-approved setting. Which cable changes, and in which direction, depends on the cam system. A generic instruction to twist the top cable is incomplete because bows route and load their cables differently.
Many cable operations require an approved bow press and correct adapters. Pressing at the wrong points or beyond the permitted range can damage the bow. Keep fingers and tools away from loaded cams and cables; unload the system through the approved procedure before making any adjustment.
Changes can also affect draw length, draw weight and the position of the peep sight. Ask the technician to check the whole setup after correcting timing. A single stop comparison is only part of returning the bow to its intended specification.
Check launch and record the repaired setup
After the mechanical checks, verify nock fit, rest function and arrow clearance. A repeatable paper tuning test can show whether a launch problem remains. Then shoot normal groups at a comfortable distance before rebuilding longer-distance sight marks.
Keep a record of the modules, draw-stop settings and measured draw length alongside any shop notes. If the bow changes again, that record gives the next inspection a starting point. Report persistent tears or an unusual wall to the technician with the exact setup and observations.
Questions
Can I check cam timing without a draw board?
You can inspect accessible timing references at rest if the manufacturer provides that procedure. Those marks may not establish full-draw synchronization. A proper draw-board check is useful when stop contact must be observed under load. If you lack the equipment or training, have a qualified shop check the bow rather than improvising a restraint.
Does every compound bow need both cams to stop together?
No single rule covers every cam system. Many two-cam bows specify simultaneous contact at the relevant stops, but other designs use different references. A single-cam bow also needs its own timing procedure. Check the manual for the exact model, module and stop arrangement before deciding what a visible difference means.
Can bad cam timing cause a high paper tear?
A timing problem can contribute to poor nock travel and a repeatable vertical tear. High tears can also come from nocking height, rest behavior or clearance problems. Check those possibilities in a controlled order. Have the timing assessed if the tear persists or the bow's draw-stop relationship appears wrong.