How to Check the Cam Timing on a Compound Bow

Bow hunters and other archers know the advantage of the compound bow over its more traditional ancestors. Its pulley and cable network allow for increased arrow projection with less expended brawn. Key to such results is the presence of one or two cams in the bow's design. These rotors put tension on cables when the drawstring is extended -- in effect replacing human strength with mechanical power. To perform this job with maximum effectiveness, the cams must be properly timed and synchronized. When they roll over correctly, the laws of physics will favor the shooter.

Instructions

    • 1

      Pull the string to a full draw, while watching the cams roll over. Any difference in speed or position indicates a timing problem.

    • 2

      Re-set the nock point if your arrows are repeatedly landing too high or low. The nock point is where the string meets the arrow groove. Adjust the bolt on the upper limb of the bow if your arrows are high, and the lower if they are undershooting the target. Your cams may possibly work with better coordination after this adjustment.

    • 3

      Mount a piece of paper on a stand several feet in front of a target. Shoot an arrow through the paper while aiming at the target. Examine the paper: the cuts made by the arrow's perforation should be somewhat even and symmetrical, as though a bullet passed through. If any tears extend high or low, your cams will need to be re-timed.

    • 4

      Place the bow in a stationary or portable bow press to relieve tension in the drawstring and cable. Unscrew the bolts attaching limbs to the riser halfway. Twist the cable or drawstring several times, release the bow from the press, drive the bolts back into position and examine the bow again at full draw.

    • 5

      Conduct another paper test to see the effect of your adjustments. Repeat the cable and string manipulations until you achieve an acceptable bullet pattern in the paper test.