We were first made aware of cam lean at an ATA Show seminar in 2012. Prior to this bow designs meant that it wasn’t as much of a factor in tuning as it is now.

The term cam lean refers to the position the cams need to direct the power stroke to be in in-line with the arrow.

Cam lean is easy to see when paper tuning. If is out there will be a left or right tear in the paper. This assumes you can shoot with good form, and the bow had been set up in regards to cam timing, nocking point and centre shot.

As a generalisation, for most bows built prior to 2010 an errant paper tear was easily corrected by simply moving your arrow rest left or right. In the Easton Arrow Tuning and Maintenance Guide last updated in 1999, it only mentions moving the arrowrest or trying a different spine to eliminate horizontal paper tears. Now this will not help you. You need to physically adjust the position of the cams.
Today all reputable compound bow manufacturers recognise the importance of cam lean and provide the tools to optimise the position of the cams so the bow shoots as well as it can.

Early methods to adjustment cam lean were to put twists into and out of the split yokes of the bus cables. Twists into the right for a right-hand tear and the opposite for a left tear. As bow designs evolved, many models went away from adjustable yokes, hybrid and binary systems.

Mathews for example have a floating yoke so the only way to move the cam is to shim it to the left or right using spacers. Mathews make it easy with the use of their Top Hat shim system. PSE use easily removeable spacers to move the cam over. It’s very simple and effective. A bow press is required to shim the cams on Mathews and PSE bows. A press is also required for a split yoke system.

Bowtech bows with the DeadLock system fitted allow the cam to be moved left or right without a bow press, it’s an innovative system.

Once you have adjusted the cams to where they shoot a bullet hole through paper you can move onto broadhead tuning.