THEE 99% Let Off. How we achieve it. How to set your Concept Bow to 80% let off.

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THEE 99% Let Off. How we achieve it. How to set your Concept Bow to 80% let off.

Postby ca-archer » Wed Dec 20, 2017 9:08 pm

Remember, that it is the simple things in life that we often miss seeing.

Since the invention of the compound bow, let off has been on the rise. It was the let off of the compound bow so many years ago, even at approximately 30%, that was so great and beneficial to the archer. In the past few decades extreme high let off has been tried in many way and a few may have very well even achieved let off as high as 99%. Most of these tried methods were through the eccentrics (cams) and were extremely complicated. Settings and adjusting were often difficult to achieve by the manufacturer and near impossible for the bow technician behind the counter at your local archery shop.

bottom-axle-99-percent-let-off-concept-archery.jpg (20.26 KiB) Viewed 1890 times

Concept Archery achieves the 99% let off through a very simple, patented, bottom axle design. By having an over-sized axle of hardened steel, and then removing a portion of it, the bus cable can now come ever so near the center point of the bottom axle. The closer that cable gets to the center pivoting point, the higher the let off. Reverse the bottom axle with the U cut-out facing towards the archer, and the bus cable during the last of the draw cycle now hits the back of the axle where the hardened steel is not removed. The cable is stopped before the center of the pivoting point, or the “99% let off sweet spot”, and so the bow will only reach 80% let off.

bottom-axle-80-percent-let-off-concept-archery.jpg (16.87 KiB) Viewed 1890 times


To do this, place the bow in a press and slightly take the pressure off of the limbs. Just enough for the string to go slightly limp. Remove the 3/16” e-clip. IMPORTANT: from the left side, use a metal punch and hammer to lightly tap on the bottom axle. DO NOT at any time pull on the welded clip on the right hand side. Once the clip portion is out enough to rotate the bottom axle 180 degrees, stop. Rotate the bottom axle and push it back in. The clip has two settings 99% let off and 80% let off. Put e-clip back on (make sure it's secure and seated), check that your string and cables are correct and in their track, and slowly depress the limbs.

We ask that if anyone ever sees a bow with a similar bottom axle to please contact us. All of Concept Archery's contact information, including email can be found at

Concept Archery's "99% Let Off" is even mentioned on Wikipedia under “Archery” as foot note number 32.

Once you shoot and/or hunt with 99% lef off, you won't want to shoot anything less.

As a side note the hardened steel is extremely strong, but welding hardened steel to the stainless steel clip is difficult to weld as one – please don't pull on the clips!

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