From Trek’s King of the Mountain blog:

The active brake pivot puts the rear suspension pivot concentric to the rear wheel axle, as opposed to Trek’s current design or the ‘Horst’ link where the pivot is located above (Trek) or Below (Horst) the rear axel.

What is the Benefit?
-The ABP keeps the suspension active and the rider in control while braking. Lock-up, or stiffening of the suspension under braking is virtually eliminated. Skidding is reduced; the tire stays in contact with the ground. Because the tire stays in contact with the ground, the brakes are more effective when they are used, and thus the time spent braking is reduced. Less braking also equals better handling and suspension by not loading the front fork.

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