Progressive vs Linear vs Digressive Shocks

Small Bump & Washboard:

Small bumps and small washboard cause the wheel to make very fast, but very small movements. Because the movements are so small the valve disks may not have a chance to open. As a result these forces often happen around 2 to 10 in/sec on both compression and rebound. From the graph we can see that digressive pistons would be stiff and possibly harsh while progressive shocks would be very smooth. Because the movements are small tire pressure and tire stiffness can play a large roll in ride comfort.

Large Bumps & Whoops:

Large Bumps and Whoops are high speed events on both compression and rebound and it’s important to think about what happens to both the chassis and the wheels.

On compression the wheel may move at 200+ in/sec and ideally the shock will do a combination of absorbing the bump and raising the chassis to prevent bottoming out. A digressive shock may blow off so much load that it can’t sufficiently raise the chassis. An extremely progressive shock on the other hand will feel smooth and controlled.

On rebound the wheel might move around 50 in/sec. A digressive shock will start by pulling the chassis into the series of bumps before hitting the speed to freely let the wheel move. For shocks with a very digressive damping curve the change in stiffness can cause the vehicle to feel as if it is loosing control. A shock with a progressive rebound damping curve will always feel like the wheels and chassis are disconnected, making for a potentially bouncy ride.

source: accutuneoffroad.com