9/1/2023 0 Comments Fox 3 stacks![]() Handling should be tuned by the sway bar since that is it’s primary responsibility. Shocks and springs are the only tuneable elements that control performance over the various suspension events and should be tuned to provide the best ride possible. Although shocks and springs will impact handling, but that should not be their primary responsibility. Handling is a tricky one, digressive valving will provide better handling than progressive valving due to the higher force at 2 in/sec. Progressive shock valving will feel out of control because the suspension will bottom very easily and then spring back up very easily. On G-Outs and other slow speed bottoming events digressive shock valving will feel firm and controlled. G-Outs, Towing and Overloading The Suspension: A shock with a progressive rebound damping curve will always feel like the wheels and chassis are disconnected, making for a potentially bouncy ride. 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 digressive shock will start by pulling the chassis into the series of bumps before hitting the speed to freely let the wheel move. On rebound the wheel might move around 50 in/sec. An extremely progressive shock on the other hand will feel smooth and controlled. A digressive shock may blow off so much load that it can’t sufficiently raise the chassis. 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. 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. Because the movements are small tire pressure and tire stiffness can play a large roll in ride comfort. From the graph we can see that digressive pistons would be stiff and possibly harsh while progressive shocks would be very smooth. As a result these forces often happen around 2 to 10 in/sec on both compression and rebound. Because the movements are so small the valve disks may not have a chance to open. Small bumps and small washboard cause the wheel to make very fast, but very small movements. In the examples below it is assumed each of the shocks are well designed and very digressive or very progressive in order to explain the differences. ![]() Creating the perfect damping curve is all about making the right trade offs to achieve the correct performance across all suspension events. Shock design and tuning can impact performance on small bumps/washboard, large bumps/whoops, g-outs, and handling. ![]() If they were compression loads they would likely intersect around 100 in/sec. If these were rebound loads, and the shocks were tuned for the same vehicle they would likely intersect around 10 in/sec or less. The graph below is data directly off a shock dyno and is used for illustration purposes only. Most Fox shocks and most King shocks are linear, while most Icon shocks and entry level Bilstein shocks (5100 & 6100) are digressive. The terms Digressive, Linear, and Progressive refer to the shape of damping curve produced by a shock (as seen below). Shocks can be digressive on compression, rebound or both, and each has it’s own pro’s and cons. Performance of Digressive, Linear, and Progressive shocks: As a result AccuTune Off-Road is uniquely familiar with the real world pros and cons of each type of shock, how to tune them, and their proper applications. During that time he used state of the art shock dyno’s to design and/or tune premium shocks purchased by nearly every lift kit manufacturer. Our Founder and author of this article, Ryan Raker, has been designing, tuning, and manufacturing shocks with digressive, linear and progressive damping curves since 2001.
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