Shocks are an important component on all off-road trucks, giving them the ability to negotiate all types of terrain and obstacles safely and comfortably. Shocks can come out of adjustment after a while and need tuning. Thankfully, it’s fairly easy to tune many simpler types of shocks right at home without needing to drive your truck to the shop.
Below is some basic information about shocks and how to tune them so your ride is as sturdy as it needs to be without the risk of your wheels interfering with your truck's body or steel bumpers as you hit the hills.
How Shocks Work
To be able to tune the shocks on your off-road truck, you first have to understand how they work. Shocks reduce the movement of a vehicle’s suspension to provide a more comfortable, less jarring ride. They do this by compressing to force shock oil through small holes in a shock piston, converting movement energy into heat energy.
Designed with a piston at the end of a shaft, each shock has a shim on either side of the piston that controls the flow of oil through the piston based on the movement of your off-road truck. The shims control how much oil passes through the pistons, how much the shock compresses, and how quickly it rebounds again.
Shock Shim Stacks and Valving
Standard shims, also called valve discs, are stacked pyramid style over the top and bottom of the piston, getting progressively smaller the further they are from it. The stack at the top of the piston controls rebound tuning, while the one under the piston controls compression tuning.
The harder the pressure on the shock and the more oil that is pushed through the piston from the shaft, the more the shims in the stack apply opposing forces to the oil to dampen shock movement. Shims are made in various thicknesses depending on what is in your off-road truck to provide differing levels of valving as needed.
Adjusting the Valving
Valving is the adjustment of how much oil passes through the piston and between shim stacks on a shock as well as how much compression is required to push it through. It is essential to correctly tune the valving so the shock performs correctly, dampening the movement of oil through the piston in either direction in order to prevent overheating and then degrading of the oil.
Although a standard shim stack configuration generally works in most situations and at most speeds of your off-road truck, there are times when more accurate tuning involves something a little more detailed. Different stack configurations that deviate from the pyramid stack can allow greater movement of oil through the shock or apply more pressure to slow it. Valving that permits more movement of the shim creates a softer shock, while reducing flexion of the shim makes the shock harder.
Shim Stack Variances
Using this idea, a flutter shim stack that has a short shim directly under the top shim allows greater movement of the longer, top shim. A doubled shim stack reduces movement, requiring much more compression to push oil through the piston. Besides shim stack configuration, shims or discs are also available in various shapes that include bypass cutouts to provide additional means for controlling compression and oil flow through the shock. Knowing this, proper tuning depends on creating the right shim stack that will offer the required degree of compression and rebound for the vehicle while preventing shock oil from overheating.
With a good understanding of how shocks work and how valving is done to create the desired compression and rebound balance, off-road truck owners who enjoy working on their own truck can tune their own shocks to keep them functioning properly. You’ll need to research suggested settings for the specific shocks on your particular off-roading truck to achieve the adjustment you want. The good news is that doing so is as easy as removing the shaft nut and modifying the existing valving parts!