4x4 Shock Information - Absorbing Shocks

Twin Tube: Low-end, low-pressure twin-tube technology has been around for automotive ages and has not changed much since its inception. This basic design usually has soft valving and is relatively inexpensive to manufacture, providing the reason many stock vehicles are still equipped with them from the factory. While many of these shocks are nitrogen-charged, the design has the oil and gas mixed together in the same chamber, which causes issues with cavitation, heat generation, and fading.

Monotube: A monotube shock is a high-pressurized gas shock that utilizes a single-walled shock body. Because heat is one of the major factors in decreased performance and life of shock absorbers, the monotube design extends shock life by allowing excessive heat from within the shock body to transfer to the exterior, enabling it to dissipate heat more efficiently and thereby reducing fade. Monotube shocks also provide a larger internal working area, and high-end monotube shocks have a dividing piston that permits oil to expand as heat builds up, preventing cavitation and viscosity loss, helping the shock to maintain full damping characteristics as temperatures rise and offering superior performance during punishing use. Another characteristic of monotube shocks is a special seal that keeps the air and oil separate, another measure that prevents foaming. Most monotube shocks are valved specifically for the application.

Adjustable: There are several different types of construction offered in adjustable shocks, depending on the manufacturer. The one thing adjustable shocks have in common is a knob, or other means, for the user to adjust valving and shock response to the vehicle they are installed on.

Reservoir: A reservoir shock is a monotube shock that carries its fluid in a large external reservoir that resembles a second shock body. Benefits of a reservoir shock include more shock fluid volume for cooler operation, and the ability to place the reservoir in a remote area to receive better airflow.

Piggyback: The piggyback shock is an entry-level reservoir shock of monotube construction, which runs cooler and more efficiently than a standard monotube because the reservoir allows for extra fluid capacity. It is also more compact than a true reservoir shock and can mount in almost any location a traditional monotube does because of its low profile design.

Bypass: Instead of a piston that allows oil to travel through it, bypass shocks use a piston that plunges fluid into external tubes. Each tube has a specific function for either compression or rebound. At the entrance to the tubes is a check valve, which is user-adjustable to control how fast fluid can flow through this port. If the user has a setting for less oil, the shock is tuned stiffer; for more fluid, and the shock is softer. On some bypass shocks, different-length tubes allow even finer tuning as shorter tubes control low-velocity movements, while longer tubes can be tuned for high-speed movements. As the piston passes the last port on the compression stroke, the remaining few inches of travel are tuned with many shims to be very stiff in order to slow the travel of the shaft.

Bumpstop-An elastic cushion used to stiffen the suspension as it nears the end of its compressed travel.

Cavitation-The sudden formation of air bubbles in shock fluid, foaming.

Compression-The action of a shock returning from an extended state.

Damper-A fluid-filled device, which regulates fluid flow to restrain movement.

Damping-The process of absorbing energy.

Nitrogen-An inert gas used to pressurize a gas-charged shock.

Piston-The solid cylinder or disk that fits snugly into a shock body cylinder and moves under force or pressure.

Rebound-The action of a shock returning from a compressed state.

Shaft-The long slender arm that connects the piston to the moving suspension of a vehicle, also known as a rod.

Shims-A series of thin, steel, round, and flat washers with varying holes, outer diameters, and thicknesses that are arranged in sequence to provide a damping effect by exerting resistance on the oil flow through a shock piston, also known as valves.

Shock body-The part of the shock that houses the piston, valves, oil, and gas.

Stroke-The travel of a shock piston and shaft.

Spring Rate-A measurement of force needed to compress the spring.

Tuning-The changing of the shocks internal shims, or valving, to match the suspension of a specific vehicle.

Valves-A term that refers to a series of shims or valve stack that are used either for the compression or the rebound damping.