Seal System

Though there are many types of sealing arrangements, there are five main basic parts or elements in a seal system: a dust seal, a stopper ring, an oil seal, a backup ring and a slider bushing. Each performs a specific function.

• Dust Seal: It consists of a simple rubber or plastic ''grommet'' at the place where the two halves of shock assembly come together. Its main purpose is to keep dirt and debris away from reaching the actual oil seal.
• Stopper Ring: Usually, a stopper ring is a ring of steel spring wire or a large C-clip which is fitted in a machined groove in the shock housing below the dust seal. Its purpose is to keep the seal below it from being forced upward and out of position by the force of the springs during shock compression.
• Oil Seal: The oil seal lies below the stopper ring. Usually, they are made of steel with a rubber cover. It is usually pressed or ''hammered'' into its seat in the housing by a specially-fit driver. Its main purpose is to keep the fluid inside from leaking out and to keep the dirt out.
• Back-up Ring: The back-up ring is below the oil seal. It looks like a big washer. The main functions of the back-up ring are to abate the upward forces against the seal and make them to spread evenly over the sealing surface. It also protects the seal from the slider bushing being driven too far up the tube and into the rubber parts.
• Slider Bushing: The slider bushing is a sort of ''tilted pad'' bearing. It creates a compression zone from where the oil can form a low-friction film between the shock tube and the housing. It is usually made of brass.