2 CONTENTS NEED FOR SHOCK ABSORBERS WHY GAS FILLED SHOCK ABSORBERS? TYPES & ADVANTAGESMOUNTING TIPS
3 NEED FOR SHOCK ABSORBERS Springs alone cannot provide asatisfactorily smooth ride.Oscillation of spring causes the wheel torebound, or bounce up and down.Control over the vehicle can be lost.Shock absorbers prevent these springoscillations.
4 HOW IT WORKS?All shock absorbers use hydraulic fluid to convert the energy of the spring to heat.Consists of two strokesCompression &Rebound
6 WHY GAS FILLED SHOCKS?Rapid movement of the fluid between the chambers cause foaming.Results in a lag because the piston moves through an air pocket which offers resistance.Foaming results in a decrease of damping and a loss of spring control.
7 Pressure increases in front of the piston and drops behind it. All together results in foaming and loss of shock absorber control.
8 GAS FILLED SHOCKS Designed to reduce foaming of the oil. Construction is similar except the double tube, here a dividing piston is used.Two chambers – oil & gas.
10 How it works? The piston rod is moved into the shock absorber which displaces the oil.This causes the dividing piston to press on the gas chamber, reducing it in size.While returning the gas pressure returns the dividing piston to its initial position.
11 The pressure decrease behind the working piston cannot be high for the gas to exit from the oil column.Thus the gas filled shock absorber operates without foaming.
12 TYPES AND DETAILS There are two types of gas filled shock absorbers- Mono tube with high pressureTwin tube with low pressure
14 MONO TUBE COMPONENTS: Cylinder also called housing. Piston connected to a piston rod.Floating piston also called separating piston.Piston rod guide.Upper and lower attachment.
15 WORKING The cylinder is not completely filled with oil; the lower part contains nitrogen at25-30 bar.Gas and oil are separated by floatingpiston.
16 BUMP STROKE When the piston rod is pushed in the floating piston is also forced down slightlyincreasing pressure in both section.Also the oil below the piston is forced toflow through the piston, this generatesthe bump damping.
17 REBOUND STROKEWhen the piston rod is pulled out, the oil between piston and guide is forced to flow through the piston.This resistance generates rebound damping.At the same time part of piston rod will emerge from cylinder and free piston move upwards.
19 TWIN TUBE COMPONENTS: Outer tube also called reservoir tube. Inner tube also called cylinder.Piston connected to a piston rod.Bottom valve also called foot valve.Piston rod guide.Upper and lower attachment.
20 BUMP STROKE When the piston is pushed in, oil flows to the enlarged volume above the piston.Simultaneously a quantity of oil is alsoforced to the reservoir tube.
21 REBOUND STROKE When the piston is pulled out, the oil above the piston is pressurized and flowthrough the piston.Some oil flows back from the reservoirtube to the lower part.
22 ADVANTAGES Instantaneous response. Better fade resistance. Better durability.No need for re-adjustment.
23 TIPS BEFORE MOUNTING Avoid stiff suspensions. Avoid new shocks to compensate forold and tired springs.Worn shocks reduce safety andhandling.The best advice come from a mechanicwho knows your vehicle.