Shock absorbers (dampers) and struts control how your vehicle’s suspension reacts to bumps, dips, and body roll. When they wear out, the ride becomes bouncy, braking distances increase, and the vehicle feels less stable in corners. Replacing them is a common DIY job that can save significant labour costs.
Shocks vs Struts: What Is the Difference?
Shock absorbers and struts perform the same damping function but are different components. A shock absorber is a standalone damper that mounts between the vehicle body and the suspension arm. A strut is a structural component that combines the shock absorber and the coil spring into a single assembly, replacing the upper control arm. Most modern vehicles use MacPherson struts at the front and either shocks or struts at the rear. Your workshop manual will confirm which type your vehicle uses.
Signs They Need Replacing
The vehicle bounces excessively after going over a bump (more than one or two oscillations), the nose dives noticeably during braking, the body rolls excessively in corners, you can see oil leaking from the shock body (a definitive sign of failure), or the tyres show cupping wear (scalloped patches around the tread caused by the wheel bouncing). Most shocks and struts last 80,000 to 150,000 km, though this varies significantly with driving conditions.
Replacing Shock Absorbers
Standalone shock absorbers are typically held in place by a bolt at the bottom (attaching to the suspension arm or axle) and one or two bolts at the top (attaching to the body or chassis). The replacement process is to raise the vehicle on jack stands, support the axle or suspension arm with a jack to take the load off the shock, remove the top and bottom mounting bolts, remove the old shock, fit the new one, and torque the bolts to specification. Always replace shocks in pairs (both fronts or both rears) to maintain even damping.
Replacing Struts
Strut replacement is more involved because the coil spring must be transferred from the old strut to the new one (unless you buy complete strut assemblies with the spring pre-installed). Compressing a coil spring requires a spring compressor tool and is the most dangerous part of the job – a spring under compression stores enormous energy and can cause serious injury if it slips.
The general procedure is to remove the strut assembly from the vehicle (unbolt the lower mounting from the steering knuckle and the upper mounting from the strut tower), compress the spring using a proper spring compressor, remove the top mount nut, swap the strut cartridge, reassemble with the new strut, release the spring compressor, and refit to the vehicle. After strut replacement, a wheel alignment is always necessary as the front geometry will have changed.
Complete strut assemblies (with the spring, top mount, and bearing pre-assembled) are a safer and faster option for home mechanics, as they eliminate the need for a spring compressor entirely. They cost more per unit but save time and risk.
Torque Values and Alignment
Suspension fasteners are safety-critical and must be torqued to the manufacturer’s specification. Under-torqued bolts can work loose, and over-torqued bolts can stretch or crack. Your workshop manual lists every torque value for the suspension mounting bolts, top mount nuts, and knuckle bolts. It also provides the wheel alignment specifications (camber, caster, and toe) that you will need to supply to the alignment shop after completing the job.
MechanicMate offers PDF workshop manuals with complete suspension procedures, torque specifications, and alignment data for over 960 vehicle models. Find yours at mechanicmate.net/shop.
