Signs of Bad Shocks and Struts (and the Difference Between Them)

The main signs of bad shocks and struts are a car that keeps bouncing after bumps, dives forward under braking, sways in turns, leaks oil from the damper body or wears tires in a cupped pattern. A shock only controls movement, while a strut also supports the vehicle's weight and helps locate the wheel. This guide explains that difference, lists the symptoms, covers the limits of the bounce test and other causes of cupped tires, and explains replacing in pairs, complete strut assemblies versus bare struts, and alignment.

How a Shock Differs From a Strut

Both parts are dampers. They slow the up and down movement of the springs so the tires stay planted on the road. A shock absorber is usually mounted separately from the spring and does not carry the vehicle's weight or hold the wheel in position.

A strut is a structural part of the suspension. It carries spring load and, on many front-wheel-drive cars, forms the upper locating point for the steering knuckle. That is why removing a strut can change wheel alignment while swapping a rear shock usually does not. Catalogs sometimes call a rear unit a strut even when it is not a steering strut, so go by the fitment data.

Common Signs of Worn Dampers

Worn shocks and struts usually fade slowly, so drivers get used to the change. Watch for these signs, and remember that worn dampers can also lengthen stopping distances on rough or wet roads.

• The body keeps bouncing after a bump instead of settling
• The nose dives during braking or the rear squats under acceleration
• Extra body roll and sway in turns or crosswinds
• The car wanders or feels unsettled on rough pavement
• Clunks, knocks or harsh impacts over bumps
• Oil running down the outside of the damper body

Leaks and Cupped Tires

A light film of moisture on a damper can be normal seepage. Oil that runs down the body, drips or coats the spring seat means a failed seal, and that unit should be replaced. Make sure the oil is not coming from somewhere above it first.

Cupped tires show a repeating pattern of high and low spots around the tread. Weak dampers can let a tire skip on the road and cause this, but so can wheel imbalance, a bent wheel, worn ball joints or bushings and poor alignment. Treat cupping as a reason to inspect, not as proof.

What the Bounce Test Can and Cannot Tell You

To do a bounce test, push down hard on one corner of the parked car and let go. If it keeps moving up and down instead of settling quickly, that damper may be weak. It is a screening check only. Stiff springs, short suspension travel and electronic dampers can all fool it, and a damper can pass while still leaking or sitting on a damaged mount. Combine it with a road test and a close look at the dampers, mounts and tires.

Replace in Pairs and Check Related Parts

Replace shocks or struts in left and right pairs on the same axle, even when only one side leaks. A new damper next to a tired one gives uneven handling. While you are there, inspect the upper mounts and bearings, bump stops, dust boots, coil springs, sway bar links, ball joints and control arm bushings. Many clunks blamed on struts actually come from these parts.

Complete Strut Assemblies vs Bare Struts

A complete or quick strut assembly usually comes with the spring, damper, upper mount, bearing, boot and bump stop already put together. You avoid compressing the coil spring yourself and every part is new. Contents differ by brand, though, so read exactly what is included.

A bare strut reuses your spring and mount, which means compressing the spring to swap parts over. A compressed coil spring stores a lot of energy. Use a quality spring compressor made for the job, follow its instructions, keep your body out of the spring's path, and never improvise with chains or threaded rod. Replace any spring that is cracked, rusted through or sagging.

Alignment and Safe Installation

Get a wheel alignment after replacing front struts, or any part that changes suspension geometry or ride height. Strut removal can shift camber and toe even when the bolts go back in the same holes. Rear shock replacement alone usually does not require an alignment, but check it if tire wear or steering feel changes.

Raise the car on level ground and support it on rated jack stands, with the wheels chocked. Support the hub so brake hoses and ABS wires are not stretched, torque fasteners to the service manual, and take a slow test drive before highway speeds.

Choosing Replacement Shocks and Struts

Each part page carries a fitment table with years, trims, body styles and engines. Ride height, drive type and suspension package can change the part, and vehicles with electronic dampers need units with matching wiring. Use the fitment help guide if the notes list more than one package for your model.

Browse shock absorbers and struts by vehicle, for example Silverado 1500 shock absorbers or Chevrolet Equinox struts. If you are replacing several parts on a truck at once, a suspension kit such as the Silverado 1500 suspension kits can group them together.