Shock absorbers keep your car's tires flat against the surface of the road, providing even pressure so the tread wear remains consistent. Another function of the shocks involves absorbing vertical up and down impacts and movements for the rear axle and front end suspension. Without shock absorbers, the vehicle's ride would be noticeably rough and jarring, causing other components to wear much faster than normal. Shock absorbers exhibit numerous signs when they have weakened or failed.
Fully extended and with fully functioning seals and pistons, shocks have a predetermined height, positioning the vehicle at the proper distance from the ground. All sides of the vehicle should remain within a few inches of each other if the tires have the exact pressure and the front end suspension parts have no damage or wear. Any noticeable deviation in height can indicate a weakened or leaking shock tube.
Excessive bouncing or rebounding when the vehicle rolls over driveway lips or bumps can point to shocks that have lost their dampening effect. Trapped hydraulic fluid inside the shock cylinder slows the vertical movement of the shock piston; when the seals have leaked or when McPherson strut springs have weakened, there is a definite bounce to the car, a sure sign that the shocks must be replaced. A simple rebound test can be performed by shoving down hard on the front or rear bumper. Generally, a car that rebounds more than twice has a shock issue, indicating replacement.
Any visual leaks around the shock body tube, either at the top or body of the shock, indicate that the seals have worn or split. As a result, there is a loss in hydraulic fluid, and all dampening effect has disappeared. Oil will be plainly visible on the shock body along with grime and dust.
Loud clanking or knocking noises coming from the undercarriage, when driving over bumps or curves, may indicate a broken shock mount. Sometimes the bolts break, and the shock tube disengages completely, causing that side of the vehicle to sag. A broken shock can also produce a scraping or grating noise.
Worn shocks cannot keep the tires firmly planted on the road surface. With worn shocks, the tires have a tendency to wheel-hop or skip, and at high speeds this causes chunks of tire to be torn from the tread. The tire wear pattern resembles cups or "scalloping," where the tread appears wavy all around the circumference. This wear pattern specifically points to worn shocks since no other component causes such abnormal tire wear.
If the vehicle leans excessively into a tight or gradual turn, this means the shock cannot maintain its height and has lost the ability to carry the frame's load. Noises, such as creaking and groaning, can mean other suspension parts are bottoming out (touching or grazing the frame), and this can be a sign that the shocks have lost their strength.
