Guide to Shock Absorber Replacement

auto repair technician inspecting shock absorber
Inspecting shock absorber.

M_a_y_a / Getty Images

Car and truck suspension springs generally fall into three categories: leaf springs, coil springs, and torsion bars. These springs support the vehicle, allowing it to react smoothly to road height differences, bumps, and dynamic vehicle loading, like passengers, cargo, braking, and turning. While springs will continue oscillating until acted on by an outside force, shock absorbers will eventually wear out, which is why shock absorber replacement should be on your radar.

Shock absorbers are pistons filled with hydraulic fluid, connected between the body or frame and control arms or axles. The hydraulic fluid in the shock absorber flows through restrictive valves, exerting resistance to the spring’s oscillations.

left-rear coil spring and shock absorber
Here is the left-rear coil spring (red) with the shock absorber to its left (black/white). Pgiam / Getty Images

Hydraulic damping or shock absorption is important, because too much bounce can be both uncomfortable and dangerous. Worn suspensions often lead to a boat-like ride quality, which can make people queasy, and, more dangerous, lead to abnormal wear patterns and tire noise. Then, if a tire and wheel start bouncing uncontrollably—no damping—the tire can bounce right off the road. In a corner or a high-speed stop, this could lead to a loss of vehicle control.

How long do Shock Absorbers last?

Shock absorbers don’t last forever, because they’re always in motion. Even on well paved roads, shock absorbers work to smooth out out the slightest irregularities. Bumpy roads demand far more from shock absorbers, and daily driving dynamics also give your suspension a workout. On acceleration, the rear of the vehicle may squat, but the shock absorbers slow the reaction. Similarly, when braking, shock absorbers slow the “dive” effect. The more aggressively you drive, the more wear you can expect in the shock absorber.

Shock absorbers wear out in a couple of ways and the wear may lead to unexplained shaking and shimmying. When internal valves wear out, they offer little resistance and hydraulic damping. Worn external seals can cause a couple of problems. Gas-charged shock absorbers reduce internal foaming, but a leak might release the gas—air bubbles are not resistant to flow like hydraulic fluid is. External leaks can also allow hydraulic fluid to leak, not only making a mess, but eliminating any hydraulic damping effect.

auto repair technician inspecting shock absorber
Inspect shock absorbers every 20,000 miles and consider shock absorber replacement if your car doesn’t feel right. M_a_y_a / Getty Images

Shock absorbers tend to last 50,000 to 100,000 miles, but this depends much on how and where you drive. You should test every 20,000 miles or so, just to be sure. Aside for looking out for visible fluid leaks, you can bounce-test your suspension. Push down on the corner of the vehicle you’re testing, then release. If the car bounces more than once, it’s time for shock absorber replacement.

Shock Absorber Replacement Basics

Fortunately, shock absorbers are usually accessible with a jack and jack stands—but remember, never put any part of your body under a vehicle supported only by a jack. Stand-alone shock absorbers are usually held in place using a few nuts and bolts and may feature mounts for sway bar links or brake line brackets. With the vehicle lifted and suspension hanging—lift from frame or body—remove any brackets, tubes, hoses, or links, then remove the old shock absorber and fit the new one. You may need to lift the suspension slightly to get the new one to fit.

DIY coil-over spring compressor
Some DIY auto repair options can be risky, like these coil-over spring compressor tools. EyeEm / Getty Images

Coil-overs and McPherson struts are suspension spring and shock absorber in one, and this is one shock absorber replacement you may want to reconsider. Unless you have a professional spring compressor, we suggest leaving this to the professionals with quality equipment. Cheap DIY spring compressors are particularly dangerous and hard to recommend. On the other hand, some aftermarket vendors sell so-called “quick-struts,” a new pre-assembled shock absorber or strut unit. This type of installation is easy to complete and the safest option for DIYers, though slightly more expensive.

Finally, after strut or coil-over shock absorber replacement, it’s a good idea to have the wheel alignment checked and adjusted. This will ensure you have the right angles to prevent abnormal tire wear and keep your vehicle tracking straight.