CARS.COM — The answer to the question question of when to replace shock absorbers and struts hinges on several variables, including how many miles a vehicle is driven, on what kinds of roads it's driven, and whether it's driven gently or with reckless abandon.
Those variables make it virtually impossible to assign a number of years or miles as a broad stroke, though we would expect shock absorbers (or struts on vehicles with strut-type suspensions that incorporate the shocks into an assembly with springs and other suspension parts) to last at least four or five years unless the vehicle has been subjected to extreme use. It's also not unusual for shocks and struts to last 10 years before needing to be replaced on a vehicle that has lived most of its life on smooth pavement.
On the other hand, rough roads marked with potholes, large cracks, and sharp ridges that run across the pavement (the typical urban torture test) and bounce the car will cause faster wear in shocks (also known as dampers because they dampen the bounce). Frequently carrying heavy loads or driving on unpaved roads with deep divots or imbedded large rocks can cause excessive wear. And if you're the type who takes bombed-out roads' bumps at the same speed as fresh asphalt, that devil-may-care approach to road conditions and bumps is bound to exact a damage toll on shock absorbers over time. Winter weather and road salt can also shorten a car's shock absorber and strut life by contributing to corrosion.
Instead of using time or mileage to decide when to replace shocks and struts, use them as guides for when to have your entire suspension inspected for part wear, damage and leaks (shocks contain fluid). Some shock absorber manufacturers say you should replace them at 50,000 miles, but that's more for their benefit than yours. Having the shocks and suspension parts inspected at 40,000 or 50,000 miles, then annually after that, is a better idea. A thorough inspection should uncover what parts, if any, actually need replacement.
The springs in your vehicle's suspension do most of the shock damping. The shocks and struts improve the ride and reduce the bouncing caused by springs compressing and releasing so you don't go boing-boing down the road. If you notice your car has more bouncing or sway than usual, a "porpoising" motion over wavy surfaces, bottoming out over railroad tracks or having more more body lean in turns, the shocks might be in worn condition or leaking fluid and will need replacing.
Longer brake distances or abrupt reactions through the steering wheel are changes that also can be caused by worn shocks, though your first inclination might be to blame something else for those problems. The same is true of uneven tire wear: If you're having none of those issues, the shocks might still need attention. Bushings — the rubber and metal "cushions" at mounting points and connections — may be worn and allowing abnormal suspension movement or vibrations that can cause a tire to wear faster or put more stress on other suspension components.
But there are plenty of other potential culprits among the suspension system parts and components that could cause ride or handling issues or unusual noises, such as ball joints, tie rods and control arms in bad condition. Don't automatically point the finger at shock absorbers or buy a new set of replacement absorbers because new shocks are on sale at the repair shop. Have a complete checkup of the entire suspension by a qualified mechanic and repair with replacements as needed for a smoother, safer ride.
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