A shock’s internal components wear out over time, lessening efficiency. External leakage of fluid may also occur, which is the most noticeable failure symptom. The folks manufacturing shocks and struts recommend renewing them every 50,000 miles, although road conditions, vehicle type and driving habits should also be factored. I was a former shock neglecter until one day, taking a downhill turn at about 50 mph, I came to an unanticipated washboard road surface. Without obvious vehicle bumping, there was a clear decrease in tire traction as my SUV almost vibrated itself off the road. I renewed all four shocks and tried that same turn again several times. There was a significant difference in road-holding ability, as well as an improvement in general stability under other driving conditions.
With my driving routine and slower-moving, stiffly sprung truck and SUV, I won’t likely be a 50,000-mile shock replacer. Other folks with more challenging road conditions and commutes and higher-performance vehicles, driven faster, perhaps should be. Testing shocks by pushing up and down on the bumper is the traditional test, but only a terrible shock on a soft-sprung car seems to show up noticeably.
Brad Bergholdt is an automotive technology instructor at Evergreen Valley College in San Jose, Calif. Readers may send him email at firstname.lastname@example.org; he cannot make personal replies.