How do I know when it's time to replace my shock absorbers?

Dear Car Talk

Dear Car Talk | Jun 01, 1995

Dear Tom and Ray:

Do you have any good ideas on when and if shock absorbers should be replaced? Those guys who sell and install them say "now." Various mechanics I have questioned shrug. The ride in my car seems fine. What do you say?

TOM: Well, first of all, Edwin, even though your "ride seems fine," your shocks may not be. Most people don't notice the degradation in ride because it happens little by little over a long period of time. And more importantly, ride isn't the only reason to be concerned about your shocks. They play a crucial role in your car's handling.

RAY: Cars have springs, so when you hit a bump, the wheels can bounce up without bouncing YOU up, too. The problem is, left on their own, the springs would just keep bouncing, and after one bump, you'd be going boinga-boinga-boinga-boinga down the road.

TOM: What shock absorbers (or "struts") do is they stop the springs from going "boinga, boinga, boinga." They allow one "boinga" and then push the wheels back firmly on the ground. And when the wheels are planted firmly on the ground, it's a lot easier to do stuff like "turn" and "stop."

RAY: So how do you test your shocks? There are four ways. One is the "bounce test." At each corner of the car, push down hard, then watch what happens. If the body of the car bounces back up and stops, the shocks are OK. If the car bounces more than once, they're not (and by the way, it not always easy to tell the difference with an untrained eye, so if you're not sure, have your mechanic check).

TOM: The second test is a leak test. You can check the shocks themselves to see if they're leaking. This isn't a definitive test, however, because a shock can have a small leak and still be very effective.

RAY: The third test is the tire-wear test. If your tires are cupped (if they seem to have flat spots on them), they've probably been bouncing off the pavement. Why? Because the shocks aren't preventing them from bouncing. In which case, it's time for a new set.

TOM: And finally, there's the motion sickness test. If you're consuming more than two Drammamine tablets per leg of your commute due to the up and down motion of your car, it's time to perform the other three tests.

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