Are Bumps And Potholes Equally Taxing?

Dear Car Talk:

Please settle a bet: Which is more taxing on shocks -- a 6-inch bump in the road or a 6-inch pothole? I say they're equally taxing. -- Joe

I think you're right, Joe.

I haven't interviewed many shocks, so I don't know their personal feelings on this, but my guess is that they don't care.

The car has springs, to isolate your tush from the bumps and potholes on the road. The shock's job is to dampen the spring's oscillations -- so that after you hit a bump or a pothole, your tires don't bounce up and down for the next mile and a half, making it hard to turn or stop.

To dampen the motion of the springs, most shocks are filled with fluid and non-combustible gas. When the springs compress (wheels get pushed up), the shock's piston pushes inward. When the springs expand (wheels go down), the piston pushes out. And whether the piston is pushing in or out first, I don't think matters, because it always does one, then the other. As for the other suspension components, I would guess that a 6-inch pothole is worse than a 6-inch bump.

Keep in mind, that guess is -- as my late brother would have said -- "unencumbered by the thought process." But in my driving experience, the impact of a pothole is more abrupt, and therefore more severe. So, a ball joint, a tie rod end, a coil spring, not to mention a wheel or tire, has greater potential to be damaged if it takes a sudden, sharp jolt, all at once from the forward edge of a pothole, as compared to a bump -- which is rarely sharp. Bumps usually have some degree of curvature to them -- they're somewhat rounded. And I think that makes a difference.

So, if I were a coil spring (isn't that a song from "Fiddler on the Roof"?), I'd rather hit a 6-inch bump than a 6-inch pothole, Joe.

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