Here's Our Handy Shock Bounce Test Instructions

Dear Car Talk

Dear Car Talk | Nov 09, 2017

Dear Car Talk:

My 2004 Jeep Grand Cherokee has 187,000 miles on it. I bought it new. What is a reasonable lifetime for shocks? I've been told to keep them if they aren't leaking. Mine don't have signs of leakage, but the car does not ride as it first did. I've replaced the tires with ones with softer sidewalls, and have replaced the springs. Both have helped the ride, but should I be replacing the shocks as well? Many thanks! -- Jon

Jon, you should have written to me five years ago.

Actually, there's no time limit on the life of a shock absorber; its lifespan depends on how much and what type of use it gets. If you do mostly highway driving, it's conceivable that your shocks are still OK. It would be unusual, but conceivable. Since the shocks aren't leaking, then you have to give them the classic "bounce test": You start at one corner of the car, and push down as hard as you can on the bumper. When you've pushed it down as far as you can, let the bumper come back up and immediately push it hard again -- trying to amplify the movement. It's like pushing a kid on a swing. The idea is to really get that corner of the car oscillating up and down as violently as you can.

Then, when it's really moving -- or when you begin to feel the first signs of angina, whichever comes first -- push it all the way down and let it go. If the shock is good, that corner of the car will come back up once and stop immediately, and not oscillate. If it continues to go up and down at all, the shock is worn out.

I have to say that we replace shocks far less frequently than we used to. We used to routinely replace shocks at 30,000 or 40,000 miles. And now it's not at all unusual to have cars with well over 100,000 miles that still don't need replacement shocks.

Still, I think you're at the far end of the bell curve, Jon. And even if you replace the shocks, you can't reasonably expect the car to ever ride as it first did. Remember, it's 13 years old -- old enough to have pimples and a first girlfriend. So pretty much everything is somewhat worn out.

So if you want a new-car ride, look at the 2018 Grand Cherokee. But in the meantime, give your shocks the bounce test. Good luck.

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