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Rob's Garage

How to tell if your car needs new shocks and struts Add to ...

Hi Rob,

I have a 2000 Chevrolet Cavalier. I've been told that it needs new shocks and struts, which is quite a major repair bill. I'm just wondering how important this repair is? This is our 2nd vehicle, but we will probably be keeping it for a while. Am I damaging other parts of the vehicle by not having this repair done?

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Thanks for your advice, Andrea

To answer your first question in brief Andrea, yes, keeping shock absorbers (dampers) in proper condition is critical to driving in control.

The short answer to your second question is: yes, you can damage suspension bushings and tires.

Now, for the caveat.

Unfortunately, most car owners are at the mercy of repair shops. This is fine if you frequent the same shop and you have gained mutual trust. But for the rest of us, this is a source of stress and frustration.

Here’s a test to determine for yourself if you need new dampers.

• Park your Cavalier on level ground.

• The temperature shouldn’t be below seven degrees Celsius. Cold temps will affect the test. (I’ll explain later).

• At each corner of the car, press down on the bumper as hard as you can. The force you apply should cause the car to move downward at least a couple of inches.

• Let go, and watch the movement of the car.

• Dampers that are performing properly will allow the vehicle corner to bounce up once and settle to the normal ride height. The term used in the field is “one rebound – one half jounce.” Rebound is the movement of a tire downward (in relation to the body), and jounce is the reverse of this motion.

• If you find that any one of the corners of your car move more than one and half times, that damper is worn out and needs to be replaced.

Here’s the rub: dampers – and I use this term generally because most new cars use McPherson struts on the front and conventional tube shock absorbers on the rear of the car – need to be replaced in pairs. Replacing one damper at one corner of the car will not provide full performance at that end of the car because no matter what, the remaining original damper will still be weaker than the new one. Driving over an undulation will cause the side of the car with the old damper to move up and down more than the side with the new damper.

You can image what that will do to the handling of the vehicle.

Earlier I mentioned the temperature. Dampers are filled will hydraulic fluid, or oil. As oil gets cold, its viscosity (resistance to flow) will increase, increasing the stiffness of the damper. This will create the false illusion of a properly functioning damper when in fact, in warmer temps, the damper may, in fact, be weak.

To put an exclamation on your last question Andrea, by allowing the car to bounce up and down excessively due to worn dampers, the rubber bushings that act as the pivot points for the suspension are placed in a compromised position. They will be forced to work harder because of the increased up and down motion of the car due to worn or weak dampers. This will stress the bushings. And, the tires will be forced to “squirm” more. This is a term used to describe the forces that take place across the tread where the tire meets the ground. In effect, the tires will start erasing themselves – they are after all, only rubber.

Give this a try Andrea or have someone with mass lend a helping grunt.

Send your automotive maintenance and repair questions to Globe Drive experts at globedrive@globeandmail.com

 
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