Dear Tom and Ray:
I've always done the "bounce test" to check my shocks. I also go by the feel of the ride. My '99 Taurus seems solid and rides great, but I've noticed that the rear end seems to be "squatting." The front has about 3 inches between the tire and fender, but the rear end is about 3/4 inch! The trunk and back seat are empty. Seems like it would bounce if the shocks were bad, but it comes up and stops immediately. Is there something else I need to check? If the shocks are fine, along with everything else, is there a way to raise the ride height in the rear? It looks horrible! Is this unsafe? — Robert
Tom: It's moderately unsafe, and probably hugely uncomfortable.
Ray: You're confusing the job the shocks do with the jobs the springs do. Bad shocks will affect your ride and handling, but they won't change the ride height of the car.
Tom: So it sounds like you have worn-out springs in the back.
Ray: The springs are there to absorb bumps; that is, to allow the tires to bounce up without making the entire passenger compartment bounce up with them.
Tom: The shocks are there to damp those vibrations and keep the tires from continuing to bounce up and down for five minutes after you hit a bump.
Ray: Shocks wear out over time due to how much damping they have to do, whereas springs wear out from carrying a lot of weight over time.
Tom: So perhaps you've schlepped a lot of heavy cargo in the trunk throughout the years. Or driven around with a couple of mothers-in-law in the back seat on a regular basis? That kind of weight compresses the springs, and eventually they just stop bouncing back because there's no "spring" in them anymore.
Ray: Springs can also break. So it's possible that you have a couple of broken springs in the back from one particularly overloaded journey (when you moved in 2006 and decided to carry your iron-ore boulder collection yourself to make sure it arrived safely). But since the height is the same on both sides of the same end of the car, it's more likely that they've both just worn out and need to be replaced. Look into it, Robert.
(Car Talk is a nationally syndicated column by automotive experts (and brothers) Tom and Ray Magliozzi. Write to them at the Car Talk website.)