Shocks and Struts. Replacement Time?
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By Lee Holman, aka VolvoGirl
No matter what your handling objectives, your car's driveability depends on shock absorbers. The shocks perform their duties by keeping the spring rebound in check. Since shock absorbers have such a profound effect on ride control and stability, good shocks go hand in hand with driving safety.
There are a number of ways to determine if it's time for new shocks. The first is fairly subjective; if your car no longer rides as well as it used to; If it seems to bounce and drift more than you remember, or nose-dive when you brake, your shocks are probably worn out. An oil soaked shock indicates seal failure and must be replaced, however a light film of oil is normal. Torn or blown out mounting bushings can result in annoying clunks and rattles and the inability of the shock to perform as it was intended.
The difference between a better shock and a bargain priced shock may not be visibly apparent, but when you consider the shock absorber's job, it's easy to see that shocks have to be built to withstand a great deal of punishment. As the name implies, they absorb the shock in your car's suspension. In so doing, they convert the energy of the spring into heat, and must be able to dissipate that heat efficiently in order to perform well. Most conventional shocks are of twin tube construction, and are less efficient at heat dissipation, which can cause poor performance. This means that when the road gets rough, a conventional shock will actually lose damping effectiveness. Add this to the slower response to changes in road surface, and you will see why many shocks offer a wallowing ride, with diminished stability and road holding qualities.
A shock that is made with monotube construction, such as Bilsteins are better able to stay cool over varying road surfaces and performance-oriented driving. Gas charged shocks use high-pressure nitrogen gas to main-tain damping performance by preventing the shock oil from foaming. Using high-grade materials, and state of the art technology, the better shock absorber manufacturers confidently offer a lifetime warranty, making the best shocks a better bargain in the long run.
Installation Tips
In the case of front cartridges for MacPherson struts, special tools are required. Unless you've got both the tools and the skill, you may be better off having struts installed by a pro. Rear shocks, as well as front shocks on pre-200 series Volvos, are easier for the backyard mechanic to replace, with the car on jackstands and a few common tools. This is assuming rust and corrosion have not taken their toll. Use a liberal amount of your favorite penetrating oil (I use and recommend PB B'laster). On re-assembly, anti-seize compound will help keep these bolts free from corrosion.