The part of the car that absorbs road unevenness and gives you a smooth ride is called the suspension system. The key component of the suspension system is the shock absorber or strut — one for each wheel. Some cars have four shocks, some have four struts, and some have two of each.

Jan Douma

Like a toilet paper holder or drapery rod with a spring in the middle, a shock gives increasing resistance when the ends are pushed together. The engineering of a shock is a lot more complicated than a spring, of course. Shocks get their greatest power from hydraulics, or liquids.

Normal strut

A strut resembles a shock with a giant bedspring coiled around the outside. Whereas a shock’s mechanism is contained in its casing, a strut’s spring is out in the open. Struts also use hydraulics to absorb bumps and potholes.

How do you know when it’s time to replace your shocks and/or struts?

The easiest method is mileage. Manufacturers will indicate how many miles their products should securely absorb, typically in the 50,000-70,000 mile range.

Leaking shock

The most common evidence of bad shocks or struts is leakage. As with most of your car, the most vulnerable parts of shocks or struts are seals that keep liquid where it belongs. Since they run on hydraulics, any leakage in your shocks or struts indicates that their function has been permanently compromised, and they should be replaced.

Replacing shocks or struts should be done in pairs, front and rear. If one front shock is leaking, both front shocks should be replaced. This may be one of the more expensive regular maintenance items on a car, especially if you have four struts. Thus, people put off replacing them. But when the suspension is not operating efficiently, other parts of the car start wearing out faster because they are getting the stress that the suspension is no longer absorbing. Evidence of suspension failure in other parts of the car can include:

Leaking strut

• When the suspension weakens, the tires no longer have smooth contact with the road; they bounce, sometimes a little, sometimes violently. This bouncing results in a distinctive tire wear pattern called cupping.

• When the suspension weakens, the car may not stop smoothly and may take longer to stop. The chassis may dip forward and back after the brakes have stopped the wheels.

• The axle, steering system, and other parts of the suspension system are the most vulnerable to damage from the additional stress caused by weak shocks and struts. You may see loose wheels, poor alignment, torn CV (constant velocity) boots (which means replacing the axle), torn rack and pinion boots (which may mean replacing the boots or the whole rack and pinion unit), problems with wheel bearings, tie rods, and so on.

Normal shock

Finally, whenever you replace your shocks or struts, you are disrupting the car’s alignment, so you should have the alignment redone.

Jan and Carl Douma are the owners of the Meineke total car care center on upper State Street in Santa Barbara. If you’d like to have a question answered, contact Jan Douma at (805) 687-0281 or


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