The following subtopics regarding shock absorbers are included in this article -
How To Tell If You Have
Worn Shocks Or Struts
Often, it is difficult to spot worn shocks or struts, because they wear out so gradually that you get used to the difference in ride comfort and control. Generally, the first indication of shock problems will be cupping of the tires (small chunks of rubber dug out around the circumference of the tire).
Excessive bouncing after hitting a bump, excessive lean going around corners or nose diving when braking are other less noticeable indications of worn shocks.
Oil seepage at the shock is another warning that the shocks are not working as designed, however, this generally requires a close inspection under the vehicle to spot.
Most drivers state that until they installed new shocks or struts, they didn't realize that good shocks make quite a bit of difference in comfort and handling.
Remember, there are different types of shock absorbers that provide different types of ride control and comfort. Sport cars require a stiffer type of shock than a luxury sedan and trucks have even stiffer shocks than any others. The manufacturers, today, have even designed shocks to provide stability under load and comfort where you need it.
Shock absorber designs have improved immensely over the years and the consumer must specify the type of ride control that is important to them and then buy the appropriate shock to fit their needs.
The Difference Between A Shock And Strut
Shock absorbers and struts are quite similar in some ways. They both dampen the bounce of the tire and stabilize the vehicle.
McPherson Struts, however, are an integral part of the front and/or rear suspension of the vehicle. The strut assembly provides the upper suspension and wheel turning support. It is an integral part of the suspension geometry and directly affects the vehicle tracking.
Shock absorbers are installed inside or near the coil spring, leaf spring or torsion bar. They are not an integral part of the suspension system and as such do not affect vehicle alignment. Also, if broken will not keep the vehicle from being driven.
A broken McPherson strut may keep the vehicle from being driven because of the potential loss of steering control.
Struts are much more expensive than shocks because they are more a part of the vehicle and take the place of many components that must be used in the conventional front suspension.
Why Shocks Wear Out
Many people wonder why shocks wear out. There are several reasons and obviously the most common is driving habits and road conditions. There are however, other reasons vehicle related. The first being the spring support. Shocks are not designed to support the weight of the vehicle, but as suspension springs weaken, more and more of the vehicle's weight is being carried by the shock. Also, as suspension parts wear and create excessive movement, the shock has to absorb some of that as well.
Therefore, remember to have your suspension checked before and after installing new shocks, to make sure your shocks are not required to do more work than they have to.
How Do You Know If Your Vehicle
Really Needs New Shock Absorbers?
You need new shocks (and/or struts) if your original shocks (or struts) are worn out, damaged or leaking. Leaking is easy enough to see (just look for oil or wetness on the outside of the shock or strut) as is damage (broken mount, badly dented housing, etc.). But wear is often more of a subjective thing to judge. There are also instances where the original equipment shocks may not be worn, damaged or leaking, but may not be adequate for the job they're being asked to do. In such cases, upgrading the suspension with stronger, stiffer or some type of special shock (or strut) may be recommended to improve handling, for trailer towing, hauling overloads or other special uses.
Shocks and struts do not require replacing at specific mileage intervals like filters or spark plugs, but they do wear out and eventually have to be replaced. How long a set of original equipment shocks will last is anybody's guess. Some original equipment shocks may be getting weak after only 30,000 or 40,000 miles. Struts usually last upwards of 50,000 or 60,000 miles.
But when exactly a shock or strut needs to be replaced is hard to say. Because the damping characteristics of shocks and struts deteriorate gradually over time, the decline in ride control often passes unnoticed. So by the time to think you need new shocks or struts, it's usually way past the point when they should have been replaced.
One way to evaluate your need for new shocks or struts is to consider how your vehicle has been handling and riding lately. Does it bounce excessively when driving on rough roads or after hitting a bump? Does the nose dip when braking? Does the body roll or sway excessively when cornering or driving in crosswinds? Does the suspension bottom out when backing out of the driveway or when hauling extra passengers or weight?
A "bounce test" is still a valid means of checking the dampening ability of shocks and struts. If the suspension continues to gyrate more than one or two times after rocking and releasing the bumper or body, your shocks or struts are showing their age and need to be replaced.
Why Replace Them?
Weak shocks and struts won't necessarily create a driving hazards if you continue to drive on them, but there are studies that show worn shocks increase the distance it takes to stop a vehicle on a rough surface. Increased body sway due to weak shocks or struts can also increase the risk of skidding on wet or slick surfaces.
Worn shocks and struts also increase suspension wear (though marginally) but can have an effect on tire wear. If the shocks are really bad, the tires can develop a cupped wear pattern .
The reason why most people decide to have worn shocks or struts replaced, however, is to improve overall ride quality. If you're sick of bouncing and rocking on rough roads, a new set of shocks or struts will firm up your suspension and restore proper ride control.
If you're interested in performance handling, you can upgrade to premium "gas" charged shocks or struts. These are charged with high pressure nitrogen gas to help minimize foaming in the hydraulic fluid inside the shock. This lessens "fade" on rough roads and helps the vehicle maintain better ride control when cornering.
There are also "heavy-duty" replacement shocks and struts that have larger diameter pistons than stock. These too, provide increases resistance for greater control -- but may be a little too harsh for everyday driving. So some shocks have special valving or adjustable valving that allows the amount of resistance to vary.
Another option to consider if you tow a trailer or haul extra cargo are overload or air-assist shocks. Overload shocks have a coil spring around them to increase the load carrying capacity of the suspension (these also tend to ride stiffer than standard replacement shocks). Air-assist shocks have an adjustable air bladder that acts like a spring to carry extra weight. With this type of shock, air can be added on an "as needed" basis when hauling extra weight.
Shocks and struts are generally replaced in pairs -- though this isn't absolutely necessary if only one shock or strut is leaking or has suffered damage at a low mileage.
Shocks are a popular do-it-yourself item on most vehicles because they're fairly easy to replace. But struts are not. Most struts require a fair amount of suspension disassembly as well as a spring compressor. What's more, the wheels must usually be realigned after replacing a strut. For this reason, you're probably better off letting a professional replace your struts.
Do wheels need to be realigned after the struts have been replaced? On most vehicles they do. Here's why:
MacPherson struts are more than overgrown shock absorbers. They're an integral part of your vehicle's suspension. They replace the upper control arms and ball joints and serve as the steering pivots for the front wheels. When the strut assembly is unbolted and removed from the vehicle, the original alignment of the suspension is lost -- unless the position of the camber bolts and upper strut plate are first marked so they can be reinstalled in exactly the same position as before. But this only works if the same original strut is being put back into the car. If the strut is being replaced because it is leaking, damaged or worn out, the dimensions of the new strut will usually vary enough to cause a change in wheel alignment. So wheel alignment should at least be checked to see if adjustment is necessary (which it usually is).
On some import cars, the struts are "rebuildable." The housing has a removable nut that allows the old guts inside to be dumped out and a new cartridge installed. On these vehicles, it should not be necessary to realign the wheels after rebuilding the strut.
- Used by permission from Olson
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