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SHOCK ABSORBER TECH
INFO
ARE SHOCK ABSORBERS
REALLY THAT IMPORTANT?
Shock absorbers are a
critical component for eliminating unwanted and excess motion in the body and
suspension. Without shock absorbers, cars and trucks would bounce down the road
in an uncontrollable fashion.
Without shocks, tires would lack adhesion and braking and cornering
would be somewhere between dangerous and impossible. Shock absorbers play a
critical role in vehicle stability and safety.
HOW DO SHOCK
ABSORBERS DO THEIR JOB?
By forcing a piston
through oil, shocks develop the hydraulic friction necessary to resist unwanted
and excess suspension motion. Shocks work in two directions called compression
(the closing motion) and rebound (the opening motion). Shock absorbers are
supposed to minimize
unwanted and uncomfortable body motions such as pitch and side to side rocking.
They must also keep the tire in maximum contact with the road surface.
HOW CAN I TELL IF MY
SHOCKS NEED REPLACEMENT?
The best way to
determine whether you shocks are working properly is to drive your car or truck
over familiar roads with various surfaces and bumps. And while a leaking shock
is an obvious candidate for replacement, many shocks wear out without losing any
oil. If your vehicle is exhibiting any of the following characteristics, then
you may need new shock absorbers. The more characteristics you experience the
more likely it is that your shocks should be replaced.
IS MILEAGE A GOOD
INDICATOR OF SHOCK WEAR?
Mileage alone is a
poor indicator of shock performance. Some shocks are still working well after
30,000 to 40,000 miles. Others need replacement in as little as 4,000 miles. In
fact some shocks are so poor that they do not work properly when brand new!
Another test was the old "bumper bounce test". This test is a worst
case evaluation. Shocks are usually performing poorly well before this test
shows anything. If your vehicle has very stiff springs, like some trucks, the
bumper test is almost impossible to perform.
HOW DO SHOCK BRANDS
DIFFER?
Virtually everyone
who manufactures shock absorbers claims to use the best materials and have the
best design. However not all of these "bests" are equal. There are
very real differences in the materials, tolerances, and actual internal designs
of different manufacturers. Keep in mind that quality has an effect on how long
the shock will last and how even or consistent the performance will be. Design
has a major effect on how the shock actually works.
Good quality and
sophisticated designs tend to be more expensive to manufacture than poor quality
outdated designs. Controlling both excess body motion and the tires and wheels
properly requires sophisticated oil flow management. Inexpensive shocks simply
cannot do both jobs correctly.
WHAT ARE GAS SHOCKS?
The oil used in shock
absorbers has some air in solution. The rapid movement of the shock piston
causes what is called cavitation. This results when the air in the oil comes out
of solution to form foam. Foamed oil will not provide proper resistance. This
affects shock performance. By pressurizing the oil, engineers can eliminate the
negative effects of cavitation. The result is better more consistent control and
superior ride quality. There are two types of gas pressurized shock absorbers.
Monotube-high pressure units and twin-tube low-pressure shocks. There are also a
number of designs within these two categories. It is important to realize that
simply adding gas pressure to a poor quality shock will not make it into a high
quality unit.
DOES A WARRANTY MEAN
ITS A GOOD SHOCK?
Warranties are like
ears, virtually everyone has them. They are marketing tools, and they offer no
indication of the quality or design of a shock absorber. In fact some
manufacturers simply raise the price of their inexpensive shocks to cover
warranty costs. A warranty may get you a free replacement, but warranties rarely
cover labor costs. It is better to invest in the type of quality that rarely
requires replacement.
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