Monroe's Technical Support will help you find
answers to the most frequently asked product and installation questions
and provide invaluable technical training information. If you need
additional information or assistance, Monroe's Ride Control Technical
Assistance Team can assist you.
Our most frequently asked questions are below. Don't see your question? Ask the expert.
What is the difference between shock absorbers and struts?
Struts and shocks are very similar in function, but very different in
design. The job of both is to control excessive spring motion; however,
struts are also a structural component of the suspension. Struts can
take the place of
two or three conventional suspension components and are often used as a
pivot point for steering and to adjust the position of the wheels for
alignment purposes.
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How many miles do shocks and struts last?
Experts recommend replacement of automotive shocks and struts at 50,000
miles. Testing has shown that original equipment gas-charged shocks and
struts degrade measurably by 50,000 miles*. For many popular-selling
vehicles, replacing these worn shocks and struts can improve the
vehicle's handling characteristics and comfort. Unlike a tire, which
rotates a specific number of times per mile, a shock absorber or strut
may compress and extend several times per mile on a smooth road, or
several hundred times per mile on a very rough road. There are other
factors that affect the life of a shock or strut, such as, regional
weather conditions, amount and type of road contaminates, driving
habits, loading of the vehicle, tire / wheel modifications, and the
general mechanical condition of the suspension and tires. Have your
shocks and struts inspected by your local Monroe Expert Plus dealer or
any ASE Certified Technician once a year, or every 12,000 miles.
*Actual mileage may vary, depending upon driver ability, vehicle type, and the type of driving and road conditions.
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How do I know when my shocks or struts need to be replaced?
It's relatively easy for most vehicle owners to determine when their
tires, brakes and windshield wipers are worn out.
Shocks and struts, on the other hand, aren't nearly as simple to
inspect, in spite of the fact that these safety-critical components are
high susceptible to everyday wear and tear.
Shocks and struts should be inspected by your local Monroe Expert Plus
dealer or any ASE Certified Technician every time it is brought in for
tire, brake or alignment services.
During a road test, a technician may notice an unusual noise originating
from the suspension system. The
technician may also notice that the vehicle exhibits excessive bounce,
sway, or dive during braking. This could warrant additional
inspection. If the shock or strut has lost a large amount of fluid, if
it is bent or broken, or if it has damaged brackets or worn
bushings, it should be repaired or replaced. Generally, replacement of
parts will be required if a part no longer performs the
intended purpose, if the part does not meet a design specification
(regardless of performance), or if a part is missing. Replacement
shocks may also be installed in order to improve the ride, for
preventative reasons, or to meet a special requirement; for example,
load-assisting shock absorbers can be installed for leveling a vehicle
that is often used to carry additional weight.
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A technician pointed out that I have a light film of oil covering my shocks or struts, should they be replaced?
If the shocks or struts are functioning correctly, a light film of
oil covering the top half of the working
chamber does not warrant replacement. This light film of oil results
when oil used to lubricate the rod gets wiped from the rod as
it travels into the painted part of the shock or strut. (The rod is
lubricated as it cycles in and out of the working chamber).
When the shock / strut is manufactured, an extra amount of oil is added
to the shock / strut to compensate for this slight loss.
On the other hand, fluid leaking down the side of the shock / strut
indicates a worn or damaged seal, and the unit should be
replaced.
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I have replaced my shocks / struts several times within a few months due to excessive oil
leakage. What is causing them to fail prematurely?
The main cause of oil leakage is seal damage. The cause of the
damage should be identified and corrected
prior to replacing shocks or struts. Most suspensions incorporate some
type of rubber suspension stops called "jounce" and "rebound"
bumpers. These bumpers protect the shock or strut from damage due to
topping or bottoming. Most struts also utilize replaceable
dust boots to keep contaminants from damaging the oil seals. To prolong
the life of the replacement shocks or struts, these
components should be replaced if they are worn, cracked, damaged or
missing.
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What will happen if I don't replace worn shocks or struts?
Shocks and struts are an integral part of your suspension system. They
work to prevent suspension parts and
tires from wearing out prematurely. If worn, they could jeopardize your
ability to stop, steer and maintain stability. They also
work to maintain tire contact with the road and reduce the rate at which
vehicle weight transfers among the wheels when negotiating
corners or during braking.
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My new tires are starting to wear unevenly. Is this due to the ride control parts?
There are many factors which affect tire wear. The five main items are:
- Driving habits
- Alignment settings
- Tire pressure settings
- Worn suspension or steering components
- Worn shocks or struts
A "cupped" wear pattern is typically caused by worn steering /
suspension components or by worn shocks / struts. Typically, worn
suspension components (i.e. ball joints, control arm bushings, wheel
bearings) will result in sporadic cupping patterns, whereas
worn shocks / struts will generally leave a repeating cupping pattern.
To prevent replacement of good components, all parts should
be inspected for damage or excessive wear prior to replacement.
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A service technician said my struts had failed and were leaking oil; however, my vehicle
has gas charged struts. Could this be true?
Yes, gas charged shocks / struts contain the same amount of oil as
standard hydraulic units do. Gas pressure
is added to the unit in order to control a condition referred to as
"shock fade," which occurs when the oil in a shock or strut foams
due to agitation, excessive heat, and low pressure areas which develop
behind the piston (aeration). The gas pressure compresses air
bubbles trapped within the oil until they are so small that they do not
affect the shock's performance. This allows the unit to ride
better and to perform more consistently.
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I've had my shocks / struts replaced; however, my vehicle still makes a metallic "clunking
noise" when driving over bumps. Are my new struts / shocks bad?
There is most likely nothing wrong with the replacement units, but a
metallic "clunking noise" typically
indicates loose or worn mounting hardware. If the noise is present
with a replacement shock absorber, check that the mountings are
tightened securely, and look for other worn suspension parts. Some
shock absorbers utilize a "clevis" type mount, which must squeeze
the sides of the shock's "mounting sleeve" very securely (like a vise
would) in order to prevent noise. If the noise is present with
a strut, then the upper bearing plate should be inspected and replaced
if necessary. Old mounting bolts can stretch if over-torqued
or if they have been loosened and retightened multiple times, resulting
in a noise. If mounting bolts no longer hold their original
torque, or if they have been stretched, they should be replaced.
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Are there any other parts I should consider replacing while having my struts / shocks
serviced?
Definitely! Because removal, replacement and alignment of struts or
shock absorbers can be labor intensive,
it is a good idea to have the "bearing / mounting plate", and mounting
bolts inspected along with other parts that are designed to
protect the strut / shock such as the "jounce bumper" and "dust boot".
You'll not only be saving yourself from paying for the same
labor charges again, but you will also be protecting the investment you
made in new parts.
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Does my vehicle need to be aligned after I have my struts replaced?
Yes. Monroe recommends alignments anytime replacement struts are
installed. However, there are a few
exceptions where the vehicle manufacturer does not provide alignment
provisions, or where the alignment angles are not affected by
a strut replacement. Examples include certain double wishbone, some
modified type struts, and suspension systems which utilize shock
absorbers. For more detailed information, contact your local Monroe
Expert Plus Dealer •
Dealer Locator • or our Technical Assistance Team.
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I recently had the struts replaced on my vehicle and now the coil spring rubs on the inner
fender well when I turn the wheels. What is causing this?
When installing existing components onto a replacement strut, care must
be taken to insure the upper spring
seat is installed with the correct orientation to the lower spring seat
or mount. The orientation of the upper spring seat determines
the direction that the coil spring is bowed to allow for inner fender
clearance. If the orientation is off, the spring may rub on the
inner fender well when the wheels are turned or when the suspension is
compressed.
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The steering wheel on my strut-equipped vehicle does not return to center after negotiating
a corner. What could be causing this?
The main cause for this is a strut bearing plate that will not rotate
freely due to contaminants, over-torqued
rod nut, or wear. Other causes can include: low tire pressure,
incorrect alignment angles, and binding steering components such as
ball joints, tie-rod ends, and steering rack.
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I am trying to install new shock absorbers on my vehicle; however, they are too short to
install with the wheels hanging. Do I need longer shocks?
In most cases, no… many vehicles use shock absorber length to limit the
suspension travel when the wheels are
hanging in order to protect components from damage. For this reason,
shocks should be installed with the vehicle suspension at normal
ride height. Replacement could be performed on drive-on type ramps,
over a mechanics pit, or on an alignment rack. Examples of
components typically protected against damage from over-extension are:
ball joints, tie-rod ends, 4WD half shafts / CV joints,
U-joints, brake lines, ABS sensor lines, and height sensors. If the
vehicle has been modified with an aftermarket suspension
system, specially designed longer shocks are typically required.
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I have just had a snowplow installed on the front of my pick-up truck; can I adjust the
tension of the torsion bars to level the truck without damaging the shock absorbers?
When a heavy snowplow is added to the front of a truck, the ride height
must be set (raised) to fall within
the vehicle manufactures specifications. This will prevent premature
failure of the shock absorbers, damage to other suspension
parts and will ensure correct tire alignment. However, if the plow is
removed (during the off-season), the ride height should be
readjusted again (lowered) back to the manufacturer's specified ride
height, or suspension/ shock damage may occur.
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I would like to retrofit shock
absorbers to my camper/ trailer which did not originally
come equipped with shocks. Is this possible? If so, how do I figure
out what length shock to use on an application which did not
originally come with shocks?
Monroe manufactures Trailer Retrofit Kits for both leaf and torsion
axles. These kits are designed to work
on 1,500 lb. all the way up through 7,000 lb. GVW axles. They will also
work with C-Channel, I-Beam and rectangular tube frames.
For detailed kit information, refer to
www.monroeheavyduty.com.
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Can shock absorbers be mounted upside down (rod end down) and still function properly?
Most modern shock absorbers utilize a twin (dual) tube construction; in
order to work properly the inner of
the two tubes (working chamber) should stay completely filled with oil.
The outer (reserve) tube contains an oil reserve along with
air or a pressurized gas. If the unit is mounted inverted (rod side
down), the air or gas in the outer chamber can enter the inner
working chamber, resulting in poor damping performance. Therefore, twin
tube shock absorbers should not be mounted upside down (or
on their side), with the exception of specially designed units that
incorporate a gas cell, or cellular gas material, designed to
keep the gas retained in the outer reserve tube.
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My older vehicle originally came equipped with expensive electronically controlled
adjustable struts. Can I replace these with less expensive non-adjustable struts?
Yes, certain vehicles can be modified to accept non-electronic replacement units if the owner desires to
remove the O.E. electronic ride control system. For more information, refer to the attached pdf:
Electronic to Standard, Shock / Strut Conversion Instructions.
Monroe also manufactures conversion kit, part number 90001, designed
to convert the air suspension used on the 1988-1994 Lincoln Continental
to conventional coil spring struts.
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Why is the spring seat on the replacement strut much larger than on the original strut
I'm replacing?
As a safety feature, some replacement struts are equipped with a large diameter lower spring seat. This
seat is designed to prevent a broken coil spring from contacting the tire. Clearance should be checked if larger tires, tire
chains, or replacement wheels are being used.
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