When to replace shock absorbers?

When driving, a vehicle’s shocks are always in use. Like many other car components, overtime this continuous use will lead to general wear and tear and they’ll lose their ability to function properly. There are signs you need new shocks that are right under your nose. Once you know them you’ll be able to determine if you need to take your vehicle to the workshop. Here are 6 tell-tale signs you can notice for when to replace shock absorbers.

When to replace shock absorbers:

Longer stopping distance

Having worn shock absorbers on your vehicle can increase your stopping distance by up to 20%. As you increase your travelling speed this will also increase the distance it takes your vehicle to completely stop. This 20% extra distance can be enough to cause a fatal incident and should be attended to as soon as possible.

Swerving & nose-dives

Does your car dip or swerve under braking? If so you need to have your shock absorbers checked. If you do dip or swerve under braking it decrease your control over the car which can be very dangerous in wet weather.

Vibrations

Are you getting vibrations through the steering wheel as you’re driving along? If your shocks are working properly they should keep your tyres in optimal contact with the road and there shouldn’t be any vibrations. If this problem occurs you need to be cautious, at high speeds the vibrations can be more intense and decreasing overall control of the vehicle.

Car sliding & veering

Do you have to correct car sliding or veering across the road in mild winds? This is a tell-tale sign of worn shocks and can be easily fixed with a shock replacement.

Rocking & rattling

If your vehicle rattles and rocks over bumps, railway tracks and uneven surfaces it is highly likely your shocks are heavily worn. Along with an unpleasant ride this rocking and rolling can be putting unwanted pressure on other car components and should be seen to as soon as possible.

Uneven tyre wear

Can you see bald patches or uneven wear on your tyres? This usually means your tyres don’t have optimal contact with the road, which can be caused by worn shocks. This will have an affect on car control and tyre grip and both should be checked and replaced.

REMEMBER: Only 4 postcard sized areas of your tyres are ever in contact with the road. It makes sense to have your shocks functioning properly to make sure you’ve got all the grip and control available.

Not sure about your shocks? Contact LEACREE and replace our shock struts!

How to Check Shock Absorbers?

If you feel like your vehicle’s ride quality is not what it used to be, it is a good idea to know how to check shock absorbers. It is fairly simple and easy to do. And it can save you from an unnecessary visit to a garage, or inversely, indicate that you need to get the car to a professional.

1. Observe your car from the front. With the car on a flat surface, it should appear perfectly level, i.e. both sides being the same height off the surface.If you actually know the specifications of your car’s suspension, you can measure the height. If the height is at or below the minimum specs, then you should take the car to a professional for further evaluation and repair. Being at the “minimum” is just that. It is no longer at the ideal, and something has changed.
2. 2Push down on the front of the car to test for weak shock absorbers. This is not a scientific test and is somewhat subjective. But it can be helpful when taken in conjunction with other checks made.Stand in front of the car and carefully place your foot on the bumper, or your knee on a surface that won’t dent or bend; it doesn’t have to be center. Shift your weight onto that point, pushing the car down. Then quickly remove your foot, or weight. The car should bounce up and return to its original position rather stiffly, without continuing to bounce. If it bounces more than a couple of times, this is an indication that perhaps the shock absorbers are weak.
3. 3Visually inspect the struts or shock absorbers. Look for signs of liquid that is or has been running down the shock absorber. If present, then your shock absorbers could be bad. Once the seals begin leaking, the shock absorber becomes ineffective.You will need to get the car into a garage to confirm your observations and replace the shock absorbers. Note that you want to get a confirmation that the liquid tracks you observed are indeed emanating from leaking shock absorber seals. It could easily just be something splashed up from the road.

What’s the Air suspension System?

Speaking about the air suspension system most people think too far too upset, because in our minds it is either to please the big boss of high-end luxury car, or is for those who deal with ultra-running speed humps or bad road, orIt is used to give the opportunity to run wild in a luxury SUV. But in fact the air suspension system can justifiably claim to be a "simple good cause," the guy, it involves something even better than your home golf turbocharged or DSG gearbox is much less, but is improving ride comfort is far less urgent to improve combustion efficiency and necessary.

Air suspension is the use of air suspension shock absorber, mainly to adjust the air volume and pressure of the air damper by air pump, the hardness and elastic modulus can change the air damper. By adjusting the amount of air pumped, you can adjust the air damper and the stroke length of the chassis can be raised or lowered.

Air suspension with respect to conventional steel suspension system, has many advantages. Such as high-speed driving, the suspension can be hard to improve vehicle stability; and low or bumpy roads, the suspension can be softened to improve comfort.

Why use air suspension?

Very simple, because the average by a coil spring and shock absorber tube consisting of a suspension system and can not adjust the firmness and height. After the length and elasticity of the coil spring calm, suspension of height with hard and soft characteristics of curing down body will not change; the calm after the damping cylinder, the response speed and shock-absorbing characteristics of the suspension is also not changed.

But the problem is with the state of the vehicle with the road is changing, ah, for example, who do not want to run bad road when the suspension is soft and comfortable, solid and stable when running the curve. Or again a little stingy, when the rear brake if the front suspension can timely hardened alleviate nod degree, accelerated time hanging harden reduce the rise, and that nice ah, the body is always well-organized. To achieve all of these, it would require the entire suspension system, or even each individual wheel suspension damping characteristics can be quickly changed.

On the other hand there is a lot of flexibility to change the vehicle body from the need to distance. Such as customary "stick to the ground," but fear "Road see injustice," the car who needs another example of some heavy-duty commercial vehicles manned cargo. Of course, we are most likely to imagine that those who need off-road vehicles run on both sides of the city suburbs and SUV. If you have seen our era film footage of the off-road users should remember that the inside of the Q7 and Touareg, the two of them are equipped with height adjustable air suspension system, which can be described in the project day to shine, this is for us to provide today's article rich material.

As stated above ordinary coil spring suspension system's physical properties can not be changed unless replacement parts, so the manufacturer can only be based vehicle positioning and sales area, to make a compromise set to "maintaining the status quo." So not convinced engineers thought the air with readily available hardware and software to be made or height adjustable suspension system.

Air suspension How does it work?

In fact there are many types of air suspension, both soft and hard only adjustable height can not be adjusted, but also the level of hardware and software can be adjusted, for example, in the early part of the application of air suspension system limo, then adjust the two air chambers to change the air flow between the hard and soft suspension, but not with height adjustment function. This paper places the prevailing level of hard and soft adjustable air suspension as an example.

Through the above chart shows, air suspension with our body structure is actually familiar form of a coil spring + shock absorber tube is almost exactly the same, but in the upper portion of the coil spring has a closed chamber, by changing the chamber volume (up and down direction), you can change the length of the spring, to adjust the body from the ground and to some extent changed the hard and soft characteristics; additional vent damper part by changing the size of the motor, thereby adjusting the damping force of the shock absorbers.

Since you want to change the volume of the gas chamber through inflated, it is bound to involve a set of gas pumps with high-pressure gas storage mechanism. The number and level of the body to maintain inflated amount, by corresponding sensors and electronic control unit to decide. Our Volkswagen Touareg for example, the electric pump mounted on the chassis front passenger seat is probably the following location, and the high-pressure gas tank is located next to the trunk spare tire.

When the body needs to be raised, the system issued a directive to make the compressed air pump starts and the gas tank inside the compressed air supply to the spring air chamber inside, if you need to reduce the body only needs to control the exhaust valve exhaust air can be. As for the actual height of the body by the side of each vehicle wheel height sensors to monitor and revise. In the end when it needs to be raised when the need to reduce it? One can select interface to control by the driver through the car's model, on the other hand the system will automatically be automatically adjusted according to vehicle speed, road shock and other reference data.

The driver can follow the road from inside five modes need to choose, body height, while the suspension hardness change accordingly change automatically. Of course, taking into account the vehicle's stability and security, air suspension system will automatically change the condition of the vehicle from the ground. For example, in general a paved road, the Audi Q7 permanent ground clearance of 180mm; but when the vehicle speed reaches 120 km / h and kept more than 30 seconds later, the suspension will automatically lower the body's ground clearance 15mm, so better high-speed stability; if the speed for 20 seconds to keep the 160 km / h, the body will be reduced by 15 mm, the ground clearance is adjusted to just only 150mm.

Go wild and occasions, off-road mode allows the body ground clearance increased to 205 mm, helping to keep the Audi Q7 100 km / h in the general security bumpy mountain road by speed; the high-order mode allows the vehicle ground clearance increased to 239 mm, rose to the highest Q7 approach angle of up to 24 °, departure angle reaches 25 °, the maximum wading depth of 535 mm.

The other hand, the Touareg's air suspension provides four kinds of body height and three damping modes, respectively, through the back of the vehicle height adjustment lever knob and roll damping mode switching from the main regulator. On the surface can be combined 3X4 = 12 modes, but in fact the ground clearance required damping mode to select a compromise, such as when SPORT mode the damping, the ground clearance is no way to go to the maximum, so driving those who still want to grasp the actual height of the body according to prompts dashboard.

What are the limitations of the current still?

The more complex the system architecture also means more factors caused the failure, so the air suspension system problems of probability and frequency than ordinary coil spring suspension system. First, adjust the ride height of the air as a "propulsion", damper seal fiasco, if there is leakage of air suspension, then the whole system will be in a "paralyzed" state; secondly, because of the low air density relationship, with air suspension damping characteristics to make real-time adjustment, the response speed of the system and not the common hydraulic active suspension system.

In addition, compressed air from the pump, if you frequently adjust the chassis height, but also may cause overheating pump system, will greatly shorten the life of the pump, test drive the day we have encountered since the pump can overheat protection and short-term adjustment car high. Although there are limitations can not be avoided, but after I consult the brand and our service shop that, as long as the normal use of the words air suspension failure rate is not higher than other car parts, now rarely encountered because the air suspension itself damaged parts The cause of the fault. (Source: Pacific Automotive cloud lit)

★ Interpretation fast and stable flying carpet secret air suspension

Childhood, we read many fairy tales, for the future also has a variety of fantasy, although different protagonists different adventures, but there always seems to have a flying carpet, carrying us speeding. Growing up, we know that a lot of dreams are only illusions, and carpet has become a reality, it is the car. It took us rolling down the road of life, and let our "dream of flying carpet" more comfortable and more stable Secrets - air suspension, we are saying today is the protagonist.

● Define air suspension

Suspension means simply, it is the general term for the connection between the body and the wheels, by the shock absorbers, the guide means and the elastic components, air suspension with air springs is broadly as the suspension of the elastic element.

● Historical air suspension

Air suspension is not only born in recent years. In the early 1930s, Harvey • Firestone (Harvery Samuel Firestone) in his friend Henry • Ford (HenryFord) and Thomas • • Alva Edison (ThomasAlvaEdison) technical support, developed the air column form the air spring suspension system.

So in 1934, Harvey • Firestone in his own company (Firestone Tire and Rubber Company) in the first real air springs for the automotive industry. In 1938, interest in GM's happened to the air spring suspension system is installed on the bus. They cooperate with the Firestone company, he conducted the first round of tests in 1944. And in 1953 began production of passenger cars equipped with air suspension, which is the beginning of commercial vehicles using air suspension.

Before we understand the air suspension structure Let us look at the difference between the air suspension and the suspension of the ordinary, the elastic element common suspension spring, between the body and acts as an elastic contact of the tire, and bear and transfer the vertical load , ease and curb the impact caused by uneven road and so on, in order to accelerate the shock absorber damping vibrations, limiting body and wheel vibrations.

The air suspension with air springs replace the ordinary spring as the elastic member, it is because of a compressible and expandable gas, so you can play in addition to the air spring between the body and the wheels make contact elasticity to withstand and transfer the vertical load, impact mitigation and suppression caused by uneven road, you can also take the initiative to adjust the body height, which do the groundwork for the next we have to mention electronic control suspension system.

○ air suspension structure

The air suspension system generally consists of air springs, shock absorbers, guiding structure, the air supply unit (such as air compressors, single valve, gas, cylinders, etc.), height control valve. Now many brands, especially pay attention to the comfort of luxury cars or attention by a lot of SUV models are equipped or can be equipped with air suspension, here let us recently in the limelight of the new Audi A6L, for example, be carded

Air springs are added to the compressed air in the flexible sealed container utilizing the compressibility of air to achieve a non-metallic resilient spring action. It has excellent elastic properties, thereby improving the vehicle running comfort. And no matter how much the vehicle load, can be selected by changing the air pressure. For example, by adding additional air chamber means to increase its internal volume, can reduce the stiffness.

Air suspension system to resolve

Meanwhile, according to the compressed air used in different containers, air springs and membrane capsules have two forms, bagged air spring is sandwiched cords rubber balloon and enclosed therein composed of compressed air. Airtight inner layer made of good rubber balloon and the outer layer is made of oil-resistant rubber. Enclosed between the Festival and the Festival steel waist ring, the intermediate portion does not have the radial expansion and to prevent friction between the two sections. The diaphragm air spring sealed balloon made of rubber diaphragm and metal parts composition, will produce radial expansion. In the production car we've seen are mostly membrane air spring, and more applications in the modified field is bagged air spring.

○ shock absorbers

Air suspension at the rear suspension, shock absorbers and air springs are separated from the body of the level of regulation by the air spring, and we often say "Flex" has been referred to the independent shock absorbers responsible, in After the suspension of the new Audi A6L, the shock absorber using ZF company's products, this CDC variable damping shock absorber built-proportional valve, which can continuously control the fluid flow in the shock absorber to achieve adjustment damping coefficients. Front suspension is also true, but considering the space problem, it will air springs and shock absorbers CDC variable damping is integrated.

○ guide means

Air suspension with ordinary suspension guiding mechanism is not much difference, the new Audi A6L below shows the optional air suspension and anatomy ordinary suspension structure, also you can clearly see the air spring instead of the original a coil spring to become an elastic element.

Air suspension system to resolve

○ air supply unit

Air suspension system to resolve

The air supply unit consists of an air pump, air dryer, gas tank and other components, air supply assembly is generally placed in the engine compartment or trunk.

○ height control valve

Height control valve is an important part of the air spring suspension system, its role is to make an air spring under load are to maintain a certain height. Advantage of air spring, and only in the case of using a height control valve can be fully reflected. When the vehicle load increases, the body is equipped with height control valve will be down, connecting axle and height control valve pendulum rotation drive cam shaft is rotated so that the piston and the mandrel move the exhaust valve is closed, into the valve opens, at this time, coming from the intake port of the compressed air into the airbag. With the rise in pressure inside the balloon, the air spring height increases, the body will also rise, because the intake valve is closed to move the pendulum, then height control valve in a state of equilibrium. When the vehicle load is reduced, due to excess pressure inside the balloon, the air spring increases, and thus the body is also increased, and therefore, rotation of the pendulum, driven by the camshaft is rotated, so that the piston and ram down, so that the exhaust valve opens, the intake valve is closed, the balloon of excess pressure to the atmosphere. The body back to normal levels, then, the jack and on the move, the exhaust valve is closed, the height of the valve and in a state of equilibrium.

● Electronic Control Suspension System

With the continuous development of science and technology, electronic control suspension system enters into our lives. Early air suspension merely mechanical body height will remain within the set range, now equipped with an electronically controlled rear suspension car when load, speed, road conditions and other driving conditions change, the active suspension system can automatically adjust the suspension stiffness (vehicle adjustment and single wheel adjustment), but also by adjusting the air spring, to adjust the height of the purpose of the body, which can meet the cars ride and handling all aspects of stability requirements. So that the electronic control suspension system can be described as standing on the air suspension of the "shoulders of giants" on.

○ Dynamic Chassis Control Unit

Air suspension system to resolve

The new Audi A6L is equipped with a dynamic chassis control system, dynamic chassis control system and vehicle stability system (ESP) via a data bus to complete the transmission of information, based on travel demand, the dynamic chassis control system can pump, dispensing valve and CDC variable damping The proportional valve is controlled.

For example, we have chosen while driving dynamic mode, then the control system will receive instruction on the implementation of the above mentioned elements are controlled, CDC in the proportional valve can be adjusted to a minimum to reduce the flow of damping fluid velocity to achieve tight stretch of driving experience, the air spring pressure air will be reduced accordingly so highly compressed, so that the lower body; if we want to create a comfortable driving state, pump will provide more high-pressure air to tank, at the same time, the control unit which will tell the dispensing valve to give air pressure air spring delivery. Meanwhile the air suspension control unit via FlexRay in-vehicle networking standards and automotive networking, enabling cross-system and other important body acceleration signal, eliminating the need of early automobile systems require specific acceleration sensors.

Air suspension system to resolve

○ Here it is necessary to mention the body during the process of raising or lowering the details of the transition from the highest level to the lowest position, the system will this process is divided into three parts, the front will be dropping the first third of the stroke, is completed, the rear third of the stroke decreases, thereby further action will be completed twice from the highest to the lowest shift in the whole process, chassis control unit and the dispensing valve has been working in collaboration.

Air suspension system to resolve

Air suspension system to resolve

○ As the driver after you, via the MMI system in the comfort, auto, sports and choose from four modes defined in "automatic" mode, the new A6L to more than 120 km / h speed with more than 30 seconds, suspended frame will automatically be reduced by 10 mm, and provides better driving stability (speed of less than 35 km / h back to the initial height), in the "active" mode, the suspension starting height is lowered by 10 millimeters. In contrast, "elevated" mode, this mode A6L space vehicle from being an extra 10 mm increased to over small obstacles, the vehicle speed over 100 km / h will automatically fall back to the original height. And A8L compared with height adjustment range of the system is relatively small, intuitive feel for the driver may not be so obvious, variable damping and stiffness characteristics of touches for comfort have significant control or assistance.

Air suspension system to resolve

Select Dynamic mode while power output is not only more active, steering wheel feedback intensity has increased significantly, significantly improved pointing accuracy. The air suspension can be adjusted to the hard state, became very nervous the whole car tight, give the driver a sense of control purely mechanized.

Back comfort when comfort mode, the air suspension good filter road vibration, while maintaining proper firmness. Driving experience is still the familiar calm style.

Full Summary:

In fact, the air suspension is not a mystery, Airmatic suspension system such as the Mercedes-Benz S-Class is equipped with the Porsche Cayenne S and the Turbo models can optional PDCC Porsche Dynamic Chassis Control system, etc., many models are equipped with the optional air suspension or possible shelf or electronically controlled suspension system. We bring our air suspension comfort while intoxicated driving experience, we should also see the system structure is more complex because the air suspension failure probability and frequency much higher than the coil spring suspension system, if the air shock absorbers leak occurs, then the whole system will be in a "paralyzed" state. And if you frequently adjust the chassis height, but also may cause overheating pump system, it will greatly shorten the life of the pump. The so-called things are no absolutes, for his is the best.

What's the Suspension System?

When to replace struts and shocks on your car.

Your suspension soaks up the bumps in the road, keeping you comfortable and safe by allowing your brakes and tires to work as designed. Let's look at the major components and then talk a little about what can go wrong.

Spring:

Springs allow your car to absorb the energy of a bump or pothole, without jarring the occupants of the car. Most cars have 4 springs made from spring steel (huh imagine that!) and wound in a spiral shape. Some cars (Corvette) have transverse (across) springs and are made from fiberglass or other composite materials. Made to last the lifetime of the vehicle, properly sized springs seldom need to be replaced.

Shock:

Shocks work to dampen the springs natural tendancy to oscillate. A good way to test your shocks is to push on a corner of your car and observe how many times the car bounces. More than twice and your shocks are worn. The shock is designed with fluid and internal passages to control the movement of the wheel and dampen the spring, over time the fluid can leak, degrade or the valving can become damaged.

Strut:

Just a fancy unit that combines the spring and shock in to one unit. Usually a little more labor to remove the spring when replacing the shock (strut cartridge).

MacPherson Strut:

Just a fancier version of the Strut which also serves as the upper pivot point for the suspension.

Sway or Roll Bar:

When cornering the forces want to roll your car's body to the outside of the turn. You feel this same force sitting inside the car. The Sway Bar counteracts this force and helps to keep the inside wheel in contact with the ground. Stiffer Sway Bar rates give a firmer ride, but better handling.

Ball Joints:

Your suspension is designed to move up and down with the road. This is accomplished with control arms which are connected to the spindle by ball joints. They are what they sound like, a ball and socket joint which allows movement in two dimensions. Most modern ball joints are lubricated with grease, and are sealed. Older ball joint and some newer truck ball joint do have a grease fitting to allow adding grease.

Spindle:

The spindle serves as the center point for your wheel, and rotor to rotate around. The spindle also connects to the lower control arm and upper control arm or MacPherson Strut. Through the travel of your suspension the spindle should remain as parallel to the road as possible. Suspension geometry is designed to keep as much of the tire in contact with the road as possible.

Common Problems:

• Shocks and struts can wear out and affect handling. If you car bounces excessively over bumps and leans hard in corners, your shocks could be warn. Look behind the wheel for the shock or strut and look for leaking oil. This is a sure sign of a worn shock or strut. Also check your owners manual, some will give a mileage estimate for shock or strut life. As a general rule somewhere in the 60,000 - 75,000 mile range depending on your driving style and road conditions.
• Ball joints. Ball joints wear and can cause your car to wander while driving down the road. This is dangerous as they can separate and cause you to lose control.
• Sway bar bushings can wear out over time and will allow the sway bar to clunk when turning corners or at low speeds. A fairly inexpensive part to replace, but gaining access can be tricky depending on the vehicle.

Preventive maintenance:

• Check your shocks or struts for leakage frequently. Also pay attention to how your car handles. If you notice the ride deteriorating take your car in to have the struts checked. 
• Ball joints should be checked when your car is inspected, if not, have your mechanic check them at least twice a year.
• At each oil change make sure you or your mechanic lubricates the ball joints and any other suspension components. Some components can not be lubricated as they are sealed from the factory.

What a Strut Mount is and Why it is Important?

While a strut mount may sound like something simple, it can be one of the most important parts of your vehicle’s suspension system. The strut mount serves as the mounting point for the top of your vehicle’s strut assemblies to connect to your vehicle’s chassis. If you have four-wheel-independent suspension you vehicle will have four strut mounts, two in the front of your vehicle and two in the rear. If you have independent front suspension only, there are only two strut mounts. Ideally, these should be replaced when installing a new strut assembly, but they are usually not sold as part of a complete strut assembly package. Signs of a loose or worn strut mount are much similar to that of other suspension problems, so determining whether it is the strut mount or the strut assembly itself causing a problem is not worth taking time to figure out. Typically, if the strut assembly is worn out, the strut mount is worn out as well and vice versa. Just remember to remove the strut assembly before you try to remove the strut mount for your safety. Before you spend your time and hard-earned money replacing your strut assembly, you want to make sure that it has a stable foundation by replacing your strut mounts.

Where to find your strut mounts
If you only have front wheel independent suspension, you will only have two strut mounts to replace. Simply open your hood and look on both the left and right side of the motor above the front wheels. You should see a round metal plate held on by several large bolts. If you have four-wheel-independent, in addition to the two strut mounts on the front, you will also need to replace two rear strut mounts as well. To locate these you can get an idea of their location by looking up from where your strut assembly attaches to your suspension and follow it to where it connects to your vehicle at the top. To get to the strut mounts, you will need to open your trunk and pull back the carpet over each side of your wheel wells and the strut mounts should be easy to find. Keep in mind that the strut assembly is a pressurized system that is held by the strut mount. For your safety, you want to replace a strut mount only after the strut assembly itself has been removed.
Front Left Strut Top Mount For ACURA CL&TL HONDA ACCORD 

How to choose the right strut mounts and install them

It is easy to choose strut mounts for your car, truck or SUV, as you should always choose one that conforms to original equipment specifications. The only time you would choose a different type of strut mount is if you alter the suspension by installing a different type of strut assembly than what it came with from the factory. For example, if you upgrade your vehicle to heavy-duty off-road suspension or racing suspension, you will want to choose a strut mount that is compatible with that particular type of strut assembly. Replacing the strut mounts is easy, you just need the correct size wrench to remove the bolts that hold them in place. Simply remove the bolts, remove the strut mount, replace it with the new strut mount and replace the bolts. When replacing the rear strut mounts, be sure to push the carpet back where it belongs. You are now ready to install your new strut assemblies with no worries.
When it comes to auto repair, some of the smallest parts can have very important jobs in keeping your vehicle running and driving the way it should. Failure of a simple part such as a strut mount can lead to extensive damage to your suspension, chassis and even your hood or trunk if the strut mount completely fails. Complete failure of a strut mount will allow the pressure in your strut assembly to literally launch it into your hood or trunk lid and can cause both suspension and body damage. Part of successful do-it-yourself auto repair is to be sure that you cover all the bases and make sure that you research any repairs thoroughly to be sure that when you replace a part or component, you replace any other parts that may cause your repair to fail.

Do My Struts Need To Be Changed?

One of the biggest changes in the mindset of today’s shoppers is the shift from a consumption mentality to a savings mentality. And that isn’t seen any more clearly than behind garage doors across America. According to research done at Polk, there are more than 247 million cars and light trucks on the road in the U.S. today at an average age of 11.4 years old. Considering that just a decade ago, the average was 9.6 years, it’s obvious that we’re all keeping our vehicles longer and trying to get more value out of them before trading in and buying something new. But the only way to get more value is to stay on top of maintenance items. You will keep your car running better longer and it is cheaper in the long run than getting by without service until major repairs are needed.

We’ve all been to the repair shop for a routine oil change and walked out with repair estimates for thousands of dollars. The question that crosses all our minds is, “What of this stuff really needs to be done?” To answer this question, let’s start with the basics of struts and what they do. Then we’ll talk how struts depreciate and what is involved when repairing them.

What Are Struts?

Struts are the main component of a modern independent suspension system – these are what “suspend” the body and frame of a vehicle above the wheels. All the weight of the vehicle rests on the struts, which shift the weight, via a few other components, to the wheels. Struts have a possible three components: a spring, shock absorber and the optional swivel mount.

The Spring

A spring is used to “suspend” the weight of your vehicle above the wheels — allowing the wheels to travel up and down on the road without causing possible damage to the body of your car by means of bumping up and down with every crack or pothole in the road. The spring is constantly trying to find the equilibrium to smooth out the impact of the road; but without a shock absorber it would cause the body of the vehicle to move up and down several times after each bump.

The Shock Absorber

Shock absorbers (shocks) absorb the shock of an uneven road before it reaches the body of the vehicle. Instead of all the force of a bump being conveyed from the spring to the body/frame of the vehicle, shock absorbers take the force and use most of it up themselves. The force that does make it way to push up the body of the vehicle is absorbed by the shock absorber when the vehicle comes back down for a smooth transition to equilibrium and a normal ride. A strut is a combination of a spring and shock absorber.

The Mount

Most smaller vehicles today, such as sedans, with independent suspension use what is called a “MacPherson” strut —named after its inventor. The MacPherson Strut throws the swiveling mount into the spring and shock absorber combination. They have to be strong enough to not only swivel when the wheels turn, but to also be able to bear the weight of the vehicle.

What Makes Struts Go Bad?

Wear and Tear

Struts need to be replaced if any of the three components mentioned above wear out. Unlike your oil filter, brakes or spark plugs, struts are not often thought of as a normal replacement item. But like your brakes or spark plugs, they are not made to last forever. Since struts are continuously in use when you drive, bearing all the weight of your vehicle, it should not be surprising that their components eventually wear out.

The shock absorber uses the force of a bumpy road to push a fluid from an internal chamber, through an orifice, and into another chamber. It does this as the internal piston is traveling up and down, and so it needs seals to keep the fluid where it is meant to be while parts are moving all around it. These seals eventually wear out, either by externally leaking fluid, or by internally leaking fluid, allowing too much fluid to pass too easily from one chamber to another, thus reducing the amount of force the shock absorber can use up.

The mount component uses a bearing to carry the weight of the vehicle while also allowing the wheels to turn. It also further dampens the vibrations by using molded rubber between the strut and the vehicle. The mount will need to be replaced if the bearing wears out or the rubber gets old and cracks or tears.

The spring should last the longest out of the three components since it is a solid piece of metal that is tempered to be able to extend and contract many times. But, if the shock absorber component is bad, then the spring is hit with much more force than is designed for it, and will eventually wear to become weaker than it should.

How To Tell

You may notice the vehicle sagging, or that the ride is not as crisp as usual if the springs have been subjected to excessive wear and tear. In places where rusting is a common problem, springs may break, causing awful noises when turning or on bumps, steering pull, or worse. More than likely though, you will not notice any signs as your springs fail because the changes are so gradual. And since the replacement of springs goes along with struts as an economical option in today’s world, they will most likely be replaced before they ever fail.

The most easily recognized is failing mounts because they usually make a noise. Failing mounts will often make a popping or clicking noise while you’re turning the steering wheel because the bearing inside is bad. Especially if you put your vehicle in park and the noise is still occurring while turning the wheel, strut mounts are your number one suspect.

Shock absorbers that failed are much harder to notice. With oil-filled struts, external leaks are easy to spot, especially if the leak is constant. But if the leak is slow, it may never be noticed, and with gas-filled struts, external leaks are not identifiable at all. Usually struts don’t fail completely though, and not all at once. The wear of shock absorbers creep up as the internal seals lose their sealing capacity slowly. The difference won’t be noticed from one day to the next, but there is probably a minute daily performance decline of your shock absorbers as they age.

Several problems may be noticed by drivers if the failure progresses to a severe stage. These include: excessive movement up and down, tire noise and vibration from cupping caused by excessive up/down movement, excessively harsh riding over bumps or noise on every bump from too much suspension travel. Most struts should be replaced before these symptoms occur.

How Long Do Struts Last?

There is no mileage interval that covers all shocks, and relying solely on your senses as a driver to tell when struts are bad can be deceiving since strut failure is usually so gradual you may never notice it at all. Having your struts inspected regularly, including a test drive by a technician, can be helpful to monitor your struts performance.

Does It Really Need To Be Done?

Although struts may not pose the obvious safety concerns that failed brakes might, or the obvious threat of damage that neglecting to change a timing belt on time might, they do affect both these areas, though in smaller ways. Bad struts means there is more wear and tear on all suspension parts, including the steering system as well. The obvious comfort factor of new struts being a more pleasant drive. Struts are more than a cosmetic or comfort concern though. They are an important part of the way your vehicle operates and neglecting them can cause more wear and tear on the rest of your car. Always take this into consideration and plan ahead, especially for those who are budget conscious.

Shock absorber and Shock strut

A shock absorber (in reality, a shock “damper”) is a mechanical or hydraulic device designed to absorb and damp shock impulses. It does this by converting the kinetic energy of the shock into another form of energy (typically heat) which is then dissipated. A shock absorber is a type of dashpot.

HONDA CIVIC Rear copmplete Shock strut

Pneumatic and hydraulic shock absorbers are used in conjunction with cushions and springs. An automobile shock absorber contains spring-loaded check valves and orifices to control the flow of oil through an internal piston (see below).[1]

One design consideration, when designing or choosing a shock absorber, is where that energy will go. In most shock absorbers, energy is converted to heat inside the viscous fluid. In hydraulic cylinders, the hydraulic fluid heats up, while in air cylinders, the hot air is usually exhausted to the atmosphere. In other types of shock absorbers, such as electromagnetic types, the dissipated energy can be stored and used later. In general terms, shock absorbers help cushion vehicles on uneven roads.

Vehicle suspension

In a vehicle, shock absorbers reduce the effect of traveling over rough ground, leading to improved ride quality and vehicle handling. While shock absorbers serve the purpose of limiting excessive suspension movement, their intended sole purpose is to damp spring oscillations. Shock absorbers use valving of oil and gasses to absorb excess energy from the springs. Spring rates are chosen by the manufacturer based on the weight of the vehicle, loaded and unloaded. Some people use shocks to modify spring rates but this is not the correct use. Along with hysteresis in the tire itself, they damp the energy stored in the motion of the unsprung weight up and down. Effective wheel bounce damping may require tuning shocks to an optimal resistance.

Spring-based shock absorbers commonly use coil springs or leaf springs, though torsion bars are used in torsional shocks as well. Ideal springs alone, however, are not shock absorbers, as springs only store and do not dissipate or absorb energy. Vehicles typically employ both hydraulic shock absorbers and springs or torsion bars. In this combination, “shock absorber” refers specifically to the hydraulic piston that absorbs and dissipates vibration.

Types of vehicle shock absorbers

Twin-tube

Basic twin-tube

Also known as a “two-tube” shock absorber, this device consists of two nested cylindrical tubes, an inner tube that is called the “working tube” or the “pressure tube”, and an outer tube called the “reserve tube”. At the bottom of the device on the inside is a compression valve or base valve. When the piston is forced up or down by bumps in the road, hydraulic fluid moves between different chambers via small holes or “orifices” in the piston and via the valve, converting the “shock” energy into heat which must then be dissipated.

Twin-tube gas charged

Variously known as a “gas cell two-tube” or similarly-named design, this variation represented a significant advancement over the basic twin-tube form. Its overall structure is very similar to the twin-tube, but a low-pressure charge of nitrogen gas is added to the reserve tube. The result of this alteration is a dramatic reduction in “foaming” or “aeration”, the undesirable outcome of a twin-tube overheating and failing which presents as foaming hydraulic fluid dripping out of the assembly. Twin-tube gas charged shock absorbers represent the vast majority of original modern vehicle suspensions installations.

Position sensitive damping

Often abbreviated simply as “PSD”, this design is another evolution of the twin-tube shock. In a PSD shock absorber, which still consists of two nested tubes and still contains nitrogen gas, a set of grooves has been added to the pressure tube. These grooves allow the piston to move relatively freely in the middle range of travel (i.e., the most common street or highway use, called by engineers the “comfort zone”) and to move with significantly less freedom in response to shifts to more irregular surfaces when upward and downward movement of the piston starts to occur with greater intensity (i.e., on bumpy sections of roads— the stiffening gives the driver greater control of movement over the vehicle so its range on either side of the comfort zone is called the “control zone”). This advance allowed car designers to make a shock absorber tailored to specific makes and models of vehicles and to take into account a given vehicle’s size and weight, its maneuverability, its horsepower, etc. in creating a correspondingly effective shock.

Acceleration sensitive damping

The next phase in shock absorber evolution was the development of a shock absorber that could sense and respond to not just situational changes from “bumpy” to “smooth” but to individual bumps in the road in a near instantaneous reaction. This was achieved through a change in the design of the compression valve, and has been termed “acceleration sensitive damping” or “ASD”. Not only does this result in a complete disappearance of the “comfort vs. control” tradeoff, it also reduced pitch during vehicle braking and roll during turns. However, ASD shocks are usually only available as aftermarket changes to a vehicle and are only available from a limited number of manufacturers.

Coilover

Coilover shock absorbers are usually a kind of twin-tube gas charged shock absorber around which has been mounted a large metal coil. Though common on motorcycle and scooter rear suspensions, coilover shocks are uncommon in original equipment designs for vehicles, though they have become widely available as aftermarket add-ons. Coilover shocks for cars have been considered specialty items for high performance and racing applications where they allow for significant reductions in overall vehicle height, and though high-quality aftermarket options with wide sturdy springs may provide improvements in vehicle performance, there is dispute over whether or not most aftermarket coilover shocks confer any material benefits to most drivers and may in fact reduce performance over original equipment installations.

Mono-tube

Hydraulic shock absorber monotube in different operational situations:
1 ) Drive slow or adjustments open
2 ) How to “1”, but extension immediately after the compression
3 ) Drive fast adjustments or closed, you can see the bubbles of depression, which can lead to the phenomenon of cavitation
4) How to “3”, but the extension immediately after the compression
Note: The volume change caused by the stem is considered.

Absorber with gas tank connected rigidly, compared to most of the shock absorbers to separate tank is used a diaphragm instead of the membrane and is not present the control valve of the expansion of the pneumatic chamber.
Description:
1) Sheath gas tank and
2) Stem
3) snap rings
4) Plate bearing spring
5) Spring
6) End cap and preload adjustment
7) Cap gas, either in the gas valve is not in the version with the gas valve (inverted profile)
8) Diaphragm Mobile
9) Pad switch (compression)
10) Wiper
11) A seal assembly, oil seal oil seal and bases and closing damper
12) Buffer Buffer or negative limit switch (extension)
13) Piston with piston ring and strip / sliding

The principal design alternative to the twin-tube form has been the mono-tube shock absorber which was considered a revolutionary advancement when it appeared in the 1950s. As its name implies, the mono-tube shock, which is also a gas-pressurized shock and also comes in a coilover format, consists of only one tube, the pressure tube, though it has two pistons. These pistons are called the working piston and the dividing or floating piston, and they move in relative synchrony inside the pressure tube in response to changes in road smoothness. The two pistons also completely separate the shock’s fluid and gas components. The mono-tube shock absorber is consistently a much longer overall design than the twin-tubes, making it difficult to mount in passenger cars designed for twin-tube shocks. However, unlike the twin-tubes, the mono-tube shock can be mounted either way— it does not have any directionality. It also does not have a compression valve, whose role has been taken up by the dividing piston, and although it contains nitrogen gas, the gas in a mono-tube shock is under high pressure (260-360 or so) which can actually help it to support some of the vehicle’s weight, something which no other shock absorber is designed to do.

Mercedes became the first auto manufacturer to install mono-tube shocks as standard equipment on some of their cars starting in 1958, manufactured byBilstein. Because the design was patented, no other manufacturer could use it until 1971 when the patent expired.

Theoretical approaches

There are several commonly used principles behind shock absorption:

• Hysteresis of structural material, for example the compression of rubber disks, stretching of rubber bands and cords, bending of steel springs, or twisting of torsion bars. Hysteresis is the tendency for otherwise elasticmaterials to rebound with less force than was required to deform them. Simple vehicles with no separate shock absorbers are damped, to some extent, by the hysteresis of their springs and frames.
• Dry friction as used in wheel brakes, by using disks (classically made of leather) at the pivot of a lever, with friction forced by springs. Used in early automobiles such as the Ford Model T, up through some British cars of the 1940s. Although now considered obsolete, an advantage of this system is its mechanical simplicity; the degree of damping can be easily adjusted by tightening or loosening the screw clamping the disks, and it can be easily rebuilt with simple hand tools. A disadvantage is that the damping force tends not to increase with the speed of the vertical motion.

For more details on this topic, see Friction disk shock absorber.

Solid state, tapered chain shock absorbers, using one or more tapered, axial alignment(s) of granular spheres, typically made of metals such asnitinol, in a casing. 

Fluid friction, for example the flow of fluid through a narrow orifice (hydraulics), constitutes the vast majority of automotive shock absorbers. This design first appeared on Mors racing cars in 1902.[6] One advantage of this type is, by using special internal valving, the absorber may be made relatively soft to compression (allowing a soft response to a bump) and relatively stiff to extension, controlling “rebound”, which is the vehicle response to energy stored in the springs; similarly, a series of valves controlled by springs can change the degree of stiffness according to the velocity of the impact or rebound. Specialized shock absorbers for racing purposes may allow the front end of a dragster to rise with minimal resistance under acceleration, then strongly resist letting it settle, thereby maintaining a desirable rearward weight distribution for enhanced traction.

For more details on this topic, see Lever arm shock absorber.

Compression of a gas, for example pneumatic shock absorbers, which can act like springs as the air pressure is building to resist the force on it. Enclosed gas is compressible, so equipment is less subject to shock damage. This concept was first applied in series production on Citroëncars in 1954. Today, many shock absorbers are pressurized with compressed nitrogen, to reduce the tendency for the oil to cavitate under heavy use. This causes foaming which temporarily reduces the damping ability of the unit. In very heavy duty units used for racing or off-road use, there may even be a secondary cylinder connected to the shock absorber to act as a reservoir for the oil and pressurized gas.In aircraft landing gear air shock absorbers may be combined with hydraulic damping to reduce bounce. Such struts are called oleo struts (combining oil and air)[3].

Inertial resistance to acceleration, for example prior to 1966 [4] the Citroën 2CV had shock absorbers that damp wheel bounce with no external moving parts. These consisted of a spring-mounted 3.5 kg (7.75 lb) iron weight inside a vertical cylinder [5] and are similar to, yet much smaller than versions of the tuned mass dampers used on tall buildings.

Composite hydropneumatic suspension combines many suspension elements in a single device: spring action, shock absorption, ride-height control, and self leveling suspension. This combines the advantages of gas compressibility and the ability of hydraulic machinery to apply force multiplication.

Conventional shock absorbers can be combined with Air suspension springs - an alternate way to achieve ride-height control, and self leveling suspension.

In electrorheological fluid damper, an electric field changes the viscosity of the oil. This principle allows semi-active dampers application in automotive and various industries.

Magnetic field variation magneto rheological damper changes its fluid characteristics through an electromagnet.

The effect of a shock absorber at high (sound) frequencies is usually limited by using a compressible gas as the working fluid or mounting it with rubber bushings.

Features & Benefits[edit]

Some shock absorbers allow tuning of the ride via control of the valve by a manual adjustment provided at the shock absorber.

In more expensive vehicles the valves may be remotely adjustable, offering the driver control of the ride at will while the vehicle is operated.

The ultimate control is provided by dynamic valve control via computer in response to sensors, giving both a smooth ride and a firm suspension when needed.

which allow ride height adjustment or even ride height control, seen in some large trucks and luxury sedans, including Lincoln and Land Roverautomobiles.

Ride height control is especially desirable in highway vehicles intended for occasional rough road use, as a means of improving handling and reducing aerodynamic drag by lowering the vehicle when operating on improved high speed roads, as seen in the Tesla Model S.