Not only such characteristics as smooth operation and obstacle handling, but also your safety when riding depend on the correctly selected spring and proper shock absorber settings. Modern shock absorbers have a decent number of settings, and many are simply afraid to turn them. We hope this article will help you figure out what's going on with your rear shock absorber and make your suspension perform even better! A shock absorber is one of the elements of any bicycle suspension. There are many types of shock absorbers - air and spring, with and without a stable platform, but the principle of operation of the basic settings remains the same. We will return to them a little later (using the example of the Fox DHX 5 rear shock absorber), but for now we will talk about the main characteristics of the shock absorber and spring.
What is written on the shock absorber?
Each shock absorber has 2 parameters - axle length and rod stroke. Let's look at them using the example of a shock absorber with the following parameters: 8.75x2.75 (1 inch=2.54 cm=25.4 mm) The first number is the axle length in inches. Measured at the center of the holes into which elements (bolts or axles) are inserted to firmly secure it to the frame. (in millimeters it turns out to be 222.2 mm) The second number is the stroke of the rod. Also measured in inches. This value shows how many millimeters the rod fits into the shock absorber body. (in millimeters it turns out to be 70 mm). Both meanings are very important. Each frame is designed for a given shock absorber length. When installing a shock absorber of greater or lesser length, the geometry changes (most often for the worse) - the fork angle collapses or sharpens, the carriage is raised or lowered. The smoothness, progressiveness, and linearity of the suspension will change, and in rare cases, the frame or shock itself will break due to changes in shock absorber performance. The stroke of the rod directly affects the stroke of the suspension. Let me remind you that suspension travel is the distance that the rear wheel travels vertically from the state with the shock absorber fully expanded to the state with the shock absorber fully compressed (when the rod is recessed to the very end). It is worth noting that sometimes shock absorbers with the same length along the axes have different rod lengths. Example: 8.75x2.8 and 8.75x2.5.
If the frame is designed for 2.8 rod travel, and you install a shock absorber with a rod length of 2.5 (with the same length along the axes of both), then the suspension travel will be reduced while the bike geometry remains unchanged. When installing a shock absorber with a rod stroke exceeding the original value, mechanical damage to parts of the frame may occur if the suspension breaks down. Another example is the same stroke of the rod along the axes for different shock absorber lengths. Example: 8.75x2.8 and 9.0x2.8. In this case, the suspension travel remains virtually unchanged, but the geometry will change.
Advice: install exactly the shock absorber recommended by the manufacturer. If the market does not have the required sample, then choose something as close as possible to this value. From my own experience, I will say that the length along the axes should not differ from the original one by ± 5 mm, and the stroke of the rod should not be more than 3-5 mm.
Spring.
The spring can be titanium or steel. Unlike car and motorcycle suspensions, the springs on bicycles are always linear, without changing the thickness of the coils along the entire length. The spring has 5 parameters - stiffness, recommended stroke, length, internal and external diameters. Hardness is measured in lbs/inch², which means pounds per square inch. This value in most cases ranges from 200 to 700 in increments of 50 (rarely 25). The recommended stroke of the shock absorber rod is the stroke of the shock absorber rod for which the spring is designed. Most often it is written on shock absorbers: 400x2.8 The first value is the stiffness, the second is the recommended stroke of the rod. The length of the spring primarily depends on the recommended stroke of the rod. The larger it is, the longer the spring. Also, the length increases with increasing rigidity, because the coils increase in diameter, but the distance between them does not.
The internal diameter depends on the landing pad and the shock absorber washer that secures the spring. It is worth noting that two seemingly identical springs may differ in internal diameter (for example, Fox Vanilla before 2006 and Fox DHX have different mounting locations for the springs, so the springs will be different). In addition to accurately installing the spring into the grooves of the shock absorber washers, sufficient distance must be ensured from the spring coils to the shock absorber body. Otherwise, the spring will begin to rub the body. The outer diameter essentially depends on the same thing as the inner diameter. However, different spring manufacturers make springs from different materials. For this reason, the thickness of the coils may exceed the standard value for the original spring. In one case, it may simply not fit between the tank and the body, and on the other hand, it may begin to wipe the tank.
Is it possible to put a 400x3.0 spring on an 8.75x2.8 shock absorber? It is possible provided that the length of the spring does not exceed the maximum length between the fully unscrewed washer and the lower platform. If the length of the spring exceeds this value, and it must be compressed to install the spring, then its use is highly not recommended. The use of such a spring can ultimately tear off the lower pad of the shock absorber, plus, with any lifting of the rear wheel from the ground, the rod cover, oil seal, housing and the rod itself bear an increased load, because the spring is constantly compressed. In addition to everything, the 400x.3.0 spring weighs more than the 400x2.8. Is it possible to put a 400x2.5 spring on an 8.75x2.8 shock absorber? It is forbidden. Because the spring rod stroke is less than the shock absorber rod stroke, then when the suspension is fully activated, the spring coils will close together and this will be followed by destruction of the shock absorber pad and washer with possible destruction of the rod. Let us note one more point. The stiffer the spring, the thicker its coils. Because the distance between the coils must remain unchanged to avoid contact between the coils (described above), then the length of the spring and the outer diameter increase.
In our practice, there was a case where a 500x2.5 spring fit perfectly into the shock absorber, but a 850x2.5 spring exceeded the permissible outer diameter. When choosing a spring, you should be guided by the following parameters: - the recommended stroke of the spring rod should be either the same as in the shock absorber or exceed it by an insignificant value - the length of the spring should not exceed the distance with the washer and shock absorber pad fully untwisted - the internal diameter should exactly coincide with seating area for the pad and puck. The spring should not touch the shock absorber body during operation - the spring with the outer part of the coils should not come into contact with the reservoir
Adjusting the shock absorber (for exampleFOXDHX 5.0)
-selecting the desired spring stiffness
-settingBottom-Out
-selection of pressure in the tank
-rebound adjustment
-adjustmentProPedal
Frames with different types of suspension perform differently, and even with the same rider weight, the spring rate can differ by 50, 100, or even 200 pounds. The performance of the shock absorber also plays a significant role. Many manufacturers have a table of the required settings in the technical manual for frames. However, on the one hand, they will not suit every rider; on the other hand, everyone rides differently.
Spring stiffness. This is one of the main parameters of shock absorber operation. Sag is the most important indicator when selecting a spring. When you get on the bike, the suspension is compressed by a certain amount. For freeride and downhill it ranges from 25 to 40% (on average 1/3). What is a sag? Sag = length by which the shock absorber is compressed/full stroke of the rod, % With a rod stroke of 70 mm, a sag of 25 mm is approximately 1/3 What is the easiest way to measure it? Measure the length of the shock absorber along the axles in mm with the suspension fully relaxed. Let's assume it is 222 mm. The rod stroke is 70 mm. Sit on the bike (it’s better to stand on the pedals, leaning slightly on the handlebars). Ask a friend to measure the distance between the shock absorber axles. For example, it will be 195 mm. Subtract the resulting value (195 mm) from the length of the shock absorber (222 mm). 222-195=27 mm. This is the amount by which the shock absorber has compressed. Sag=27/70*100%=38.5% Our sag was 38.5%. To increase it, install a softer spring so that the shock absorber compresses under your weight by a greater amount. To reduce sag, set the spring stiffer. With little experience in selecting a spring, I would recommend choosing a spring with a sag of 33%. What does sag affect? It will be most clear if you imagine a flat road and a hole on it. When the rear wheel reaches the hole, due to the fact that the spring is compressed under your weight, the wheel will go down by the amount equal to the sag and process the hole. Spring too soft. Sag->50%. At each hole, the wheel will sink too much, which, on the one hand, will, of course, improve control over the track, and on the other hand, it will slow down the bike. If the spring is too soft, the shock absorber will constantly break through, which will lead to the destruction of both itself and the frame. The spring is too stiff. Sag<20%. Каждая кочка будет отдаваться в педали, ухудшится контроль за трассой, хоть и прибавиться стабильности (но только на ровных участках, где нужно много крутить).
SettingsBottom-Out. This adjustment is the blue cap on the reservoir. Changes the volume of the air chamber. When the shock absorber operates, oil moves from the main chamber to the reservoir. The fewer obstacles there are in the way of oil, the more linear and smoother the shock absorber will work. Bottom-Out allows you to adjust the progressiveness of the shock absorber. With the adjustment all the way out, the shock absorber will operate linearly from start to finish. With the adjustment fully tightened, progression will begin approximately in the last third of the stroke. Why is it needed? All tracks have both small and large obstacles. To handle small obstacles you need soft and smooth work, for large ones - hard and progressive. If you are jumping drops, turn the adjustment to the position at which the shock absorber stops breaking through. I note that the Bottom-Out setting does not in any way affect the performance of the shock absorber at 2/3 of the initial stroke - it remains just as soft. The result is this - tighten it to the value at which the shock absorber will not break through. However, if you do not jump drops, or there are no large obstacles on the track on which the shock absorber works for the entire stroke, then turn the adjustment until the shock absorber begins to break through. The smoother the suspension moves, the better. But remember - it should not break through. We need to find the ratio at which it will work most beneficially for a given situation.
Selecting the pressure in the tank. The pressure in the tank should be between 125-200 Psi. Pressure too low (<125 Psi) ухудшит работу, начнутся провалы в подвеске. Слишком высокое (>200 Psi) pressure will also worsen performance, the suspension will become too stiff, and the chance of shock absorber destruction will increase (from increased load on the seals and rod to explosion of the reservoir). Essentially, the pressure in the reservoir is approximately equal to the change in compression. At low pressure, the shock absorber operates most smoothly and handles bumps better. At high pressure, its operation becomes harder, it is more difficult for oil to flow through all the holes, to some extent it begins to dull on bumps and penetrate less. One important thing to remember is that if you have pumped up to 125 Psi with the Bottom-Out fully tightened, and decide to unscrew the Bottom-Out, the pressure in the reservoir will drop below the minimum. Also, with the Bottom-Out fully unscrewed and a pressure of 200 Psi, when tightening the Bottom-Out, the pressure will exceed the permissible value. My advice is to deflate the shock first, then adjust the Bottom-Out and then re-inflate. Bottom line: reservoir pressure depends on how you ride. Love it harder - the pressure is higher, softer - the pressure is lower. 4.Rebound adjustment. Rebound is the time during which the shock absorber returns from a compressed state to a decompressed state. If you ride over bumps a lot, make the rebound faster, if you jump a lot of drops, make it slower. If the rebound is too slow, the shock absorber will not have time to expand to handle the next bump. If it is too fast, the wheel will bounce with a significant deterioration in traction. Remember to take the rebound slower on drops - if you rebound quickly, the suspension will throw you over the handlebars when landing, which often ends in broken arms, collarbones and concussions. On the trails, in my opinion, adjusting the rebound on the shock absorber rather than on the fork is crucial. Despite the fact that there are always a huge number of obstacles on the track, make the rebound 1-3 clicks slower than the optimal value. This will add stability.
AdjustmentProPedal. No matter what suspension you have, the shock absorber will still sway when pedaling. Why does this happen? Human legs cannot pedal at the same speed or with the same balance as a motorcycle engine. Low rotation speeds of the connecting rods with the carriage force the suspension to tighten with each pedal press. Due to this, part of the energy is lost to swinging. This is why there is a ProPedal adjustment that prevents swinging. It has 15 positions, from completely off to fully on. It would seem - why is it needed at all, is it possible to turn it on once to isolate the build-up? No you can not. Despite Fox's assurances that turning on the adjustment does not affect the performance of the shock absorber, this is not the case. The more you tighten the ProPedal, the worse the shock absorber begins to handle bumps, and a slight knock appears. Therefore, you need to look for a compromise between reducing the buildup and working out the suspension of the bumps. If the trail is long and easy and requires a lot of spin, the Propedal can be turned on 10 to 15 clicks. If the track has a lot of bumps and turns, do not turn on the Propedal more than 8 clicks. Bottom line: Propedal position varies by track. Look for a compromise between rocking and handling bumps. Of course, ideally, the shock absorber should be adjusted for each track, and understanding what the settings should be comes only with experience. Don’t be afraid to once again climb into the suspension and turn some knob - the main thing is to remember what you did and immediately check how the behavior of the bike has changed. Good luck with the setup!
Text: Arsen “Bars-Zerwick” Khanbekyan
Photo: Fox Shox
Upgrading the car's chassis will help make your car more comfortable. Let's look at how to make the suspension softer.
What affects driving performance
Factors that determine the driving characteristics of a car:
- spring stiffness and design;
- shock absorbers;
- tire size and rubber composition;
- ratio of unsprung and sprung masses.
We do not take into account the elasticity of rubber silent blocks, since the owner rarely has the opportunity to personally evaluate the difference between manufacturers of rubber products. In addition, often the main difference is the resource of silent blocks. The difference in driving performance depending on the manufacturer of silent blocks is extremely difficult to notice. The transition to . This type of suspension is designed for sporty driving and harsh operating conditions. If your car has polyurethane products installed, then switching to silent blocks made of regular rubber will make the car softer.
Before you start tuning the chassis, carry out a comprehensive one. Perhaps a too harsh, loud reaction to irregularities is a malfunction of some component, and not a design flaw. A similar effect is observed when driving on overinflated tires. 
Springs
The elasticity of the springs and the amount of force required for compression depend not only on the thickness of the coils, but also on the alloy from which the elastic elements are made. Since it is extremely difficult for an ordinary buyer to find out the characteristics of the metal, you can focus on the thickness of the coil. Patterns affecting the driving characteristics of the car:
- spring design. Springs with variable coil thickness are considered the most comfortable. Such springs have a so-called comfort coil;
- The stiffer the spring, the more clearly the vibrations are transmitted to the car body. Accordingly, the thicker the coil, the greater the stiffness of the spring. A soft car suspension and hard springs are absolutely incompatible things;
- The length of the spring affects the compression stroke of the suspension. The shorter the suspension travel, the shorter the distance to the “breakdown” of the shock absorbers (occurs when the shock absorber, working off an unevenness, rests on its extreme position; at this moment an impact occurs on the bump stop). A shorter spring length leads to less suspension travel, which must be taken into account when installing sports springs (especially when cutting coils). That is why it is important to maintain a balance between the stiffness of the coils and the length of the spring.
Another important aspect is the rigidity of the material against which the spring rests. If you place a gasket made of a dense layer of rubber under the elastic element, the amount of vibrations transmitted to the body will be reduced. If you wish, you can calculate all the parameters of the springs and then make them to order. We recommend watching the video to better understand the essence of recycling elastic elements.
Shock absorbers
If the main purpose of springs is to absorb impact energy, then shock absorbers are designed to dissipate shock energy. Twin-pipe gas-oil shock absorbers cope with this most effectively. If your car is equipped with oil vibration dampers, then now you know how to make the suspension softer.
Both types of shock absorbers use oil as the working fluid. The difference is that during compression of oil models, there is no reverse force acting on the working fluid. To check, you can compress the shock absorber manually. You will see that the rod will remain compressed or will only return slightly to its previous position. In gas-oil shock absorbers, the compensation chamber is filled with an inert gas (nitrogen), so when compressed, a return force acts on the working fluid (the rod, after pressing, tends to take its previous position).
The use of gas in the design allows the wheel not to hang in the air after the suspension has worked out unevenness and will not hit the road surface. It is worth recognizing that when driving at low speeds, both types of shock absorbers work approximately the same. Another disadvantage of oil-based models is that during intensive work and overheating, air bubbles appear in the oil, which negatively affects the performance of shock absorbers and the level of comfort. It would be wrong to say that the suspension becomes softer after such tuning, but driving at high speed on bumpy roads becomes much more comfortable.
You should not install single-pipe gas-oil vibration dampers (often called gas dampers). This type of shock absorbers has greater rigidity, which will only reduce the level of comfort when overcoming bumps.
Rubber
In order to make a car more comfortable, you don’t always need to make the suspension softer. It is enough to install tires with a higher profile and soft rubber composition on the car. The profile height is the distance from the seat on the disk to the end of the tread. The parameter must be marked on the sidewall of the tire. Consider the marking 170/70 R13, in which 70 is the percentage that determines the profile height. In our case, the height is 70% of 170 (profile width) and is equal to 123 mm. How tire profile parameters affect handling and comfort:
Effect of mass on suspension kinematics
The unsprung mass of a vehicle is the total weight of the elements that, when the suspension is operating, are in a movable state in relation to the body. In other words, parts of the car that move along with the suspension and some elements of the chassis. In a car, these include wheel rims, tires, brake system elements, and wheel bearings (approximately 15% of the total amount of the car, the remaining 85% is sprung weight).
To increase the smoothness of the ride, you need to either increase the sprung mass (familiar to owners of spring cars, who often load the axle for a smoother ride), or reduce the weight of the unsprung elements. Since the first option leads to an increase in fuel consumption, deterioration in dynamics and controllability, you need to focus on the unsprung mass. To make the suspension softer, it is enough to install alloy wheels, without going overboard with the width and height of the tire, as well as the size of the wheels themselves.
Elastic suspension elements appeared in transport hundreds of years ago; it was too harsh to ride carts on cobblestone streets. The term “suspension” accurately conveys the essence of the design: the body of a carriage or chaise was literally suspended on leather straps. In 1804, instead of belts, leaf springs appeared, and a hundred years later, on self-propelled carriages - cars - they were replaced by more comfortable and technologically advanced coil springs.
Surprisingly, the design of the elastic elements has not changed fundamentally since then. The suspension was overgrown with advanced shock absorbers, floating silent blocks and hydraulic stabilizers, and coil springs did not disappear anywhere. Moreover, even archaic springs are still in use on trucks and pickups. Of course, there are also wonders: torsion bars (elastic rods - the progenitors of springs) and air springs. But on most passenger cars today you will find a classic spring suspension. Let's talk about them in more detail.
Springs as the basis of the suspension
Springs are the key elements of the suspension. They are the ones who keep the car above the road, and also “swallow” all the impacts from potholes and bumps. Replacing springs can dramatically change how your car behaves on the road.
Springs are selected by engineers based on the mass and purpose of the machine, and shock absorbers are selected to match the characteristics of the springs, dampening their inertia. Often, even different configurations of the same car have different spring characteristics. For example, diesel models are often equipped with stiffer and longer springs than gasoline ones due to the heaviness of the engine. There are differences depending on the market: for North America, where comfort is valued, cars are traditionally equipped with softer springs.
Spring stiffness
Stiffness is a key characteristic of the spring, affecting the energy intensity of the suspension (the ability to drive over uneven surfaces without “breakdowns”), the smoothness of the ride and the vehicle’s handling.
The opinions of car owners regarding the stiffness of springs are diametrically opposed. Someone is sure that “the stiffer the better,” arguing for the accuracy of the steering and the absence of roll. Some will say that stiff springs are evil, killing comfort and handling on bad roads. Both are right, and finding the right balance is not an easy task.
The characteristics of a spring are calculated based on its dimensions - there are even online calculators for this, like for tires. And knowing the basic patterns, some conclusions can be drawn even “by eye”.
Springs differ from each other in their response to load: it can be linear or progressive. Often, car owners replace one type with another: either they install progressive springs instead of linear ones to improve the performance of the suspension, or vice versa - in order to save money.
Linear spring- this is a classic winding with the same pitch of turns and constant stiffness. It is easy to manufacture - therefore it is cheap and most widespread. Under load, such a spring compresses linearly: at the moment of full compression, all turns close simultaneously.
Spring with progressive characteristic characterized by variable stiffness and nonlinear compression under load due to different coil pitches. The harder you press on such a spring, the stiffer it becomes. Under load, the coils with the smaller pitch close first, the total number of remaining free coils decreases, and the spring stiffness increases.
When and how to change springs
Typically, springs are changed due to their breakage or when the car noticeably sag. But it’s better not to bring it to either one or the other.
A broken spring rod is an unpleasant situation: the car is completely immobilized, and you will have to take a tow truck to get to the service station. Springs often burst from shock loads off-road, far from civilization, which further complicates the task.
But springs don’t break just like that - except in rare cases of factory defects. Typically, such failure is preceded by either metal fatigue or corrosion. The latter can be identified in advance: If you notice rust on the spring, do not delay replacing it! The source of corrosion is a likely location for future failure.
There is also nothing good about sagging of a car, and it’s not just about a decrease in ground clearance and the inability to drive onto a high curb. Sagging springs increase the load on other suspension and transmission elements - shock absorbers, wheel bearings, CV joints. And in the MacPherson suspension, because of this, the wheel alignment angles are even lost.
Slightly sagging springs are difficult to detect with the naked eye. It’s better to take a tape measure, measure the distance between the center of the disk and the wheel arch and compare it with the factory value. Besides, tilt to one side is unacceptable: both left and right heights should be the same. Often the springs on the more loaded side - the driver's side - are the first to "give up", especially if the gas tank is located there.
What is the service life of the springs? Previously, it was believed that it was equal to two shock absorber resources, i.e. springs need to be changed not together with them, but every other time. But those days are already in the past: springs are becoming thinner and lighter, and now they fail almost simultaneously with shock absorbers, having “worked out” 70-80 thousand km.
It is often more economical to replace springs together with shock absorbers - you will not have to pay for the same work twice if they are assembled. Just remember that springs, like shock absorbers, are replaced in pairs on each axle: a single replacement will lead to an imbalance in the suspension.
Spring tuning
And yet, the most popular reason for replacing springs is not a breakdown or sagging of the car, but tuning. Suspension lift or lowering, additional rigidity or smoothness of the ride - all these are reasons to change the springs. Fortunately, there are now a lot of options for non-standard springs on sale for all running car models.
But customization needs to be done wisely, without turning tuning into a “collective farm”, of which there are many examples. One of the most common is cutting springs: either your own in order to lower the suspension “with a little cost,” or taken from another car in order to adapt them to your own.
The spring is not uniform along its entire length. At its ends there are so-called support coils, the task of which is to strengthen the structure, correctly fold the spring during operation and fix it in place. Trimming the support coil disrupts the entire calculation of the spring, creates additional metal stresses and, after some time, leads to breakage of the rod. Do not cut springs under any circumstances!
The installation of “roughly suitable” springs from other cars is also questionable. The load will definitely not coincide with the calculated one, which will reduce the spring life, worsen the performance of the suspension and affect handling. The experiment can end prematurely: unsuitable springs often fly out of their seats in extreme suspension operating modes (for example, when hanging a wheel), and the car falls on its “belly.”
If you take up tuning, select springs designed specifically for your car. And don’t forget that the shock absorbers must match them not only in length, but also in characteristics: in good tuning kits they come in one set for a reason.
- Madam, why, let me ask you, didn’t you put on diamond pendants? After all, you knew that I would be pleased to see them on you.
A. Dumas “The Three Musketeers”
Let us remind you: the entire set of parts and assemblies connecting the car body or frame with the wheels is called.
We list the main elements of the suspension:
- Elements that provide elasticity of the suspension. They perceive and transmit vertical forces that arise when driving over uneven roads.
- Guide elements - they determine the nature of the movement of the wheels. Also, the guide elements transmit longitudinal and lateral forces, and the moments arising from these forces.
- Shock-absorbing elements. Designed to dampen vibrations that occur when exposed to external and internal forces
In the beginning there was a spring
The first wheeled ones did not have any suspensions - there were simply no elastic elements. And then our ancestors, probably inspired by the design of the archery bow, began to use springs. With the development of metallurgy, they learned to impart elasticity to steel strips. Such strips, collected in a package, formed the first spring suspension. At that time, the so-called elliptical suspension was most often used, when the ends of two springs were connected, and their centers were attached to the body on one side and to the wheel axle on the other.
Then springs began to be used on cars, both in the form of a semi-elliptical design for dependent suspensions, and by installing one or even two springs across. At the same time, an independent suspension was obtained. The domestic auto industry has used springs for a long time - on Moskvich cars before the advent of front-wheel drive models, on Volga cars (with the exception of Volga Cyber), and on UAZ cars springs are still used.
Springs evolved along with the car: there were fewer leaves in the spring, up to the use of single-leaf springs on modern small delivery vans.
| Advantages of leaf spring suspension | Disadvantages of leaf spring suspension |
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Spring suspension
Springs began to be installed at the dawn of the automotive industry and are still used successfully today. Springs can operate in dependent and independent suspensions. They are used on passenger cars of all classes. The spring, initially only cylindrical, with a constant winding pitch acquired new properties as the suspension design was improved. Nowadays, conical or barrel-shaped springs are used, wound from a rod of variable cross-section. All so that the force does not grow in direct proportion to the deformation, but more intensely. The larger diameter areas work first, and then the smaller ones are switched on. Likewise, a thinner rod is put into operation earlier than a thicker one.
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Torsion bars
Did you know that almost any car with a spring suspension still has torsion bars? After all, the anti-roll bar, which is now installed almost everywhere, is a torsion bar. In general, any relatively straight and long lever that exerts torsion is a torsion bar. As the main elastic suspension elements, torsion bars were used along with springs at the very beginning of the automobile era. Torsion bars were installed lengthwise and across the car and used in a variety of types of suspensions. On domestic cars, the torsion bar was used in the front suspension of Zaporozhets of several generations. Then the torsion bar suspension came in handy due to its compactness. Nowadays, torsion bars are more often used in the front suspension of frame SUVs.
The elastic element of the suspension is the torsion bar - a steel rod that works in torsion. One of the ends of the torsion bar is fixed to the frame or supporting body of the car with the ability to adjust the angular position. The lower arm of the front suspension is installed at the other end of the torsion bar. The force on the lever creates a torque that twists the torsion bar. Neither longitudinal nor lateral forces act on the torsion bar; it works on pure torsion. By tightening the torsion bars, you can adjust the height of the front part of the car, but at the same time, the full suspension travel remains the same, we only change the ratio of the compression and rebound strokes.
Shock absorbers
From the course of school physics it is known that any elastic system is characterized by oscillations with a certain natural frequency. And if a disturbing force with the same frequency acts, a resonance will occur - a sharp increase in the amplitude of oscillations. In the case of a torsion bar or spring suspension, shock absorbers are designed to combat these vibrations. In a hydraulic shock absorber, the dissipation of vibration energy occurs due to the loss of energy for pumping a special fluid from one chamber to another. Nowadays, telescopic shock absorbers are ubiquitous, from small cars to heavy-duty vehicles. Shock absorbers, called gas, are actually also liquid, but the free volume, which all shock absorbers have, contains not just air, but gas under high pressure. Therefore, “gas” shock absorbers always tend to push their rod outward. But the next type of suspension can do without shock absorbers.
Air suspension
In an air suspension, the role of an elastic element is played by the air located in the enclosed space of the air cylinder. Sometimes nitrogen is used instead of air. A pneumatic cylinder is a sealed container with walls made of synthetic fibers vulcanized into a layer of sealing and protective rubber. The design is much like the sidewall of a tire.
The most important quality of air suspension is the ability to change the pressure of the working fluid in the cylinders. Moreover, pumping air allows the device to play the role of a shock absorber. The control system allows you to change the pressure in each individual cylinder. In this way, buses can politely lean over at a stop to make it easier for passengers to board, and trucks can maintain a constant “stay”, whether packed to capacity or completely empty. And on passenger cars, air springs can be installed in the rear suspension to maintain a constant ground clearance depending on the load. Sometimes the design of SUVs uses air suspension on both the front and rear axles.
Air suspension allows you to adjust the vehicle's ground clearance. At high speeds the car “squats” closer to the road. Since the center of mass becomes lower, the roll in corners is reduced. And on off-road terrain, where high ground clearance is important, the body, on the contrary, rises.
Pneumatic elements combine the functions of springs and shock absorbers, although only in cases where it is a factory design. In tuning designs, when air springs are simply added to the existing suspension, it is better to leave shock absorbers.
Tuners of all stripes are very fond of installing air suspensions. And, as usual, some want lower, some higher.
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Dependent and independent suspension
Everyone has heard the expression “it has independent suspension all around.” What does this mean? An independent suspension is a suspension where each wheel makes compression and rebound movements (up and down) without affecting the movements of the other wheels.
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Independent MacPherson strut suspension with L or A-arms is the most common type of front suspension in the world today. The simplicity and low cost of the design are combined with good handling.
A suspension is called dependent when the wheels are united by one rigid beam. In this case, the movement of one wheel, for example upward, is accompanied by a change in the angle of inclination of the other wheel relative to the road.
Previously, such suspensions were used very widely - take our Zhiguli cars. Now only on serious SUVs with a powerful continuous beam rear axle. Dependent suspension is good only for its simplicity and is used where strength conditions require a rigid continuous axle. There is also a semi-independent suspension. This is used on the rear axle of inexpensive cars. It is an elastic beam that connects the axles of the rear wheels.
Despite the fact that car springs are structurally a very simple element, last a long time, are inexpensive, and are changed relatively rarely, this component requires sufficient attention, and its breakdown can lead to dire consequences. Together with the company KYB, one of the world leaders in the development and production of suspension elements, we will learn all the nuances of choosing and using springs.
How often do springs need to be replaced, even if they are not damaged?
— On average, a suspension spring in Russian conditions “nurses” two sets of shock absorbers. As a rule, in-depth diagnostics of springs is recommended at the turn of 100,000 km, as well as joint replacement of the spring, shock absorber, upper shock absorber support and spring support spacers in the case of joint work with the shock absorber with a mileage of more than 100,000 km.
What should you pay attention to when choosing new springs?
— First of all, to a reliable supplier with experience in supplying the assembly lines of automakers. Such companies have modern production technology, a wide range of models and high quality products.
Immediately before purchasing, the spring itself must be checked for the presence of paint chips during transportation, and the coating must not be damaged during installation, otherwise corrosion may occur, weakening the load-bearing capacity of the spring.
If the shock absorber is in good working order, is it possible to somehow determine that it is time to change the springs?
— It is necessary to conduct a thorough external examination. There are three main points: the integrity of the turns, the presence of traces of corrosion and contact of the turns. If there are traces of contact of the coils with a working shock absorber, the springs have sagged, that is, they have lost their load-bearing capacity and require replacement. Next, you need to measure the vehicle’s ground clearance in the area of each wheel on a level surface and, comparing it with the control values from the vehicle’s repair documentation, make a final decision about the serviceability of the springs.
Springs come in completely different types. Why is this necessary and is there any difficulty in replacing one type of spring with another?
— There are several dozen types of suspension spring designs. The type of spring is determined by the car manufacturer, and when choosing a replacement option, it is highly advisable to follow the rule: the new spring must completely match the shape of the original one.
The design of the spring is selected based on the ratio of the available free space, that is, the layout, and the required parameters: suspension strokes and elastic properties. The most complex spring designs - barrel-shaped with a variable cross-section rod and side-loading - were invented for the best combination of comfort and suspension energy intensity, as well as load capacity. The new spring may have a different number of turns or unloaded height, but the mounting diameters and outer diameter at the widest point must match. It is important to remember that the key to correct selection of springs is the use of branded catalogs from the manufacturer of the part.
What can reduce the life of a spring?
— The service life of automobile suspension springs depends on many factors that must be taken into account both at the production stage and at the stage of direct operation of the car. First of all this technological defect when errors are made during the production process.
For example, this is the choice of material (certain grades of steel) from which the springs will be made. It is very important to select a steel grade with the appropriate parameters, which can subsequently provide the required degree of spring elasticity over a long period of time. Accordingly, proper quality of bar production is required. Compliance with spring production technology at all stages of the production process (preparation, winding, hardening, tempering, preparation for painting, painting, etc.). Quality control at all stages. High-quality preparation of the rod surface for painting and proper painting. The use of a special coating with elastic properties for painting, capable of withstanding various mechanical loads and chemical influences under conditions of a wide range of ambient temperatures.
During operation There are also many factors that can shorten the service life of springs. The most common factor is a violation of the manufacturer's recommendations for the selection of springs, as well as the selection of unsuitable shock absorbers. Actually, untimely replacement of “original” but worn shock absorbers also negatively affects the service life of the springs. A faulty shock absorber does not do a good job of damping the vibrations of the suspension spring, which is why the spring performs a greater number of compression cycles per unit time.
A suspension shock absorber whose wear is more than 50% reduces the service life of the suspension spring by approximately 1.5 times.
Of course, constant use of the car on bad roads or regular overload also does not add life to the springs. The worse the quality of the road surface, the more “actions” of the spring occur per unit time. The amplitude of body sway is also important. With constant mechanical stress, metal fatigue occurs earlier.
Damage to the surface of the spring rod (by stones, sand, salt or reagents) leads to damage to the paintwork and, accordingly, to the appearance and development of rod corrosion processes.
Various suspension tuning, especially homemade ones, have an extremely negative effect on the performance of the springs. By the way, you also need to be careful when getting carried away with expensive, geometrically complex springs. Such springs have more critical compression points, which means there is a greater likelihood of premature mechanical deformation.
In addition, other, not so obvious, operational factors can shorten the service life of suspension springs: a faulty upper support bearing, constant uneven loading of the vehicle, the use of tires and wheels with different parameters on the same axle, and even incorrect tire pressure.
What consequences can an incorrect spring choice have on suspension and handling?
— Illiterate selection of springs is the primary reason for deterioration in controllability and comfort, as well as an increase in braking distance.
Purely technically unsuitable springs increase the load on the valve mechanisms of the suspension shock absorbers, as well as on its other elements. Very stiff springs increase the load on the power elements of the body, which causes distortion, jamming of doors, cracks in glued glass, etc.
There are frequent cases of incorrect operation and malfunctions of auxiliary electronic systems responsible for safe vehicle control (ABS and ESP). Problems with “electronic assistants” up to the ECU entering emergency mode. The more modern and “complex” the car is, the more pressing the problem.
Installing springs that dramatically change ground clearance is another problem for the suspension and other parts of the car. Wheel alignment angles change. There is increased wear on tires, silent blocks, drive shafts, CV joints, bearings and wheel hubs, upper shock absorber mounts, bump stops and suspension travel limiters, as well as shock absorber boots.
In addition, after installing suspension springs to increase ground clearance, the location of the vehicle's center of gravity changes, which increases body sway (both longitudinal and lateral), worsens the vehicle's behavior during maneuvers and negatively affects handling control.
The possibility of using suspension springs, after installation of which a significant change in ground clearance occurs, is limited by the requirements of the current technical regulation “On the safety of wheeled vehicles” TR TS 018/2011. In this case, such arbitrary changes are not certified, and therefore may lead to a ban on the operation of the vehicle with all the ensuing consequences.
