What is the difference between suspension type and structure? It also explains the life and replacement time | MOBY [モビー]

What is a suspension? What is the structure?

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The suspension of a car works in combination with a spring, a shock absorber, and a suspension arm.

Suspension arms with two or more support points per wheel maintain the horizontal position of the tires so that they do not shift significantly, the vehicle height is determined by the balance between the vehicle weight and the hardness of the four springs, and the vertical width of the tires is shocked. The stroke amount of the absorber becomes the maximum value.

In addition, these parts are arranged according to the second principle of leverage, the suspension arm corresponds to the lever, the contact patch of the tire is the point of effort, and the location of the spring and shock absorber is the point of action. Become.

By adjusting the positions of the three points, it can be said that the structural feature of the suspension in the car is that the shock absorption performance of the spring and damper is effectively exhibited while effectively using the limited space of the car. ..

There are several fixed forms of suspension that meet the required performance, and this is called the suspension type.

What is a spring?

A spring is a part that supports the weight of a vehicle, and the hardness of the spring determines the amount of front-back, left-right tilt that occurs during driving. It expands and contracts according to the unevenness of the road surface, keeping the tires on the road surface and reducing the impact and vibration transmitted to the car and occupants.

What is a shock absorber (damper)?

It suppresses the movement of the oscillating spring. Without shock absorbers, the oscillating springs would keep the car rocking all the time. It is also a component that controls the speed at which the spring swings, which greatly affects cornering performance and ride quality.

What is a suspension arm?

The suspension arm is a support arm that determines the position of the tire with respect to the body and guides the tire and suspension as they move up and down. The tire moves up and down by making a circular motion around the fixed part of the car body.

Car suspension type

Strut suspension | Cheap and almighty

Strut suspension
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The strut suspension is a simple type that supports the tire with a single suspension arm and a shock absorber with springs arranged coaxially.

Due to its low cost and the advantage of being able to be installed in a small space, it is used in many vehicles as a front and rear suspension for small and medium-sized vehicles. It is sometimes called “MacPherson Strut” after the designer’s “Earle MacPherson”.

Double wishbone suspension | Tire grip can be pulled out

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It is a suspension type that supports the tire with the alphabet “A” type arms arranged above and below.

Since the tilt of the tire does not change easily even if it moves up and down, there is an advantage that the grip of the tire can be used effectively. Since the two A-type arms receive the lateral force, the suspension moves up and down smoothly and is comfortable to ride.

However, since it requires space for long upper and lower arms to be adopted, it is generally used as a front and rear suspension for large sedans with ample space and sports cars that require high-performance suspension.

Multi-link suspension | Features a high degree of freedom in design

Nissan multi-link suspension

Multi-link refers to all suspension types made by combining four or more rod-shaped links.

The feature of multi-link is that it can be designed with a higher degree of freedom while imitating the movement of double wishbones. As a higher version of double wishbone, it is a high-performance suspension type used in sports cars and luxury cars.

In addition to double wishbone suspensions, anomalous suspensions with additional arms to improve performance are sometimes called multi-links.

Torsion beam suspension | Inexpensive and highly stable rear suspension

The torsion beam features a left and right integrated suspension arm. Since the number of parts is small and the manufacturing cost is suppressed, it is mainly used as a rear suspension for small FF vehicles.

Another advantage is that the spring and shock absorber can be placed separately to reduce the installation space in the vertical direction.

When a large force is applied from the side when cornering, the entire suspension including the tires faces inward, which ensures stability.

Although it is inferior to struts and double wishbones in terms of ride comfort, it is a suspension model with high cost performance that can obtain the performance required for practical use while keeping costs down.

Rigid axle | Dust high rigidity and running performance

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Rigid axles have excellent traction performance on rough terrain. It is mainly used as a front and rear suspension for off-road cars and as a rear suspension for small 4WD vehicles.

The power transmission mechanism built into the steel pipe (hosing) that connects the left and right wheels drives the tires. Furthermore, when the tire on one side is lifted, the tire on the other side functions as a suspension arm that presses against the ground, demonstrating powerful traction performance.

The springs and shock absorbers are mounted directly on the hosing to ensure a large suspension operating range.

Rigid 3 links

The simplest configuration of a rigid axle is a “3-link rigid axle”. The hosing is held by a total of three arms, one arm called the lateral rod placed on the upper part of the hosing and two support arms on the left and right front.

Rigid 5 links

“5-link rigid axle” is used for models that assume high-speed driving. The lateral rod and the front left and right are supported by two arms each to suppress changes in the wheelbase when the suspension moves up and down.

Air suspension | Luxury suspension with unique ride quality

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Air suspension refers to a structure that supports the weight of the vehicle with air springs instead of metal springs, regardless of the suspension type.

Since the air-filled airbag functions as a cushion, it is characterized by a fluffy and unique ride quality with low resilience, and the ride quality and vehicle height can be changed by changing the air pressure inside the airbag. The point is also a feature of the air suspension.

However, in order to install the air suspension, it is necessary to mount a compressor that produces compressed air on the vehicle, the structure is very complicated, and the cost of parts is high.

In addition to being sold as after-parts, the air suspension is genuinely installed on some luxury cars, and it not only improves the ride quality but also helps to improve the ease of getting on and off by lowering the vehicle height when the car is stopped.

Famous manufacturer of car suspension

Suspension manufacturers are divided into spring manufacturers and shock absorber manufacturers.

In addition, the manufacturers that manufacture both of them may supply not only after-parts but also genuine parts to automobile manufacturers.

In particular, KYB in Japan and Bilstein in Germany are very well-known comprehensive suspension manufacturers that handle both genuine and after-parts.

Famous spring makers include Eibach in Germany, Hypercoil in the United States, Tokyo in Japan, and RS-R. The most common high-performance shock absorber manufacturers are Orleans in Sweden, Zack in Germany, and Monroe in the United States.

Famous domestic after-parts suspension manufacturers such as TEIN, Tanabe, CUSUCO and KW in Germany sell harmonic drive and suspension kits that are intended for use under specific conditions. increase.

In addition, comprehensive after-parts manufacturers such as HKS and BLITZ also sell in-house developed harmonic drive.

Suspension life and replacement time

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The life of the suspension varies depending on the parts and driving environment, and it is recommended to replace the shock absorber at around 50,000 km and the spring at about 100,000 km.

The suspension arm does not need to be replaced unless it is damaged or extremely rusted.

In addition, the life of the rubber bush used for the mounting part of each part is about 80,000 km.

Deterioration of the spring is a change to the extent that the vehicle height drops slightly, but as the deterioration of the shock absorber progresses, it is clearly difficult for the shaking of the car body to subside, and the rubber bush hardens and cracks, making it easier for small vibrations to be transmitted. increase.

Deterioration of the suspension is hard to feel, and even if it deteriorates, it does not hinder normal driving, so it tends to be left unattended.

However, if there is a large change in behavior such as when driving at high speed, the deteriorated suspension will not perform as designed, and the risk of the car becoming inoperable by causing a momentary decrease in tire grip increases.

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