Front double wishbone and rear multi-link suspension characteristics analysis!

Cold knowledge of automobile suspension: front double wishbone and rear multi-link suspension characteristics analysis

The suspension system of the car is divided into two parts, namely:

Elastic element + shock absorber = body dimensions

Linkage rocker arm is responsible for the "support of the wheels. Many car enthusiasts always put "suspension" on their lips, but do not know that the suspension is divided into two parts; analysis of the characteristics of the suspension first to understand this point of knowledge, because the coil spring-based elastic components may seem unimportant, but it is also an important part of the decision of the vehicle's handling. For example, the strength and compressible travel of the springs will determine the degree of lateral inclination of the vehicle when cornering, and the damper is used to limit the frequency of spring (body) bounce when the vehicle undulates, and you can get a feel for the function of this part through the diagram below.

What exactly is the difference between double wishbone suspensions?

The definition of double suggests that there are two sets of "wishbones" in this type of suspension, so if there's double, there's single - let's start with the "single wishbone", which is the most widely used and best known type of suspension. This suspension is the most widely used and well-known "McPherson suspension", there are also called "McPherson suspension" area; but the essence is that there is only a set of lower fork arm of the single fork arm suspension, the structure composition is very simple.

Lower control arms connect to the subframe

Dampers with integrated springs

Sway bars are also an important component, so why have them?

This is the structural characteristics of the McPherson suspension, McPherson suspension is basically the lowest standard of independent suspension; the so-called independent suspension refers to the four road suspension linkage rocker arm does not contact each other, the respective suspension linkage rocker arm of the movable ball joints are connected to the vehicle chassis individually, in the single or unilateral wheels when the slight undulation will not significantly affect the opposite side of the position of the wheel camber.

The lower control arm (A-type fork arm) of the McPherson suspension can go up and down, but more importantly, it can still play a role in supporting the tires laterally. The car will generate lateral force when turning, and this force not only pushes the bodywork to a different degree of lateral inclination, but also acts on the wheels, refer to the following figure.

When the lateral force pushes the wheels, the lower control arms of the MacPherson suspension can effectively support the bottom of the wheels, and the angle of this part is very difficult to change; however, the lateral force will also act on the upper part of the wheels, then the wheels will be tilted from the upper part of the wheel - the function of the "anti-sway bar The function of the "sway bar" is to support the wheel to control the angle of tilt, if the camber is too large will cause the tires to reduce ground contact, reduce wheel grip, cornering speed is too high, the camber may be so large as to skim the suspension.

So McPherson suspension is actually worse, but also has the advantage of occupying less space and low manufacturing costs; this suspension is actually a "U-shaped", to put it bluntly is a combination with the body will be like a cylinder, occupying a large transverse space transverse engine and transmission can sit in the U-shaped space. However, some strong power or more focus on vehicle handling (steering feeling) of the vehicle, always use the "McPherson PLUS".

Isn't it simple to characterize the structure of the double wishbone? In fact, it is McPherson to add a set of upper control arm, this control arm is also A-type; with the lower control arm can also swing up and down, and can play a wheel in the corner of the upper part of the support, the wheel's camber control ability is far from McPherson's sway bar can be compared.

Driving these cars can deliberately experience the directionality of the steering, the feeling will generally be better than McPherson; unless it is a very high level of tuning McPherson will be Pretty good, such as the Grandview McLaren the two front-wheel drive sedan McPherson suspension is pretty good, Han DM / EV also has a high standard, the Porsche 991 is also also also use the front McPherson suspension, the level of technology can be achieved "reversed", just double wishbone to the same level of technology tuning may have a higher level.

Why is the rear suspension predominantly multi-link?

"McPherson + multilink" or "double wishbone + multilink" is a relatively common type, only very few vehicles have used front and rear McPherson or front and rear double wishbone; with double McPherson is because basically do not pay attention to the handling of the vehicle, in order to control the cost and The reason for using double McPherson is that it is basically not important for vehicle handling, so in order to control the cost and show the selling point of four-wheel independent suspension, this structure is used. However, the cost of front and rear double wishbones is actually on the high side. There is a "double wishbone" in the rear suspension, which can be interpreted as a "single wishbone split", i.e., an A-type rocker arm is divided into two separate rocker arms, which can control the manufacturing cost, can it not? Of course both arms would have to be reinforced.

The front suspension "double ball joint" is also similar to the double wishbone structure, the same is the A-type rocker arm split; multi-link refers to "≤ 3 link", and double wishbone comparison level is comparable to the main is also a product of cost control. The double wishbone rear suspension is equivalent to four or five-link, but the structural strength is generally more than 4/5-link, so there will be some rally cars will use this "anti-build" suspension.

The 3/4/5 link is characterized by a more precise control of the wheel camber, but the overall strength is not suitable for professional standards of intense driving; therefore, this type of suspension is mostly used for civilian-grade mobility vehicles, which focuses on ride quality. But because of the relatively high cost of research and development and manufacturing, the result is that only some high-end cars will be used; balanced handling and comfort will be like the 3 Series as the use of "double ball joints + multilink", or like the E-class as the use of "front and rear multilink", Audi is the use of the front and rear five-link A4L, but the power and comfort of the A4L, but the power and comfort of the A4L, but the power and comfort of the A4L, but the power and comfort of the A4L. Audi has a five-link front and rear A4L, but the power and drive system is more crotch pulling. The least expensive car to use front double wishbones and rear five-links was the BYD F6, but because consumers didn't seem to buy it, BYD wasn't as stupid later on.

Specialty vehicles: Off-road vehicles and hardcore SUVs tend to use "double-wishbone + multi-link axles" for a simple reason. First of all, this type of vehicle will always drive on rough roads, the wheels will always have exaggerated camber, the control arm will bear the force will be very large, relying on the McPherson suspension can not control the wheel angle and ensure the reliability of the lower control arm; so you can only use the structure of the stronger double-wishbone, such as the tank 300, BJ40, Haval H9, Datsun D90Pro and so on.

The rear suspension, although also multi-link or five-link, is not the concept of independent suspension; the overall axle is a non-independent suspension, both sides of the wheels are fixed in the basic can not be twisted (to change the angle of the drive axle at both ends, a single side of the body of the inevitable ups and downs of the drive axle through the prying of the wheels at the other end, which affects the wheels of the grip and is easy to damage the wheel hubs. Adding a multilink then is only used to control wheel angle, which doesn't achieve the same high standard as independent suspension but is effective in improving grip; or via a Watts link, which is also possible, except that the Peugeot isn't as desirable as a multilink or five-link.

The picture above shows the characteristics of the Watts link, which can be simply understood as pulling up at one end and pushing the other through a movable rocker arm, which is also effective in controlling camber; in the hardcore models there is the Ford Shaker which uses a Watts link integral axle, which is also of a good standard.

This is the "double-wishbone + multilink" characteristics of the two models, the family car is limited by manufacturing costs, with MacPherson plus multilink is acceptable, after all, the power will not be very strong; but choose to equip displacement ≥ 2.0T front-wheel drive, rear-wheel drive or four-wheel drive, there are double-wishbone option is naturally better, unless the McPherson is also tuned to the same level. McPherson is also tuned to a high level.