How Automotive Suspension Systems Work

Today we're going to talk a little about

automotive

suspension

s and how they

work

to smooth out the ride of your car. Now, the purpose of the

automotive

suspension

system is, first, to support the weight of the vehicle, second, to maintain precise contact of the tires with the ground, so that the vehicle remains controllable and number three to absorb any impact it receives. on the road when you hit a pothole, now most modern vehicles come with an independent front suspension, what that means is that if one wheel hits a pothole, it doesn't bother you. the other wheel and, as a result, you end up with a more refined and calm wheel.

Right now the coil spring is used to support most of the weight in the car as it has really good characteristics to absorb any bumps as you go up and down the road. However, on the road, the springs are not very good at dissipating that energy and that is why you have the shock absorber which is there to soften the ride and ensure that the tire maintains contact with the road. Now, in modern passenger vehicles, the two most popular suspensions are yours. McPherson strut and double wishbone suspension style, so in this rendering you can see the differences between McPherson and a double wishbone front suspension setups.

Here we have the strut that is connected to the body with the bearing on the top here and then we. We have the lower ball joint here that attaches at the knuckle, now the knuckle is connected to the wheel, so essentially the steering axle goes from the upper strut bearing to the lower ball joint and rotates around this point here now on this vehicle. a McPherson strut suspension, so we have a coil spring here with a shock absorber inside and then at the bottom here we have this ball joint where it rotates and it's attached to this lower control arm, so let's just demonstrate how this strut actually rotates when you turn the steering wheel.

You can see that it actually rotates on the lower ball joint, now the lower ball joint attaches to this lower control arm or lower wishbone and that is responsible for locating the steering shaft lodge. for Denis, as well as laterally on the vehicle, now the control arm is attached to the subframe through these bushings here that we'll talk about later if you can imagine the lower ball joint on the bottom and the strut mount on the top and you draw an imaginary line between the two, you will notice that it is slightly tilted back, which is called steering axis tilt and is done this way for greater stability.

Now if you look closely you will also notice from the front that the strut is mounted slightly this way. The way I was, a McPherson suspension navigates a corner, which will happen when this tire moves in an arc and basically gains negative camber as the strut compresses and that's where we get to the main disadvantage. of the McPherson strut front suspension because the chamber angle will change with the suspension travel, the tire contact area will only be minimized to one side or the other when you are taking tight corners and that is why McPherson suspensions They are not ideal for the vehicles we drive.

Important feature, however, the main advantage of the McPherson suspension is that it is really cheap and simple, which is why many manufacturers are moving towards this design now if we look closer at the free body diagram of their McPherson suspension for the individual components. Most of the force will act in a vertical motion in any type of suspension system and that is simply because it has to support the weight of the vehicle, so if we have the force coming from the steering wheel acting through the knuckle of the steering, It will go straight through the spring and be held by the body on the strut mount all the way to the top here which is quite strong as a result the lower ball joint does not require any vertical force and is now just there to locate the axle laterally because the strut is taking all the load from the wheel.

The ball joint on the bottom is simply a follower ball joint and is not a loaded ball joint, therefore it does not wear out as quickly. Now what joins the two independent suspensions to the body is this subframe where the control arms bolt to the top this is where your strut mounts to the body as well as the bolt for the shock absorber now under the subframe there is a pair of nineteen millimeter bolts that go on the monocoque that I go to remove, with all the bolts free from the bottom, the subframe is now free of the monocoque and simply hanging from the struts.

No, I can read it here. We have a subframe with the front suspension completely removed from the vehicle. Here we have the strut on top here we have this bearing that allows the strut to rotate the strut attaches to the steering knuckle via these two large 19 millimeter bolts now the knuckle itself is responsible for holding the brakes, the wheel hub and the wheel itself. the suspension now I'm going to remove these strut bolts and what they removed the strut bolts I can remove the strut itself from the steel this here is the stabilizer linkage that is attached to the stabilizer bar and that goes to the other side we We'll talk about that more late and this is where the ball joint connects to the steering knuckle.

It has this castellated nut. Here we have the brake caliper. I'm going to remove it, we leave the caliper support and then we stay. with the bare knuckle with the ball joint and of course the bushing on the inside now back here on the control arm you can see how the control arm will flex up and down with the suspension attaching to the subframe with this cap here too. like a bushing on the rear here, so I removed the control arm from the vehicle and you'll actually notice that there are two bushings that are mounted perpendicular to each other.

Now the rear bushing here is a softer bushing and is meant to absorb. Any vibration that is not absorbed by the spring and gives you a nice, smooth and comfortable ride. Now this bushing is much stiffer, it is more aligned with the wheel and that gives you good feedback in terms of handling. Now you will notice it too. That this bushing is directional, there is a little arrow here and there are two gaps on this side, which means it only allows it to flex in one direction. Now your strut consists of the strut mount with the bearing on top, it has a stop on top here in case this maxes out when we have the dust boot followed by the shock absorber itself where it mounts to the knuckle. the address at the bottom.

This here is called the sway bar or stabilizer bar and what does it connect the left side driver to the right side driver now because the control arms actually rotate up and down with the suspension when you take a corner, the inside wheel Will it tend to rise while the outside wheel will tend to move? down and that can cause body roll which can be dangerous and that's where the stabilizer bar comes into play. It basically acts as a torsion beam where it connects the right side control arm to the left side control arm to equalize body roll for cornering.

Much flatter now on my Lexus we have a double wishbone front suspension which is a form of multi-link suspension system. Now in this design you have the upper control arm here that connects from the body to the steering knuckle and the steering knuckle drives everything. On the way to the actual axle, you have the lower ball joint here at the bottom and that connects the lower control arm that goes to the body. Now the strut is enclosed in this coil here and is mounted firmly to the body. doesn't allow you to rotate now, that will mount directly to the lower control arm here instead of mounting to the axle like in the McPherson design, so you don't need to rotate the body lower driver notes again using a ride and a steering bushing now, if we compare it to the double wishbone suspension, you have this very big, long steering knuckle that goes from the lower ball joint to the upper ball joint and it rotates between these two ball joints, so it turns like this, notice when I turn the steering wheel, how the knuckle turns, you can see it here and this is a rear wheel drive vehicle so it has the steering tire that connects in front of the lower ball joint and it's called front steering and then inside here we have the little one stabilizer link that goes to the stabilizer bar to the other side and the main advantage of a double wishbone design is of course handling and with a double wishbone design with the body as the fourth linkage, you essentially have a four-bar mechanism and that's great because it allows the wheel to stay perpendicular to the body while navigating a corner or going over a bump and that maintains a good contact patch with the tires no matter where the wheel is located.

Now another advantage of this design is that it can be made adjustable where you can control the position of this ball joint of the upper control arms this way or this way or in and out to control the camber and camber angles. Now probably the main disadvantage of its double wishbone suspension is that you will see the ball joints wear out much faster than the Anna McPherson design. Now the free body diagram for the double wishbone suspension is a little more complex because the spring is now attached through the lower control arm and the lower ball joint so the resulting force that passes through the steering wheel has to pass through the steering knuckle through the lower ball joint and then into the spring to be supported by the body.

In this case the upper Bulger does not require any vertical force and is only there to locate the axle laterally, in this case we have a lower ball joint which is essentially a loaded ball joint because it has to support the weight of the vehicle, whereas in a Macpherson design the lower ball joint is not loaded because the upper strut support is taking most of the force that goes through the wheels, now the main disadvantage of the double wishbone design and the reason why I am Zahra from this design, I'm moving towards the McPherson design is simply simplicity and the reason for that is you.

I can see that there are a lot more extra components here, they wear out a lot faster, they're a little harder to

work

on, and as you know, nowadays most people prefer fuel economy over driving dynamics, so that it makes no sense to have this design en masse. vehicles on the market, so here we have my Lexus that has a double wishbone front suspension driving down the road. Here you can see how all the links move. We have the strut that attaches to the lower control arm and then goes through the lower control arm. ball joint to connect to the knuckle and you can see when we hit a bump here how the shock absorbs it through the lower driver and here we have the McPherson suspension that is on my Toyota Camry.

You can see that the strut on the top is mounted on the knuckle and it directly takes the impact coming through the wheel and the lower ball joint just follows it and those are pretty much the two main types of automotive suspension

systems

used in automotive vehicles. passengers. Now of course there are some other suspension designs that we have. I didn't talk about its solid axle design, its torsion bar design, and its multi-link design, but that's all for now, both longitudinally and latitudinally.