Suspension | How it Works

Suspension | How it Works


(hip-hop music) – “All I wanna do is see ya
bounce with me, bounce with me.” Those are the words of young Lil Bow Wow from the song “Bounce With Me” (“Bounce With Me” by Lil’ Bow Wow) The concept of bouncing is
great in this classic song. You know where bounce is bad? Suspensions! (electronic music) There’s billions of types of
suspension, not literally, but I’m not gonna go
look up the exact number like some kind of a nerd
so maybe not billions, but there’s a lot of
different types of suspension. There’s suspensions like when
you’re suspended from work for biting the camera man, there’s suspensions like
the suspension of disbelief which allows you to believe
in make believe stuff like Superman can fly or
life’s gonna work out, and there’s the suspension
system on your vehicle, and those vehicle suspensions have a huge variety of types as well. There’s more types of vehicle suspensions than the types of DNA strands
that were found in my bedroom nine years ago on that
fateful night in September. (crowd gasps)
That number was three. We got a knife. With such a wide variety of types, we’re barely gonna
scratch the surface here and touch on the basics in a
few of the most common types. So all of you in the comments saying I forgot about
this thing or that thing, nah, I didn’t, I know all about it, In fact, I just left
it out to tick you off. (crowd booing)
So get off my back, David. Alright, when they invented
the car it was awesome, they’re all smoking cigars and patting each other on the
back, eating some cold cuts and congratulating each others like, “This will revolutionize travel. “The piston engine will
get us places so fast.” “I love cold cuts.” But then, record scratch,
(record scratches) they realized all the power
generated by an engine’s useless if the driver can’t control the car. (engine revving) And almost as soon as the four stroke internal combustion engine was mastered, engineers went to work on
perfecting the suspension. Horse drawn carriages had suspensions, but they only went so fast. You hit those same bumps in
the road at a greater speed, it’s gonna get a lot bouncier. – Ow! – The job of a car suspension is to one, maximize the friction between
the tires and road surface during acceleration,
cruising, and braking, and two, provide steering
stability with good handling, and three, ensure the
comfort of the passengers. If all roads were perfectly flat with no irregularities or
bumps or waves or anything, suspension wouldn’t be as necessary, but unlike me, even fresh laid pavement has some imperfections. Now, let’s get science-y
up in this garage. Newton’s Law of Motion
says forces have both magnitude and direction. A bump in the road causes the
wheel to move up and down, perpendicular to the
road surface, direction. The magnitude depends on whether the wheel is striking a giant bump or a tiny speck. The wheel experiences
a vertical acceleration as it passes over an imperfection, and that means the wheel goes up. Without an intervening structure, the vehicle’s vertical energy is transferred to the car’s frame, which moves the same direction, up. The wheels can lose contact
with the road completely and then, ’cause of gravity, the wheels would slam back
down into the road surface, and that is bounce, brother. And if there was no gravity, that bump could send
you hurdling into space until you go out into hyper
space and see the event horizon. Spooky. You need a system that absorbs the energy of the vertically accelerated wheel, allowing the frame and
body to ride undisturbed while the wheels follow bumps in the road, and that’s all part of vehicle dynamics, the study of forces at
work on a moving car. Auto engineers come at this
from two perspectives, ride, (engine revving)
a car’s ability to smooth out a bumpy road and handling, oop, and handling, a car’s
ability to safely accelerate, brake, and corner and those break down
into these principles, road isolation, the
vehicle’s ability to absorb or isolate road shock from
the passenger compartment, cornering, the ability of a
vehicle to travel a curved path, and road holding, the degree
to which a car maintains contact with the road surface in various types of directional changes and in a straight line. For example, the weight
of a car will shift from the rear tires to the
front tires during braking because the nose of the
car dips toward the road. This type of motion is known as dive. The opposite effect, squat,
occurs during acceleration, which shifts the weight of the car from the front tires to the back. These are the challenges that the suspension system has to handle. Like I said earlier, there’s a buttload of suspension varieties and a car can, and usually does, have a different type of
suspension on the front and back, and in those you can either
have a dependent system, where a rigid axle binds the wheels, or an independent system where the wheels are permitted to move independently, but the three fundamental
components of any suspension are springs, dampers, and anti sway bars. Those are the bars that hate
former MTV News reporter, Sway. Wait, oh no, I’m being told that they’re actually just used
along with shock absorbers or struts to give a moving
automobile additional stability. Sway bars a metal rod
that spans the entire axle and effectively joins each side
of the suspension together. You suck, Sway. Let’s get back to talking about one of three fundamental
components of suspensions, and my third favorite season, spring. Now there’s a couple of types
of springs that can be used, there’s leaf springs,
several layers of metal bound together to act as a single unit, and these are usually
used on a lot of trucks. They haven’t been on a
ton of US cars since ’85. There’s torsion bars, here one end of a bar is anchored
to the vehicle frame and the other end is attached to wishbone. The wishbone acts like a lever that moves perpendicular to the torsion bar. When the wheel hits a bump, vertical motion’s
transferred to the wishbone, and then, through the levering
action, to the torsion bar. The torsion bar then
twists along it’s axis to provide the spring force. These are more common on European cars, and there’s coil springs, basically a heavy duty torsion
bar coiled around on an axis. These are the most common. Anything above the springs and supported by ’em on
the vehicle is sprung mass. Anything below the spring
between the springs and the road, like the wheels, for
example, is unsprung mass. Unsprung mass was my nickname in college, or it was until that fateful night three years ago in September. Spring stiffness effects
how the sprung mass responds while the car’s being driven. Loosely sprung cars, such as luxury cars, swallow bumps for a smooth ride, but they’re prone to dive and squat during braking and acceleration, and can have body sway,
or roll during cornering. Tightly sprung cars, like sports cars, are less forgiving on bumpy roads, but they minimize body motion so they can be driven
aggressively, even around corners. (engine revving) (ding) But you can’t use just
springs, you silly goose. Springs absorb energy but they stink when it
comes to dissipating it, that’s why you need dampers. One common dampening
structure is a shock absorber. Shock absorbers slow down
and reduce the magnitude of vibratory motion by turning the kinetic
energy of suspension movement into heat energy that can be dissipated through hydraulic fluid. A shock absorber’s upper
mount connects to the frame and the lower mount connects to the axle. In a twin tube design, the upper mount is
connected to a piston rod which is connected to a piston and sits in a tube filled
with hydraulic fluid. Feels like I said that. The inner tube’s known
as the pressure tube, and the outer tube is
known as the reserve tube. The reserve tube stores
excess hydraulic fluid. When a wheel hits a bump in the road and causes the spring to coil and uncoil, energy of the spring is
transferred to the shock absorber through the upper mount,
down through the piston rod, and into the piston. Orifices perforate the piston
and allow it to leak through as the piston moves up and
down in the pressure tube. Because these orifices
are relatively tiny, only a small amount of
fluid, under great pressure, passes through. This slows down the piston, which in turn, slows down the spring. Shock absorbers work in two cycles, the compression cycle
when the piston moves down compressing the hydraulic fluid in the chamber below the piston, and the extension cycle, when the piston moves toward
the top of the pressure tube compressing the fluid in the
chamber above the piston. All modern shock absorbers
are velocity sensitive. The faster the suspension moves, the more resistance the
shock absorber provides, so they can adjust to road conditions and control all the unwanted motion that can occur in a moving vehicle, including bounce, sway,
ah, I hate that guy, brake dive and accelerating squat. Another common dampening
structure is the strut. Basically it’s a shock absorber mounted inside a coil spring. Struts provide two jobs, dampening function like
the shock absorbers, and structural support for
the vehicle’s suspension. They do a bit more than shock absorbers, which don’t support vehicle weight, they only control the speed at which the weight is
transferred in a car, not the weight itself. The Mac Daddy of struts is the MacPherson strut
invented by Earle S. MacPherson. No one knows what the S stands
for except for Wikipedia, which says is stands for Steele, cool. The MacPherson strut consists
of a single control arm in a strut assembly which allows tire and wheel
to move upward and downward. Its design allows for a
reduction in a number of parts, lowering unsprung mass, as
well as smooth driving comfort. These are pretty small,
not too complicated, and not too expensive,
so they’re pretty common. They don’t take up much
space horizontally, so they’re super common
in front suspensions on the front wheel drive vehicles. They do take up a lot of
space vertically, though. Another common type of front
independent suspension, the double wishbone
suspension or an A-arm, doesn’t take up as much space vertically, but is a horizontal hog. That one guy in the comment section. While there’s several different
possible configurations, this design typically uses
two wishbone shaped arms to balance the wheel. Each wishbone, which has two
mounting positions to the frame and one at the wheel, has a
shock absorber and a coil spring to absorb vibrations. Double wishbone suspensions
allow for more control over the camber angle of the wheel which describes the degree to which the wheel tilts in and out. (car squeaking) They also help to minimize roll and sway, and they provide for more
consistent steering feel. That’s why double wishbone
suspension’s so common on the front wheels of larger cars. (claps)
Real quick, let’s look at a couple of rear suspensions and a split second picture
of my belly button. These are usually a little simpler ’cause you don’t need to
integrate the steering for a dependent rear suspension, if a solid axle connects with
the rear wheels of a car, then it’s pretty simple, based either on a leaf
spring or a coil spring. Leaf springs clamp
directly to the drive axle, and the ends of the leaf springs attach directly to the frame. The shock absorber’s attached at the clamp that holds the spring to the axle. You can have the same basic
design with coil springs but in this case, the
spring and shock absorber can be mounted as a single
unit or as separate components. When they’re separate, the
springs can be much smaller, which reduces the amount of space that the suspension takes up. For independent rear suspensions, if both the front and back
suspensions are independent, then all the wheels are mounted
and sprung individually, resulting in what some ads call four wheel independent suspension. Any suspension that can be
used in the front of a car can be used on the rear and versions of the
front independent systems described in the previous section can be found in rear axles. Of course, the rear of the
car, the steering rack, the assembly that keeps
everything together and lets ya turn, well, it’s not there, so that means rear independent suspensions can be simplified versions
of the front ones, but the basic principles are the same. Suspensions! Hey, thanks to Bombfell for
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About the Author: Michael Flood

100 Comments

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  2. Ok, I have to nit pick here. A shock with a spring around it is not a strut. That is called a coilover shock, or just a coilover.

    Many cars have coilovers without having struts (most 1990s Honda cars, for example), and many cars have struts that are not coilovers (2nd generation Geo Metro rear suspension, for instance).

    A strut is a shock that also replaces the upper control arm. It is the defining feature of McFerson type suspension. Basically, they started with a double-wishbone arrangement, except the upper control arm (or wishbone) is removed, and the shock is used to control the angle of the steering knuckle instead.

    This works because as the end of the lower control arm moves up, it also moves outward, away from the center of the car. That causes the shock/steering knuckle assembly to rotate inward, compensating for body roll.

    Not all McFerson suspension systems use coilover struts (as in my example above), although most do, particularly in the front of a car.

    I hope you'll excuse my rant, but this does particularly any me because I have owned a car with non-coilover struts in the back and people will see those and think they're not struts because the design of the car made it more convenient to put the springs next to the struts, rather than around them. Also, my current car is a CR-V which has no struts because its suspension is double-wishbone front and rear, but everybody (including parts stores and manufacturers who should know better) thinks my car has struts because they are all coilovers.

  3. You left out that any suspension that is used on the back of the car can be used on the front as well, if the vehicles form factor allows. I cite Jeep Wranglers here.

  4. How come, Top fuel cars (drag race) have no suspension, and yet you mentioned suspensions are needed to maximize friction?

  5. Does anyone know of any books like this but for all systems. Where it goes through all main parts of the car, their purpose, how they work, etc.

  6. This is honestly a really helpful channel bc my bf is always talking about his truck and I have no clue what hes talking about and ive only picked up a few things from him. But with this channel, I picked up a little more so its helping a little

  7. my car use to stock one side to the passenger when i enter bump or if i carry people what may be the problem pls help

  8. If your car has double wishbone, and multilink suspension, your manufacturer cares about handling. Anything less, and you might as well have leaf springs.

  9. Yo what ever happened to science garage???!! I haven't seen a new episode and this was one of the best shows from donut !!

  10. Please increase "information per minute" just a bit more. It's painful watching you throwing stupid jokes around and not learning anything…

  11. Can anyone tell me what kind of suspensions would be used for something like a off road dirt track rally muscle car.

  12. How you showed the shock absorbers is slightly incorrect. Technically the bottom would move up but in the video the top moves down while the bottom stays still.

  13. Which is better: reputable strut/shock(gonna use blistein b8 struts) with progressive lowering springs(from reputable company like whiteline) or decent coilovers (1000 to 1500 with no dampening adjustability)
    Car will be used just for street with comfort with improved handling with less body roll. I really dont play with height setting. Once I find the height I want, I hardly change height setttinh.

  14. I love it!! I wish Bart touched on air suspension. Maybe a video on air suspension vs coil overs🤷🏻‍♂️🙆🏻‍♂️🚘

  15. ok, how many takes when you referenced the belly button shot, LOL. Awesome information and presentation!!!! you deserve a BEER !!!

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