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Suspension (vehicle)

The front suspension components of a Ford
Model T.

The rear suspension on a truck: a leaf spring.

From Wikipedia, the free encyclopedia

This article needs additional citations for verification.
Please help improve this article by adding reliable references. Unsourced material may be challenged and removed. (April


Suspension is the term given to the system of springs, shock absorbers and linkages that
connects a vehicle to its wheels. Suspension systems serve a dual purpose — contributing to
the car's roadholding/handling and braking for good active safety and driving pleasure, and
keeping vehicle occupants comfortable and reasonably well isolated from road noise, bumps,
and vibrations,etc. These goals are generally at odds, so the tuning of suspensions involves
finding the right compromise. It is important for the suspension to keep the road wheel in
contact with the road surface as much as possible, because all the forces acting on the vehicle
do so through the contact patches of the tires. The suspension also protects the vehicle itself
and any cargo or luggage from damage and wear. The design of front and rear suspension of a
car may be different.

This article is primarily about four-wheeled (or more) vehicle suspension. For information on two-
wheeled vehicles' suspensions see the suspension (motorcycle), motorcycle fork, bicycle
suspension, and bicycle fork articles.

Contents [hide]

1 History
1.1 Horse drawn vehicles
1.2 Automobiles

2 Important properties
2.1 Spring rate

2.1.1 Mathematics of the spring rate
2.2 Wheel rate
2.3 Roll couple percentage
2.4 Weight transfer

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Bahasa Indonesia


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Part of car front suspension and steering
mechanism: tie rod, steering arm, king pin axis
(using ball joints).

2.4.1 Unsprung weight transfer
2.4.2 Sprung weight transfer
2.4.3 Jacking forces

2.5 Travel
2.6 Damping
2.7 Camber control
2.8 Roll center height
2.9 Instant center
2.10 Anti-dive and anti-squat
2.11 Flexibility and vibration modes of the suspension elements
2.12 Isolation from high frequency shock
2.13 Contribution to unsprung weight and total weight
2.14 Space occupied
2.15 Force distribution
2.16 Air resistance (drag)
2.17 Cost

3 Springs and dampers
3.1 Passive suspensions

3.1.1 Springs
3.1.2 Dampers or shock absorbers

3.2 Semi-active and active suspensions
3.3 Interconnected suspensions

4 Suspension Geometry
4.1 Dependent suspensions
4.2 Semi-independent suspension
4.3 Independent suspension

5 Armoured fighting vehicle suspension
6 See also
7 References
8 External links


Please help improve this article by expanding it. Further information might be found on the talk
page. (April 2010)

Leaf springs have been around since the early Egyptians.

Bahasa Melayu

Norsk (bokmål)
Simple English


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and the tire construction. Oftentimes, too much camber will result in the decrease of braking performance due to a reduced contact patch size
through excessive camber variation in the suspension geometry. The amount of camber change in bump is determined by the instantaneous
front view swing arm (FVSA) length of the suspension geometry, or in other words, the tendency of the tire to camber inward when compressed
in bump.

Roll center height
This is important to body roll and to front to rear roll stiffness distribution. However, the roll stiffness distribution in most cars is set more by the
antiroll bars than the RCH. The height of the roll center is related to the amount of jacking forces experienced.

Instant center
Due to the fact that the wheel and tire's motion is constrained by the suspension links on the vehicle, the motion of the wheel package in the
front view will scribe an imaginary arc in space with an “instantaneous center" of rotation at any given point along its path. The instant center for
any wheel package can be found by following imaginary lines drawn through the suspension links to their intersection point.

A component of the tire's force vector points from the contact patch of the tire through instant center. The larger this component is, the less
suspension motion will occur. Theoretically, if the resultant of the vertical load on the tire and the lateral force generated by it points directly into
the instant center, the suspension links will not move. In this case, all weight transfer at that end of the vehicle will be geometric in nature. This
is key information used in finding the force-based roll center as well.

In this respect the instant centers are more important to the handling of the vehicle than the kinematic roll center alone, in that the ratio of
geometric to elastic weight transfer is determined by the forces at the tires and their directions in relation to the position of their respective
instant centers.

Anti-dive and anti-squat
Anti-dive and anti-squat are expressed in terms of percentage and refer to the front diving under braking and the rear squatting under
acceleration. They can be thought of as the counterparts for braking and acceleration as jacking forces are to cornering. The main reason for the
difference is due to the different design goals between front and rear suspension, whereas suspension is usually symmetrical between the left
and right of the vehicle.

To determine the percentage of front suspension braking anti-dive, it is first necessary to determine the tangent of the angle between a line
drawn, in side view, through the front tire patch and the front suspension instant center, and the horizontal. Then, divide this tangent by the ratio
of the center of gravity height to the wheelbase. Finally, multiply by 100. A value of 50% would mean that half of the weight transfer to the front
wheels, during braking, is being transmitted through the front suspension linkage and half is being transmitted through the front suspension

Forward acceleration anti-squat is calculated in a similar manner and with the same relationship between percentage and weight transfer. Anti-
squat values of 100% and more are commonly used in dragracing, but values of 50% or less are more common in cars which have to undergo
severe braking. Higher values of anti-squat commonly cause wheel hop during braking. It is important to note that, while the value of
either case...means that all of the weight transfer is being carried through the suspension linkage, this does not mean that the suspension is

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incapable of carrying additional loads (aerodynamic, cornering, etc.) during an episode of braking or forward acceleration. In other words, no
"binding" of the suspension is to be implied.

Flexibility and vibration modes of the suspension elements
In modern cars, the flexibility is mainly in the rubber bushings.

Isolation from high frequency shock
For most purposes, the weight of the suspension components is unimportant, but at high frequencies, caused by road surface roughness, the
parts isolated by rubber bushings act as a multistage filter to suppress noise and vibration better than can be done with only the tires and
springs. (The springs work mainly in the vertical direction.)

Contribution to unsprung weight and total weight
These are usually small, except that the suspension is related to whether the brakes and differential(s) are sprung.

Space occupied
Designs differ as to how much space they take up and where it is located. It is generally accepted that MacPherson struts are the most
compact arrangement for front-engined vehicles, where space between the wheels is required to place the engine.

Force distribution
The suspension attachment must match the frame design in geometry, strength and rigidity.

Air resistance (drag)
Certain modern vehicles have height adjustable suspension in order to improve aerodynamics and fuel efficiency. And modern formula cars, that
have exposed wheels and suspension, typically use streamlined tubing rather than simple round tubing for their suspension arms to reduce
drag. Also typical is the use of rocker arm, push rod, or pull rod type suspensions, that among other things, places the spring/damper unit
inboard and out of the air stream to further reduce air resistance.

Production methods improve, but cost is always a factor. The continued use of the solid rear axle, with unsprung differential, especially on heavy
vehicles, seems to be the most obvious example.

Springs and dampers
Most conventional suspensions use passive springs to absorb impacts and dampers (or shock absorbers) to control spring motions.

Some notable exceptions are the hydropneumatic systems, which can be treated as an integrated unit of gas spring and damping components,

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[show ]v • d • e

[show ]v • d • e

This Grant I tank's suspension has
road w heels mounted on w heel trucks,
or bogies.

Armoured fighting vehicle suspension
Military AFVs, including tanks, have specialized suspension requirements. They can weigh more than
seventy tons and are required to move at high speed over very rough ground. Their suspension
components must be protected from land mines and antitank weapons. Tracked AFVs can have as
many as nine road wheels on each side. Many wheeled AFVs have six or eight wheels, to help them ride
over rough and soft ground.

The earliest tanks of World War I had fixed suspension with no movement whatsoever. This
unsatisfactory situation was improved with leaf spring suspensions adopted from agricultural machinery,
but even these had very limited travel.

Speeds increased due to more powerful engines, and the quality of ride had to be improved. In the
1930s, the Christie suspension was developed, which allowed the use of coil springs inside a vehicle's
armored hull, by redirecting the direction of travel using a bell crank. Horstmann suspension was a
variation which used a combination of bell crank and exterior coil springs, in use from the 1930s to the

By World War II the other common type was torsion-bar suspension, getting spring force from twisting bars inside the hull — this had less travel
than the Christie-type, but was significantly more compact, allowing the installation of larger turret rings and heavier main armament. The
torsion-bar suspension, sometimes including shock absorbers, has been the dominant heavy armored vehicle suspension since World War II.

See also
Automotive suspension design
Active suspension
Bicycle fork
Bicycle suspension
Bump Steer
Magnetic levitation and maglev train.
Motorcycle fork
Strut bar
Suspension (motorcycle)
Sway bar

Automotive handling related articles


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Wikimedia Commons has media
related to: Automotive
suspension technologies

1. ^ Adams, William Bridges (1837). English Pleasure Carriages . London: Charles Knight & Co..
2. ^;words=Paris+races+Berlin+race+Race|The Washington Times,

Sunday 30th June 1901
3. ^ Jain, K.K.; R.B. Asthana. Automobile Engineering . London: Tata McGraw-Hill. pp. 293–294. ISBN 007044529X.
4. ^ Pages 617-620 (particularly page 619) of "Race Car Vehicle Dynamics" by William and Douglas Milliken
5. ^ "Mitsubishi Galant" , Mitsubishi Motors South Africa website
6. ^ "Mitsubishi Motors history 1981-1990" , Mitsubishi Motors South Africa website
7. ^ "Technology DNA of MMC" , .pdf file, Mitsubishi Motors technical review 2005
8. ^ "MMC's new Galant." , Malay Mail, Byline: Asian Auto, Asia Africa Intelligence Wire, 16-SEP-02 (registration required)
9. ^ "Mitsubishi Motors Web Museum" , Mitsubishi Motors website

10. ^ Electromagnetic suspension
11. ^ Alex Moulton Mgf Hydragas

External links
How Car Suspensions Work

Categories: Automotive suspension technologies | Armoured fighting vehicle equipment | Vehicle technology;words=Paris+races+Berlin+race+Race|The

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