Difference between revisions of "Independent suspension"

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An '''Independent Suspension''' is an [[automobile]] [[suspension (vehicle)|suspension]] system that allows the wheels on an [[axle]] to move independent of each other. This is contrasted with a [[live axle]] or [[deDion axle|deDion]] system in which they are linked.
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[[Image:Independent rear suspension AWD.jpg|thumb|right|A [[MacPherson strut]] type rear independent suspension on an [[Four-wheel drive|AWD]] car. The anti-roll bar has some orange paint on it.]]
  
Most modern vehicles have independent suspensions on the front wheels at least.  An '''Independent Rear Suspension''' ('''IRS'''), as the name implies, has the rear wheels independently sprung.  A '''fully-independent suspension''' has an independent suspension on all wheels.
 
  
Early independent systems used [[swing axle]]s, but modern systems have use [[Chapman strut|Chapman]] or [[MacPherson strut|MacPherson]] [[strut]]s, [[trailing arm]]s, [[multilink|multiple links]], or [[double wishbone suspension|wishbones]].
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'''Independent suspension''' is a broad term for any [[automobile]] [[suspension (vehicle)|suspension]] system that allows each wheel on the same [[axle]] to move vertically (i.e. reacting to a bump in the road) independently of each other.  This is contrasted with a [[beam axle]], [[live axle]] or [[deDion axle|deDion]] system in which the wheels are linked - movement on one side affects the wheel on the other side.  Note that “independent” refers to the motion or path of movement of the wheels/suspension.  It is common for the left and right sides of the suspension to be connected with anti-roll bars or other such mechanisms.  The anti-roll bar ties the left and right suspension spring rates together but does not tie their motion together.
  
Another key difference which sets an independent layout from the conventional [[live axle]], is that, for driven wheels, the [[differential (mechanics)|differential]] unit does not form part of the [[unsprung weight|unsprung elements]] of the suspension system.  Instead it is either bolted directly to the vehicle's [[chassis]], or more commonly to a [[subframe]].
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Most modern vehicles have '''independent front suspension''' ('''IFS'''). Many vehicles also have an '''independent rear suspension''' ('''IRS''').  IRS, as the name implies, has the rear wheels independently sprung. A '''fully independent suspension''' has an independent suspension on all wheels. Some early independent systems used [[swing axle]]s, but modern systems use [[Chapman strut|Chapman]] or [[MacPherson strut]]s, [[trailing arm]]s, [[multilink|multiple links]], or [[double wishbone suspension|wishbones]].
  
The relative movement between the wheels and the differential is achieved through the use of swinging driveshafts connected via [[universal joint|universal (U) joints]], analogous to the [[Constant Velocity Joint|Constant Velocity (CV) joints]] used in [[front wheel drive]] vehicles.
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Independent suspension typically offers better [[ride quality]] and [[car handling|handling]] characteristics, due to lower ''unsprung weight'' and the ability of each wheel to  address the road undisturbed by activities of the other wheel on the vehicle. Independent suspension requires additional engineering effort and expense in development versus a [[live axle]] or [[beam axle]] arrangement. A very complex ''IRS'' solution can also result in higher manufacturing costs.
  
[[Image:Independent_Suspension_Diagram.gif|center|thumb|400px|Independent suspension characteristics: No [[camber]] changes on compression or rebound, low [[unsprung weight]]]]
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The key reason for lower unsprung weight relative to a [[live axle]] design is that, for driven wheels, the [[differential (mechanics)|differential]] unit does not form part of the [[unsprung weight|unsprung elements]] of the suspension system. Instead it is either bolted directly to the vehicle's [[chassis]], or more commonly to a [[subframe]].
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The relative movement between the wheels and the differential is achieved through the use of swinging driveshafts connected via [[universal joint|universal (U) joints]], analogous to the [[constant-velocity joint|constant-velocity (CV) joints]] used in [[front wheel drive]] vehicles.
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{{Automobile configurations}}
  
 
[[Category:Automotive suspension technologies]]
 
[[Category:Automotive suspension technologies]]

Latest revision as of 00:08, 7 December 2010

A MacPherson strut type rear independent suspension on an AWD car. The anti-roll bar has some orange paint on it.


Independent suspension is a broad term for any automobile suspension system that allows each wheel on the same axle to move vertically (i.e. reacting to a bump in the road) independently of each other. This is contrasted with a beam axle, live axle or deDion system in which the wheels are linked - movement on one side affects the wheel on the other side. Note that “independent” refers to the motion or path of movement of the wheels/suspension. It is common for the left and right sides of the suspension to be connected with anti-roll bars or other such mechanisms. The anti-roll bar ties the left and right suspension spring rates together but does not tie their motion together.

Most modern vehicles have independent front suspension (IFS). Many vehicles also have an independent rear suspension (IRS). IRS, as the name implies, has the rear wheels independently sprung. A fully independent suspension has an independent suspension on all wheels. Some early independent systems used swing axles, but modern systems use Chapman or MacPherson struts, trailing arms, multiple links, or wishbones.

Independent suspension typically offers better ride quality and handling characteristics, due to lower unsprung weight and the ability of each wheel to address the road undisturbed by activities of the other wheel on the vehicle. Independent suspension requires additional engineering effort and expense in development versus a live axle or beam axle arrangement. A very complex IRS solution can also result in higher manufacturing costs.

The key reason for lower unsprung weight relative to a live axle design is that, for driven wheels, the differential unit does not form part of the unsprung elements of the suspension system. Instead it is either bolted directly to the vehicle's chassis, or more commonly to a subframe.

The relative movement between the wheels and the differential is achieved through the use of swinging driveshafts connected via universal (U) joints, analogous to the constant-velocity (CV) joints used in front wheel drive vehicles.