What are the BMW suspension Systems?(+23 BMW Terminology explained)
In this brief article we are going to discuss what exactly is a BMW suspension system, what are the different types and what are the different terminology used to describe the various suspension parameters.
What type of suspension does BMW Use?
The BMW Suspension system consists of the following types depending on Model year and series:
|Models Series||Model Years||Front Suspension Features||Rear Suspension Features|
|E30E36 (except 318ti)3-series, including M3E85/E86 Z4)||1992-2006 3-series, 2003-2008 Z4||The front suspension was derived from the E30 3-series. It consists of a single boomerang-shaped control arm combined with a MacPherson strut||The rear evolved from a simple trailing arm on each side to a more complicated “Z-link” rear suspension anchored by large semi-trailing arms and an upper and lower link|
|E82 1-seriesF22 2-seriesE9X 3-series F30 3-seriesG20 3-seriesF32 4-seriesG22 4-series, including 1M/M2/M3/M4 modelsG29 Z4||2006-current 1,2,3,4 & series||Major changes done in the 2006 model year. The front now has Upper and Lower control arms combined with a MacPherson strut||Instead of a semi-trailing arm there are multiple smaller arms, but still attached to the car’s rear subframe. This layout is still used today on the latest G20 3-series and G22 4-series models (with unique and non- interchangeable parts)|
BMW suspension Diagram
The BMW Suspension components are described in the following diagram that describes a F10 chassis M model:
|1 – Coil over Shock Absorber2 – Upper Control Arm/Wishbone3 – Knuckle4 – Anti-Roll Bar Drop arm5 – Lower Control Arm/Wishbone||6 – Wheel Spindle7 – Tie Rod9 – Front suspension Subframe10 – Anti-roll Bar11 – Steering Rack/Gearbox12 – Stiffening Plate|
|1 – Stiffening Plate2 – Anti-roll Bar3 – Shock Absorber4 – Upper Control Arm – Rear5 – Wheel Hub6 – Wheel Spindle7 – Lower Control arm-to-Hub front Bushing||8 – Upper Control Arm – Front9 – Lower Control Arm10 – Subframe body mounting Isolators11 – Rear Suspension Subframe12 – Lower Control Arm-to-frame Bushing|
Glossary of BMW Suspension Terms
It is a crucial part of the driveline. It is a shaft that connects the differential to the wheel-spindle and hub. They are also known as half-shafts or axle-shafts. The “axle”, in some contexts, also refers to the entire front or rear suspension, which consists of the shocks, control arms, bushings, anti-roll bar, axles, wheel-spindle, and the brakes.
It is nothing but a ’Pivot’ consisting of a steel ball encased in a metal, plastic, or rubber isolated cup and a threaded stud for mounting. The ball will rotate within the cup and allowing the suspension linkage to change direction. Ball joints are typically used to allow horizontal movement. They are susceptible to wear as the internal plastic or rubber isolator tends to break down, thereafter unable to contain the ball.
A Bushing is a formed rubber piece used to connect as well as isolate one component to another component. The Anti-roll bar is mounted to the body using a rubber block. Rubber is a more common Bushing material but is often replaced with a stiffer Polymer compound like urethane or ABS.
The angle ‘tilt’ of the tire circumference in relation to the ground surface on which the car rests in front view of the vehicle. BMWs usually have negative camber as the initial ‘camber setting’ – which means, the top of the tire tilts inward of the car. As a consequence of this setting, when the car corners, the outside tires spread flatter to the road, thus increasing the tire’s contact patch. It is also common to increase negative camber in the ‘camber setting’ in order to increase grip on a race track. Excessive negative camber, however, causes the tire to contact the road on its inside shoulder while driving straight.
A rear suspension component designed to control and/or adjust camber. On the BMW E36/E46/Z4 it is the rear lower wishbone. It is usually made of sheet metal.
A front suspension component that is designed to adjust camber. The camber plate often doubles up as the upper strut mount. Increased negative camber is desirable for track use to improve front-wheel grip and reduce understeer. Cars that have a lowered suspension often need to reduce negative camber in order to avoid this kind of tire wear.
It is defined as the forward/rearward tilt of the front steering axis centerline, expressed in degrees. In the case of a MacPherson strut suspensionstrut suspension the Caster is the angle between a vertical line extended up from the steering pivot point and the center-line of the strut. BMWs have non-adjustable positive caster, which means that the strut is tilted backwards towards the driver. The caster angle is engineered just enough such that stability at high speeds is increased but at the same time not too much so as to keep the steering effort low.
A Coil-over is defined as a shock absorber with the spring mounted around the body of the shock. A MacPherson strut can be called as one type of coil over. In the context of aftermarket parts, Coli-over means performance shock and spring package that has a threaded spring mounting in order to allow for adjustments in ride height.
A Control Arm is a suspension component designed to maintain a certain suspension alignment during suspension movement. It also has a function of absorbing vibrations and impacts because it is connected by bushings. Multiple control arms will control alignment better.
Damper is another term used to refer to a shock absorber or strut. Damper is a general term that can apply to both a front strut as well as a rear shock-absorber. The damper’s primary job is to absorb energy from the motion of the suspension. The shock-absorber must be supple enough in compressive motion in order to increase ride comfort but also hard enough in expansion to prevent suspension oscillation and keep the tire in contact with the ground at all times.
Shock is just another word for Damper. A shock differs from a strut in that it is a linkage, or load bearing member of the suspension. In theory, the control arms, spring, and hub could function without a shock, but in practice, your suspension would just violently bounce the car.
A MacPherson strut/damper is constructed such that it becomes one more link in the front suspension. It is an alternate to the upper and lower control arm layout, where the shock is mounted independently from the arms. In a MacPherson strut type of design, the strut is a crucial component of the suspension assembly. The strut is mounted directly to the spindle and the strut damper moves at nearly 1:1 ratio in relation to the vertical wheel motion. In the past, almost all BMW 1, 2, 3 & 4-series models had a MacPherson strut front suspension.
Multi-Link is a generalized term for a suspension set-up that has multiple control arms and linkage points to the chassis. The E9X series rear suspension has a 5-link layout.
A Radius Arm is BMW-terminology for a control arm. It often functions as a front upper control arm.
A Spindle is a central mount location for suspension linkages, including the control arms outer pivots and the lower strut mount. It also provides a mounting point for the wheel bearing, hub, and brakes. In some contexts, ‘Hub’ is used interchangeably with ‘spindle’.
Every BMW uses either a coil spring made of steel or an air-bellow. Each BMW model as per its included option, has its own Spring unique in length and Spring rate. Suspension ‘Ride stiffness’, is majorly influenced by spring rate. Hence, a spring that is too stiff or too soft can either positively or negatively affect tire grip, ride comfort and handling characteristics of the car. Based on engineering, the stiffness arrived at has to provide the best compromise between all three aspects.
A Subframe is a steel or Aluminium frame structure bolted to the car’s chassis and is used to anchor all the suspension parts. The BMW’s front subframe usually performs the additional function of anchoring the engine mounts. The rear subframe has the additional function of anchoring the differential and axle-shafts.
Sway Bar or Anti-Roll Bar:
A solid or Hollow steel bar that resists the vehicle “Roll” motion during cornering. It is like a lever that twists only when the left and right wheels move in opposite vertical directions. When one suspension (left or right wheel) compresses, the bar twists to force the opposite suspension in Rebound to contact the road. The bar is anchored to the car body using rubber mounts or bushings.
Sway Bar or Anti-Roll Link:
The sway bar is attached to the suspension through an intermediate arm called a link. A ball joint is located at each end of this link which allows the link to rotate and move when the Anti-Roll bar rotates.
‘Toe’ is an alignment specification for the suspension. It is defined as the angle of the tire circumference in relation to the car’s longitudinal center-line when viewing the car from the top. Toe is measured at the forward/leading edges of right and left side tires of either the front or the rear of the vehicle.
If the forward edges point ‘Away’ from each other then this condition is called “toe out”. When the forward edges point ‘Towards’ from each other then this condition is called “toe in”. Adjustments to the front suspension toe is achieved by varying the length of the tie rod. Rear suspension toe is sometimes adjusted by either a provision in the trailing arm or a separate toe-control arm within the linkage.
The Trailing Arm is the principal control arm of the rear suspension. It is also known as a ‘semi-trailing’ arm since the arm’s forward mounting point is located forwards of the rear subframe. In the case of the E36/E46 the trailing arm is a steel structural member that includes the rear wheel-spindle as well as the hub. In subsequent model years, the trailing arm has been modified to be a lot smaller with the spindle being separate.
A Wheel bearing is used at each wheel hub. Its function is to allow the wheel and brake rotor to spin freely and frictionless. The bearing usually is press-fitted into the hub. The hub is then bolted on to the spindle.
The control arm of the suspension is also known as a Wishbone because of its similarity in shape to a ‘Chicken Leg Piece’ that was referred to as ‘Wishbone’. A wishbone has three mounting surfaces – one at an end and two at the opposing end. In the front suspension it is used as the “lower control arm” and on the rear in multiple points.
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In this brief article we have discussed what exactly is a BMW suspension system, what are the different types and what are the different terminology used to describe the various suspension parameters.
If you have any questions or comments please let us know.
Frequently Asked Questions (FAQs): BMW Suspension System?
What type of suspension does BMW use?
The front suspension was derived from the E30 3-series. It consists of a single boomerang-shaped control arm combined with a MacPherson strut.
The rear suspension is a “Z-link” consisting of large semi-trailing arms and an upper and lower link.
Does BMW have good suspension?
The BMW suspension unique design results in one of the worlds ride qualities in any car. Many of BMW’s competitors use lower control arms and a single ball joint, but BMW uses dual-link struts with their individual ball joints.
This arrangement makes a significant impact. It allows for better Camber control that a single ball joint/lower control arm setup just doesn’t have. Depending on which model of BMW, the suspension system includes coils, coil-over springs, sway bars, and shocks. In some latest model BMW’s they use an adaptive suspension that adjusts itself depending on what you select.
How much does a BMW suspension cost?
The average cost for a Suspension Shock or Strut Assembly Replacement for a BMW 328i should be around $2000 but can vary from car to car.
How do I tell if my BMW has adaptive suspension?
On your iDrive Screen, Press the driver control switch on the center console (ECO PRO > COMFORT >SPORT etc). If you have Adaptive it will ask you on the iDrive screen if you want to change ‘CHASSIS & DRIVETRAIN’.