a torsion bar is a spring that is a long, round, hardened steel bar similar to a coil spring except...
TRANSCRIPT
TORSION BARSA torsion bar is a spring that is a long, round, hardened steel bar similar to a coil spring except that it is a straight bar.
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Figure 85–26 A torsion bar resists twisting and is used as a spring on some cars and many four-wheel-drive pickup trucks and sport utility vehicles. The larger the diameter, or the shorter the torsion bar, the stiffer the bar.
STEERING KNUCKLESA steering knuckle servestwo purposes:
To join the suspensionto the wheel
To provide pivot pointsbetween the suspensionand the wheel
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The only steering knuckle that uses a kingpin is on an I-beam or twin I-beam front suspension.
CONTROL ARMS
A control arm is a suspension link that connects a knuckle or wheel flange to the frame.
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Figure 85–33 Control arms are used to connect the steering knuckle to the frame or body of the vehicle and provide the structural support for the suspension system.
One end of a control arm attaches to the knuckle or wheel flange, with either a ball joint or bushing.
The opposite end attached to a frame member, pivots on a bushing. It pivots to allow the axle or knuckle vertical travel.
BALL JOINTS
Ball joints are ball-and-socket joints, similar to the joints in a person’s shoulder. They allow the front wheels to move up and down, as well as side to side (for steering).
A vehicle can be equipped with coil springs, mounted either above the upper control arm or on the lower control arm.
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Figure 85–34a Ball joints provide the freedom of movement necessary for steering and suspension movements.
Figure 85–37 All ball joints, whether tension or compression loaded, have a bearing surface between the ball stud and socket.
The type used is determined by the design engineer, the tech cannot change the type of ball joint used for a particular application.
The load-carrying (weight-carrying) ball joint is subjected to the greatest amount of wear and is most frequently replaced.
STABILIZER BARS
Most cars and trucks are equipped with a stabilizer bar on the front suspension, a round, hardened steel bar (usually SAE 4560 or 4340 steel) attached to both lower control arms with bolts and rubber bushing washers called stabilizer bar bushings.
See Figure 85–40.
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A stabilizer bar is also called an anti-sway bar (sway bar) or anti-roll bar (roll bar). A stabilizer bar operates by twisting the bar if one side of the vehicle moves up or down in relation to the other side, such as during cornering, hitting bumps, or driving over uneven road surfaces.
See Figure 85–41.
Figure 85–40 Typical stabilizer bar installation.
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Figure 85–41 As the body of the vehicle leans, the stabilizer bar is twisted. The force exerted by the stabilizer bar counteracts the body lean.
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Figure 85–42 Stabilizer bar links are sold as a kit consisting of the long bolt with steel sleeve and rubber bushings. Steel washers are used on both sides of the rubber bushings as shown.
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Figure 85–43 Notice how the stabilizer bar pulls down on the mounting bushing when the vehicle is hoisted off the ground, allowing the front suspension to drop down. These bushings are a common source of noise, especially when cold. Lubricating the bushings with paste silicone grease often cures the noise.
SHOCK ABSORBERSShock absorbers are used on all conventional suspension systems to dampen and control the motion of the vehicle’s springs.
Without shock absorbers (dampers), the vehicle would continue to bounce after hitting bumps.
See Figure 85–44.
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Figure 85–45 Shock absorbers work best when mounted as close to the spring as possible. Shock absorbers that are mounted straight up and down offer the most dampening.
Most shock absorbers are direct acting because they are connected directly between the vehicle frame or body and the axles.
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What Are Remote Reservoir Shocks?
Remote reservoir shock absorbers are units designed for heavy-duty use that use a separate container for the working fluid. The purpose of the remote fluid reservoir is to keep the temperature of the fluid stable, which helps the shock provide consistent dampening under all conditions.
Figure 85–50The shock absorber is on the right and thefluid reservoir for the shock is on the left.
Air Springs Some electronically controlled suspension systems use air springs. A basic air spring consists of a rubber air chamber, generally closed at the bottom by a piston fitted into a controlarm, or by a strut shock absorber.
Electronically controlled suspension systems that use air springsas the only springs are available on some Hummer, and manyFord, Mercury and Lincoln vehicles.
See Figures 85–52
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Figure 85–52 (a) The front suspension of a Lincoln with an air-spring suspension. (b) Always check in the time for the cutoff switch for a refile equipped with an air suspension before hoisting or touring the vehicle.
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Figure 85–53 Some air springs are auxiliary units to the coil spring and are used to control ride height while the coil spring is the weight-bearing unit.
Some air springs are in effect auxiliary springs inside a coil-spring strut.
In these designs, the coil spring supports the weight of the vehicle, while the air spring raises or lowers the body to adjust ride height according to load.
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Figure 85–54 A coil-over shock is a standard hydraulic shock absorber with a coil spring wrapped around it to increase stiffness and/or take some of the carrying weight off of the springs.
Coil-Over Shocks A coil-over shock absorber uses an external coil spring to boost the performance of the basic shock absorber.
The spring usually extends from the upper shock mount to a seat on the lower portion of the cylinder.
The spring rate added to the hydraulic resistance makes the shock stiffer.
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STRUTS
A strut is a sturdy shock absorber that is also a structural component of the suspension.
A strut is a suspension link as well as a shock absorber. The casing of a strut must be strong and rigid to function as a suspension link.
The shock absorber assembles inside the casing of a strut, andmay be either a removable cartridge or an integral part of thestrut.
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STRUT Bars
A Strut Bar is a performance modification that helps
eliminate/ reduce body roll
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Figure 85–55 A strut is a structural part of the suspension and includes the spring and shock absorber in one assembly.
MacPherson StrutsThe MacPherson strut, namedafter Earle S. MacPherson, who developed the suspension designin the late 1940s and patented itin 1953, is the most commonly
used type.
A MacPherson strut includes the suspension spring—a coil springthat surrounds the strut casing—so that it transfers weight of thebody to the wheel.
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Shocks and Struts
• Helps to keep tires from hopping
• Keeps body from bouncing after bumps
• Filled with oil and a gas
Tire Care and Maintenance
• Tire wear
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Tire Care and Maintenance
• Tire Wear Indicator Bars• Set at 2/32nds of an inch (1.6 mm)
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Tire Care and Maintenance
• Tire Rotation
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Things You Can Do• Lubricate steering and suspension parts?• Check power steering fluid• Check/change power steering belt• Check tires for abnormal wear• Check shocks/struts • Check parts for wear