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Suspension is the system of tires, tire air, springs, shock absorbers and linkages that connects a vehicle to its wheels and allows relative motion between the two. Suspension systems must support both road holding handling and ride quality, which are at odds with each other. 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 road or ground 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.
start Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 OBJECTIVES: After studying Chapter 85, the reader should be able to: • Prepare for ASE Suspension and Steering (A4) • • certification test content area “B” (Suspension System Diagnosis and Repair) List various types of suspensions and their component parts Explain how coil, leaf, and torsion bar springs work Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 OBJECTIVES: After studying Chapter 85, the reader should be able to: • • Describe how suspension components function to allow wheel movement up and down and provide for turning Describe how shock absorbers control spring forces Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 KEY TERMS: air spring • anti-dive • anti-squat ball joints • bulkhead • bump stop center bolt • coil springs • composite leaf spring • control arms • cradle full frame • gVW • hooke’s law independent suspension • insulators kingpin • ladder frame • lateral links leaf springs • load-carrying ball joint Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman Continued ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 KEY TERMS: mono leaf • non-load-carrying ball joint perimeter frame • platforms • rebound clips shackles • shock absorbers • space frame • spring pocket • spring rate • springs • sprung weight • stabilizer bars • steering knuckles • stress riser • strut rod • struts • stubtype frame torsion bar unit-body • unsprung weight wheel rate Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 Street-driven cars and trucks use a suspension system to keep the tires on the road and to provide acceptable riding comfort A vehicle with a solid suspension, or no suspension, would bounce off the ground when the tires hit a bump If the tires are off the ground, even for a fraction of a second, loss of control is possible Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 FRAME CONSTRUCTION Frame construction consists of channel-shaped steel beams welded and/or fastened together The frame supports all the “running gear”, including the engine, transmission, rear axle assembly (if rear-wheel drive), and all suspension components Referred to as full frame, it is so complete that most vehicles can usually be driven without the body Most trucks and larger rearwheel-drive cars use a full frame Ladder Frame A common name for a type of perimeter frame where the transverse (lateral) connecting members are straight across is ladder frame When viewed with the body removed, the frame resembles a ladder Most pickup trucks are constructed with a ladder-type frame See Figures 85–1 and 85–2 Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 Figure 85–1 A typical truck frame is an excellent example of a ladder-type frame The two side = members are connected by a crossmember Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 Perimeter Frame A perimeter frame consists of welded or riveted frame members around the entire perimeter of the body Figure 85–2 Rubber cushions used in body or frame construction isolate noise and vibration from traveling to the passenger compartment This means frame members provide support underneath the sides as well as for the suspension and suspension components Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 Stub-Type Frames A stub-type frame is a partial frame often used on unit-body vehicles to support power train and suspension components (a) It is also called a cradle on many front-wheel-drive vehicles Figure 85–3 (a) Separate body and frame construction; (b) unitized construction: the small frame members are for support of the engine and suspension components Many vehicles attach the suspension components directly to the reinforced sections of the body and not require the rear frame section (b) Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458