chap93 pps Automotive technology at University of Cambridge

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chap93 pps  Automotive technology at University of Cambridge

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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 93, the reader should be able to: • • • Prepare for ASE Suspension and Steering (A4) certification test content area “D” (Wheel Alignment Diagnosis, Adjustment, and Repair) List the many checks that should be performed before aligning a vehicle Describe the proper alignment setup procedure 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 93, the reader should be able to: • • • Explain how to correct for memory steer, torque steer, pull, drift (lead), and wander Describe the use of unit conversion and diagnostic charts Discuss tolerance alignment and how to check for accident damage 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: Degrees eccentric cam five-wheel alignment • four-wheel alignment • fractional geometric centerline memory steer • minutes prealignment checks ride height 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 KEY TERMS: shim chart • spoke angle thrust line • tolerance adjustment • torque steer • total toe 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 Proper wheel alignment of all four wheels is important for the safe handling of any vehicle When all four wheels are traveling the same path and/or being kept nearly vertical, tire life and fuel economy are maximized and vehicle handling is sure and predictable A complete wheel alignment is a complex process that includes many detailed steps and the skill of a highly trained tech 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 PREALIGNMENT CORRECTION TECHNIQUES A thorough inspection of the steering, suspension, and tires should be performed before the alignment of the vehicle is begun There are four basic steps in the correction of any problem: Verify What, when, where, and to what extent does the problem occur? Isolate Eliminate known good parts and systems Always start with the simple things first For example, checking and correcting tire pressure and rotation of the tires should be one of the first things performed whenever trying to isolate the cause of an alignment-related problem 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 Repair the problem This step involves replacing any worn or damaged components and making sure that the alignment is within factory specifications Recheck Always test-drive the vehicle after making a repair Never allow the customer to be the first to drive the vehicle after any service work Figure 93–1 The owner of this Honda thought that all it needed was an alignment Obviously, something more serious than an alignment caused this left rear wheel to angle inward at the top Continued 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 Align and Replace at the Same Time Magnetic bubble-type camber/caster gauges can be mounted directly on the hub or on an adapter attached to the wheel or spindle nut on front-wheel-drive vehicles Besides an alignment setting tool, a magnetic alignment head is great tool use when replacing suspension components Any time a suspension component is replaced, the wheel alignment should be checked and corrected as necessary An easy way to avoid having to make many adjustments is to use a magnetic alignment head on the front wheels to check camber with the vehicle hoisted in the air before replacing front components, such as new MacPherson struts Figure 93–2 Magnetic bubble-type camber/caster gauge To help it keep its strong magnetism, it is best to keep it stored stuck to a metal plate as shown here 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 PREALIGNMENT CHECKS Before checking or adjusting the alignment, these items should be checked and corrected, as part of the prealignment checks: Check all the tires for proper inflation pressures Tires should be approximately the same size and tread depth, and the recommended size for the vehicle See Figure 93–3 NOTE: Some alignment techs think that the vehicle must have new tires installed before an accurate alignment can be performed Excessively worn tires, especially if only one tire is worn, can cause the vehicle to lean slightly It is this unequal ride height that is the important fact to consider If, for example, all four tires are equally worn, then the vehicle can be properly aligned (Obviously, excessively worn tires should be replaced, and it would be best to align the vehicle with the replacement tiresinstalled to be assured of an accurate alignment.) 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 ALIGNING ELECTRONIC-SUSPENSION VEHICLES Verify exact type of electronic suspension This step could include checking the regular production order (RPO) code Check that the ride height (suspension height) is within factory specifications The steering wheel angle, as well as the radar cruise control sensor, will often need to be recalibrated using a scan tool The steering wheel may be in a different position after the alignment, and the steering wheel position sensor needs to be reset because the rear toe setting was changed The rear thrust line could also have been changed The radar cruise control needs to be calibrated to the revised rear thrust angle using a scan tool 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 ALIGNING MODIFIED VEHICLES If different springs or smaller wheels and tires were installed, many alignment shops would reject doing an alignment Because the ride height is changed from stock factory setting, the following can occur: The steering axis inclination (SAI) is now incorrect Because the steering linkage and the control arms are no longer parallel, bump steer can occur Bump steer cause the vehicle to dart to one side when a wheel hits a bump Because the ride height changed, camber and toe also changed The camber change is often enough to prevent it from being able to be adjusted to within specifications 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 Alignment alone will not correct these concerns To allow for proper handling, the following aftermarket kits and part are available: Camber kits—These kits usually include a replacement control arm or offset cam, which provides additional camber adjustment Bump steer kits—A bump steer kit can include a modified steering arm or rack-and-pinion steering gear repositioning components The kits available can be found listed on the alignment screen of many newer alignment machines, such as the Hunter Engineering Company’s WinAlign Tuner Custom Alignment for Modified Vehicles During this alignment, the tech selects one of two options: Maximum tire wear Maximum handling 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 The technician has to determine from the customer which of these two parameters are most important After the alignment, the instructions often state the vehicle should be driven and temperature of the tires measured and recorded Using a tire pyrometer, be sure to measure the temperature of each tire at the following locations for each tire: Approximately 1.5 inches (38 mm) from the outside edge of the tire in the tread rubber In the middle of the tread Approximately 1.5 inches (38 mm) from the inside edge of the tire in the tread rubber The temperatures are then typed into the alignment machine, and the program calculates the final alignment settings See Figure 93–45 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 93–45 A typical tire temperature pyrometer The probe used is a needle that penetrates about 1/4 inch (7 mm) into the tread of the tire for most accurate readings 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 HIDDEN STRUCTURAL DAMAGE DIAGNOSIS If alignment angles are out of spec tolerances, then accident damage should be suspected Look for newly replaced suspension parts, body work, or repainted areas of the body A body and/or frame of a vehicle can be straightened, and done by a knowledgeable person using body-measuring equipment A datum plane must be established Datum means a basis on which other measurements can be based The datum plane is the horizontal plane The service tech can use a common steel rule to measure several points of the vehicle to determine if the vehicle is or is not damaged or needs to be sent to a frame shop for repair 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 Frame/Body Diagonals If the frame or body is perfectly square, the diagonal measurements should be within 1/8 in (3 mm) of each other Diagonal measurements can be made from almost any point that is repeated exactly on the other side, such as the center of a bolt in the suspension mounting bracket Figure 93–46 Jig holes used at the assembly plant to locate suspension and drivetrain 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 TSBs Can Save Time Technical service bulletins (TSBs) are issued by vehicle and aftermarket manufacturers to inform technicians of a situation or technical problem and give the corrective steps and a list of parts needed to solve the problem TSBs are often released by new vehicle manufacturers to the dealership service department They usually concern the current-year vehicle of a particular model While many of these TSBs concern minor problems covering few vehicles, many contain very helpful solutions to hard-to-find problems Most TSBs can be purchased directly from the manufacturer, but the cost is usually very high TSBs can also be purchased through aftermarket companies that are licensed to include TSBs on CD-ROM computer discs Factory TSBs can often save the technician many hours of troubleshooting 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 ALIGNMENT TROUBLESHOOTING Common alignment problems and probable causes See the chart on Page 1200 of your textbook 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 PHOTO SEQUENCE Alignment Step-by-Step 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 PHOTO SEQUENCE Alignment (cont.) 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 PHOTO SEQUENCE Alignment Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman (cont.) ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 SUMMARY (cont.) Before attempting to align any vehicle, it must be checked for proper ride height (trim height), tire conditions, and tire pressures A thorough inspection of all steering and suspension components must also be made Memory steer is a condition that causes the vehicle to lead or pull to the same direction it was last steered Binding steering or suspension components are the most frequent causes of memory steer Torque steer is the pull or lead caused by engine torque being applied to the front wheels unevenly on a front-wheel-drive vehicle Out-of-level drive train, suspension components, or tires are the most common causes of excessive torque steer 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 SUMMARY (cont.) Lead/pull diagnosis involves a thorough road test and careful inspection of all tires There are three types of alignment: geometric centerline, thrust line, and total four-wheel alignment Only total fourwheel alignment should be used on a vehicle with an adjustable rear suspension The proper sequence for a complete four-wheel alignment is rear camber, rear toe, front camber and caster, and front toe 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 end 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 ... tire pressure and rotation of the tires should be one of the first things performed whenever trying to isolate the cause of an alignment-related problem Continued Automotive Technology: Principles,... the alignment of the vehicle is begun There are four basic steps in the correction of any problem: Verify What, when, where, and to what extent does the problem occur? Isolate Eliminate known good... be assured of an accurate alignment.) Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc

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  • PowerPoint Presentation

  • OBJECTIVES:

  • Slide 3

  • KEY TERMS:

  • Slide 5

  • Slide 6

  • PREALIGNMENT CORRECTION TECHNIQUES

  • Figure 93–1 The owner of this Honda thought that all it needed was an alignment. Obviously, something more serious than an alignment caused this left rear wheel to angle inward at the top.

  • Slide 9

  • PREALIGNMENT CHECKS

  • Figure 93–3 Typical tire wear chart as found in a service manual. Abnormal tire wear usually indicates a fault in a steering or suspension component that should be corrected or replaced before an alignment is performed.

  • Slide 12

  • Figure 93–4 Measuring points for ride (trim) height vary by manufacturer. (Courtesy of Hunter Engineering Company)

  • Figure 93–5 Measuring to be sure the left and right sides of the vehicle are of equal height. If this measurement is not equal side-to-side by as little as 1/8 in. (3 mm), it can affect the handling of the vehicle.

  • Slide 15

  • LEAD/PULL

  • Slide 17

  • MEMORY STEER

  • Slide 19

  • Slide 20

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