chap73 pps Automotive technology at University of Cambridge

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 73, the reader should be able to: • • • Prepare for Suspension and Steering (A4) ASE certification test content area “C” (Related Suspension and Steering Service) Discuss the various types, designs, and parts of automotive antifriction wheel bearings Describe the symptoms of defective wheel bearings 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 73, the reader should be able to: • • • Explain wheel bearing inspection procedures and causes of spalling and brinelling List the installation and adjustment procedures for front wheel bearings Explain how to inspect, service, and replace rear wheel bearings and seals 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: antifriction bearings • axial load ball bearings • brinelling cage • C-lock axle • cone • cup dynamic seals garter spring • GC-LB • grease • grease seal inner ring National Lubricating Grease Institute (NLGI) 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: outer ring radial load • retainer plate-type axle • roller bearings spalling • static seal tapered roller bearings 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 ANTIFRICTION BEARINGS Bearings allow the wheels of a vehicle to rotate and still support the weight of the entire vehicle Antifriction bearings use rolling parts inside the bearing to reduce friction Four styles of rolling contact bearings include ball, roller, needle, and tapered roller bearings, as shown here Figure 73–1 Rolling contact bearings include (left to right) ball, roller, needle, and tapered roller 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 All four styles convert sliding friction into rolling motion All of the weight of a vehicle or load on the bearing is transferred through the rolling part In a ball bearing, all of the load is concentrated into small spots where the ball contacts the inner and outer race (rings) Figure 73–2 Ball bearing point contact 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 Ball Bearings Hardened steel balls between the inner and outer race to reduce friction in ball bearings They cannot support the same weight as roller bearings, however, there is less friction in ball bearings and they generally operate at higher speeds Ball bearings can control thrust movement of an axle shaft because the balls ride in grooves on the inner and outer races The groove walls resist lateral movement of the wheel on the spindle The most frequent use of ball bearings is at the rear wheels of a rear-wheel-drive vehicle with a solid rear axle These bearings are installed into the axle housing and are often press fitted to the axle shaft Many front-wheel-drive vehicles use sealed double-row ball bearings as a complete sealed unit and are nonserviceable except as an assembly See Figure 73–3 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 73–3 Radial load is the vehicle weight pressing on the wheels The thrust load occurs as the chassis components exert a side force during cornering 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 Roller Bearings Rollers between the inner and outer race to reduce friction allow roller bearings a greater (longer) contact area that can support heavier loads than a ball bearing Figure 73–4 Roller bearing line contact A needle bearing is a type of roller bearing that uses smaller rollers called needle rollers The clearance between the diameter of the ball or straight roller is manufactured into the bearing to provide the proper radial clearance and is not adjustable 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 73–35 (a) When corrosion etches into the surface of a roller or race, the bearing should be discarded (b) If light corrosion stains can be removed with an oil-soaked cloth, the bearing can be reused (Courtesy SKF USA Inc.) (a) Continued (b) 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 73–36 (a) When just the end of a roller is scored, it is because of excessive preload Discard the bearing (b) This is a more advanced case of pitting Under load, it will rapidly lead to spalling (Courtesy SKF USA Inc.) (a) Continued (b) 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 73–37 (a) Always check for faint grooves in the race This bearing should not be reused (b) Grooves like this are often matched by grooves in the race (above) Discard the bearing (Courtesy SKF USA Inc.) (a) Continued (b) 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 73–38 (a) Regular patterns of etching in the race are from corrosion This bearing should be replaced (b) Light pitting comes from contaminants being pressed into the race Discard the bearing (Courtesy SKF USA Inc.) (a) Continued (b) 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 73–39 (a) This bearing is worn unevenly Notice the stripes It should not be reused (b) Any damage that causes low spots in the metal renders the bearing useless (Courtesy SKF USA Inc.) (a) Continued (b) 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 73–40 (a) In this more advanced case of pitting, you can see how the race has been damaged (b) Discoloration is a result of overheating Even a lightly burned bearing should be replaced (Courtesy SKF USA Inc.) (a) Continued (b) 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 73–41 (a) Pitting eventually leads to spalling, a condition where the metal falls away in large chunks (b) In this spalled roller, the metal has actually begun to flake away from the surface (Courtesy SKF USA Inc.) (a) Metal Fatigue Long vehicle usage, even under normal driving conditions, causes metal to fatigue & crack (b) The metal between the cracks can break out into small chips, slabs, or scales of metal, called spalling 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 Shock Loading Dents can be formed in the race of a bearing, which eventually leads to bearing failure Figure 73–42 These dents resulted from the rollers “hammering” against the race, a condition called brinelling (Courtesy SKF USA Inc.) 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 What’s That Sound? Defective wheel bearings usually make noise The noise most defective wheel bearings make sounds like noisy off-road or aggressive tread, or mud and snow tires Wheel bearing noise will remain constant while driving over different types of road surfaces while tire tread noise usually changes with different road surfaces In fact, many defective bearings have been ignored by the vehicle owners and technicians because it was thought that the source of the noise was the aggressive tread design of the mud and snow tires Always suspect defective wheel bearings whenever you hear what seems to be extreme or unusually loud tire noise 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 Rear Axle Bearing 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 Rear Axle Bearing 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 Wheel bearings support the entire weight of a vehicle and are used to reduce rolling friction Ball and straight roller-type bearings are nonadjustable while tapered roller-type bearings must be adjusted for proper clearance Most front-wheel-drive vehicles use sealed bearings, either two preloaded tapered roller bearings or double row ball bearings Most wheel bearings are standardized sizes 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.) A defective bearing can be caused by metal fatigue that leads to spalling, shock loads that cause brinelling, or damage from electrical arcing due to poor body ground wires or improper electrical welding on the vehicle Bearing grease is an oil with a thickener The higher the NLGI number of the grease, the thicker or harder the grease consistency Tapered wheel bearings must be adjusted by hand tightening the spindle nut after properly seating the bearings A new cotter key must always be used 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.) Defective wheel bearings usually make more noise while turning because more weight is applied to the bearing as the vehicle turns All bearings must be serviced, replaced, and/or adjusted using the vehicle manufacturer’s recommended procedures as stated in the service manual 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