Bearings seals and greases
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Bearings, Seals, and Greases. Chapter 60. Objectives. Understand terms that relate to wheel bearings Select the correct grease to use for a particular application Describe the various wheel and axle bearing arrangements Service wheel bearings on front and rear axles. Introduction.

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Bearings seals and greases

Bearings, Seals, and Greases

Chapter 60



  • Understand terms that relate to wheel bearings

  • Select the correct grease to use for a particular application

  • Describe the various wheel and axle bearing arrangements

  • Service wheel bearings on front and rear axles



  • Automobiles contain many types of bearings

    • This chapter deals with fundamentals of bearings, seals, and lubricants

    • Last part of chapter covers bearing service

Plain bearings

Plain Bearings

  • Example: engine crankshaft bearings

    • Do not use rolling parts

    • Provide sliding contact between two mating surfaces

    • Also called friction bearings

Frictionless bearings

Frictionless Bearings

  • Provide a rolling contact

    • Ball, roller, or needle bearings

      • Made of hardened steel alloys

      • Ground to a precise finish and size

      • Must be lubricated

      • Some are sealed

  • Ball or roller bearings

    • Balls or rollers ride between an inner race and an outer race

    • Bearing cage holds balls or rollers in position

Bearing loads

Bearing Loads

  • Bearings are made to handle different loads

    • Radial load: bearing load in up-and-down direction

    • Thrust load: load in front-to-rear direction

      • Also called axial thrust

Ball bearings

Ball Bearings

  • Ride in machined grooves

    • At rest: load is distributed equally wherever balls and races are in contact

  • Control end thrust and radial movement

    • Must control thrust: groove in bearing race will be offset to one side

  • Single-row bearings

    • Susceptible to damage when shaft is misaligned

Roller bearings

Roller Bearings

  • Used great load-carrying capacity is needed

    • Provide more surface area of contact with the race

    • Several types

    • Do not control end thrust

  • Most popular is the tapered roller bearing

    • Used for front-wheel bearings

    • Can control end thrust when installed with tapers facing in opposite directions

  • Needle bearing

    • Very small roller bearing

Wheel bearings

Wheel Bearings

  • Found on all wheels of a vehicle

    • Axle bearings are on live axles

  • Drive axle bearings

    • Located at ends of rear axle housing on RWD car or on hub on FWD car

  • Full-floating axles

    • Found on ¾ ton and larger trucks and vans

  • FWD bearings

    • Compact and need to fit in a tight space



  • Greases are used in:

    • Wheel bearings and chassis joints

    • Universal joints and gear boxes

  • Properties and characteristics of grease

    • Limited by quality of oil it is made of

    • Greases are fibrous

      • Different sizes of fibers available

    • Greases do not have a sharp melting point

    • Viscosity of oil used in making grease is important to grease's apparent viscosity

Greases cont d

Greases (cont'd.)

  • Automotive grease

    • Classified by NLGI

  • Grease types

    • Extreme pressure lubricants

      • Same as those found in gear lubricants

    • Chassis grease

      • Consistency allows application through zerk fitting

    • Wheel bearing grease

      • Resistant to heat

Greases cont d1

Greases (cont'd.)

  • Universal joint grease

    • Made for universal joints

  • Multipurpose grease

    • Satisfies requirements of chassis, wheel bearing, and universal joint lubricants

  • Solid lubricant grease

    • Often used to lubricate speedometer cables, emergency brake cables, splines, and leaf springs

Wheel bearing seals

Wheel Bearing Seals

  • Automobiles and equipment use seals to:

    • Seal in lubricants

    • Keep different lubricants separated

    • Keep out dirt

    • Maintain vacuum or pressure

Seal materials and design

Seal Materials and Design

  • Most popular seals are made of synthetic materials

    • Most lip seals made of nitrile

  • Silicone seals

    • Often used in engines and transmissions

  • Fluoroelastomers

    • Used with special lubricants and chemicals

  • Non-synthetic seals

    • Leather, felt, etc.

Seal tolerance

Seal Tolerance

  • Seals can accommodate shaft that is undersized up to 1/64” if parts are in perfect alignment

    • RMA recommends runout tolerance be held to ±0.003” for shafts up to four inches in diameter

  • Surface finish should be smooth

Wheel bearing diagnosis and service

Wheel Bearing Diagnosis and Service

  • Seal and bearing failure

    • Lubricant can leak out

      • Moisture can leak in

  • Boat trailer bearing failures

    • Common wheel bearing problem: trailer is towed for a long distance before launching

      • Possible solution: Bearing Buddy®

Wheel bearing adjustment

Wheel Bearing Adjustment

  • Wheel bearings must be adjusted correctly

    • Designed to operate with very little clearance

    • Generic method of adjusting a loose bearing can be done with tire raised off ground

  • Spindle nuts are kept in place with a cotter pin

    • Remove to tighten

    • Washer under spindle nut has a tab that fits into spindle groove

      • Prevents bearing from loosening or tightening

  • Wheel bearing nuts are typically hexagonal

Wheel bearing adjustment cont d

Wheel Bearing Adjustment (cont’d.)

  • Selecting and installing a cotter pin

    • Use largest diameter cotter pin that will fit into hole

    • Pull longer end of cotter pin to seat fully in its hole

    • Cut it off

    • Cut off remaining end flush with spindle

Disc brake caliper removal

Disc Brake Caliper Removal

  • Procedure for repacking disc brake wheel bearings

    • Same as that followed for drum brakes

      • Except disc caliper must be removed in order to gain access to the inside wheel bearing

      • Caliper must be supported or wired to the steering knuckle support

Repacking wheel bearings

Repacking Wheel Bearings

  • Major steps and considerations

    • Remove hub and bearings from spindle

      • Seals are replaced during a bearing repack

    • Use a long dowel or drift to remove the seal

    • Clean out the old bearing

    • Look for metal flakes

    • Let the clean bearing air dry

Bearing inspection and diagnosis

Bearing Inspection and Diagnosis

  • After cleaning inspect for damage

    • Spalling: pieces break off the bearing metal

    • Brinelling: bearing or race has indentations

  • Add grease to bearing

    • Pack with new grease by hand or pressure bearing packer

    • Put small amount of grease in cavity of hub

  • Inspect the spindle

    • Clean and lubricate

Diagnosing wheel bearing noise

Diagnosing Wheel Bearing Noise

  • Driving car can help pinpoint problem

    • Check tires and bearings

    • Make slow left and right turns

      • Shifts weight of vehicle from one side to the other

      • Weight increases on bearing: noise increases

Replacing bearing races

Replacing Bearing Races

  • Anti-friction bearings usually have one race that is pressed fit and the other is push fit

    • When a damaged wheel bearing is replaced: pressed-fit race must be removed

    • Old bearing race: removed by pounding it with a drift punch or special tool

    • New race must fit the hub tightly

    • New race can be chilled in refrigerator to make easier to install

Servicing front wheel drive bearings

Servicing Front-Wheel-Drive Bearings

  • Most bearings on FWD vehicles are sealed

    • Require no service

  • Remove axle to get to bearing

    • Puller often required

  • Front-wheel bearing

    • Pressed or bolted onto the steering knuckle

  • Some manufacturers recommend bearing replacement any time FWD assembly is removed

    • Special care required during reassembly

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