Wheel Bearings

Ball Bearings vs. Roller Bearings
- Ball bearings have less surface area in contact, leading to reduced friction, which is beneficial for high-speed applications.
- Roller bearings consist of long rollers situated between an inner race and an outer race, providing greater surface area for load support compared to ball bearings.

All bearings ('roller' or 'ball') consist of two main components:
- Inner race: The inner component that directly houses the rotating mechanism.
- Outer race: The outer component that serves as a mounting point or attachment for the housing.
Roller bearings enable greater sustained contact area to support loads effectively compared to ball bearings.

Definition of Tapered Bearings: Tapered bearings have a conical shape enabling them to handle both vertical and lateral loads efficiently.
Utilized in applications that require stability during vertical motion, e.g., spindle or tire mount locations in vehicles.
Vehicles will typically feature an inner bearing and an outer bearing in their assembly.

Sealed Non-Adjustable Wheel Bearing:
- Designed without the ability to tighten or adjust post-installation.
- Once worn or damaged, they must be replaced.
Interchangeable Bearings:
- Some tapered bearings may use a plastic cage instead of a metal one to reduce weight.
- Both forms of bearing are adaptable to the same assembly with either plastic or metal races.

Installation typically might involve pressing the bearing into the steering knuckle.
For a four-wheel drive vehicle, removal of the axle is necessary before bearing replacement, usually needing a press to disassemble the assembly.
Removal Techniques: Heating components to detach them can be risky and may result in damage if not done correctly.

The National Lubricating Grease Institute (NLGI) defines grease performance levels:
- Grease classification starts at triple-zero (000), a liquid grease suitable for low-pressure applications.
- Standard grease for wheel bearings: NLGI grade number 2 is appropriate for wheel bearing lubrication, maintaining viscosity under pressure conditions.
- Differentiation between wheel bearing grease and chassis grease is crucial; they serve different purposes and are formulated differently.

Definition of Seals: Seals are designed to retain lubricants or impede contaminants in rotating mechanisms, differing from static gaskets utilized in non-moving applications (e.g., head gaskets).
- Seals typically include springs that enhance contact with moving surfaces to improve sealing capability and prevent lubricant leakage.
- Static Seals: Gaskets that remain stationary and hold fluid between surfaces.

Distinguishing between noises related to wheel bearings and tires is essential:
- Noises may change with cornering: if turning left unloads the noise, it may indicate a bad wheel bearing on the opposite side.
- For diagnosing, observing shifts in noise when changing the load on each wheel aids in testing.
Testing for Wheel Bear Noise:
- Use of stethoscopes or screwdrivers to isolate noise source when bearings are loaded.

Cleaning Process: Bearings should be completely cleaned prior to installation:
- Utilize professional parts washers to eliminate old grease and contaminants.
- Inspect for wear and damage, including bent cages, pitting, or surface abnormalities.
- Ensure bearings are thoroughly dried after washing before reassembly.

Proper installation involves:
- Positioning the tapered side of the bearing correctly based on design specifications.
- Ensure the inner and outer races are properly seated to prevent wear.

Traditional Method for Greasing: Involves taking grease and forcing it through the bearings until clean grease comes out on the other side.
- Bearing Packer Tool: Modern methods may utilize a bearing packer for more effective and less messy repacking.
- When reassembling, always check that the races are appropriately lubricated, and ensure seals are installed to maintain lubrication integrity.