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Wheels and tires are crucial components of a car, and the bearings within the wheel hubs are equally important, requiring essential maintenance.
Wheel Hub Bearing Maintenance
Generally, non-maintenance-free wheel hub bearings require maintenance every 10,000 kilometers. How to perform this maintenance?
Removing Old Grease: After removing the wheel hub, clean the bearings, journals, and wheel hub cavity, scraping off the old grease. Then, use a cleaning agent or diesel fuel to thoroughly clean the wheel hub bearings and journals, and wipe them dry with a cloth. Finally, wipe the inner cavity of the wheel hub clean with a cloth.
Bearing and Seat Ring Inspection: After cleaning, inspect the wheel hub bearings and bearing seats. If cracks, fatigue spalling, or loose bearing rollers are found, replace the bearing immediately.
Bearing Fit Clearance Inspection: Check the fit between the bearing inner diameter and the journal. The fit clearance should not exceed 0.10 mm. Measure at two points on the wheel diameter perpendicular to the ground; these are the points of greatest wear. If the fit clearance exceeds this range, the bearing should be replaced.
Grease Application: During maintenance, fill the gap between the inner bearing race and the cage rollers with new grease (#2 lithium-based grease), and apply a thin layer of grease to both the inner and outer surfaces of the bearing. Applying a thin layer of grease inside the hub cavity and axle cap helps prevent rust; excessive grease will affect heat dissipation and braking.
Bearing Installation: After applying grease to the inner bearing, place it in the hub. Reinstall the hub and outer bearing onto the journal. Tighten the axle end adjusting nut by hand, then use an axle end wrench to tighten the adjusting nut to the specified torque (front axle: 275±25 N·m; rear axle: 530-570 N·m). Rotate the hub several times to ensure proper fit between the bearing and race. Then, back the adjusting nut to a certain angle (front axle: 60°; rear axle: 1/3~2/3 turn, tighten the outer nut, torque 530-570 N·m). At this point, the bearing should be properly tight, and the wheel should rotate freely without any noticeable axial play.
Precautions
1. Wheel bearing preload should be within the specified range:
Excessive preload will result in insufficient bearing clearance, causing bearing burn-out and affecting bearing lifespan. Insufficient preload will cause slippage between the bearing and the shaft or hub, leading to wheel wobbling and instability, and in severe cases, wheel ejection.
2. Appropriate amount of grease:
During maintenance, applying a suitable amount of grease to the wheel bearing is sufficient. Full lubrication is ideal; excess grease will not participate in the lubrication process and may lead to poor heat dissipation, potentially causing vehicle fire or brake failure. Insufficient grease will increase friction between the bearing and the hub, causing bearing damage and shortening its lifespan.
The above information highlights the importance of bearing maintenance and how to perform it properly. Car owners should take good care of their vehicles and pay close attention to the details of wheel bearing maintenance.
