* Bearing Stability: Preload helps to eliminate bearing play or looseness. Without sufficient preload, the bearings can move and shift under load, leading to increased friction, noise, and premature wear. This is particularly important under heavy loads or during aggressive driving.
* Reduced Vibration and Noise: Proper preload minimizes vibrations and noises generated by the axle's rotation. Loose bearings are a major source of these problems.
* Consistent Wheel Tracking: A properly preloaded axle contributes to more consistent wheel tracking and handling. Inconsistent preload can lead to wandering or pulling.
* Preventing Damage: Insufficient preload can lead to axle component failure, especially under stress.
How Preload is Achieved (Methods vary depending on the axle type):
* Adjusting Nut(s): Many rear axles use adjustable nuts on the axle shafts to control the preload on the bearings. Tightening these nuts increases the preload. This adjustment usually requires specialized tools and knowledge of the correct specifications.
* Shims: Some axles use shims (thin metal plates) between components to fine-tune the bearing preload. Adding or removing shims changes the spacing, affecting the preload.
* Preload Springs: Some designs incorporate springs to provide a consistent preload.
Importance of Correct Preload:
It's critical to set the preload correctly. Too little preload results in the problems mentioned above. Too much preload, however, can also be detrimental:
* Increased Bearing Friction and Wear: Excessive preload increases friction and heat, leading to premature bearing failure.
* Difficult Axle Rotation: It may make the axle harder to turn, leading to binding.
In summary, preload in rear axle adjustments is a vital aspect of ensuring the axle functions properly, safely, and efficiently. Improper preload can lead to a range of issues, from annoying noises to potentially dangerous mechanical failures. Proper adjustment requires careful attention to detail and often specialized tools and knowledge.
