The wheels on your truck experience massive amounts of stress, thanks to the fact that they remain in contact with the ground at all times. A wheel has to be strong and steady enough to resist constant jolting and bouncing while still remaining supple enough to allow your tires to rotate correctly. Your wheel bearings play a crucial role in this process.
Wheel bearings provide stability while ensuring the low-friction conditions necessary for smooth rotation. Of course, to provide reliable results, your wheel bearings require a specific amount of end play. If you would like to learn more about this vital concept, keep reading. This blog goes over four key things to know about end play.
- Excessive End Play Leads to Loose Wheels
The wheel bearings lie inside of the hub assembly. The concept of end play refers to how tightly the bearings sit inside the hub. For many years, common trucking wisdom has held that wheel bearings should have between 0.001 and 0.005 inches of end play. This incredibly small range ensures that the bearings enjoy full range of motion while preventing too much looseness.
When end play exceeds the recommended limit, the bearings sit too loosely inside of the hub. This extra room means that the wheel does not stay locked snugly in place. Instead, the wheel can jiggle slightly on its axis. Such unwanted movement leads to a range of ill effects.
- Loose Wheels Lead to Premature Tire Wear
Excess end play often leads to problems with alignment. Specifically, wheels with loose bearings tend to develop negative camber, which means that the top side of the wheel tilts slightly inward. As a result, the surface of your tire does not contact the road as evenly as it should.
Negative camber leads to uneven tire wear, and ultimately to premature tire failure. Likewise, the uneven pressure exerted on the wheel hub can cause the seals to wear out too quickly. The angled wheel hub also affects your brake shoes. Because the brake shoe cannot contact the rotor flatly, it tends to wear down unevenly.
The greater the end play in the wheel bearings, the more pronounced such problems become. For this reason, you must have your bearings’ end play measured on a regular basis. If necessary, a service technician can then tighten up the bearing assembly to bring your end play back within the recommended range.
- The Opposite of End Play Is Preload
Technicians refer to the opposite of end play as preload. Whereas all end play involves a controlled amount of looseness, preload means that your hub can no longer move at all relative to your wheel axle. Like end play, preload operates along a spectrum. In an ideal world, mechanics would tighten the bearings just enough to cross over into preload.
At that point, the hub would remain stationary, while the bearings would still enjoy complete freedom of movement. Yet performance quickly drops off as preload increases. Too much preload restricts the movement of the bearings, creating friction that can lead to total bearing failure.
- Technicians Can Measure Preload
Historically, technicians have had no reliable way to measure preload. Thus mechanics usually erred on the side of caution, opting for a small known quantity of end play in favor of an unknown quantity of preload. In other words, end play was seen as a necessary — and controllable — evil.
In recent years, technological advances have given technicians ways to more accurately measure preload. As a result, truck owners can now achieve perfect bearing tightness without risking overtightening. Of course, mechanics must take extreme care in order to achieve controlled preload.
To learn more about what a true expert can do to keep your wheel bearings at an optimal tightness, please contact the trucking industry veterans at Godfrey Brake Service & Supply.