Loose wheel bearings mean that not getting wheel bearing adjustment right can cause adverse effects such as; negative camber, irregular tyre wear, tapered wear on brake shoes, premature hub seal failure, and persistent ABS faults.
Even though these symptoms may take some time to develop, you may still have a problem if the wheel bearings are out of adjustment. Please note that the following instructions are general in nature. Actual wheel end inspections should be performed as per the equipment manufacturer’s service manual.
It is important to know that rocking the wheel with a lever or iron bar may be a good way to check relative movement, but it is not a good indicator of end play. When applying force to a pry bar underneath the wheel, we’re combining end play and spindle wear which is then multiplied by the diameter of the wheel. These factors will affect the amount of movement seen at the wheel end. For this reason, it is highly recommended to remove the wheels and hubcap, and then use a dial indicator.
With the wheels off and prior to taking measurements, spinning the hub and listening for unusual bearing noises will help determine if further inspection is needed. It is also a good opportunity to check the hub seal for leaks. Major leaks or splatter should be addressed immediately while slight weeping can be cleaned up and monitored. After inspection, always clean the excess dirt and dust from the seal area on the hub and spindle to ensure the build-up does not cause excessive seal wear.
Prior to removing the hub cap, it is important to clean the surrounding area to prevent grease contamination. With the hubcap removed, thoroughly clean the gasket material from the hub surface, taking care not to contaminate the grease. Spin the hub five full revolutions to ensure the bearings are fully seated. Attach the dial indicator’s magnetic base to the spindle then verify the plunger is centred between the bolt holes and reads at least 0.1524 mm (0.006”) of free movement in each direction. At this point zero the dial indicator.
End Play Measurements
While holding the hub at the 3 and 9 o’clock positions, push in and slightly rotate the hub in both directions, maintaining the plunger between the bolt holes until the dial indicator reading is steady. Record the reading. Hold the hub in the same positions and pull out in the same manner as previously described. Record the reading. Calculate the difference between both recorded readings to determine end play and record the value. The industry standard is 0.127 mm (0.005”).
End Play Adjustment
If end play is within the specification, then no action is required. If end play is greater than 0.127 mm (0.005”) then do not place the unit back into service. If out of specification and there are no other issues with the bearings or seal, tighten the spindle nut to remove the excessive end play and retake the measurements. Continue to adjust end play until it is within specification. Once completed. Replenish any lost grease and install the hubcap with a new gasket.
The importance of getting wheel bearing adjustment right cannot be over-stressed.