Well before I had my old man’s moment this week and wrote about the sap runnin’ and Maple Sugarin’ as it called up here we were talking about jacking the rig safely up to get ready to pack the wheel bearings.
Now if you remember, we have the rig up and on safety stands so that it won’t fall. I suggested that I controlled the bottle jack so that just the weight of the rig was off the studs but that the tire was still on the ground, and that then you could roll the wheel off the studs. Steffen wrote in and said that he did about the same thing but put his creeper under the wheel and then rolled it away and back into place. Good tip, thanks.
Some wheel bearings are in an oil bath. They are filled with about the same lubricant that is used in the differential and have a sight glass to check the fluid level. There is also a fill plug to add lubricant. These are great except that once in a while it is a smart idea to jack up the rig and check the play in the bearing. Remember that looseness in the bearing will translate to changes in alignment and looseness in the steering. Excessive looseness in the wheel bearing can also cause a problem with the brakes.
If your rig has hydraulic brakes it will show up as a low soft brake pedal in the first application while you are moving down the road. What happens is that the brake rotor, which is attached to the hub, will wobble and push the inner brake pad and the piston back into the caliper. Then the first pump of the brake pedal is used to push the piston back out and then the second pump of the brake will bring the pedal back up. It can also cause problems with air brakes but not as severe.
Most wheel bearings are the tapered roller bearing and and work best when running under a preload. That is the bearings are squeezer together lightly. This eliminates wiggle in the bearings and makes the wheel run true. After packing the bearing with the proper grease (the proceedure will come in the next blog) the bearing retaining nut is tightened to as much as 200 foot pounds on a big rig. On a class C it is tightend to 50 or so foot pounds while the wheel is turning. This seats the bearing and distributes the lubricant. The nut is backed off and retightend to between 12 and 50 foot pounds. Yep, you need a torque wrench here.
Then back the nut off to the next castilation (slot for the cotterpin) and cotter pin the nut. If the rig runs a second nut as a lock nut or jamb nut check your manual for the correct torque for it. Once the bearing is adjusted the rotor should spin free and have no wiggle.
Well catch ya next week when we get our hands all gooey with grease.
Brad