1. WHEN IS A GOOD TIME TO CONVERT TO THE WHEEL BOSS SYSTEM?
Any time is a good time to convert to the WHEEL BOSS wheel-end system. With the conversion, a fleet will immediately see the benefits of reduced wheel-end maintenance and more road time moving freight. Some fleets schedule this conversion when routine maintenance is performed such as brake changes.
2. HOW LONG DOES IT TAKE TO CONVERT AN OIL WHEEL-END TO THE WHEEL BOSS SYSTEM?
In general, it should not take any longer to convert a wheel-end to WHEEL BOSS than it takes to perform today’s bearing and seal replacement. However, the time it takes to do the conversion ultimately depends on individual fleet shop practices.
3. IF PRESSURE IS DEVELOPED IN THE WHEEL-END, HOW WILL IT BE RELIEVED?
The patented HDL™ grease seal can purge excess pressure through the seal lips. The seal construction can be compared to a check valve. It can relieve pressure while maintaining a seal against external sources of debris or moisture.
4. HOW MUCH GREASE PURGE OUT OF THE SEAL IS OK AND WHEN DOES IT INDICATE A WHEEL-END PROBLEM?
A small amount of grease purge is normal during operation. Small uniform beads of grease around the outside of the seal face are considered normal. DO NOT wipe these beads off. They serve as extra contaminant protection. If the grease purge has migrated past the seal flange, this is considered excessive. If excessive leakage has occurred, the wheel-end should be inspected and the seal replaced.
5. WHY OSCILLATE OR ROTATE A WHEEL-END WHILE TIGHTENING THE ADJUSTING NUT TO A SPECIFIED TORQUE?
Oscillating or rotating the wheel-end works the bearing’s rollers against the cone large rib (often referred to as seating the bearing). Gravity pulls the roller down the incline of the cone raceway and away from the cone large rib; this creates clearance between the rollers and the rib. This clearance will not be present during operation so accurate bearing setting requires that this clearance be removed while tightening the adjusting nut. Oscillating or rotating the wheel-end helps move the roller up the incline of the cone raceway.
6. WHEN SHOULD YOU REPACK THE GREASE?
Since all fleets operate differently; each establishes its own maintenance procedures. Check grease for contaminants or milky texture. This will indicate the need to change the grease. Meanwhile, check wheel-ends for causes of grease contamination.
7. WHAT IS #2 GREASE?
Number 2 grease is a NLGI (National Lubrication Grease Institute) designation for the consistency (hardness) of grease. Grease is oil suspended in a thickener, sometimes referred to as a soap. Timken has tested and approved Mobilith SHC 220 as an approved #2 grease. There are other #2 greases that are commercially available and appropriate for wheel bearings.
8. WHY PUT A LAYER OF GREASE IN THE HUB CAP?
The grease is needed to absorb any moisture that may condense on the internal cavity of the hub cap due to change in altitude or temperature. The grease also protects the internal surfaces of the hub cap from corroding.
9. WHY USE A NON-VENTED HUB CAP?
A non-vented hub cap should be used with the WHEEL BOSS seal. Using a vented hub cap will introduce a potential leak path to the WHEEL BOSS system, jeopardizing system performance.
10. WHY REPLACE THE GASKET EACH TIME THE HUB CAP IS REMOVED?
A gasket is a type of a seal that works by being compressed between two solid surfaces. The gasket will be compressed as the hub cap bolts are tightened to the specified torque. When the hub cap is removed the gasket will not take its original form (it will maintain its compressed shape). In order to achieve a positive seal a new gasket needs to be used.
11. WHY DO THE WHEEL BOSS HUB CAPS USE DIFFERENT GASKETS?
Hub cap flanges have different geometries and different stiffness properties. Therefore, the hub cap flange will flex differently on the aluminum and stamped steel WHEEL BOSS hub caps. The gaskets were selected to maximize the integrity of each individual gasket based on how the hub caps flex.
12. WHY IS MOBILITH SHC 220 BLACK AFTER IT IS USED?
According to ExxonMobile, the dye used to color the grease is sensitive to temperature. As the grease is worked, it may darken to black. This is normal. Check the grease for consistency – it should be similar to the dark red grease that has not been worked.
13. WHAT IS BETTER ABOUT A GREASED WHEEL-END WHEN COMPARED TO A TRADITIONAL OIL OR SEMI-FLUID LUBRICATED WHEEL-END?
Grease is easier to keep in the wheel-end than oil or semi-fluids. This means grease is less likely to get on the brakes. Since grease is easier to seal, the WHEEL BOSS grease seal is self-venting and designed with lower operating torque. Therefore, the self-venting grease seal permits the use of the non-vented hub cap.
14. WHAT IS THE RECOMMENDED SERVICE INTERVAL FOR THE WHEEL BOSS WHEEL-END SYSTEM?
Please refer to WHEEL BOSS Wheel-End System Service Inspection Procedure for service intervals. In general, a quick inspection for end play or grease purge should be performed whenever the wheel-end is in for maintenance, every 100,000 miles or
once a year.
15. WHY USE THE WHEEL BOSS END PLAY GAUGE?
Use an end play gauge to verify the proper end play in a wheel-end that uses any multiple or single spindle nut arrangement. The Technology & Maintenance Council’s (TMC) Recommended Practice 618 (RP618) identifies the need to verify wheel-end settings with a dial indicator.
16. WHAT ARE THE BENEFITS OF LIGHT PRELOAD?
Light preload eliminates wheel-end wobble. More technically, it allows the seal, bearing and tire to travel in a consistent path each revolution without misalignment. The consistent wear path on the seal, bearing and tire allows the components to last longer and maximize their design life.
17. WHAT ARE THE RISKS OF PRELOAD?
Care must be taken to ensure that preload force does not exceed the recommended amounts. Excessive preload can cause high operating temperatures, reduced lubricant life, reduced seal life, and premature bearing damage. Bearing lock-up and/or wheel-end assembly separation may occur if the preload force is excessive.