Heavy Duty Wheel Seals Centennial College

Heavy Duty Wheel Seals There are six failure modes that will account for virtually all of the premature failures of a wheel seal:  Improper installation (wrong tool, or no tool used) Cocked installation Improper bearing adjustment Seal spinning on the spindle (hit spindle, or imperfections in spindle) Hub imperfections Installed over a wear ring (if not designed to use one)

Heavy Duty Wheel Seals Design – Cutaway Seal designs are most often represented by a flat view of the seal cut crosswise, like the one shown below. Only the top cross section is used.

Heavy Duty Wheel Seals The three-quarter view to the right shows how the flat drawing is derived from the three-dimensional seal. Some common terms used throughout this guide follow.

Heavy Duty Wheel Seals Main Components The main components of the seal are: (A.) the inner cup, (B.) the packing (the bonded rubber component of the seal) and (C.) the outer cup.

Heavy Duty Wheel Seals Sealing Elements The Scotseal is a unitized seal, which means all of the sealing surfaces are protected inside the seal. The sealing lips remain stationary on the shaft, while the outer cup rotates with the hub and wheel.

Heavy Duty Wheel Seals The sealing elements are: (A.) the primary sealing lip, (B.) the secondary sealing lip, (C.) the dirt lip (D.) Bore-Tite®. Bore-Tite, is unique to seals from SKF. This distinctive green material is a non-hardening sealant that  helps fill small imperfections in the bore without reducing the heat dissipating ability of the seal

Heavy Duty Wheel Seals The first step in examining the seal is removing it from the hub. You do this by inserting a pry bar (crow's foot) between the seal and the bearing cone. The bar should rest on the inner race to avoid damaging the bearing. 

Heavy Duty Wheel Seals External Inspection Outer diameter Normal scuffing. This view is looking straight down on the edge of the seal. The Bore-Tite will show some normal signs of scrapes and scuffing. Nicks, scratches or metal particles are warning signs that something's amiss. Make sure the hub bore is smooth and free of burrs.

Heavy Duty Wheel Seals Radial grooves across the seal. The Bore-Tite reveals a path that cuts across the full width of the seal. The mark doesn't have to be as deep and pronounced as this one is to be a leak path. Any continuous channel should be a suspect.  Most likely this leak is caused by a burr or damage to the inside surface of the hub.

Heavy Duty Wheels Seals The best way to avoid this type of leak is to make it a standard practice to inspect and clean the hub before every installation.  An emery cloth or a fine file should be used to remove any imperfections that could damage the seal. On this design, the Bore-Tite (green area) is applied only across the contact surface of the O.D.. You will notice different applications on different Scotseal designs, but the interpretation of markings still applies.

Heavy Duty Wheel Seals Angled or Axial Lines The seal could be the wrong part number for the application and thus might be spinning in the hub. The seal was installed crooked (or cocked).  The marks on this seal clearly indicate it was not squarely seated in the bore.

Heavy Duty Wheel Seals A seal that's been ground down to make installation "easier.“ The mistaken theory is that by rounding off the leading edge, the seal will go into the bore easier. (So someone doesn't have to go and find the right installation tool?)

Heavy Duty Wheel Seals Shiny Leading Edge, continued Grinding the seal Distorts the O.D. creating a potential leaker, Weakens the seal wall so that it's liable to come apart in operation. Some innovation by technicians should be encouraged. This is not one of them

Heavy Duty Wheel Seals Outer Cup Damage Dents and Dings. Caused by installing the seal without a proper tool (or the tool was damaged). Gashes and Sharp Indents Caused by the use of a screwdriver or drift. It is virtually impossible to seat a seal correctly with this type of installation method. On this illustration, the shiny metal is the “air” side.

Heavy Duty Wheel Seals Inner Diameter Wear Polished Packing/Axial Scratches. Seal was spun on the shaft. Cocked installation. When installed “crooked”, the contact surface between the seal and the shaft is reduced, and the leverage of the large hub diameter increases. Wrong seal was installed. Double-check the part number!

Heavy Duty Wheel Seals Installed Backwards Caused by rubbing against the bearing race. And the only way that that can happen is by installing the seal backwards.

Heavy Duty Wheel Seals Damaged I.D. A severely damaged I.D. indicates that the seal has banged into something pretty hard. The most likely culprit is the spindle shaft caused by a mis-adjusted dolly, a rushed installation or even a dirty shop floor.

Heavy Duty Wheel Seals Distorted packing Tried to install the seal over a wear ring. The spindle should be cleaned and inspected before every installation. A thorough inspection procedure will eliminate leaving a wear ring or any other contamination on the shaft.

Heavy Duty Wheel Seals Foreign Matter On The I.D Seal that has a mysterious, tacky substance on it. Most likely suspect is silicone. With modern seal design and quality control, additional sealant is not required and it will do more harm than good.

Heavy Duty Wheel Seals Internal Inspection Lip grease Seal is pre-lubed at the factory and there should be grease (arrow) between the primary lip and the dirt lip. Absence of lip grease Excessive end-play (improper bearing adjustment) A cocked installation Improper ventilation of the wheel end (dirt, corrosion or paint clogging the vent)

Heavy Duty Wheel Seals Internal Inspection Brittle Sealing Lip Broken Dirt Lip The cause is most likely overheating. And the leading suspect should be a lack of lubrication. Carefully inspect the bearings when you find this type of damage.

Heavy Duty Wheel Seals Internal Inspection Cocked installation The two lip tracks will be parallel to each other, but they'll appear to move closer and then farther from fhe outer cup edge. This is confirmation that the seal was installed crooked. No marks indicate the seal was never used. Once the seal turned, tracks will appear within the first few revolutions .

Heavy Duty Wheel Seals Wear Tracks: A good pattern Two parallel lines that look like they've been drawn with a sharp pencil. They are the wear paths of (A.) the primary lip and (B.) the dirt lip. You'll also most likely see some dirt and crud (C.) that has built up outside the dirt lip. The tracks should be approximately the same size and equidistant from the edge all the way around the seal.

Heavy Duty Wheel Seals Wear Tracks Wide & Wide Tracks If both tracks (A.) and (B.) are wider than a pencil line, it means that the sealing lips have been moving in and out. This is most likely the result of improper bearing adjustment.

Heavy Duty Wheel Seals Wide, Thin Pattern If the primary lip track (A) is wide, but the dirt lip track (B) is thin, pressure has built up inside the housing and is rolling the sealing lip over. For steer and trailer applications, you should check the hubcap for plugged or painted vents. On the drive axles, you'll want to make sure the tube vent is clear.

Heavy Duty Wheel Seals Applause!

Heavy Duty Wheel Seals Centennial College