The sealing lip on a wheel seal must face which direction?

• A. The fluid to be confined
• B. The wheel hub
• C. The atmosphere outside
• D. The opposite lip

Answer: (A)

The sealing lip is oriented toward the fluid inside the hub because internal lubricant pressure helps press the lip against the sealing surface, creating a tight seal that keeps grease in and dirt out. If the lip faced outward toward the atmosphere, internal pressure would tend to push it away from the surface, increasing leakage and letting contaminants in. In wheel seals, the primary lip faces the grease inside the bearing, while any outer features provide additional protection from outside dirt.