Very frequently, I receive a common question from customers and followers: Which bearing is best, shielded or sealed? To provide better understanding, I created a simple document that compares shielded bearings and sealed bearings. The comparison is self-explanatory when looking at the pictures.

The shelf life of an open bearing is equivalent to the life of the steel, if maintained correctly. However, the shelf life of shielded and sealed bearings is typically no more than 3-4 years. This is because these bearings are pre-filled with grease during manufacturing, and the grease’s shelf life expires after 3-4 years, depending on the type of grease used. Most manufacturers prefer to use mineral oil-based grease due to cost considerations.

Never attempt to re-lubricate or change the grease. As shown in the picture, the actual grease quantity used to operate the bearing in the application is highly optimized. Remember, over-lubrication or under-lubrication is always dangerous for bearings.