Category: mechanics

Sealed bearings are not entirely waterproof

With December, January, February, March, and April showers come flooded roads and paths. We all do what we’ve got to do to get through these areas, but it’s best to avoid biking through deep water. Prolonged water contact will damage any type of bearing surface in your bicycle, but don’t get too confident if you think you have sealed bearings: sealed cartridge bearings in your bottom bracket and hubs are not completely waterproof, especially with prolonged immersion.

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Your bicycle likely has different types of bearings, but I’ll mostly discuss ball bearings here. These reduce rotational friction while supporting loads. On your bicycle, you probably have ball bearings in your wheel hubs, your bottom bracket (the mostly cylindrical thing at the bottom of your bike frame where the cranks attach), and in your steering tube.

The ball bearings come in various styles: cup and cone, cartridge, and sealed. All of these are used on bicycles, and all of these, including sealed bearings, are subject to water intrusion.

Sealed bearings are “sealed” by a plastic cover to protect the bearings and grease inside the cartridge from dust contimination. The covers also protect against splashing, but provide little to no protection against total immersion. When you dunk the moving parts of your bicycle into water, the water contaminates the grease. Even if the water is completely clean, the steel bearings begin to rust and no longer provide a smooth, low-friction surface.

Maybe you’ll be fine biking through deep water, maybe not. I personally try to avoid riding through anything deeper than the bottom of my bottom bracket. If you do ride through water deep enough to soak your bottom bracket, do what you can to dry the insides out.

Miss January 2009

The 2009 Female Mechanics Calendar features New York wrench Susan Lindell (pictured above) in January. The calendar is attractively laid out and nicely produced. Anyone looking for a holiday gift for an independent female could do worse than choosing this calendar.

And, if that weren’t enough, there’s a Calendar Release Party at the Luscious Garage in San Francisco on Saturday evening, December 13.