Loose ball bearings left, sealed cartridge bearings right

Some bike parts get all the attention. Saddles, wheels, and glossy paint are like the stage talent in a performance. They’re the face of the production and get the easy accolades. But any great production has a crew working hard behind the scenes to make sure everything runs smoothly, or in your bike's case, turns smoothly.

There are around 150 steel ball bearings inside your bike. It's those bearings in your hubs, bottom bracket, headset and pedals that allow a smooth revolution or turn. Without them, there’s no commute to school or the office, no exploration, no weekend joyrides.

All the components illustrated above spin and need silky smooth bearings: rear hub, bottom bracket, pedals, front hub, headset.

Loose vs. Sealed Cartridge

Steel bearings start out as wire that is cut, milled, and machined into a perfect sphere of high density and strength. Those bearings are then packaged in two flavors: loose and sealed.

Loose bearings are usually housed in a "cage." The cage makes handling and manufacturing easier. Since loose bearings are more exposed to contamination, they need to be "repacked." Repacking means disassembling the component to expose the bearings, thoroughly cleaning, adding a new batch of grease, and reassembling.

Loose bearings in a cage on the left, sealed cartridge on the right

Sealed cartridge bearings however come complete as an enclosed unit. The cartridge shields the bearings and can be dropped in or plucked out with no mess.

Many bikes (some expensive models, but mainly inexpensive) employ loose bearings. We use sealed so the bearings are protected from road debris and weather, so they spin cleaner and with less friction for longer. Sealed bearings perform as well or better than loose bearings, without the maintenance.

Sealed cartridge bottom bracket

Should you ever need a new cartridge - which for a casual commuter is unlikely -  a replacement will run you around $25-$40 including the labor your local bike shop will be happy to provide.

You've likely thought more about your bike's bearings while reading this post than all previous bearing thought combined, and that's the goal. We use sealed cartridges so you don't have to think about your bearings any more.

P.S. We've got a few spots left for this Sunday's (May 4th) Mission Secrets bike tour. No matter how well you think you know the hood, you don't know these secrets. Reserve your spot here.