Getting Your Bearings

Of the three major forces which work against you as a cyclist — air resis­tance, gravity, and friction — it’s friction that our tireless little friends the ball bearings are designed to overcome.

Bearings are one part of the bike that has changed little over the last century. In fact, the first use of bearings goes back thousands of years. Ever since the wheel was invented, humans have looked to bearings to help with the prob­lem of friction from a moving part rubbing against a nonmoving part.

Bearings, like those shown in Figure 2-3, are hardened steel balls designed to reduce friction among the moving parts of a bike. When your wheel rotates smoothly around its axle, it’s the bearings that enable this to happen with minimum resistance and friction. Bearings are found in many parts of a bike including the wheel hubs, pedals, bottom bracket, and headset.

On some more expensive bikes, bearings are made of ceramic, which has a number of properties that improve the reduction of friction.

Figure 2-3: Bearings from the bottom bracket.

Bearings are an amazing feat of engineering, designed with a precision to mil­lionths of an inch. When examining them, you should see a smooth, rounded, and shiny surface. If the bearings are dull or chipped with tiny divots, they need to be replaced.

Although it would appear that the round shape of bearings is all that’s required to reduce friction, the fact is that bearings still require significant lubrication for reliable performance. In many cases, bearings inside the parts of your bike are packed in water-resistant grease specially designed for bearings.

If you perform a procedure that requires bearings to be installed, make sure the parts are clean before you pack the bearings in grease. Grease can become contaminated with grit and break down over time.

You may wonder how these little metal balls are kept in place. They’re secured with something called a race. A tried-and-true race design, still popular after more than a century, is the cone-and-cup. In this design, a ring of bearings sits in a cup and is secured in place by a cone, which is screwed onto an axle or spindle.

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The cone is typically adjusted to be tight enough so that there is no side-to — side looseness and the part (that is, the hub) rotates smoothly. Over­tightening could cause unnecessary force to be applied against the ball bearings, leading to wear and tear — not to mention the fact that it could make it much harder to pedal.

Bearings will either be in a “cage” or retainer ring, or be set as independent “loose” bearings. (Also, retainers are typical for all bearings on a bike, and perform inferiorly to loose bearings. The only benefit they have is conve­nience in building the bike).

One of the modern advances in bikes is the use of sealed bearing cartridges, which eliminate the need for adjustment or lubrication (less work for you!) and prevent grit and other contaminants from entering. Buy a bike with car­tridges and you’ll save yourself the hassle of playing with tubes of grease and chasing bearings across your bike-shop floor.

Your inner gear geek may be disappointed if you use cartridges, because bearings are cool, shiny little balls that are fun to work with. Dennis feels like he hasn’t really worked on a bike until he’s juggled a few bearings in his hands and packed them in some fresh grease. But even so, cartridges do require less work.