The best things come in packages: The cassette

Cassette systems (see Figure 11-2), which are found on most modern bikes, improved many of the deficiencies with freewheels (see the preceding sec­tion). One of the biggest changes with cassettes is that the ratcheting system is built into the hub itself. Cassettes use a free hub, which looks like a tra­ditional hub but with a thick extension on one side with grooves or splines built into it. This design allows the bearings to be spaced farther apart, pro­viding greater support for the axle.

Another advantage of the cassette system is removal: Cassettes have cogs that are normally held together as a unit and that slide on and off the hub. After the lock ring (which holds the cogs in place) is removed, the cogs slide off together as one. Freewheels, on the other hand, are a group of cogs held together as a unit but must be threaded onto the hub.

Cassettes come with a variety of different gearing options. The gears are defined by the number of teeth on each cog and, depending on your biking needs, you may need a specific range of gears. For example, if you’re planning on touring, you’ll want high enough gears to help you ascend inclines while your bike is weighed down with packed pannier bags.

Some cogs are manufactured with the number of teeth marked on the side. These markings will save you from having to count the teeth in order to deter­mine the gear.

If you’re shopping for a cassette, be sure you buy one that’s compatible with your hub. Manufacturers like Shimano and Campagnolo have designed cas­settes that work only with their hubs. If you aren’t sure about which cassette will work with your hub, check with the folks at your local bike shop.