Bike wheels consist of a tire, rim, spokes, hub and axle. The spokes connect to the hub, at the center of the wheel, and to the rim of the wheel, creating even tension around the wheel that holds the rim in shape. The hub’s ball bearings allow the axle, which is tightened into the bike frame, to turn smoothly. Rear wheels also have one or more gear sprockets.
Attachment
Bike wheels are attached to the frame by placing the axles in the dropouts. The axle is a tube that runs through the wheel’s center, or hub. The axle’s ends slide into the U-shaped dropouts. The axle is tightened into place with a quick-release clamp, if the axle is hollow, or nuts that screw onto the axle ends.
Rotation
The hub rotates around the axle. The outside of the hub forms two O-shaped rounded cups, into which are placed a number of ball bearings. The cone, a type of nut that screws onto the axle and has a rounded O-shape edge, contacts the ball bearings. When the bearings, cup and cone are thoroughly coated in grease, free of scratches, properly tightened and placed on a straight axle, your wheel rotates smoothly.
Speeds
Rear wheels are outfitted with one or more sprockets which control the ease with which you can pedal. The larger the sprocket, the easier it is to pedal. On fixed-gear and single-speed bicycles, the wheel has only one sprocket, which turns as the pedals rotate forward. On a fixed-gear bike, the sprocket also turns backward when the pedals rotate backward. On multiple-speed bicycles, the rear derailleur controls the bike chain’s position on the sprockets.
Shape
A spoke usually has one end that's flat, which hooks into the hub, and one threaded end, which screws into the spoke nipple, a small enlongated type of nut inserted into the rim. You can adjust the tightness of the spokes to maintain your wheel’s roundness. A wheel that appears to wobble when it spins, but does not move back and forth on the axle, has spokes that are pulling the wheel rim too hard or too gently left, right, up or down.
In Use
As a bicycle wheel turns during a ride, different forces of friction operate on it. If brakes are applied, the wheel turns more slowly. The wheel’s tire generates different levels of friction based on the type of tread, whether slick, semi-slick or knobby, as well as the type of surface it contacts: road, gravel trail, dirt trail, grass, sand, etc.
Member Comments