Why Spokes Break
Bike spokes are a pretty simple part of your bike. They support your weight and transfer power from the hub to the wheel. Problems with spokes are pretty infrequent, but still do happen from time to time. The most common problem a cyclist will have with their spokes is the occasional broken spoke. This happened to me with some regularity as I’m what they used to call in boys’ jeans sizes, “husky.” You’ll just be going down the road and suddenly hear a noise like TWANGGG! (and it does sound like that). Even if you don’t hear the spoke break, you’ll likely feel it, because the your wheel will usually go all wobbly. Sometimes if you mash down particularly hard on the pedals or hit a pothole it can spur spoke breakage too, but usually it just kinda happens. Spokes break most frequently where the head of the spoke laces into the hub, because the curved head of the spoke is the weakest part and yet still has to bears a lot of the weight and force of power transfer. If you have this happen, stop, get off your bike and inspect your wheel. You want to make sure your spoke isn’t flopping around to where it can get entangled with your frame or chain as your wheel turns. To keep it secure, you can tape it to a neighbor or unscrew it from the nipple and remove it completely. You’re okay to ride it a bit longer if necessary to get home, but you don’t want another forty miles or continue riding days and days with a broken spoke if you can help it. It puts additional stress and strain on your other spokes (which can then cause them to break prematurely at some point down the road too) and can make your wheel go out of tru
How Spokes work?
How the spokes accomplish these terrific and heroic feats? First, spokes don’t push outward, holding the rim at bay, like it might seem. Rather, the rim is evenly pulled inward by spokes that are laced through the hub, the center part of the wheel that rotates around the axle, which makes it extraordinarily strong. These spokes coming from the hub then radiate outward to the rim, where they attach to nipples, which are almost like little nuts resting in the rim. The nipples can be screwed down onto threaded tips of the spokes, which increases tension on the rim, and also pulls it slightly to the left or right.
No, its not when they’re lying to you… its when they’re not straight. A true wheel is rounder, centered, easier to pedal and they wobble less.
Thus knowing how to make a wheel perfectly round, replacing broken spokes and damaged nipples and fixing damaged rims can be quite important for keeping a bicycle in tip-top shape.
A lot of the tasks required to true a wheel require tools only found in a well-equipped bicycle shop (like a truing stand), so you will likely need to contact a local bicycle mechanic.
The information are taken from About.com and the Bike Mechanic