To find out whether the worn out chain or not, put it on a third star (the largest one), and then try to pull the chain with your fingertips from the stars. If all becomes clear two teeth on the star and the chain are worn, three teeth – chain murdered.
A sign of a strong deterioration of the tape or chain also serves as the chirping of the circuit when driving, even when it is oiled. If the circuit and no load makes these sounds, it is very badly worn.
And here's another way to check chain wear, more accurate: take a ruler and measure the chain the distance between the center of any pin and the center 24 after the pin. If the result is equal to 304,8-306,4 mm, the chain is fine. If the result is equal to 306,4-of 307.9 mm, the chain is worn and should be replaced. When the measurement result becomes more of 307.9 mm, this means that worn out chain and cassette, and possibly even the entire system.
If you "wound" for the season is over 3-4 thousand km, the chain must be changed. The cassette has a resource in the 2-3 times greater than the resource chain, but iznesenie chain, the faster it destroys the tape. If you drive 300-500 miles with a worn chainYu, you have to throw it together with tape.
In order to increase service life of chain and cassette, I advise you not to wait until the chain wears out and will start to "eat" the tape, and change the chain early. Then again change the chain, then start with the first circle and so on.
And remove the delay chain to the side, after 500-600 km. Put new chain the same distance. Then a third. After that choose the shortest chain and ride on it for another 500-600 miles and so on. Changing three times three chains, throw away along with the tape.