A WORN-OUT CHAIN WILL BEGIN TO DETERIORATE ANY COMPONENT IT TOUCHES, LIKE THE CASSETTE COGS, DERAILLEUR PULLEY WHEELS, AND CHAINRINGS.
The chain is the first component in the drivetrain to wear out. A chain will typically last around 1,000 miles of riding but the wear interval can change drastically based on many different factors like riding style, riding conditions, and even how the chain is lubricated. As you ride, metal from the chain's roller bushings wears away, creating a poor fit on any component with teeth on it.
You can check the condition of your chain with a special chain-checker tool or when taking your bike in for service at almost any bicycle shop.
Your pulley wheels will wear as you ride, degrading the quality of your shifting.
Rear derailleur pulley wheels are usually made of a hardened plastic to keep your drivetrain feeling smooth and quiet under shifting.
Since plastic is softer than metal, pulley wheels will conform to a wearing chain. The wearing chain will grind material from the square edges of the pulley wheel teeth, turning them to sharp points.
Unworn rear derailleur pulley wheel.
Edges of the pulley wheel teeth have square edges, indicating good condition.
Worn rear derailleur pulley wheel.
Edges of the pulley wheel teeth turned to sharp points from chain wear.
THE CHAIN WILL WEAR DEEPER GROOVES INTO THE COGS OF YOUR CASSETTE THROUGH PROLONGED USE, JUST AS IT DOES ON THE PULLEY WHEELS.
While this is harder to spot visually, a telltale sign of a worn out cassette is poor shifting or skipping when you shift to or from the gears you use most often. Much like the cassette cogs, the chainrings wear at different rates depending on which ones you use most often. Much like the cassette cogs, the chainrings wear at different rates depending on which ones you use the most. Unlike the cassette, however, you can replace chainrings one at a time. A worn chainring may have very sharp teeth. Shifting to and from a worn chainring will not only be difficult, but may even result in a dropped chain.
SHIMANO recommends that you get your bike worked on by a professional mechanic at your local bike shop. Mechanics at our SHIMANO SERVICE CENTERS are up to date on all our latest technologies and can provide the highest quality service.