Your drivetrain is made up of your crankset, chainrings, derailleurs and pulley wheels, cassette and chain.

These components work together as your shift cables are pulled through the shift housing to turn a click of the shifter into a gear shift of the derailleur at the other end of the bike. All of these parts wear out as you ride, degrading the quality of your shifting. The chain is the first component in the drivetrain to wear out. 

A chain will typically last for hundreds of miles on a mountain bike, but how many hundreds depends on riding style, conditions, gearing, and how often the chain is lubricated. As you ride, metal from the chain's roller bushing wears away, creating a poor fit on any component with teeth on it. 

As we see here, the chain is misaligned as if the rear derailleur has been shifting but the chain has not moved to the next gear. A grinding sound may also be heard. 

A WORN-OUT CHAIN WILL BEGIN TO DETERIORATE ANY COMPONENT IT TOUCHES, LIKE THE CASSETTE COGS, DERAILLEUR PULLEY WHEELS AND CHAINRINGS.

You can check the condition of your chain with a special chain-checker tool or when taking your bike in for a service at almost any bicycle shop. 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. The chain will wear deeper into the cogs of your cassette through prolonged use, just as it does on the pulley wheels. The cogs you use the most, the easiest gear for many riders, will wear first. A tell-tale sign of a worn-out cassette is poor shifting or skipping when you shift to or from the gears you use most often. 

A worn chain will grind material from the square edges of the pulley wheel teeth, turning them to sharp points.

Much like the cassette cogs, the chainrings wear at different rates depending on which ones you use the most. On a single ring drivetrain, the chainring will wear quickly since you use it all the time. Many chainrings have chain-retaining features to keep the chain on while you ride over bumpy terrain. However, the chainring's ability to keep the chain on will degrade as the chainring wears. 

WE DON'T OFTEN THINK ABOUT THE CABLES AND HOUSING ON OUR BICYCLES, BUT THESE SMALL PARTS CAN MAKE A BIG DIFFERENCE IN HOW WELL OUR BIKE WORKS. 

Shift cables are responsible for carrying out the shifter's instructions to move the derailleur exactly the right amount for a perfect gear shift. If the cables are rusty, corroded, or the housing is clogged with debris from the trail, the shifter will have trouble pulling the cable enough to execute the perfect shift. Keep in mind, the average rider whould replace their cables and housing once a year, preferably in the spring whe the harsh winter weather has subsided. 

SHIMANO makes some of the slickest, most durable cables and housing you can buy. Choose SHIMANO's Optislik cables and SP41 housing for excellent shifting performance and durability. For the absolute slickest cable money can buy, the standard for XTR, choose SHIMANO's polymer coated cables. These have grease injected directly into the polymers surrounding the cable, creating unrivaled shifting performance. 

Have your local bike shop check your drivetrain, cables, and housing for wear to make sure you are getting the most out of your ride.