Drivetrain Care That Prevents Costly Wear

A drivetrain wears as a system. Look after the chain and the rest follows, but check the cassette, chainrings and cables before they cost you a ride.

The drivetrain is the most expensive system on most mountain bikes, and it wears as a set. Catching wear early is the difference between replacing a chain and replacing everything it touches.

Start with the chain

Chain wear drives cassette and chainring wear, so check it often with a gauge or a ruler. Once a chain stretches past about 0.5 percent it starts to reshape the teeth it runs on, and a new chain on worn teeth will skip. If the chain is worn but the cassette still looks sharp, replace the chain now and the cassette lasts far longer.

• Skipping under load: worn cassette or chainring teeth.
• Slow, vague shifts: cable tension or a bent hanger.
• Chain dropping: worn chainring or a badly set clutch and guide.

Inspect the cassette and chainrings

Look at the teeth from the side: healthy teeth have a slight even hook and a flat tip. Teeth that look like shark fins, or that are noticeably asymmetric, mean the part is worn and will not hold a new chain. Chainrings usually last longer than cassettes because the chain wraps less of them, but narrow-wide teeth can wear faster in gritty conditions.

If a new chain skips on the old cassette, the cassette was already gone. The chain told you the truth.

Cables, housing and adjustment

Shifting is only as good as the cable. Frayed cables, kinked housing or a dirty derailleur pivot all cause vague, hesitant shifts. Replace cables and clean the housing when shifts feel slow, and check the derailleur hanger is straight; a slightly bent hanger is one of the most common causes of a drivetrain that will not index cleanly.

Adjusting the rear derailleur

Work in order: set the high and low limit screws so the chain cannot fall off either end, then tune cable tension so each shift lands cleanly. Small quarter-turns of the barrel adjuster are enough. If you cannot get indexing right, suspect a bent hanger before blaming the derailleur.

Keeping it clean

Brush the cassette and derailleur pulleys after muddy rides, keep lube off the outside of the chain, and never use a high-pressure hose near bearings or the bottom bracket. Done consistently, these habits add years to a drivetrain and keep shifting crisp all season.

Look after the chain, check the teeth, and keep the cable clean, and the drivetrain quietly does its job.

Frequently asked questions