Why Does My Bike Keep Skipping Gears?

A bike that skips gears, hesitates while shifting, or suddenly jumps under pressure can be frustrating—and sometimes unsafe. Gear skipping is especially noticeable when climbing or accelerating, when more force is being applied to the drivetrain.

Here are some of the most common causes:

1. The Rear Derailleur Needs Adjustment

A small indexing adjustment may be all that is needed. Each click of the shifter should move the chain cleanly into the next gear. If the derailleur is slightly out of alignment, the chain may hesitate, make noise, or jump between gears.

2. The Shift Cable Has Stretched

New shift cables often settle and lose a small amount of tension after being used. Older cables can become dirty, corroded, or difficult to move inside the housing. Either condition can affect shifting accuracy.

3. The Chain or Cassette Is Worn

Chains gradually wear as the internal pins and rollers develop additional clearance. If a worn chain is used for too long, it can also wear the cassette. Installing a new chain on a badly worn cassette may cause the chain to skip under load.

Checking chain wear regularly can help extend the life of the cassette and chainrings.

4. The Derailleur Hanger Is Bent

The rear derailleur attaches to a replaceable part called the derailleur hanger. Even a small bend—sometimes caused by the bike falling over—can prevent the derailleur from lining up correctly with the cassette.

A bent hanger should be checked with a derailleur-hanger alignment tool before attempting to fine-tune the shifting.

5. The Drivetrain Is Dirty

Excess dirt, old lubricant, and debris can interfere with smooth chain movement. Cleaning and properly lubricating the chain may improve shifting, but cleaning cannot correct worn or damaged components.

Learn to Diagnose It Yourself

At Bike Teacher, students learn how to inspect a drivetrain, measure chain wear, check derailleur alignment, adjust shifting, and recognize when parts need replacement.

Classes are hands-on, beginner-friendly, and kept small for better individual instruction. Students are also allowed to bring bikes to class, making it possible to learn while working on a familiar bicycle.

Bike Teacher also provides bicycle repair and service for riders who would rather have the problem professionally diagnosed and corrected.

Bike Teacher is located in San Jose, California. Classes are available Monday through Friday from 8:30 a.m. to 5:00 p.m., with some Saturdays offered. Classes are scheduled around your availability.

To learn more about bicycle mechanic classes or schedule a repair, visit www.biketeacher.com or call or text 408-210-2980.