How To Fix Gears
Step 1
Raise the bike off the ground on the bike stand
You need to be able to spin the wheels freely without the bike moving
Step 2
Locate the derailleurs
Derailleurs are the machines that physically shift your gears and keep your chain in place
Step 3
Find the shifting problem by testing each gear
Use one hand to lightly pedal the bike and shift through 1 gear per click
Step 4
Locate the cable adjusters
Follow the cables leading to the derailleurs to find the adjusters
These make small adjustments to the derailleur cables which can help make minor tweaks to shifting
Step 5
Shift to the gear that is bad
shift your gears up until the chain won't shift, has trouble staying on the gear, or skips a gear, etc.
Step 6
Loosen your cable adjuster if the chain won't shift down
Tighten your cable adjuster if your chain won't shift up