When you own a bike it is important to maintain it so that your cycling experience is the best it can be. Tuning your rear derailleur is something that many people think is too complicated to do yourself but it is doable. By using this instructable you won't have to take your bike to the shop just to tune the rear derailleur. Depending on your level of expertise this can take between 10-30 minutes.

The three main parts for tuning your derailleur are the pulley cage, limit screws, and the barrel adjuster. There are two limit screws H and L. The H limit screw is used for tuning the high gears and the L limit screw is used for tuning the low gears.
They only tool you need to tune your derailleur is a standard phillips screw driver.

Caution: When turning limit screws and the barrel adjuster, always turn gently and never force them.

Step 1: Setting Your Bike Up

Put your bike on a bike stand.

If you don't have a bike stand that is fine. There are many different ways to lift the back tire off the ground so it can turn freely. If you can not find anything to hang your bike on you can turn it upside down so that the bike is resting on the seat and handlebars.

Step 2: Checking Your Bike

1. Inspect the gear cable for the rear derailleur.

The cable should not be rusted, kinked, or frayed. If the cable has any of these characteristics it should be changed.

2. Check the chain for stiff links.

Turn the crank backwards and watch it go through the pulleys. If the cage jumps then there is probably a stiff link. If there is a stiff link the chain must be replaced.

3. Check the alignment of the cage.

The cage should be in line with the gears. If it is not you may have to take the bike to a bike mechanic.

4. If everything looks good then it is time to move on to tuning the derailleur.

Step 3: Tuning the High Gear

Shift into the highest gear.

The highest gear is the smallest cog and the one that is the furthest away from the wheel.

See if the cage is in line with the cog.

If the cage is to far outwards, turn the H limit screw clockwise until the cage is properly aligned.
If the cage is to far in, turn the H limit screw counter-clock wise. If the cage doesn't move far enough out the cable tension is too high.
Use the barrel adjuster on the rear of the derailleur to adjust the cable tension. Turn the barrel adjuster clockwise until the cage is aligned with the cog.

Step 4: Check Shifting

Turn the crank and shift to the next cog.

If the chain moves smoothly and quietly than you can move on to the next step.
If the chain does not shift smoothly than adjust the cable tension by turning the barrel adjuster until the chain moves smoothly and quietly between cogs.
Check the shifting between the gears and eliminate noise and clanking by using the barrel adjuster

Always turn the crank while shifting.

Step 5: Tuning the Low Gear

Shift into the lowest gear.

The lowest gear is the largest cog and the one closest to the wheel.

Check the cage. It should be directly beneath the cog.

If it is turn the L limit screw clockwise until the cage just barely moves then turn the L limit screw back by about 1/16 of a turn.
If it isn't use the L limit screw and the barrel adjuster to align it directly beneath using the same techniques as the high gear.

Step 6: Check Shifting

1. Shift to the next highest cog.

If the cage is a little outward you can turn the L limit screw counter clockwise.

2. Shift through all the gears.

They should all shift smoothly now. If they don't you can use the barrel adjuster to adjust the cable tension.

Step 7: Your Done!

Your rear derailleur is tuned up and ready to be used. Get out there and go for a ride. You can tune your rear derailleur anytime you feel like the shifting is clunky, in preparation for a trip, or just so that your bike runs smoothly for the rest of the season. Now you can tune your derailleur yourself and can get out on your bike in no time.