Most expensive bike shop visits can be prevented just by doing small maintenance and knowing how to prevent bigger problems in the future. Also less frequent visits to shops will decrease the chance that an employee will try to sell you new parts that you may or may not need.
This instructable will go over the basic steps to get your bicycle back in working order. With practice, following these steps will have you tuning the rear derailleur with high quality in no time at all.
Step 1: Gather Necessary Tools.
A list of necessary basic tools:
1. Phillips Head Screwdriver.
2. Allen wrenches. Necessary sizes, 4, 5, and 6. (metric). Also a three way tool as shown can be used.
3. Open ended wrenches, can vary by derailleur model. Metric sizes 8 or 10. combination wrenches can be used.
4. Cleaning materials. A simple degreaser, a one step clean and lube, and a shop rag. Note: do not use WD-40 as it will clog up the pulleys.
1. Flat nose pliers to aid in pulling cables.
2. Cable cutter to cut excess cable as needed.
3. Bicycle stand. I am using a park tool portable stand.
Step 2: Optional Step: Place the Bicycle in the Stand.
In the image it is on the frame.
Step 3: Clean the Derailleur and Gears.
Using your cleaning equipment ensure that all excess grease and dirt is removed from the components.
Once the equipment is cleaned you are now ready to start tuning the derailleur.
Step 4: Remove Tension From the Cable.
Step 5: Tension the Cable.
The next step in properly adjusting the cable is to add tension back into the cable. This is where the flat nose pliers will help.
Pull the cable to a moderate tension. Pulling too tight will cause the derailleur to not have full range of shifting and not enough will cause the shifting to be very slow or not work at all. While holding the cable at moderate tension tighten the bolt that will hold the cable. Note: ensure not to tighten the bolt too much or the cable may begin to fray or even break.
Step 6: Set the Limit Screws.
Properly setting the low limit screw labeled with L:
Turn the screw either in or out to align the derailleur pulleys with the small chainring. (image 2)
The bicycle must still be able to shift to the small ring, test until it is properly set.
Properly setting the high limit screw labeled with H:
Turn the high limit screw in to prevent the chain from jumping over the top of the chain. Ensure that the chain will still reach the large chain ring. To test, push on the derailleur while pedaling to move the chain over by hand. (image 3)
Step 7: Fine Tuning the Shifting.
Currently the bicycle should shift into all the gears although it may be slow or clicking in certain gears. This will be resolved by adjusting the tension with the barrel adjuster. Turning the barrel adjuster into the derailleur will remove tension from the derailleur shifting into a smaller ring. Turning the barrel adjuster away will add tension, shifting the bike into a larger chainring.
Proper shifting will occur when the chain is in the next ring in under one full revolution of the pedals. This will take practice and is not always necessary for all applications depending on what type of riding you will be doing.
An optional final step is to take the bike for a test ride. Occasionally there will be a difference in how the bicycle shifts when it is on the stand and when it is in use.