Sunday, September 5, 2010

How to Adjust Derailleurs for Cable Stretch, or How to Get That "Skip" Out of Your Step

I talked to friend that recently really started mountain biking seriously, and she is loving it, but as I talked to her she had a lot of questions about adjusting the basic things. The latest one was her rear derailleur. She told me that her derailleur needed adjusting and that she was going to bring it in to the shop. She said that the chain was “skipping” and that it wouldn’t stay in gear. Well, I knew that the derailleur had been working fine the last time we rode together, so I figured that what the problem really amounted to was the shift cable had stretched, which is common with new cables. Now, I’m going to explain how to do a simple adjustment to compensate for cable stretch. This can be done at any time at home or on the trail.

The first thing is to understand what parts of the derailleur, or cable system, you are going to be actually adjusting. To adjust for cable stretch you will only need to use the “barrel adjusters” located either on the shift pod, or derailleur, no tools required. Both barrel adjusters work equally well, it just seems to be a personal preference as to which one you choose to use. The following pictures show the two barrel adjusters that you can use:

The first, just in case you don’t recognize it, is on the rear derailleur. The second picture is the right shift pod on the handlebars.

What happens when the cable stretches is that it allows the derailleur to move toward the higher gears (harder to pedal) just as though you were partially switching gears. What you want to do is pick a barrel adjuster and rotate it counter clockwise (out) a half turn. Then check your adjustment by shifting the derailleur a few times and returning to the gear that was causing problems. At this point you should be able to hear a difference in the “skipping” sound. If it seems to be getting better then rotate the barrel adjuster another half turn out and repeat the process. The sound should get better and eventually be eliminated as you make the adjustments. Be careful not to over adjust, as this will cause the same sound, but now the derailleur is trying to move up to the next gear (lower gear, easier to pedal). If this happens, just rotate the barrel adjuster the opposite direction (clockwise) until the skipping goes away. Remember that multiple smaller adjustments is always the preferred way to do things.

I just have to warn you that there are some derailleurs that have been made that shift to the lower gears when the cable gets slack, or stretches. The procedure for this adjustment is the same, but you just need to know that you will be moving the derailleur in the opposite direction (rotate the barrel adjuster clockwise). I’ve been working on bikes for years and have not encountered one of the reverse pull derailleurs, so chances are you most likely don’t have one. They are nothing to worry about, just a little different. Also, if your front derailleur is having the same problems, it can be adjusted the same way, but the front derailleur only has the barrel adjuster on the shift pod.

This is a real basic instruction about doing the cable stretch adjustment. It’s good for you to know how to do this as cables have a way of stretching and becoming annoying at the worst times…like when you are on that really cool ride and having loads of fun. This adjustment will keep you riding happy and “skip” free after just a few minutes. My advice is to try doing these adjustments a few times at home, that way you get the hang of it and gain that confidence for doing it out on the trails. (Plus, if it all goes bad, you still have the local bike shop to run to…and your ride isn’t ruined).

Please let me know if this was helpful and if there are any other adjustments or bike related questions that you have. 

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