The Different Personalities of the Rear Derailleur
When adjusting a rear derailleur I like to break it down into segments. There is a starting point I like to refer to as home base or restarting the computer. This is the place you will start when first installing a rear derailleur on to the bike and the the place you will start when you get confused and need to re-establish what exactly is going on. Home base, just like playing hide n go seek as a kid, you need to establish common meeting ground. It will also help you to find the problem of why the rear derailleur is having trouble.
The derailleur and the chain will be referred to synonymously. The chain is going nowhere unless the rear derailleur tells it to move. The chain and the shifter should always be on the same page. It’s up to you to keep track at all times. One of the best ways to do this is to pay close attention to the clicks in the shifter at all times. If you hear or in some cases feel a click then there should be chain movement.
One click should equal one gear change of the rear derailleur (cassette or cog, chain). In some cases two clicks of the shifter can happen very quickly but are often missed by the operator and the operator ends up lost immediately. People are surprised at how intricate a shifting system can be. There are a lot of variables and every bike has a different temperament. Not all derailleurs and bikes are created equally.
You must take into consideration the age of the component and the level or model. Cost plays a big part I this. Typically the more you pay the better the materials, engineering and quality in most cases. What this means is the more you pay the lighter the part and performance is enhanced. If a rear derailleur, shifter, cable and housing are tired or dirty and has many miles on it then you must take this into consideration as well.
If the moving parts of the component are not working the way they use to when they were new, this usually means the pivot points in a rear derailleur are not as tight, there is more play between hinges. All this adds up to looseness or play that may not be felt all the way back to the shifter. It’s like having a worn out shoe or loose shoe laces. Your foot will slide even it is a small amount but this will add up over time causing a blister.
When this happens to a rear derailleur some of this can be addressed with the barrel adjuster until it can no longer, then what? How do you diagnose a worn out rear derailleur? How can you tell if the derailleur alignment is incorrect? Which one is to blame? Stay tuned.