Rear Derailleur

Over time, the cables in bike transmissions stretch, the chains wear, things slip out of alignment.  Eventually the chain doesn’t shift cleanly from cog to cog when the rider moves the shifter on the handlebar.

Both of my frequently ridden bikes, the Trek 2.1 and the Jamis Coda Comp, had gotten to that point.  It’s annoying, because then I have to anticipate an extra tap or two to get the chain in place.  If the chain overshoots the desired cog I have to tap it again to get it on the next cog, and then shift back to the cog I want.  If it undershoots I have to tap the shifter again.  Meanwhile, I am not in the gear I want to be in, and the chain may be riding on top of the sprockets without settling into any gear at all.  On a climb, for instance, the delay can cause significant unnecessary deceleration while I get it sorted out.

As a radically amateur mechanic, I waver between the idea that I can learn to be a passing-level bike fixer for the simpler repairs, and that the idea that I’d rather have the easy expertise and the perfect result of a professional.  Of course I know (a) that the professional result may not be perfect and (b) I’m smart enough to learn.  The questions are (a) If I screw it up, will I damage an expensive part, (b) how many tools will I need to buy, and (c) do I have a good enough touch to sense when I have it right?  In this case the answer to questions (a) and (b) are “no” and “none” respectively, so I forged ahead.

One of the joys of the Internet these days is YouTube.  It has an incredible array of amazing clips, and among them, relevant to my purposes, are a number on bicycle repair.  Several of them address my topic—adjusting a rear derailleur.

Among the ones I checked, I liked this one best:

I had never thought of several nuances it brings up, such as loosening the cable clamp and re-setting the cable tension when you begin.  In fact, that’s the only time in the process I needed a tool, a socket wrench to loosen and tighten the clamp screw.

Other than that, assuming the jockey wheels are properly aligned, it’s all about starting with the least tension on the chain, which is to say the chain must be on the smallest chainring and the smallest cog.  The rest, after adjusting basic chain tension, involves getting the chain squarely on the sprockets by using the cable adjustment barrel.  The mental challenge there for me is to remember that turning the barrel “outward” will increase cable tension and “inward” will decrease it.  Somehow that seems entirely counter-intuitive to me.  Another thing I learned is that in some cases the adjuster needs turning quite far, while I thought the turns would be minute.  Actually they are when the final adjustment is made.  I found that the processes are similar for each of my bikes, but I guess they should be since the two cassettes are virtually the same.

The acid test was the road test—how did they feel on a ride?  In both cases, the improvement was noticeable.  I do think that I could adjust them a bit more finely, but they really “chunk” into place solidly now.  New skill learned.

©Arnold J. Bradford, 2013.





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