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Shifting problem

Catrin2010-12-12 14:40:51 +0000 #1
I do not know what to think. Last Sunday my LBS adjusted both front and rear derailleurs because they were shifting very roughly, chain making lots of noise, and my chain was falling off the front.

Took it for a short ride twice since then - those were fine. Today went for a 55 mile ride and the problems started up again. This time, however. I noticed that the problem was only in the middle ring (I have a triple). Lots of noise and long after shifting the chain "catches" and so forth. This has been known to cause my foot to come off the pedal!

I wound up spending as much time as I could in the big or granny gears - and things were as smooth as silk.

Any ideas what might cause this? I am going to ride to my LBS tomorrow afternoon - and thankfully they do not charge for that. I am starting to get concerned that something else might be going on. I only have 750 miles on the bike - 710 miles since my LHT conversion.

Is this sort of thing normal sometimes, that it needs adjustment so often? If so - then I need them to teach me how to do it myself....


Muirenn2010-12-12 14:53:21 +0000 #2
I'm not a shifting expert. But the chain needs to be in one of the center cogs on the rear before using the left shifter. If it is not, then the chain in the front may jump between the rings a little too much when you shift, causing it to become loose, etc.

For example: You don't want the chain in the back to be on the largest cog (near the bike), and suddenly have the chain in the front go from the smallest (inside) and get hung-up as it jumps to the middle and outside. In other words, the chain is at a crossed angle rather than straight. Prevent this by having the chain in the back more centrally located before changing the front ring.

Make sense?

Simple version again: Only use the left shifter if the chain is in the middle of the rear cog.

(Now someone else chime in please!)

Edit: Video From YouTube:(link)


This video is pretty basic. But peddling with your chain straight is the goal. If it is crossed, it puts pressure on the links in the wrong way, and leads to the problems you describe.
Catrin2010-12-12 14:51:18 +0000 #3
I do this. The rear cog is somewhere in the middle when I shift the front - but I am not talking about what happens when I shift the front (that is fine) the problem is when I shift the rear cog. Pretty much ANY shifting of the rear cog when I am in the middle chain causes all kinds of noises and catching and not-fun things to happen. Other two chains are fine when I shift the rear cog.

Sorry for any confusion.
Muirenn2010-12-12 15:13:46 +0000 #4
I see

In that case hopefully the earlier post might pertain to someone else. Because I've no idea what would cause that.
Catrin2010-12-12 16:24:48 +0000 #5
Quote:

Originally Posted by Muirenn

I see

In that case hopefully the earlier post might pertain to someone else. Because I've no idea what would cause that.

Oh it certainly pertained to me in the not so distant past

Last weekend it was happening with any shifting, regardless of what chain I was in. They adjusted both derailleurs - actually they worked with it for quite a bit. They probably just need to tweak that adjustment.

It was the only thing that kept me from having a perfect ride today - and I did figure out how to get around it - by avoiding the middle chain entirely
OakLeaf2010-12-12 15:15:57 +0000 #6
If they did a big adjustment - i.e., had to re-position the cable in its clamp rather than just using the barrel adjusters - then the cable and housings will re-seat a bit just as they did when everything was brand new. So, probably normal.

You should learn to do this yourself. It's very simple. Most LBS will be happy to show you.
Catrin2010-12-12 15:23:56 +0000 #7
Quote:

Originally Posted by OakLeaf

If they did a big adjustment - i.e., had to re-position the cable in its clamp rather than just using the barrel adjusters - then the cable and housings will re-seat a bit just as they did when everything was brand new. So, probably normal.

You should learn to do this yourself. It's very simple. Most LBS will be happy to show you.

He appeared to do a fair amount to both front and back - he did more than adjust the barrel adjusters. He also adjusted the stops(?) on the FD to help prevent the chain from falling off.
KnottedYet2010-12-12 15:43:54 +0000 #8
I'm trying to remember what kind of shifters you have on your flat bars, so I may be completely off here.

Has anyone explained "trimming" the derailleur to you?

Indexed brifters have pretty much one click or two half clicks and BOOM the front der is where it is gonna be. Some of the bar shifters have lots and lots of clicks, and your front der has several choices of where it can be. They act almost like friction shifters.

For sake of illustration, assume here I'm talking about a bar shifter with infinite clicks, or friction shifters:

Whaling the shifter to one extreme or the other pops the chain onto the big or small ring, and the derailleur cage (if the limiter screws are set just so) is pretty much out of the way of the chain as you merrily zip through the rear cassette. (assuming here you are not cross-chaining, which I know you know about)

The middle ring can get kind of exciting, because the cage can be centered on the ring, or more toward the big ring, or more toward the small ring. The chain can be merrily whipping through the cage in the middle ring and rub against the cage sides if it is too far one way or the other. If it is a bit too far one way or the other, the chain will rub as you shift the rear der and the line of the chain changes.

There is nothing wrong with the shifter or the der. This is just how it works. It has an arc of travel. At each end of the arc there is a ring ready and waiting. Somewhere in the middle of the arc is the middle ring. You get the chain onto the middle ring, and if you hear chain hitting der cage, you finesse the cage away from the running chain by moving the der a smidgen. (on my twist shifts, it was a couple tiny clicks, on my trigger shifts it was one click, on my friction shifts it is a smidgen) That trims the derailleur.

Here's your experiment for the day:

Take the bike out, ride around, shift into the middle ring. Get off the bike. Look at the chain, see where it sits relative to the two sides of the der cage. Now, move your left shifter a smidgen. See how the cage moves but the chain is still on the middle ring? Move that cage until the inside plate is touching the chain. Now move it until the outside plate is touching the chain. Now move it until it is centered. Get on the bike again. Ride a few yards. Does it make noise? Shift up and down the cassette. If it makes noise, move the left der a smidgen. If that causes MORE noise, move the left der the other way TWO smidgens. Voila! You've trimmed your front derailleur!

Of course, if you can't move the front der a smidgen and eliminate the noise you get from changing rear cogs.... then what I've just told you is useless and your shop needs to give you a hand.

But maybe it would be useful for someone else.

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