Way to check a derailleur
 

Is there a way to check a derailleur for alignment?

My shifting is difficult to micro-adjust, especially when shifting from 4th to 5th gear.

I already checked my dearailleur hanger and it's straight as it should be, well, I have bent it back straight anyway. The shift cable is also not tight and not loose.

Is there a guide somewhere on how to check my derailleur's alignment?

It's a Shimano Deore 12 speed.

No, there really isn't. If the hanger is straight you have to basically just eyeball the derailleur. It's odd to have a shifting issue between just 2 cogs, unless those 2 are worn a bunch more than the other cogs on the cassette.

Define "12 speed"

There is a tool: Amazon.com : Park Tool DAG-2.2 Derailleur Hanger Alignment Gauge : Sports & Outdoors and of course there are cheaper knock offs also. Or you can try to eyeball it by looking at the derailleur "arm" . It should be parallel with the cogs, not tilting inward or outward--this is not super accurate, but if bent, you may notice.. Your LBS will (or should) have the alignment tool, can't imagine it would be expensive to have them check it.

"I have bent it back straight anyway". The difference between "actually aligned" and "looks straight" is tiny. I'd never try to align a derailleur hanger by sight, unless it was just a quick fix to finish the ride. The Park Tool align tool works great.


What are your shifting symptoms? Noise or chain pops in certain gears? Slow or difficult to shift to a larger cog? Won't easily drop down to a smaller cog?
Does it shift to the largest cog easily? And down to the smallest?

For shifting problems, I put the bike on the repair stand (or you could hang it by the saddle nose, I suppose). I shift to 2 or 3 smaller cogs, then shift back to the target cog.
Now I turn the crank very slowly (like 1 link per second) and watch the chain as each link gets near the cassette. Is it catching on the next largest cog? I can see the chain plate get pushed a little, then pop back in line. Or is it touching the next smallest cog? I'll do a few wheel revolutions to see what's going on.

There are two pivots that der pulleys are located by. The der hanger aligns one pivot, the "B". The cage rotates about the other pivot. If either pivot bolt is not straight the pulley cage can be not parallel to the cogs. We see quite a few ders that when installed show a "wiggle" movement to the der as the bolt is turned. The threaded portion of the bolt is not coaxial w/ the rest of the bolt, machined or bent it doesn't matter why. Generally this is not a big deal but with decreasing tolerances, of the more and more cog counts, even these slight miss alignments can add up.

I'm not claiming this is your problem but that this does exist and can be a reason why a straight hanger is not a promise of a straight cage. Andy

Hmmmm...how do I know that you didn't really understand the OP?

You have a point--he did ask if there was a way to check if the DERAILLEUR was in alignment. He also mentioned he bent the hanger back to being straight. Yes, there is no way to check the derailleur itself, but much more likely to be a hanger misalignment than a faulty derailleur, thus my reply. I would start with making sure the hanger alignment (especially since it has been manually bent without a tool), and if hanger alignment is accurate, then I'd suspect the derailleur, but not before confirming the hanger is aligned.

Sorry I forgot to mention, I did use the parktool DAG-2.2 to align my hanger.

Other symptoms I have are, the chain is noisy on the first (smallest) cog, and yes, I have removed the chain and lined up the cog and the top derailleur jockey wheel. When I shift to the second cog and I backpedal (this is on a stand, not riding it) I can see there are parts when the chain rubs on the third cog and jumps a little. It doesn't disappear when I microadjust, it's always there. The jockey wheels, cassette, and chain are clean, I just cleaned them all. The bike is only 4 months old, and I don't see any worn out teeth on the cogs, though I see rub marks on the chainring. I also measured the chain and it's still has not stretched.

If your cassette has a 10 tooth small cog it wouldn't be surprising that the chain makes extra noise when you use it. Small cogs are noisier and wear out faster
​​​​​​2.2.1 Chordal Action

Feel like I'm wearing some "egg on my face", but I'll try anyway. Guessing it's the original chain, and that it is a Shimano HG chain? I've not owned a derailleur with "Shadow" technology, but they have built in "clutch" tech, don't they, and it's adjustable as well as being able to turn on or off.. Don't see why all other combos would work other than just those two, but might be worth checking. Hope you get it sorted out, reading up on it, sounds like a great drivetrain for mtn.biking. And I'll try to pay more attention the the ? next time.

1) Of course it does, there isn't a derailleur to guide the chain onto the cog when you back pedal. There is no way you can adjust anything to stop that from happening. You'll obviously get noise in the smallest and largest cogs as the chain line is at it's most extreme.
2) Chains don't 'stretch', they wear.