I have no experience adjusting the derailleur until recently. I followed the nice instructional video from Shimano. After I finished with the bike, a final test on the rack showed I was able to spin through the gears without excessive clacking and everything look centered and squared off. But when I tested it on the ground in a ride, the shifting character was noticeably worse. The chain is not overly tight, so I assume the added load through the pedal is not affecting performance. Any idea what the issue could be?
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4It is more likely that the hanger is bent. There are tools to check for that and bike shops have them. The derailleur must be taken off for that check. Sometimes, the bend is even visible if it is big enough.– Vladimir F Героям славаCommented Jan 11 at 14:08
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To expand a bit on @VladimirFГероямслава 's comment: It's usually not the derailleur, but the derailleur hanger that is bent. The hanger is weaker than the derailleur, by design, because it's inexpensive and meant to bend in order to protect the much more expensive derailleur. It can usually be bent back (with the appropriate tool preferably), or replaced if it breaks– BurkiCommented Jan 11 at 14:19
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@VladimirFГероямслава Does that mean I can save a bit of time and money by just taking it off myself and bringing it down to the LBS for a check? I am all for LBS but my city is expensive, and it's quite a bit harder to afford the service fees these days :)– AdamOCommented Jan 11 at 14:23
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1@AdamO The hanger must be on your bike frame for the test.– Vladimir F Героям славаCommented Jan 11 at 14:33
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1Maybe it’s the B-screw?– MichaelCommented Jan 15 at 7:32
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2 Answers
Most likely it is the derailure hanger. This attaches to the derailure and the frame so that when the derailure gets impacted, its bends instead of the derailure. This is so you can replace a $20 part instead of a $100+ derailurer. To check the condition of the hanger, you can take it off and place it in a flat surface, press down on opposite sides and if it is bent you will feel movement up and down like a seesaw. If this happens it needs replacement.
If it is still shifting bad, it may be the shifter cable, but most of the time it’s the hanger. Hope this helps
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1In my opinion, you should add that it doesn't always need replacement and in many cases, derailleurs can be straightend rather then requiring instant replacement.– DoNuTCommented Jan 14 at 12:19
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Donut is right in one sense, but some mechanics may prefer not to bend back an aluminum hangar. You will make it brittle and crack it if you do that too much. That said, they make RD hangar gauges with the assumption that mechanics will bend the hangar back - and almost all of them are aluminum. Commented Jan 14 at 20:31
I’ve had several badly bent derailleur hangers caused by crashes last year and every time I was surprised how well shifting still worked despite the hanger being obviously bent (I roughly bent back by hand just to get back home). So I’d say a degree of bendy-ness which is not visible to the naked eye is unlikely to cause significant problems.
Make sure you not only look at the derailleur cage from behind but also from above. Quite often the hanger is not simply bent sideways but also twisted.
