Replace derailleur?
 

I have a 2x9 on my Sirrus. I wore the chain out pretty badly and replaced it at over 4000 miles. At the time it started skipping, and I thought the new chain would eliminate the problem. Well, the new chain did remove the grinding BB noise. (That's another story, and I don't know why a stretched chain would even cause that noise.). However, the skipping and shifting problems were still there.

I adjusted the derailleur but it still persisted. Then, I replaced the cassette. Same issue. It shifts fine from smaller to larger cogs but in the reverse it doesn't always shift down, or it hesitates badly, or needs 2 clicks, or shifts when I apply force to the pedals. Once it's in gear it rides fine, except when I go over a bump or dip. Then the mech may hop and it skips. I will state that this happened before even when the bike was newer, but not as frequently. Now, it happens regularly.

I have the Alivio mech. My son also has Alivio on his bike and the spring tension at the dropout is much higher on his. Is it possible to wear out the spring in under 5000 miles?

If that is the problem, then should i get the new Alivio RD-3100 or older Deore RD-M592-SGS? They are about the same price.

The hesitation in dropping from larger to smaller cogs may be the cable fraying or otherwise binding inside the housing. You may have two separate problems. If replacing the RD, I would get the M591 not the M592. The 592 is "Shadow" and doesn't have a barrel adjuster.

Wd40 is worth a go first.
Spray the cable where it goes in and out of outer cables and the derailleur.
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In the scenario you're laying out, the derailleur would not be my first guess.

More likely issues:
-Cable friction. You should definitely replace the cable and housing if you haven't already.
-Derailleur hanger alignment.
-Derailleur setup.

Have you bent the hanger?

Barry

No. It bolts directly to the frame.

to me this sounds like a textbook cable issue. When you’re shifting to a larger sprocket, you’re providing the pulling force to shift the RD - enough force to overcome cable friction or anything else that’s restricting smooth cable movement. When shifting to smaller sprockets, you’re basically “letting out line” from the shifter and the relatively weak RD spring is doing the pulling. Any excess friction or restriction in the cable will be enough to defeat the RD spring - so shifting works OK in one direction (ie, the RD works) but not in the other (cable friction exceeds RD spring strength). This isn’t a flaw in the RD, it’s your cable gumming up. A decent RD will last 100,000 miles with some basic maintenance. Change the cable and housing, make sure that there are no sharp turns in the housing, and carefully cut the housing square, and ensure that the housing and liner aren’t crimped at the cut. I bet your shifting will be 100% better

Thanks. I'm ordering some cables and housing now. Hopefully that will fix the issue.

My wife needed a new bike due to bending a frame integral derailleur hanger.
If you change the cables and still have issues, getting it checked is cheap (assuming you can't do it yourself with an additional rear wheel)

Barry

I thought about that possibility too. What do you mean by having an extra wheel?

Thread on most QR rear axles is 10 x 1, the same as the RD dropout. You can screw an extra wheel into the dropout to have a plane adjacent to the wheel to measure against. You can even use the wheel as a lever to bend the dropout, but with care.

A picture is worth..............


I did this to mine twwo weeks back and determined it o be bent.
Although I did chicken out using a wheel to effect the straightening. It's the wheel off my Fixed/Track bike.
So I ran to to the store and paid to have them straighten it with the correct tools.
Barry

The "Derailleur Hanger" is the part that extends down below the frame that the derailleur bolts onto. It can either be integral to the rear dropout, or can bolt onto the rear dropout, or can be a "claw" as part of the derailleur.

The part is easy to bend.

As a simple check, by hand extend the derailleur cage fully downward. It should be roughly parallel to the rear wheel (same at other angles).

If the derailleur cage isn't parallel to the rear wheel, then it could be either a bent cage, or a bent hanger.

If not bent badly, you might be able to get the hanger bent back close with an adjustable wrench and eyeballing it, or any shop should be able to fix it.