Is this RD considered "bent"?

[cpml123]

Hi,
I always thought my RD/cassette/chain is a little noisier than the DF bike that I haven't ridden for a while. However, since I have nothing else to compare to, I just thought it's normal. Today when I happen to look at it straight on, it looked a little "bent" to me. What I mean is that the cage angle does not look exactly parallel to the cassette. It is slightly angled towards the cassette at the bottom, as if the bike fell over and bent the RD. It has fallen over a few times before when I first learned to ride it and when it was juts sitting in the bike stand and fell over.

Can you please take a look at your RD cage/cassette "parallelness" and see if this this normal?

Thanks.

 

[Greg S]

It's hard to say from the photos but in the middle of the cassette and looking straight down (so the top and bottom of the chain are on the same line) mine is straight.

By the way, it's far more likely that the derailleur hanger is bent rather than the derailleur itself - that's what it's supposed to do. I still have the original unused spare derailleur hanger that came with my S40 and I use that as a reference. Mine wasn't shifting very well, I took off the hanger and compared to the new one and sure enough it was bent. A brief session in a vise and all's well.

 

[cpml123]

It's hard to say from the photos but in the middle of the cassette and looking straight down (so the top and bottom of the chain are on the same line) mine is straight.

By the way, it's far more likely that the derailleur hanger is bent rather than the derailleur itself - that's what it's supposed to do. I still have the original unused spare derailleur hanger that came with my S40 and I use that as a reference. Mine wasn't shifting very well, I took off the hanger and compared to the new one and sure enough it was bent. A brief session in a vise and all's well.

The first picture I posted has the chain line overlap the cage, and it looks like it's at an angle to the cassette.

 

[Greg S]

The first picture I posted has the chain line overlap the cage, and it looks like it's at an angle to the cassette.

Yes, but you're toward the smallest cogs which, depending on chainline (double? single?) does cause the derailleur arms to angle inward toward the wheel somewhat.

Overstating to make the point: if you were fully crosschained on a double (big chainring, biggest cog) the chain is going to be at an angle. In order to accommodate that angle the uppermost jockey wheel is going to need to be more or less straight with the big cog, the lower jockey wheel is feeding the chain back to the big ring which is to the right of its position. That difference (between the upper and lower jockey wheels) will make the derailleur arms look "bent". This is normal.

Conversely, if you were crosschained in the opposite direction (small chainring, smallest cog), the upper jockey wheel is going to be outboard and lined up with the small cog. The lower jockey wheel is feeding the chain back to the small ring so it's going to be tilted inward (toward the wheel). Again, this is normal.

That's why I said mine was in the middle of the cassette (and small chainring). The chainline is more of less straight at that point, as is the derailleur.

Hope this helps.

Edited to add an additional example and to correct some errors.

 

[benphyr]

Nice description. Very clear.

Another possible solution is a local bike coop or bike store. You take off the derailleur and screw in this special tool which can rotate around and measure the gap between the tool’s long arm and the rim. The tool exaggerates anything bent out of plane from the rear wheel. You do need a reasonably true wheel for this tool to work well. It will be really obvious with this tool if there is enough bend to be causing shifting issues.

Wishing you perfect shifting in your near future.

 

[Greg S]

For reference, the "special tool" @benphyr mentions is called a "deraillleur alignment gauge" and just about any bike shop worth its salt will have one (I have one and I'm not even a bike shop!).

All you need to do is take your bike into your LBS and say you want the derailleur alignment checked. After they get through saying "we don't work on recumbents" and you get through slapping them, they should be able to use the alignment gauge to check and straighten your derailleur hanger if it's bent.

 

[cpml123]

Conversely, if you were crosschained in the opposite direction (small chainring, smallest cog), the upper jockey wheel is going to be outboard and lined up with the small cog. The lower jockey wheel is feeding the chain back to the small ring so it's going to be tilted inward (toward the wheel). Again, this is normal.

That's why I said mine was in the middle of the cassette (and small chainring). The chainline is more of less straight at that point, as is the derailleur

That makes sense. So it can't be parallel all the time. I will try shifting to the small chain ring and middle of the cassette and see how it looks.

I am avoiding local bike shops right now until the rain season starts. They have told me they are really busy, so just drop the bike off, tell them what needs to be done, and wait for 1-3 weeks.

 

[Greg S]

The easiest thing to do if you have a known straight hanger is either to just change it or take the old one off, compare to the known one and straighten it if needed. No more difficult than fixing a flat.

Even if you don't have one that you know to be straight, you could use a straight edge. As I said previously, it doesn't take a whole lot to bend the derailleur hanger, that's what it's supposed to do.

Bad shifting/noisy drivetrain makes me crazy.

 

[cpml123]

The easiest thing to do if you have a known straight hanger is either to just change it or take the old one off, compare to the known one and straighten it if needed. No more difficult than fixing a flat.

Even if you don't have one that you know to be straight, you could use a straight edge. As I said previously, it doesn't take a whole lot to bend the derailleur hanger, that's what it's supposed to do.

Bad shifting/noisy drivetrain makes me crazy.

I watched a couple YouTube videos on derailleur hanger replacement. Seems simple enough. I took the old one off and compared to the new one. They looked the same. I just went ahead and put the new one in and put everything back. Still sound the same. I guess that's just how it is. I did notice the place where the derailleur screws to the hanger has a slight play. I know it's supposed to allow the derailleur to rotate, but I don't know if it's supposed to have some play. The end of the cage, due to the play, can move a couple millimeters.

 

[Tuloose]

Your noise might be caused by improper adjustment of the b screw allowing the upper jockey pulley to come in contact with the large cog on the cassette.
Turning the screw in a bit might be the solution.
Check out the Sheldon Brown site for excellent info on rear derailleur adjustment.
https://www.sheldonbrown.com/derailer-adjustment.html