Replaceable Rear Derailleur Hanger

[KnottedYet]

Mechanical engineering question:

Is the hanger on a carbon fiber bike made made of aluminum so that the aluminum will fail rather than sending the stress into the delicate carbon fiber?

Sort of a 'sacrifice the hanger to save the frame" situation?

My cheap-o aluminum frame bike has a steel hanger. (magnet sticks to it, so I assume it's steel)

[ridebikeme]

Very wise thoughts on replacing the hanger... you definitely have to be concerned with the material of the frame vs the hanger. If the hanger is stronger than the material of the frame, you could potentially damage the frame... which is a much bigger expense. I would generally NOT think about bending the hanger back unless I didn't have a choice ...if I had to order one or needed to get myself back home. Even though your LBS can bend it back very accurrately, it still is NOt the same strnegth that it once was. The other issue could be that the bike may have some sort of chain line problem... other than the obvious of cross chaining... you might have them check that as well.

The idea of the compact crank will definitely give you lower gearing, and might just fill that need!

Good luck!!

[Batbike]

Very wise thoughts on replacing the hanger... you definitely have to be concerned with the material of the frame vs the hanger. If the hanger is stronger than the material of the frame, you could potentially damage the frame... which is a much bigger expense. I would generally NOT think about bending the hanger back unless I didn't have a choice ...if I had to order one or needed to get myself back home. Even though your LBS can bend it back very accurrately, it still is NOt the same strnegth that it once was. The other issue could be that the bike may have some sort of chain line problem... other than the obvious of cross chaining... you might have them check that as well.

The idea of the compact crank will definitely give you lower gearing, and might just fill that need!

Good luck!!

Two questions based on above:
1. Are you saying it is NOT a good idea to get a new hanger in a stronger material because it would be too heavy?
2. What sort of "chain line problem" ... I don't understand what this could mean?

Thanks!

[ridebikeme]

To answer your questions.... first chainline can be determined by putting the chain on your small chainring and the middle cog on your rear cassette. At that point, it should be in a perfect straight line, if you were standing behond the bike looking at it. If there is any deviation, then I would recommend you taking it to your LBS and have them look at it.. sometimes you can make it a bit better.

Secondly, by having a derailleur hanger stronger than ithe orginal will definitely put more stress on the frame.. exactly where you don't want it. I would also recomend NOT straightening it out .. when that happens the integrity of the aluminium is compromised by bending and then again when we s straighten it.

Have you put more thought into the compact crank?

[Batbike]

To answer your questions.... first chainline can be determined by putting the chain on your small chainring and the middle cog on your rear cassette. At that point, it should be in a perfect straight line, if you were standing behond the bike looking at it. If there is any deviation, then I would recommend you taking it to your LBS and have them look at it.. sometimes you can make it a bit better.

Secondly, by having a derailleur hanger stronger than ithe orginal will definitely put more stress on the frame.. exactly where you don't want it. I would also recomend NOT straightening it out .. when that happens the integrity of the aluminium is compromised by bending and then again when we s straighten it.

Have you put more thought into the compact crank?

first, to answer your question about the compact crank -- if changing the derailleur hanger is a bad idea, then that would be my next plan of action.

now, a quetion for you ... if the chainline is "off", what would cause that and how would the LBS fix it?

Thanks!

[ridebikeme]

Let me see if I can answer your questions...

First, as I mentioned earlier, if you are indeed bending your hangers, you should replace them and NOT straighten them. Obviously there is some sort of problem, so taking it to your LBS is something that I would definitely recommend. Perhaps changing your crank would give you the gearing that would be more beneficial for you and your bike... but it's still something that should be checked just in case.

Secondly, if your chain line is off there are a few options. It can be off because the frame itself is off(and happens more than one would believe). It can also be something very minor... perhaps a spacer behind your cassette.But regardless of what the problem is, it sounds like this is something that should be investigated. You obviously have a nice bike, and it's worth the extra time to figure out what the problem might be.

Good luck!!

[Batbike]

Mechanical engineering question:

Is the hanger on a carbon fiber bike made made of aluminum so that the aluminum will fail rather than sending the stress into the delicate carbon fiber?

Sort of a 'sacrifice the hanger to save the frame" situation?

My cheap-o aluminum frame bike has a steel hanger. (magnet sticks to it, so I assume it's steel)

I believe that is true ... instead of having to replace the entire frame, you end-up saving frame and replacing hanger.