Do I need a derailleur hanger extender?
 

Hey guys -

So I'm working on my vintage Bridgestone MB-3 1x11 conversion and the Box Two derailleur I bought won't shift into the three biggest cogs on the Box 11-46 cassette I bought along with it. It seems like the upper derailleur pulley wheel won't clear the cassette. Is this just because I'm testing it without a chain on it yet? Or do I need a derailleur hanger like this or this one?

Video below:

Notice the cage position in the following photos.....


https://cimg1.ibsrv.net/gimg/bikefor...22e29aa75a.png

When you've got a chain on the bike with the correct length and the derailleur is properly adjusted, you probably won't have a problem if the derailleur is rated for the cassette that you have.

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have you adjusted the b tension screw? might just need adjusted to move the top cog out form the cassette. the box derailleur is going to be fitted to the cassette you are using most likely. b tension is that screw that pushes the derailleur against the hanger, in your case you have an integrated hanger since its an older bike. the only reason for extensions is for derailleur designed for smaller range cassettes.