N00b bike tuning/building question

Triathlon Forum
1

Building a bike from scratch for the first time.

Having a problem with rear derailleur tuning. Shimano 7900 w/ 11-28 cassette.

I followed the instructions and got it tuned so that the big and small cogs work great. The limits are fine. However, while the big cog is fine, the 19,21, and 24 have some chatter and sometimes skip around. If I tune it so those cogs work fine, then all the rest chatter.

I’m pretty sure I have the new 7900 chain on the right way - lettering out. Also pretty sure it’s the correct length.

I’m also pretty sure the cassette was put on the wheel hub. There’s no play - it’s rock solid. And the 21,24, and 28 are all one big chunk of metal so I couldn’t have screwed up too bad.

Thanks for any help.

2

For the Most part, the big and little cogs are going to be adjusted using the H and L screws.
Everything in between is done with the barrel adjuster.

Check out:
http://parktool.com/repair/readhowto.asp?id=64

3

  1. Is the cassette new? If not, the new chain may not fit the “worn” cogs of the used cassette. Replace the cassette.

  2. Have you had your dropout aligned? This may also cause your problem.