Rear Derailler

[GDR]

Hi,

I just put a new rear wheel on and changed my cassette to an 11-25 from an 12-25. The shifting is working fine except when the chain is in smallest cassette cog, the rear derailleur hops. I checked the alignment already and everything looks fine. Please help.

[locustfist]

Could be 2 things

B screw: put it in the largest cog and set the upper pully so it just clears the cog and runs smooth.

Cable too tight: if it's aligned right and jumping on the smallest cog there is most likely too much tension. bring the barrel adjuster IN until it settles down. I usually set the limiter on the small cog with the cable completely undone and slack.

[cxwrench]

could be what locustfist suggested, those are the most likely things. slim chance, but if you have a wipperman connex link on your chain, and it's installed upside down...that could also be it. more likely a very small difference in limit screw/cable tension adjustment from your other cassette.

[redondoaveb]

It's not the chain skipping on the 11 cog? I know when I changed from an 12 to an 11, I didn't know any better and used the lockring from the 12, not knowing it was a little larger. When I was on the 11, the chain would skip on the cog.