Originally Posted by
jimc101
Sounds like the issue is with the RD, and it's capacity, not the cassette, if probably have a short cage (SS), when you need a medium cage (GS). To work out exactly what you need, you need to know the number of teeth on the cassette & crank, see here for more details
http://sheldonbrown.com/harris/derailers-rear.html
As DiabloScott posted, cage length normally has absolutely nothing to do w/ max cog size...a longer cage only does one thing...it wraps more chain. It does NOT allow larger cogs to be used. A derailleurs
capacity is not related at all to its
max cog size.
Originally Posted by
Homebrew01
Did you get a longer chain ? Perhaps a slight b-screw adjustment would help move the pulley away a bit ?
Originally Posted by
Homebrew01
If you get a larger cassette, you should get a longer chain. If your chain is too short, you run the risk of damage when shifting into big-big.
Advice from not-so-experience armchair mechanics...no one here knows for sure if you need a longer chain. If your chain was sized correctly (small/small) you most certainly do NOT need a longer chain. If your chain was originally sized using the big/big method, you probably do need more links.
As posted by a couple of people a B-tension screw adjustment will most likely take care of your problem as even the older D/A derailleurs w/ a stated max cog of 27 will work just fine w/ a 28.
Carefully check your chain length...big ring and slow shifting up to the big cog in a work stand.