bacchant

Can this work? Shimano says no, but that doesn't necessarily mean I can't...

I've got a 1998 Waterford and a pile of 10-speed 6600 components that I'm planning on putting on it. I'd really like to include the new Ultegra 12-30 cassette for those steep hills, but Shimano's documentation indicates that this particular cassette isn't compatible with any other group. How true is this? Can I really not use an earlier, long cage derailleur with this?

shelbyfv

I used the 6600GS with the 12-30 Tiagra. Swapped to a 6700 short cage and it works fine as well.

HillRider

Shimano officially says most of their road rear derailleurs are compatible with a 27 or 28T maximum cog size. Generally you can exceed this by a couple of teeth with no problems.

aramis

I'd only worry about the long cage if the derailleur looks stressed on the big/big with a usable chain (not too loose) in the small/small, otherwise you can go with the short cage. Funny thing is the road medium cage derailleurs aren't spec'd for cassettes any bigger than the short cage afaik, the upper pulley will sit the same distance from big cassettes as the short cage one.

If you want to be 100% safe or it won't work with a short or mid cage you can always use a 9 speed mountain derailleur. I use a deore 9 speed rear derailleur with a 10 speed 105 drivetrain on one of my bikes with a 11-32 and the btrim is almost all the way out.

bacchant

Thanks everyone, based on your comments I've decided to buy the 12-30. I'll post the result!