Originally Posted by
scirocco
Sure you're talking about an Ultegra 6600 RD? In that thread you quoted, you say that the RD is rated for 28T. The 6600 RD is not, it's only rated for 27T. The OP has 6600, not 6700.
I was using a 6600 RD with 28T for a while and it just, only just fitted with the B-screw wound all the way out to stop the pulleys hitting the ring. There is no way I could have got a larger ring on. But I guess it depends on the RD hanger length - if it's long enough you could get enough clearance I suppose.
Try this: take the rear derailleur off, remove the B screw, and reinstall the B screw from the other side. The result is that you effectively get a bit more B screw length by having the head of the B screw against the derailleur hanger. It might make the difference when trying to run a 28t cassette. Might even work well enough to allow the OP to use a 30t cassette. Worth a try anyway.
Right now I'm using this method on one of my bikes to make a 105 9spd rear derailleur work with a 12-32 cassette. It clears the 32t cassette and works fine. But there isn't enough room, though, for a 34t cassette.
It's been suggested to me that you could also just go down to the hardware store and get a longer screw of the same diameter and threading as a B screw. I haven't gone looking yet, so I don't know if a screw like this is something the neighborhood hardware store is likely to have.