fstshrk

I swapped the Tiagra RD to an Ultegra RD that I received as a gift.
I have to say, the Ultegra 6700 RD works with the 12-30 tiagra cassette, but it took a lot of fiddling with the RD, especially the B set screw to get it to work and IMHO, this combination is not the best. On my good wheelset, I do have an 11-28 ultegra cassette so I am not terribly worried about this, but in case you are thinking of running a 12-30 with the 6700 RD, I think you may need to adjust the B screw quite a bit to get it to work. Strangely enough, the problem manifests itself as a vibration in the smallest three cogs in the back with associated shifting issues.
In my case, the cassette had < 300 miles, the bike had less than <300 miles and the chain (6700), the crankset (6700) and the RD are brand new.

I finally got it to work OK, but it took a lot of time to get it shifting right especially under load.
Of course, YMMV, as I am kind of a perfectionist when it comes to shift quality. I think it is time to upgrade the FD and the brifters to 6700 and get another 11-28 cassette for the wheelset that came with this bike.

Andy_K 

Strange. I've been using a 12-30 Tiagra cassette with a 6600 RD with no problems whatsoever. What's your front gearing?

revchuck 

I had installed a Tiagra 12-30 cassette on my Allez, which had a DA7800 RD, and it barely worked. I got the Tiagra 4600 RD and it worked fine on both extremes - 50-30 and 34-12. I actually used both of those extremes by accident during the race I got the 12-30 for. With the DA RD, when the chain was long enough to use the 50-30 combination, there was no tension in the 34-12; when the chain was shortened so that there was tension in the 34-12, the 50-30 was at the forward limit of travel. I originally had a 12-27 cassette on that bike, and the DA worked fine, and would probably be okay with a 28t cog, but going to the 30t was just too much.

The Tiagra stuff is heavier, but it's such a small increase - the bike and I weigh 215 lbs. together - that it's not noticeable. It works well enough that I'm leaving both the cassette and RD on the bike.

shelbyfv

I recently installed the 12-30 and it works fine with my 6600 triple RD and a 6600 compact crank. I don't recall any b screw issues. Not that it has any bearing on 6700 stuff

fstshrk

According to Shimano, the Ultegra 6700 RD is not compatible with the 12-30T cassette. As I wrote yesterday, I got mine to work, but to get the shift quality that I wanted, I had to spend a lot of time and set the B screw about halfway of travel.

I may put the Tiagra 4600 RD back on the bike if it gives me any more grief in the future.

revchuck 

I know you didn't ask , but that would be my recommendation. The 4600 RD works quite well, with positive shifts. The peace of mind that comes with using something within its design parameters vs. making something kinda work is worth it.

fstshrk

I completely agree with you. I had no complaints with the 4600 RD either.

fstshrk

Minor update.

I just took a short test ride (mainly climbing since I live on a hill). I am quite happy with the shift quality of this combo after spending several hours tuning it. Quick shifts up or down and even shifting while climbing (which I would not normally do unless in dire straits) out of the saddle, no hesitation at all. I am recovering from a hamstring injury, so I probably should not have gone for a ride today, but could not resist the 50+F weather.
I just hope it doesn't flare up.