I’m trying an Ultegra CS 6700 11-28 cassette for size. I originally run a DA CS 9700 11-25. I have a couple of questions:
I’m planning to constantly switch between the two cassettes. Any advice is greatly appreciated.
If the chain was originally sized to fit the 11-25, you might have to add links to fit the 28 big sprocket. If the chain was originally sized to fit the 28, it’ll fit the 25 as well with no changes. In any case, the derailleur shouldn’t need any changes when switching cassettes. Different brand cassettes might sit slightly off from each other, though, not sure.
You may have to adjust the cable a little bit, most likely not the end stops.
Probably not unless your chain was on the short side to start with.
Only adjustment on rear mech will be the b-tension screw.
Chain length will require confirmation on 28t as mentioned.
Aim for 6 mm gap between upper jockey wheel and lowest tip of 28t cog. Set at that and leave it for the 25t if you intend to change regularly. Else make Same clearance on 25t if you intend to run it for some time .
Thanks all for the feedback. It seems that the chain length was long enough for the 28t. Shifting was very smooth until the largest gear (28t). Also, as I’m rolling I’m hearing a slightly higher noise from the rear derailleur. It seems that it is vibrating.
Do you think the b-tension screw will fix both issues?
Don’t cross chain and chain length won’t be an issue.
Yes, your mech is likely trying to shift across the tips of the 28t cog teeth… Set clearance as mentioned.
If insufficient length on b-tension screw due to your hanger design.
Consider flipping the screw from the other side and using the screw head as the stop… Look up reversed b tension screw on google of you are unsure what this means .
Also google shimano tech file for rear mech set up…
Tells you everything you need to know there…
What about switching from a 12-25 to an 11-25 ? Any adjustments anticipated or should they be pretty much the same ?
Chain length should be the same, but depending on the make/model of cassette, you might have to adjust the derailleur because the cassette will sit further in or further out from the centerline of the bike. If this is the case, you should be able to use a thin cassette spacer to space them the same. However, in all likelihood, it’ll just work fine as is with no adjustment needed. Best way to find out is to try it. B-tension will not have to change, as the large cog isn’t changing.
Most important adjustment is always lower gear (inner) limit stop. I always shift to the second-lowest (second from inside) gear, then slowly tug the rear inner wire by hand to make sure derailleur won’t rub or hit spokes. But it sounds like you have that all dialed in. There’s very little difference between an 11-25 and 12-25 as far as RD and chain adjustment is concerned.
Great thanks. It’s the same cassette, Shimano Ultegra CS-6700 just with the minor difference.
I would anticipate no adjustment needed then. Would be very surprised if they didn’t sit identically.