Rear Derailer adjustments with new cassette?

[Cusp]

My OEM 12-25 rear cassette isn't helping me out much on the hills here in the Northeast. I was looking at the Ultegra 9-speed (12-27) cassettes. If I opt for the higher gear cassette, will I need to adjust my rear derailer? Or is it "Plug-n-play"?

Thanks!

 

[pistole]

- 25 to 27 should be okay.

- maybe a tweak of the B-screw.

 

[capwater]

My OEM 12-25 rear cassette isn't helping me out much on the hills here in the Northeast. I was looking at the Ultegra 9-speed (12-27) cassettes. If I opt for the higher gear cassette, will I need to adjust my rear derailer? Or is it "Plug-n-play"?

Thanks!

No adjustment should be necessary. I'm always swapping cassettes depending if I'm hill riding (25), training (23) or racing (21).

 

[daveornee]

My OEM 12-25 rear cassette isn't helping me out much on the hills here in the Northeast. I was looking at the Ultegra 9-speed (12-27) cassettes. If I opt for the higher gear cassette, will I need to adjust my rear derailer? Or is it "Plug-n-play"?

Thanks!

You should verify that the "Big-Big" combination has sufficient chain length just in case you mistakenly cross chain to this combination.

 

[Cusp]

No adjustment should be necessary. I'm always swapping cassettes depending if I'm hill riding (25), training (23) or racing (21).

Does this mean anything?

I have 9 speed 105 RD. Shimano does not sell any 9 speed cassettes with a tooth greater than 25T. Only the 9 speed ultegra level has the 27 tooth cassette.

Will my chain have enough length to accumodate the 27T cassette? And also I am just realizing that RD are either SS or GS styles. (huh?) haha. Gonna do some more research before I drop 50 bucks for the new cassette.

Thanks!

 

[alfeng]

My OEM 12-25 rear cassette isn't helping me out much on the hills here in the Northeast. I was looking at the Ultegra 9-speed (12-27) cassettes. If I opt for the higher gear cassette, will I need to adjust my rear derailer? Or is it "Plug-n-play"?

Thanks!

YES & NO ...

You shouldn't have to adjust your rear derailleur ... unless there is something peculiar going on.

BUT, the next time you change your chain, you'll probably want to add 1" (a pair of links) ... AND, depending on how the bike was set up, you'll probably need to avoid the LARGE-LARGE combination (which you should avoid, regardless).

BTW. You might want to get a SRAM or IRD 12-28 cassette ... I think a 12-30 may also be available, but there may be some conflict with the rear derailleur's upper pulley which is usually "fixed" by adjusting the B-screw (done with the derailleur OFF the frame). If the larger rear cog almost-but-doesn't work for you, you can also change the inner chainring to one with only 38t.

You DON'T have to worry about the SS or GS cage length -- I used an SS (regular, "short" cage) 105 rear derailleur with a 52/39 & a 12-30 cassette ("custom" stack ... I added/swapped a 30t cog that I cannibalized from a MTB cassette for one of the "middle" cogs, but you can theoretically buy cogs separately if your LBS is inclined to assist you). The rear derailleur is generally capable of handling an 8t difference between adjacent cogs.

You CAN have a slightly slack chain on the "return" (I did NOT find this to be the case with the 52/39 & 12-30 combination & short cage 105 rear derailleur) ... a slack chain on the "return" is more of a cosmetic issue UNLESS you are doing some MTB-type curb-jumping or hucking OR possibly if you have a really bad pedaling style.