Advice on cassette/RD mismatch
07-12-20, 04:39 PM
#1
Senior Member
Thread Starter
Join Date: Sep 2012
Location: Los Angeles
Posts: 755
Bikes: 2019 CAAD12, 2015 Specialized Sirrus Comp
Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 562 Post(s)
Likes: 0
Liked 64 Times
in
46 Posts
Advice on cassette/RD mismatch
Got a question for the bike mechanics among us. I have a CAAD12/Ultegra with the short-cage R8000 derailleur. I recently replaced the 11-30 cassette with an 11-32, which is beyond spec for the short-cage RD.
It shifts fine and runs quiet on the larger cogs including the 32T. However, when up-shifting to smaller cogs, the chain hesitates and sometimes skips over a gear. The chain is new (DA). The bike's been to my LBS and I believe they've adjusted the RD to be as good as it can be, but it's still not ideal.
My thinking is that I need to install the long-cage R8000 derailleur to truly fix this issue. It's not that much money (around $85). Here are my questions:
1) Is changing the RD a likely fix for the shifting problem?
2) Do I need to lengthen the chain to accommodate the larger RD? Shimano's instructions say to measure chain length without the RD in the path, so this implies the choice of RD has no effect on optimal chain length.
3) When adjusting the replacement RD, I'm familiar with how to adjust the limit screws, the "B" screw (for height) and the barrel adjuster. Are there any other special things I need to know?
Thank you.
It shifts fine and runs quiet on the larger cogs including the 32T. However, when up-shifting to smaller cogs, the chain hesitates and sometimes skips over a gear. The chain is new (DA). The bike's been to my LBS and I believe they've adjusted the RD to be as good as it can be, but it's still not ideal.
My thinking is that I need to install the long-cage R8000 derailleur to truly fix this issue. It's not that much money (around $85). Here are my questions:
1) Is changing the RD a likely fix for the shifting problem?
2) Do I need to lengthen the chain to accommodate the larger RD? Shimano's instructions say to measure chain length without the RD in the path, so this implies the choice of RD has no effect on optimal chain length.
3) When adjusting the replacement RD, I'm familiar with how to adjust the limit screws, the "B" screw (for height) and the barrel adjuster. Are there any other special things I need to know?
Thank you.
Last edited by Robert A; 07-12-20 at 06:44 PM.
07-13-20, 12:28 AM
#2
Senior Member
Join Date: Apr 2012
Location: Nor Cal
Posts: 6,016
Mentioned: 17 Post(s)
Tagged: 0 Thread(s)
Quoted: 1814 Post(s)
Likes: 0
Liked 923 Times
in
569 Posts
If it goes into the big/big OK, then the worst to expect is slight slack in small/small.
If the chain was too short, disaster would have already happened in the big/big, so it is long enough.
Checking the hanger alignment and cable/housing issues are standard for hesitant shifting.
Possible issues from new chain/older cassette that may settle after some miles.
If the chain was too short, disaster would have already happened in the big/big, so it is long enough.
Checking the hanger alignment and cable/housing issues are standard for hesitant shifting.
Possible issues from new chain/older cassette that may settle after some miles.
Likes For woodcraft:
07-13-20, 10:14 AM
#5
Klaatu..Verata..Necktie?
Join Date: May 2007
Location: SF Bay Area
Posts: 17,958
Bikes: Litespeed Ultimate, Ultegra; Canyon Endurace, 105; Battaglin MAX, Chorus; Bianchi 928 Veloce; Ritchey Road Logic, Dura Ace; Cannondale R500 RX100; Schwinn Circuit, Sante; Lotus Supreme, Dura Ace
Mentioned: 41 Post(s)
Tagged: 0 Thread(s)
Quoted: 10424 Post(s)
Liked 11,886 Times
in
6,090 Posts
Hey, do those really work? I've got a Bianchi with 50/34 in front and 12-25 in back, and a short-cage Veloce 10sp. derailleur. I'd like to run a bigger cassette, but it would exceed specs.
__________________
"Don't take life so serious-it ain't nohow permanent."
"Everybody's gotta be somewhere." - Eccles
"Don't take life so serious-it ain't nohow permanent."
"Everybody's gotta be somewhere." - Eccles
07-13-20, 10:21 AM
#6
Senior Member
Thread Starter
Join Date: Sep 2012
Location: Los Angeles
Posts: 755
Bikes: 2019 CAAD12, 2015 Specialized Sirrus Comp
Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 562 Post(s)
Likes: 0
Liked 64 Times
in
46 Posts
I'm not having any problems when the chain is on the largest cog, so I'm not sure how an adapter would help. The issue occurs when shifting from a small cog to a smaller cog.
