rear derailleur issues
08-10-13, 05:22 PM
#1
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rear derailleur issues
just put in a new 8 speed cassette on my caad 3, its a 12-30 tooth and the issue im having is when i put it on my small chainring and my biggest tooth cog (30) the derailleur starts to skip up and down. I'm thinking its because there isn't enough spacing in between the derailleur and casette. When its on the big ring it doesn't have that issue.
derailleur being used is a shimano tiagra, which came stock with the bike, so i'm thinking that it might not have the right amount of clearance for a cog size that big when the chain is on the lowest gears.
any help would be appreciated
derailleur being used is a shimano tiagra, which came stock with the bike, so i'm thinking that it might not have the right amount of clearance for a cog size that big when the chain is on the lowest gears.
any help would be appreciated
08-10-13, 05:32 PM
#2
Really Old Senior Member
Have you adjusted the B screw?
It may be that your RDER simply can't handle a 30T.
That's why they make "Mountain" RDER's.
It may be that your RDER simply can't handle a 30T.
That's why they make "Mountain" RDER's.
08-10-13, 05:41 PM
#3
Mechanic/Tourist
Look up capacity of your derailleur (largest cog). If you're close then you might be able to get it to work with b-tension or different chain length or different wheel position (horizontal dropout only). If not then you need a derailleur that is designed to handle it and that is compatible with your shift levers .
08-10-13, 07:42 PM
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Shimano and Campagnolo have center mounted idler cages. That means that the upper pulley moves up and down with changes in chain length (or chainring size). For that reason, the B-screw adjustment has to be rechecked in all gear combinations. This is part of Shimano's instructions, but most people stop reading after initially setting the B-screw and miss this critical step.
Adjsut the B-screw to bring the RD lower, then confirm that you have good clearance in every possible gear combination, including the crossed combinations you don't plan to ride in.
Adjsut the B-screw to bring the RD lower, then confirm that you have good clearance in every possible gear combination, including the crossed combinations you don't plan to ride in.
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An ounce of diagnosis is worth a pound of cure.
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FB
Chain-L site
An ounce of diagnosis is worth a pound of cure.
Just because I'm tired of arguing, doesn't mean you're right.
“One accurate measurement is worth a thousand expert opinions” - Adm Grace Murray Hopper - USN
WARNING, I'm from New York. Thin skinned people should maintain safe distance.
