Cassette & Upper Cage Pulley Too Close
05-19-14, 05:38 PM
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Cassette & Upper Cage Pulley Too Close
After replacing a 12-30T Tiagra Cassette Today with An Ultegra 12-30T, I Noticed A Clanging Noise When The Chain Was In The 30T Cog & The 39T Small Chain Ring On The Crank. Note: A few weeks ago, I had a LBS Change The Crank From A 50/34 Compact Crank To The 53/39 Crank. I "could of" Had This Problem Since Then, I just Noticed It Today, When They Swapped Out Cranks, The Chain Was NOT Replaced. I'm Running A Shimano 105 Short Cage. When I Look At The Top Pulley & The 30T Cog, They Are Over Lapping, Or Over Meshing. Once I Shift Over To The Large Chain Ring, The Tension Pulls The Pulley Away From The 30T Cog. I am wandering If My Chain Is Now Incorrect... See Pics Below... THANKS.
05-19-14, 05:50 PM
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Please shift your gears to small-to-small and take a picture showing the back part of the bike. I want to see the rear wheel and the entire RD and cassette. In other words - shift so the chain is on the smallest cog of the cassette and the small chain-ring of the crank.
Can't really tell from that close-up.
Can't really tell from that close-up.
05-19-14, 05:57 PM
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Try a quick experiment. Pull the lower loop forward and see if that brings the upper pulley lower as the cage rotates. If so, the solution lies in either the B-screw adjustment or adjusting the chain length (subject to an absolute minimum based on big/big +1").
Shimano and Campagnolo derailleurs are sensitive to chain length because the cage pivots between the pulleys, causing the height of the upper pulley to change with cage angle. Shimano's detailed instructions cover this with a reminder to check the chain length and "B" screw adjustment in all gears.
Sram RDs are insensitive to chain length since the cage pivots through the upper pulley. That's why Sram can advise setting chain length to the minimum as determined by the big/big + 1" method without any other considerations.
Shimano and Campagnolo derailleurs are sensitive to chain length because the cage pivots between the pulleys, causing the height of the upper pulley to change with cage angle. Shimano's detailed instructions cover this with a reminder to check the chain length and "B" screw adjustment in all gears.
Sram RDs are insensitive to chain length since the cage pivots through the upper pulley. That's why Sram can advise setting chain length to the minimum as determined by the big/big + 1" method without any other considerations.
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05-19-14, 06:17 PM
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Did you try pulling the lower loop forward?
If it helped, shift to the big/big combination and pull the lower loop forward to see if shortening the chain is an option. If it is, therein lies the solution.
If it helped, shift to the big/big combination and pull the lower loop forward to see if shortening the chain is an option. If it is, therein lies the solution.
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FB
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Just because I'm tired of arguing, doesn't mean you're right.
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05-19-14, 06:20 PM
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FBinNY: I Pulled Lower Loop Forward.... Upper Pulley "Gained" Distance - Clearance. I went Big to Big... I may be able to remove one link... If I can have "more" spring forward, I could remove more than one link.
Last edited by Bradwallace; 05-19-14 at 06:31 PM.
05-19-14, 06:55 PM
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One other consideration.
You're running a short cage derailleur which typically has a capacity of 27 teeth or so (didn't look it up, left that to you), with a combination that calls for a take up of 32t. (18+14). There's usually some fudge room and you might get it to work with very careful balance of chain length and B-screw setting, but you're pushing the limits and may not succeed.
One trick you might try if you're right on the edge, is to use a larger pulley in the lower position. This incrases the take up capacity by a tooth or so, and if you're right at the edge might do the trick.
Otherwise, the easy answer is a medium cage RD, which has far more latitude.
You're running a short cage derailleur which typically has a capacity of 27 teeth or so (didn't look it up, left that to you), with a combination that calls for a take up of 32t. (18+14). There's usually some fudge room and you might get it to work with very careful balance of chain length and B-screw setting, but you're pushing the limits and may not succeed.
One trick you might try if you're right on the edge, is to use a larger pulley in the lower position. This incrases the take up capacity by a tooth or so, and if you're right at the edge might do the trick.
Otherwise, the easy answer is a medium cage RD, which has far more latitude.
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FB
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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.
05-19-14, 08:15 PM
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Good luck!
05-19-14, 08:42 PM
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It's a 30t cog, not 32t the bike came from Trek with a 12-30 cassette, I just changed out the crank from compact to standard, as stated above.
05-19-14, 08:45 PM
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Yes, it's a 3t0 sprocket, but a 12-30 combined with 39-53 = 18+14 = 32 teeth take up capacity required, 5 more than the 27t? capacity of the RD.
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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.
FB
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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.
