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Old 08-01-05, 01:17 PM   #1
SaddleBags
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FD Rubbing on Middle Chainring (triple)

I've done some searching on adjusting the FD and the H & L screws and those cable twisty devices for cable tension. I've looked at the Park Tool site and Sheldon Brown's site too. And I know that you should get some chain rub if you are on the largest chainring and the smallest cog, right? However, I'm experiencing some rub from my middle chainring (42) to my 12, 13 & 14 sprocket. Is this normal? How can I fix this? Cable adjustment? H&L screws? (For what it's worth, the rub still occurs when i have the bike in the stand and not putting too much pressure on the cranks)

Here's my setup:
Ultegra FD & RD 6600 (just replaced my Tiagras)
Truvativ Elita Triple (30/42/52)
Shimano 12/25

Also, please correct me if my terminology on the gizmos I mentioned are incorrect.
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Old 08-01-05, 01:27 PM   #2
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You say you just replaced the derailleurs - maybe the FD isn't quite high enough?
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Old 08-01-05, 01:31 PM   #3
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The H&L screws are irrelevant to the middle chainring. Make sure the front derailleur cage is aligned parallel to the chainrings and just high enough to clear all of the teeth by 1-2mm. Is your front shifter indexed? That could be a big part of your problem, as friction and/or quasi-indexed systems permit some feathering of the cage position, and its sounds as though you want your cage to sit a bit farther outboard in the offending gear combinations. Tightening the cable may help.
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Old 08-01-05, 01:38 PM   #4
SaddleBags
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Quote:
Originally Posted by John E
Is your front shifter indexed?
I don't know - they're Tiagra shifters ('04).
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Old 08-01-05, 03:08 PM   #5
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Quote:
Originally Posted by SaddleBags
I've done some searching on adjusting the FD and the H & L screws and those cable twisty devices for cable tension. I've looked at the Park Tool site and Sheldon Brown's site too. And I know that you should get some chain rub if you are on the largest chainring and the smallest cog, right? However, I'm experiencing some rub from my middle chainring (42) to my 12, 13 & 14 sprocket. Is this normal? How can I fix this? Cable adjustment? H&L screws? (For what it's worth, the rub still occurs when i have the bike in the stand and not putting too much pressure on the cranks)

Here's my setup:
Ultegra FD & RD 6600 (just replaced my Tiagras)
Truvativ Elita Triple (30/42/52)
Shimano 12/25

If the chain rubs on the derailer cage, it is an indexing adjustment, which is mainly done with the cable tension adjusting barrel. Could also be related to incorrect placement where the derailer clamps to the seat tube...too high, or rotated too far clockwise in the yaw axis.

if the chain rubs on the inside of the 52 tooth chainring, this might be a chainline issue. Get a ruler and measure the chainline (should be about 45 mm for a Road Triple).

If you're not sure how to do this see: http://sheldonbrown.com/chainline

It's also possible that your frame is bent. See: http://sheldonbrown.com/frame-spacing for an easy way to check this.

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