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Bicycle Mechanics Broken bottom bracket? Tacoed wheel? If you're having problems with your bicycle, or just need help fixing a flat, drop in here for the latest on bicycle mechanics & bicycle maintenance.

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Old 04-25-11, 03:01 PM   #1
dynne
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Correct front derailleur/chain length for vintage touring rebuild?

I'm rebuilding an old touring frame, and I've got most everything good to go - except for the front derailleur. I'll need one that will attach onto the 28.6 tube and isn't clamp-on. I assumed that since the front derailleur will be running friction, whatever road triple I had sitting around would work. But, as we all know, nothing with bikes is ever this simple.

Relevant info:
Running Ultegra road triple (52-42-38?) with 11-32 9 speed cassette.
Using Dura-Ace 3x9 barcons.
Rear derailleur is Shimano LX (was advised would be better than 105)

The problem: Need RD that doesn't take clamp-on, 28.6 seems an odd size. The Tiagra road triple I hoped to use looks to be too wide.

What would be the best choice for a front derailleur? Shim the Tiagra? Use a mountain triple?

Additionally, once I've got that one up, how long should I trim the chain for? I don't foresee running 52-32, so is the typical rule of chain length measurement out the window?

I apologize if this has been covered in other threads, but since I had two problems simultaneously, I figured I would consult the experts directly. Thanks so much for your time.

Can't wait to get this baby on the road.
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Old 04-25-11, 03:30 PM   #2
operator
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For the FD.

Don't bother finding the right clamp size if it's a pain in the ass. Get the braze on version and a braze-on adapter. FD-6503 is what you want.

Chain length should be sized using the big/big + next closest link method. It doesn't matter if you don't use the 52 + 32 combo. If you cut the chain for something smaller, your derailleur blows up.
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Old 04-25-11, 04:20 PM   #3
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http://www.parktool.com/blog/repair-...-length-sizing

Quote:
SIMPLE EQUATION: L = 2 (C) + (F/4 + R/4 + 1)

L = Chain length in inches. Round the final result to closest whole inch figure.
C = Chain stay length in inches, measure to closest 1/8”.
F= Number of teeth on largest front chainring.
R= Number of teeth on largest rear cog.
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