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I'm attempting to setup my front derailleur. I've slackened off the cable, adjusted the L screw so the derailleur just clears the chain. What position should the adjusting barrel on the handles be set to and how tight should I pull the cable before tighten it to the derailleur?

I seem to be getting rub in the middle gear at the front, but no run on the top and bottom cog.

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It's not a matter of "tension". Study the shifter and the derailer and note that the derailer limit screws control where the derailer stops directly over the innermost and outermost cogs. You initially (after setting the limit screws) clamp the cable (with the barrel adjusters screwed all the way in) so that there's (almost) no slack with the lever all the way in the slack direction, then adjust the barrel adjuster to hit the middle cog correctly. Sheldon Brown and Park Tool will both have good descriptions of this process. –  Daniel R Hicks Jul 17 '13 at 20:02
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There's not a set, single tension that works for all bikes. It's just trial and error.

You need to pull it pretty tight before clamping it to the derailleur. Probably as tight as you can. Usually I find that's still not tight enough, so I screw the barrel adjuster down all the way before putting the cable in and then open it up until the tension is correct.

Assuming that you do in fact have everything else set up correctly: if the derailleur is rubbing on the outside of the chain, you need a little more tension. If it's rubbing on the inside, you need a little less.

Also, if you've swapped any parts out, you may be having some compatibility issues. Derailleurs have minimum and maximum chainring sizes. If you're just a smidge over or under those sizes, you're almost sure to get some rubbing.

If you can find it, it wouldn't be a bad idea to look at the owner's manual for your particular derailleur.

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Thank you for the info. Any idea what would cause the chain to rub on the derailleur only on the middle cog? All the parts are original to the bike –  totalitarian Jul 17 '13 at 19:47
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@totalitarian -- Sounds like the barrel adjuster is not adjusted correctly. For the front derailer it ONLY affects the positioning for the middle cog. –  Daniel R Hicks Jul 17 '13 at 20:04
    
Thank you. I will give it a go –  totalitarian Jul 17 '13 at 20:07
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