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chain rubbing on inside front derailler

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chain rubbing on inside front derailler

Old 03-16-09, 05:13 PM
  #1  
Butterthebean
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chain rubbing on inside front derailler

Need a little help. All of my bikes are friction shift so this is not usually a problem for me. My wife wanted a bike set up with these shifters....



8 speed triple. The front crankset is 52-42-30. Front derailler is sora triple.

From above, the derailler looks perfectly lined up with the chainrings. It shifts just fine from small to middle and from middle to large. But while in the middle chainring, the chain rubs the inside of the derailler cage on the smallest 3 cogs. Now I know I can't cross chain too much, but I ought to be able to use those combinations with no problem.

Does this have anything to do with cable tension? My front derailler cable is pretty slack when on the smallest chainring. Here's a pic showing the slack...



The front shifter has one of those extra indents below the "1" when you let the cable all the way out. You click to the "1" and the cable gets taught. You click again to the "2" and you shift to the middle chainring with no problem. When you hit the trigger to go back to "1", the shifter falls all the way past "1" to the previous indent. The chain falls to inner chainring with no problem...not sure if I got this cable set up right for this kind of shifter...

here's my cable routing...



In this pic, you can see how slack it is with the shifter in the pre indent...but if you push the thumb shifter half a click to the "1", it trims it up nicely. Unfortunately, there are no more pre indents after this one....there is just 1,2 and 3...so no trimming...

Any advice would be appreciated.
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Old 03-16-09, 05:44 PM
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calyth
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Are you sure those shifters are compatible with the Sora FD?

AFAIK, the shifters determines the correct pull to shift the FD into the correct place to minimize rub.
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Old 03-16-09, 06:10 PM
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Originally Posted by calyth View Post
Are you sure those shifters are compatible with the Sora FD?

AFAIK, the shifters determines the correct pull to shift the FD into the correct place to minimize rub.
They are the Shimano ST-R222 Shift/Brake Levers. I bought them from Universal Cycles a while ago on clearance. I thought they were flatbar road bike shifters. The brake levers work perfectly with my caliper brakes. I can't find any info on them now. If they are mountain bike, then I guess I need to put a mountain bike rear derailler on there...right?

BTW...what does AFAIK mean???

Last edited by Butterthebean; 03-16-09 at 06:15 PM.
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Old 03-16-09, 06:25 PM
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Maybe I'm missing something but if you are rubbing the cage when on the small cogs and the middle chainring, you need a bit more tension on the cable. This should pull the cage a bit further out which should eliminate the rub. I would think you could get it adjusted to hit all of your cogs from the middle chain ring with no rubbing. On a triple, the large and small ring adjustments are the limit screws and the middle ring is cable tension.
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Old 03-16-09, 06:26 PM
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It sounds like you have not set your low limit screw on the derailler and are instead relying on cable tension to position your front derailler over the little chainring.

To set the low limit screw, get your chain on the little chainring and biggest rear cog. Turn the low limit screw until you have about 1-2mm of clearance between the chain and derailler cage. The reconnect the cable and try to shift into the middle ring. You'll probably need to add some tension at this point to get the shift to complete. Add tension until the chain shifts quickly from one ring to the next keeping in mind that the tension you add is what positions the derailler over the middle ring.

If you get rubbing using the smallest cogs, add tension. If you have rubbing in the largest cogs, remove tension. You'll likely end up having to compromise on one end or the other though.
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Old 03-17-09, 09:23 AM
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Originally Posted by CACycling View Post
Maybe I'm missing something but if you are rubbing the cage when on the small cogs and the middle chainring, you need a bit more tension on the cable. This should pull the cage a bit further out which should eliminate the rub. I would think you could get it adjusted to hit all of your cogs from the middle chain ring with no rubbing. On a triple, the large and small ring adjustments are the limit screws and the middle ring is cable tension.
That was it. A few turns of the barrell adjuster and it quit rubbing. Thanks.
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