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Shimano triple front derailleur will not shift to large sprocket

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Shimano triple front derailleur will not shift to large sprocket

Old 08-21-19, 07:00 PM
  #1  
jacksbike
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Shimano triple front derailleur will not shift to large sprocket

Hi Folks,

I need some mechanical advice. I am working for a non profit bike group and have run into a problem with a Trek or Gary Fisher mountain bike. It appears to have a Shimano C050 , possibly Allivio, front derailleur that clamps on the seat tube just above the bb, with the derailleur cage above the clamp. So, it appears to be a top swing cage, since there is no evidence of a bb cable guide. There is a black plastic cable routing piece next to the vertical cable clamp. So it appears that the cable comes down from the top tube and attaches straight to the clamp, cirucumventing the entire black plastic routing piece. I cannot get the left triple shifter ( a Shimano shift/brake combo) to shift the cage up to the largest sprocket. There is a new cable, the shifter will click up to the #3 high position, the L and H adjuster screws are OK- but no go. All other parts - crankset, shifters, rear derailleur appear stock with the bike. I tried running the new cable around the black routing piece but absolute no go. Can't figure this one out.

?Not enough tension on the cable wire through the shifter tension adjuster piece ? Wrong front derailleur ? Help !
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Old 08-21-19, 07:29 PM
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andrewclaus
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That sounds like a dual pull set-up. With top pull, you don't use the pulley.

Have you tried manually pulling the cable, see if you can get it to shift?

If the high limit is adjusted all the way out and it's not shifting, maybe the chain line was messed up with an improperly sized bottom bracket or spindle. Does it look like excessive clearance between the crankset and the chain stay?
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Old 08-22-19, 05:19 AM
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jacksbike
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Hi
Yes, when you pull the wire on the top tube by hand it does shift up to the large sprocket. Will check the shifter, bb,etc, again today.
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Old 08-22-19, 06:22 AM
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andrewclaus
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I think the best way to diagnose shifting problems is to check all components separately. As obvious as this sounds, it seldom gets done. An easy way is to manually shift into the large chain ring, stop pedaling, click the shifter into low, then you should be able to pull a cable housing out of a slotted frame stop. Now everything is separated and you haven't messed up the current cable adjustment. You can move housings to inspect and clean the cable, manually check limit screws, and check the shifter operation with no load on it.

Make sure your shifter is making two firm clicks with an equal pull on the cable.
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Old 08-22-19, 09:44 AM
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Has the shifter been replaced. Have you inspected it for issues?
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Old 08-22-19, 09:51 AM
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The derailleur is meant for flat bar shifters not road brifters. The cable pull is different. Don't ask me how I know that.
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