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Chainring switching

Old 03-05-18, 07:51 AM
  #1  
Gummomarx
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Chainring switching

Hello comrades!

On switching between chainrings, I can go to 2 and 3 in the normal way.

However, if I'm on 3 and I want to go to 2 - I must go straight to 1 and up to 2 again.

Help!


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Old 03-05-18, 08:03 AM
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When shifting to a smaller chainring on a low normal derailleur it is only spring tension pulling on the cable that allows the shift. So first check for excess friction in the cable/housing.
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Old 03-05-18, 08:45 AM
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We don't know if the problem is in the shifter pod or at the ft der and rings. can you move the ft der with only tugging on an exposed section of cable? Will the ft shift well with only the cable being pulled by hand? If the cable is loosened and removed from the anchor bolt and then the cable is held in your hand will it move by using the shifter into and out of all three shifter positions? Andy
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Old 03-05-18, 10:52 AM
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Basics; Cable pulls 1 way, a return spring pulls back.
friction in the cable housing can resist the force of the return spring enough to make it work poorly.
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Old 03-05-18, 11:03 AM
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Not mentioned is that the chain will resist shifting when under tension. Unlike the rear that can be shifted under power, the front requires that you ease up a bit to allow the chain to lift over the teeth and shift.

Another factor might be as simple as poor trim. It's possible that the FD i9s trimmed outboard a bit, so it doesn't move inward enough to begin the shift on it's own, until you overshift to low then can come back.

If your bike has a cable adjuster for the front, ease up the cable tension a hair and see if that improves things. If so, continue to adjust cable tension until the crispness both of up and down shifting are OK.

BTW - if your bike does not have a cable adjuster, this might be a good time to install an inline adjuster for the FD
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Old 03-05-18, 03:25 PM
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Originally Posted by Gummomarx View Post
Hello comrades!

On switching between chainrings, I can go to 2 and 3 in the normal way.

However, if I'm on 3 and I want to go to 2 - I must go straight to 1 and up to 2 again.

Help!
Your post isn't very clear to me (but it may be to others). For my own edification, are you saying that when you're on 3 (the big ring), and you try to downshift into 2 (the middle ring), the derailleur will move, and try to drag the chain over, but it doesn't quite move enough to complete the shift? It'll only complete the shift if you shift it down in to 1 (the small ring), at which time the chain does indeed jump all the way down to 1, and then you can upshift back to 2?

If that is the case, then it sounds like your front derailleur is not in perfect adjustment. This assumes that you've checked things like proper spring tension, proper cable travel and shifter function as mentioned by others above. If all of that checks out, Park Tool has an excellent video series on adjusting derailleurs. Here is a direct link to their front derailleur video:


I would recommend against skipping any steps. Walk through the whole thing, because Calvin shows you how to verify the fit and function of just about every variable. There could always be outlying odd factors at play in your particular case, but I suspect some tuning on the adjustment will get it working again.
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Old 03-05-18, 03:38 PM
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Suggestions: do everything you can to minimize friction. Oil (perhaps with Tri-Flo or the like) all the pivots in the derailleur body. There are at least 4 and maybe as many as 8. Make sure the cable runs smoothly inside the housing with no kinks, especially where the cable goes into or emerges from the housing, the pod and the derailleur. See to it the pod is operating smoothly. Also see to it the cable isn't too tight. Try backing off just a touch. You will have a barrel or nut on the cable run, either at the pod or the derailleur (usually. Do loosening by very small amounts, then ride and test your shifts. Loosening will make shifting back up more difficult and may not be the right answer here. (This advise overlaps with FBs. Follow his advise also.)

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Old 03-06-18, 04:24 AM
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Thanks very much for your kind suggestions - plenty to be getting on with.
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Old 03-08-18, 05:56 PM
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Originally Posted by FBinNY View Post
If your bike has a cable adjuster for the front, ease up the cable tension a hair and see if that improves things. If so, continue to adjust cable tension until the crispness both of up and down shifting are OK.
That worked - thanks!
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Old 03-08-18, 06:59 PM
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IF you have not done so already it's still a good idea to make sure the cable is moving smoothly.
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Don't tell me what "should" be - either it is, it isn't, or do something about it.

If you think I'm being blunt take it as a compliment - if I thought you were too weak to handle the truth or a strong opinion I would not bother.

Please respect others by taking the time to post clearly so we can answer quickly. All lowercase and multiple typos makes for a hard read. Thanks!
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