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-   -   Front derailleur post-shift "rebound" (https://www.bikeforums.net/bicycle-mechanics/625997-front-derailleur-post-shift-rebound.html)

norbikes 03-04-10 12:03 PM

Front derailleur post-shift "rebound"
 
Am hoping someone can provide an explanation and solution for f. der. post-shift "rebound". That is, when I shift from the small ring to the big ring the der. cage duz not stay in its outermost position, but moves inboard a bit, causing chain rub when I'm on the outermost rear cogs. Is the front shifter worn out, or is there an adjustment to solve this...? The front shifter is a D-A double brifter, the f. der. an Ultegra.
Thanx!

helicomatic 03-04-10 12:16 PM

It's normal, your cable is probably just slack.

It moves out farther during the shift to make the front indexed shifting just that little bit nicer.

HillRider 03-04-10 12:34 PM

The extreme outward movement of the cage is controlled by the high limit screw. The cage's position once you release the shift lever is controlled by the shifter and the cable tension.

If the shifts are clean and the chain doesn't want to "spill" to the outside, your high limit screw is set properly. If, after the shift, the cage "relaxes" back too far, increase the cable tension with the barrel adjuster.

Al1943 03-04-10 12:36 PM

It's not normal and you may have too much cable tension.
When on the smallest chainring there should be little if any cable tension.
Try the derailleur setup instructions found at http://www.parktool.com

Al

HillRider 03-04-10 01:09 PM


Originally Posted by Al1943 (Post 10480620)
It's not normal and you may have too much cable tension.
When on the smallest chainring there should be little if any cable tension.
Try the derailleur setup instructions found at http://www.parktool.com

Al

Actually a small amount of rebound it is normal. The OP has problems with shifting TO the big ring so the cable tension is inadequate. He shouldn't overdo the cable tension or he will indeed make the shift to the small ring problematic

Al1943 03-04-10 01:37 PM


Originally Posted by HillRider (Post 10480764)
Actually a small amount of rebound it is normal. The OP has problems with shifting TO the big ring so the cable tension is inadequate. He shouldn't overdo the cable tension or he will indeed make the shift to the small ring problematic

I don't know if the cable has too much tension but I think it may, and that can cause a rebound. If I could work on it I'd try changing the tension one way or the other and see what works.
I had not seem your post when I made mine.

Cheers,
Al


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