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Freewheel skipping the middle ring on upshifts

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Freewheel skipping the middle ring on upshifts

Old 01-15-18, 11:13 AM
  #26  
dddd
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Originally Posted by palincss View Post
A bigger issue is that some double front derailleurs won't swing out far enough to fully reach the big ring enough to actually complete a shift. You can live with needing to trim when running cross-chained, but you really can't live with the chain not staying on the big ring.

Yes, and much like when using old rear derailers (such as Prestige or Allvit) with six speed freewheels, the position of the chainrings or freewheel cogs needs to be "centered" within the travel range of the cage.

I can usually find big increases in cross-chaining clearance by use of a narrower chain, and use of a Shimano HG chain (with it's typically more aggressive tooth-grabbing character) similarly can often shift to the furthest reaches of a wider (laterally wider) stack of cogs or chainrings.

Bending every third tooth of the big chainring a half-mm to the left can get the most upshifting effect out of the front derailer's limited outward throw, and slightly beveling the outer side of the big ring's teeth (by holding a file against the rotating chainring's teeth) helps the chain stay on the big ring.

I often also achieve a bit of extra high-gear running clearance with the chain by spreading the outer cage plate outward (just behind the cage bridge) using the plier below by placing the tips within the cage and pulling the handles apart.
One does not want to flare the lower end of the cage in the process, and the front edge of the outer cage plate should then be bent inward for chain control just short of where it would actually contact the chain while in the big ring.
The (usually thicker/stiffer) inner cage plate can also be bent outward at it's forward tip to assist with upshifting, which can really speed things up when there is some clearance to play with (usually the case).


Last edited by dddd; 01-15-18 at 11:36 AM.
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Old 01-15-18, 11:46 AM
  #27  
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On vintage road triples, usually double FD are better. I can't remember exactly when triple specific FD were introduced, but originally there was no such thing. Believe it or not. Only concern was that it had enough swing and that the chain didn't drag on the back of the cage when in the small chainring.

An older triple FD is may work, but as previously mentioned, today's modern MTB FD will not work on anything other than a very specific tooth count triple.
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Old 01-15-18, 12:18 PM
  #28  
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Originally Posted by Salamandrine View Post
On vintage road triples, usually double FD are better. I can't remember exactly when triple specific FD were introduced, but originally there was no such thing. Believe it or not. Only concern was that it had enough swing and that the chain didn't drag on the back of the cage when in the small chainring.

An older triple FD is may work, but as previously mentioned, today's modern MTB FD will not work on anything other than a very specific tooth count triple.
There's definitely that.

When I started setting up my Trek 720 10 speed- I wanted to go all Dura Ace 7800 Triple with a Sugino AT triple. I got a long cage 7803 rear and a triple 7803 FD. I could not get the FD to work reliably. In the end I used a 7700 double FD and it works fantastically.

I've never had trouble with old ATB FDs at all. If the user is going with a Euclid RD and he's not too tied to matchy-matchy stuff- you could try a simple regular double FD. Otherwise a stylish Mountech FD.
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Old 01-16-18, 01:17 PM
  #29  
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Any chance he can post a video (from multiple angles) of what is happening?
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Old 01-16-18, 10:46 PM
  #30  
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Originally Posted by The Golden Boy View Post
There's definitely that.

When I started setting up my Trek 720 10 speed- I wanted to go all Dura Ace 7800 Triple with a Sugino AT triple. I got a long cage 7803 rear and a triple 7803 FD. I could not get the FD to work reliably. In the end I used a 7700 double FD and it works fantastically.

I've never had trouble with old ATB FDs at all. If the user is going with a Euclid RD and he's not too tied to matchy-matchy stuff- you could try a simple regular double FD. Otherwise a stylish Mountech FD.
For sure. I'm kind of against matchy matchy at this point.

I wonder if he has a Euclid front derailleur too? Euclid is a little fuzzy in my mind, as it's been so long since I worked on the stuff. Technically euclid was an old ATB FD. They were rare, and IIRC kind of clunky compared to the Japanese offerings of the time. That era was sort of a nadir for campy. The build quality was there, but they were a little behind on mountain bike tech. Still, should work better than missing the middle chainring entirely. I still suspect the inner is on backwards.

FWIW I really really like the modern Shimano CX70 FD with my pseudo old ATB bike (Clem) triple crankset. For that matter I really like it on the compact double (50/34) on my Mercian. Great FD for not much $.
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Old 01-17-18, 07:44 AM
  #31  
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Originally Posted by Salamandrine View Post
For sure. I'm kind of against matchy matchy at this point.

I wonder if he has a Euclid front derailleur too? Euclid is a little fuzzy in my mind, as it's been so long since I worked on the stuff. Technically euclid was an old ATB FD. They were rare, and IIRC kind of clunky compared to the Japanese offerings of the time. That era was sort of a nadir for campy. The build quality was there, but they were a little behind on mountain bike tech. Still, should work better than missing the middle chainring entirely. I still suspect the inner is on backwards.

FWIW I really really like the modern Shimano CX70 FD with my pseudo old ATB bike (Clem) triple crankset. For that matter I really like it on the compact double (50/34) on my Mercian. Great FD for not much $.
I'll confirm that his granny ring isn't backwards--don't think I did that before.
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Old 01-17-18, 07:55 AM
  #32  
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What sort of shifting is he using (and what I'm curious to know is whether it is indexed, or friction)? If it is indexed, a slight adjustment to the cable length (quarter to half turn of the barrel adjuster) might solve everything.
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Old 01-22-18, 05:08 AM
  #33  
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One other overlooked area that has been mentioned with this issue on CR is what type of chain is being used? 7-10 speed chains are much more flexible and can be shifted over quite a ways before they actually pick up on the front chainrings. What was suggested is to use chains much more suited to 5 to 6 speed (stiffer and maybe thicker - 7-10 speed chains tend to be bushingless and thinner in width) that will not give so much when shifting, and move over perhaps more precisely.

I have a similar setup on my Italvega, using a Campagnolo factory triple 52-42-31 Merz ring with a Campagnolo Nuovo Record FD. Shifting from the small ring to middle ring sometimes results in a direct shift to the 52, which then is compensated by backshifting down to the middle ring, usually almost in one motion (very common method of shifting Campagnolo Nuovo Record rear derailleurs). I have been using a KMC Z51 6 & 7 speed chains which might be a tad too flexible. Some have recommended the appropriate Sedisport or SRAM chains instead.
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Old 01-22-18, 08:36 AM
  #34  
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I don't think any derailleur tweaks will help until that 55 ring is replaced with a 50 or 48. When looking from above shifting up from the smallest chain ring as the chain gets pushed right it will completely miss the middle chain ring and contact the large chain ring first instead. The middle chain ring is in the shadow of the the large chain ring.

It's not a problem when shifting the other way, the chain just drops onto the next ring. But for going to a larger ring the chain has to be able to contact another ring, grab a tooth, and climb out of the lower gear.
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