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Braze-on front derailleur alignment

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Braze-on front derailleur alignment

Old 11-17-07, 02:29 AM
  #1  
gazer
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Braze-on front derailleur alignment

I'm having issues getting good alignment out of my front derailleur (triple, braze-on).

It's a low-end Shimano (R443), and the rear/tail of the cage is the closest to the chainrings. I'm used to the top of the derailleur being closer to the chainrings. As a result, I have to raise the derailleur ridiculously high so that the back of the cage doesn't rub the chainring when I'm on the middle chainring. With such a gap between the top of the chainring and the front part of the derailleur, shifting is pretty poor.

Is this a problem with the derailleur or my braze-on? Any way to fix it?


thx.
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Last edited by gazer; 11-17-07 at 02:48 AM.
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Old 11-17-07, 04:55 AM
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It isn't hard to bend the braze-on to correct for a minor mis-adjustment like that.
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Old 11-17-07, 07:56 AM
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I'm not familiar with that model fd but if it's intended for MTB or Hybrid use with relatively small chainrings (say 44/34/24) and you are using it with a road crank (52/42/30) then the cage curvature will be too sharp to match the large chainring and you will have to space it too far away as you have done.
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Old 11-17-07, 09:20 AM
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You are right HillRider but not many Bike Fridays are set up for running small chainrings and that mech is designed for road triples.
http://techdocs.shimano.com/media/te...9830605977.PDF
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Old 11-17-07, 04:13 PM
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Originally Posted by LWaB View Post
It isn't hard to bend the braze-on to correct for a minor mis-adjustment like that.
Hmm, I'm a little hesitant to try that - I'd need to rotate the braze-on in the plane of the picture, and I'd be fighting the weld there (as opposed to bending it around the seat tube). No?

Last edited by gazer; 11-17-07 at 04:21 PM.
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Old 11-17-07, 05:26 PM
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Originally Posted by LWaB View Post
You are right HillRider but not many Bike Fridays are set up for running small chainrings and that mech is designed for road triples.
http://techdocs.shimano.com/media/te...9830605977.PDF
If it's a Bike Friday road bike, they often come with 62T big rings to compensate for the small wheels. The same problem then occurs using a road fd intended for a 52 or 53T big ring with a 62T ring. The cage curvature is too tight.

Break out the Dremel. Another possibility is to shim the braze-on tab at the lower front edge where the the fd bolts to it to tilt the tail away from the chainring.
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Old 11-17-07, 06:11 PM
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Originally Posted by HillRider View Post
If it's a Bike Friday road bike, they often come with 62T big rings to compensate for the small wheels. The same problem then occurs using a road fd intended for a 52 or 53T big ring with a 62T ring. The cage curvature is too tight.
Good eyes on being a Bike Friday. Unfortunately, it's a 52T big ring. (9 on the rear!)

Still, I like the idea of dremelling the derailleur... Glad it's not Dura-Ace.

Thanks.
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Old 11-17-07, 08:28 PM
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Originally Posted by gazer View Post
Hmm, I'm a little hesitant to try that - I'd need to rotate the braze-on in the plane of the picture, and I'd be fighting the weld there (as opposed to bending it around the seat tube). No?
You only actually need a few degrees to make a big difference and the extra-long braze-on that Bike Friday use is more pliable than a standard cast Campag braze-on. You aren't going to break the weld (what holds the rest of your bike together?). Removing too much metal from the cage could reduce stiffness and shifting crispness.

I expect the braze-on/front mech got tweaked in transit. It is less likely that Bike Friday brazed it in the wrong position.

It is your call and I can't see the problem in the metal, so suit yourself regarding a repair but I've cold-set front braze-ons previously without hassles.
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Old 11-17-07, 08:52 PM
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Iv'e found these rules/tricks help on almost any front derailleur: The outer plate shoud be parallel with the chainring, ( look down). The bottom of the outer plate should clear the outer chainring 2 to 3 mm, (look from side). If you can't shift well to the outer without overshift- try bending the outer plate, with a small crescent, so that the bottom of the plate is slightly inboard of the top,(that helps keep the chain from shifting off and you my need to grip more than one spot), and/or bend the front tip of the inner plate toward the chain slightly

Last edited by pat5319; 11-17-07 at 08:53 PM. Reason: spelling/typo
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Old 11-18-07, 11:39 AM
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Yeah, I'm not sure I wouldn't rather bend the cage than the mount.

IMO the best solution is the proper dérailleur.
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Old 11-18-07, 03:10 PM
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From the look of the photo the trailing edge of the dérailleur cage is closer to the big ring than the front of the cage by several mm's. Is this correct? For a start I'd lower the dérailleur until the rear cage is about 1mm above the chain ring - looks like it's 5mm above right now. If you still have shifting issues, remove the dérailleur and using a large crescent wrench, tweak the brazeon a little. Shouldn't hurt anything if the brazing is sound. Worse thing that can happen is the hanger cheeses off which will be no loss - you can go with a clamp on.
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