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Braze-on derailleur mount is too low

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Braze-on derailleur mount is too low

Old 08-18-21, 01:51 PM
  #26  
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Originally Posted by Doug Fattic View Post
Braze-on front derailleurs vary a lot in where the attaching bolt is in height above the bottom bracket. This is one reason I gave up using front derailleur braze-ons (as well as the reason JDT mentioned already). I remember a new model of a Dura Ace front derailleur needed to be 4 mm higher than the last model. So one answer is to look for a different model front derailleur. As a frame builder I would look closely at the boss and perhaps take a file to the slot to make it a bit longer going higher (and perhaps it needs to be widened too?).
Actually if it was on my workstand I would look at the backside of the braze on mount, to review the uniformity of that trough.
Note First generation Campagnolo Corsa Record front mechanisms had their point point at the near Bottom of the body!?! That would be one way to solve the problem.
Campagnolo soon enough modified that. But they are out there.

timeline note, investment cast braze on mount parts were a mid 80's thing.
early 80's and it was stamped steel, also pre SLX and lots of flex, never liked them as a mechanic.
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Old 08-18-21, 01:54 PM
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Originally Posted by Road Fan View Post
I agree with Doug Fattic, some re-shaping of the slot should be possible. I had this on one frame of mine. It looks (from the front side) like your slot is narrower at the top than the rest of the slot, certainly at the middle. I would try to widen the slot so the curvature at the top of the slot matches the curvature of the threaded area of the derailleur clamp bolt. Needs to be done delicately to prevent marring the paint.

I could see trying that minor surgery with a round file which matches the bolt, or a tapered hand reamer. Both tool types can be extremely helpful or cause irrevocable damage, so go carefully. In both cases you're going to expose some steel, so you need to find some method of touch op to restore protection of the underlying steel.

This ignores whether there is an additional blockage on the concave side of the braze-on, perhaps caused by brazing material. I would take a look at that. If that's the problem I'd look for a real expert like Doug to approach the problem. If there is a blob and it is forcing your front mech to move downward as you snug up the bolt, there should be some kind of witness mark on the derailleur mounting surface itself, indicating that the softer aluminum has "lost a battle" with the harder steel or perhaps braze material.

Doug, are small frame braze-ons like this for steel frames case-hardened? My guess would be no, but if they are then amateurs like me should ot even do a careful trimming of the slot.
Investment cast, which has a reputation for being harder to file than stamped parts.
Think about it, case hardened then heat it up to silver or bronze melting point, bye bye the heat treating.
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Old 08-18-21, 01:57 PM
  #28  
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Originally Posted by karldub View Post
Thanks for all the good input! I went with idea of using a file (flat) and made the area on the bolt side of the derailleur flatter, this made the derailleur stay up higher when the bolt is seated.

The next problem (which I've never encountered with clamp-on derailleurs) is that the derailleur won't shift to the big cog even the shifting action is manually moved by hand. See video on this below.


Link to video of shifting attempt. https://vimeo.com/588746743 . Do you see anything strange with my set-up and do you have any ideas what is causing the issue? List of some possible causes:
1) The mounting of the derailleur gives the derailleur cage a faulty angle
2) This derailleur and frame/clamp combination can't handle the size of the largest chainring (Big one is 52t, the small is 40t) or the tooth difference between them
3) Other causes
check the chainline. the virtual line in between the front rings should pass through the middle of the rear cog array. a good straight edge should tell the tale.
if the rings are too far outboard, cannot catch the big ring.
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Old 08-18-21, 02:35 PM
  #29  
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Looks like the angle, which makes the derailleur cage hit the outer ring before it has lifted the chain onto it.

Bend and try again.
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Old 08-19-21, 07:22 AM
  #30  
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Hand Fitted

Originally Posted by SurferRosa View Post
Rotary tool?

50t ring and smaller rear cog?

Drew?
Bout fell out of my chair! HaHaHa!

I have a few bikes with brazed on FD mounts. My problem has been in the opposite direction... I like 48-49-50T large chainrings so the FDs need to be at the bottom of the mount.

Lots of good suggestions above but one thing that I haven't seen mentioned: the bottom edge of the derailleur cage should be about 1-3mm above the top of the large chainring teeth. Also as mentioned several times above, the cage should be parallel to the chainring too.

The way the cage is pictured you'll never get the chain to lift up onto the large chainring.



I had to bend both the derailleur cage and the braze on mount to get the proper angle and clearance on my De Rosa. Note how the cage has been bent to lower the rear.



Cage parallel to chainring.



WORD OF CAUTION: use care when bending the braze on mount. Filing is safer.

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Old 08-19-21, 12:04 PM
  #31  
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Originally Posted by verktyg View Post
One thing that I haven't seen mentioned: the bottom edge of the derailleur cage should be 1-3mm above the top of the large chainring teeth.


Also ... the cage should be parallel to the chainring.
I use the travel of the arm instead of the chainring to position the angle of the front derailleur. I feel like that's more "exact." This has always worked for me, and I avoid any part of the derailleur hitting the arm (or chain) when tolerances are very narrow in the biggest gear. This seems to be more crucial on older bikes from the '60s and '70s with narrow cages like pre-'80s Campy. For me, on these older bikes, silent and efficient trimming in the big gears is most important.
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Old 11-01-21, 09:20 AM
  #32  
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Thanks for the input! I had to take a break from this, but I found out there was supposed to include a concave washer with this derailleur that lets the angle be adjusted on braze-on type derailleurs (see picture below). This was not included when I purchased it.



However, I can't get a hold of one for under 40 € with shipping, which is about the price of the derailleur itself on ebay. So I might just buy the exact same derailleur (not many other type availible that fit the description Shimano - Double chainring - Chrome - 10x compatible.)

Any input on wether this washer will this solve my issues of the mounting angle?

Best regards,
Karl
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Old 11-01-21, 11:22 AM
  #33  
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Does the FD need to be that specific one? Wouldn't any braze-on FD work there?
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Old 11-01-21, 11:47 AM
  #34  
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I'm open to other derailleurs but all the other parts of the groupset are shimano so it needs to be compatible with indexed STI-Shifters, 2 x 10 (Dura Ace ST-7800) and silver colour to fit the bike. I'm guessing campagnolo won't work because of different cable pull/shift-ratio in conjunction with the shifters?

Also, I'm guessing older derailleurs from the 70's and 80's are probably dimensioned to work better with 6-8 speed casettes?

Any recommendations?
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Old 11-01-21, 11:53 AM
  #35  
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Originally Posted by karldub View Post
Thanks for the input! I had to take a break from this, but I found out there was supposed to include a concave washer with this derailleur that lets the angle be adjusted on braze-on type derailleurs (see picture below). This was not included when I purchased it.



However, I can't get a hold of one for under 40 Ä with shipping, which is about the price of the derailleur itself on ebay. So I might just buy the exact same derailleur (not many other type availible that fit the description Shimano - Double chainring - Chrome - 10x compatible.)

Any input on wether this washer will this solve my issues of the mounting angle?

Best regards,
Karl
Yep, washer is key.

Not sure if anyone has tried this, but for slipping or creeping derailleurs, I have put a thin rubber washer cut to size when I tighten the bolt attaching the FD to the braze on. Also allows me to back off a bit on over torqueing.
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Old 11-01-21, 04:49 PM
  #36  
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Originally Posted by karldub View Post
I'm open to other derailleurs but all the other parts of the groupset are shimano so it needs to be compatible with indexed STI-Shifters, 2 x 10 (Dura Ace ST-7800) and silver colour to fit the bike. I'm guessing campagnolo won't work because of different cable pull/shift-ratio in conjunction with the shifters?

Also, I'm guessing older derailleurs from the 70's and 80's are probably dimensioned to work better with 6-8 speed casettes?

Any recommendations?
If it were a RD then obviously you couldn't just throw any derailleur on there, especially with Dura Ace. Since its a FD and only shifting between two chainrings, the amount of pull much just has to be enough to get it from one to the other and back, something easily done regardless of ratios. If you NEED it to be the exact same group and model number for personal reasons then have at it, but if you care more about functionality then there are a lot of options.
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Old 11-01-21, 05:30 PM
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Not sure where you're located but I've had only good luck with this company. And they have exactly what you need to mount your FD.
I'm new here so I guess I can't post external URLs. Try - universalcycles.com/shopping/product_details.php?id=62651&category=530

Good luck,
Bob
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Old 11-01-21, 05:55 PM
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Originally Posted by degan View Post
If it were a RD then obviously you couldn't just throw any derailleur on there, especially with Dura Ace. Since its a FD and only shifting between two chainrings, the amount of pull much just has to be enough to get it from one to the other and back, something easily done regardless of ratios. If you NEED it to be the exact same group and model number for personal reasons then have at it, but if you care more about functionality then there are a lot of options.
Thanks. When you say easily done, what kind of modification/solution do you mean (if I were to put a campy FD on for example?)
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Old 11-01-21, 05:56 PM
  #39  
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Originally Posted by bob_in_pa View Post
Not sure where you're located but I've had only good luck with this company. And they have exactly what you need to mount your FD.
I'm new here so I guess I can't post external URLs. Try - universalcycles.com/shopping/product_details.php?id=62651&category=530

Good luck,
Bob
Thanks, Iím in Sweden so Iím guessing shipping/import taxes may be steep from there but Iíll check it out.
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Old 11-01-21, 06:40 PM
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Originally Posted by karldub View Post
Thanks, Iím in Sweden so Iím guessing shipping/import taxes may be steep from there but Iíll check it out.
Go to a local bike shop? Maybe they have one or could order one?

Option 2, buy another Ultegra FD, and make sure what parts it has. You can probably recoup most of the extra expense by reselling the rest...?

Option 3, buy a cheaper Shimano braze on FD and cannibalize the part you need...
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Old 11-01-21, 09:07 PM
  #41  
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Originally Posted by karldub View Post
Thanks. When you say easily done, what kind of modification/solution do you mean (if I were to put a campy FD on for example?)
No modifications needed, its just a slotted hole. Most should just work in there as long as its complete. Lots of people go back and forth between brands on the same bike with little issue, even bikes with FD tabs. What I'm getting at is that earlier Ultegra FD (or whatever) can be had for about half of what your thinking of spending on a bolt and washer, if that matters to you.
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Old 11-02-21, 09:32 AM
  #42  
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Hacksaw.
File.
Touch-up paint.
Bolt on front derailleur.

That is, if what you want is best performance out of your front derailleur.

I've yet to braze on a front derailleur hanger, and hopefully never will.
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Old 11-02-21, 09:38 AM
  #43  
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Originally Posted by gugie View Post
Hacksaw.
File.
Touch-up paint.
Bolt on front derailleur.

That is, if what you want is best performance out of your front derailleur.

I've yet to braze on a front derailleur hanger, and hopefully never will.
Yes, now I'm thinking I maybe should've done that in the first place. A bit worried it might damage the frame or leave an ugly scar - have you tried doing this?

Best regards,
Karl
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Old 11-02-21, 10:00 AM
  #44  
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Originally Posted by karldub View Post
Yes, now I'm thinking I maybe should've done that in the first place. A bit worried it might damage the frame or leave an ugly scar - have you tried doing this?

Best regards,
Karl
Not specifically a hanger, but I've removed other brazed on bits with this method. One has to be careful (of course!), use the saw to remove the bulk of the metal, file more along the length of the tube rather than "around and around". That will keep you from accidentally filing into the tube. You might want to use thin tape to mask the area so that a wayward file stroke doesn't nick the paint where you don't want it. When there's just a bit of material left, use a fine file to finish. 80 grit garnet paper in a "shoe shine" action at the end to remove file marks. Your white paint job won't be too hard to match, and with a front derailleur clamped around it, you'll probably be the only person that knows the mod was done.
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Old 11-02-21, 11:02 AM
  #45  
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Originally Posted by karldub View Post
Yes, now I'm thinking I maybe should've done that in the first place. A bit worried it might damage the frame or leave an ugly scar - have you tried doing this?
Yes, I have removed hundreds of braze-ons before I have repainted frames. You weren't addressing me with that question but I am a LOT worried you would damage the seat tube and leave an ugly scar. I bet more than half of my frame building class students would have been unsuccessful hacking the boss off and then filing it carefully so as to not damage the very thin tube it is brazed onto (before they took my class). And it is not all that easy to patch paint so it doesn't look ugly afterwards.

This is how it is likely to go. The derailleur boss is fairly thick metal. It isn't that easy to hack saw it off and get your cut close enough so you are not filing forever. It is normal for those that don't file regularly to get a bit impatient and then hustle a bit faster and then unintentionally file into the tube. And in the unlikely possibility you successfully file off the boss, where are you going to get the 80 grit emery cloth to smooth it out some more? And how much are you willing to spend on touch up paint? If it was my frame, I'd want to apply primer 1st before the color and then the paint needs to be polished out with rubbing compounds so it blends with the surrounding area. So my point is that in my opinion, it is easier to make your boss work than get rid of it.

A braze-on front derailleur can be made to work with the right knowledge and skills. Once you acquire the right concave washer, you might have to file the slot in the boss some more so that the position of the front derailleur is correct. That is a lot easier and less difficult than trying to file it off without damaging your seat tube. I recommend you do these tasks:
1. Learn where the correct position of your front derailleur is supposed to be (start with verktyg's explanation).
2. Aquire the concave washer. They aren't common but not rare either.
3. See if the braze-on boss slot allows the derailleur to be positioned properly and if not:
4. File the slot until it does. I recommend a round file that has a diameter just smaller than the width of the slot.
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Old 11-02-21, 08:07 PM
  #46  
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Originally Posted by Doug Fattic View Post
Yes, I have removed hundreds of braze-ons before I have repainted frames. You weren't addressing me with that question but I am a LOT worried you would damage the seat tube and leave an ugly scar. I bet more than half of my frame building class students would have been unsuccessful hacking the boss off and then filing it carefully so as to not damage the very thin tube it is brazed onto (before they took my class). And it is not all that easy to patch paint so it doesn't look ugly afterwards.

This is how it is likely to go. The derailleur boss is fairly thick metal. It isn't that easy to hack saw it off and get your cut close enough so you are not filing forever. It is normal for those that don't file regularly to get a bit impatient and then hustle a bit faster and then unintentionally file into the tube. And in the unlikely possibility you successfully file off the boss, where are you going to get the 80 grit emery cloth to smooth it out some more? And how much are you willing to spend on touch up paint? If it was my frame, I'd want to apply primer 1st before the color and then the paint needs to be polished out with rubbing compounds so it blends with the surrounding area. So my point is that in my opinion, it is easier to make your boss work than get rid of it.

A braze-on front derailleur can be made to work with the right knowledge and skills. Once you acquire the right concave washer, you might have to file the slot in the boss some more so that the position of the front derailleur is correct. That is a lot easier and less difficult than trying to file it off without damaging your seat tube. I recommend you do these tasks:
1. Learn where the correct position of your front derailleur is supposed to be (start with verktyg's explanation).
2. Aquire the concave washer. They aren't common but not rare either.
3. See if the braze-on boss slot allows the derailleur to be positioned properly and if not:
4. File the slot until it does. I recommend a round file that has a diameter just smaller than the width of the slot.
I guess Doug's message is "don't try this at home. I get that, first time trying to modify a frame you're likely to bung it up. That and my standard for paint matching are far below Mssr. Fattic's
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Old 11-03-21, 06:05 AM
  #47  
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Originally Posted by gugie View Post
I guess Doug's message is "don't try this at home. I get that, first time trying to modify a frame you're likely to bung it up. That and my standard for paint matching are far below Mssr. Fattic's
I'm sure you could do a nice job getting rid of the front derailleur boss. What makes me advise caution for the OP doing the job is my years of experience teaching students how to build frames. The majority need to be taught how to use a hacksaw properly and almost all of them require instruction on the best filing techniques. I spend considerable time in class having them file on rusty tubing until they "get it". Adding to the complexity of the OP doing the filing right is the possibility he won't have the best selection of files to choose from either. And patching the paint well so it isn't an obvious repair requires both special knowledge and materials he is unlikely to have.

I wouldn't be surprised the OP's front derailleur braze on is not in exactly in the right position. They are kind of a pain to set up so the boss is in just the right position before brazing. It always took me a while to set the height, rotation around the tube as well as make sure it isn't twisted. And then with heat applied, the melting flux makes the bottom of the boss slippery to possibly move unless held in position security. Just a bit of inattention of the brazer's part and the boss ends up a bit out of place. However a less drastic solution than removal is to use a small round file to widen the slot so that will allow the front derailleur to be attached so its plates are in phase with the chainrings.

These problems of positioning and brazing a front derailleur boss is why I discourage my students from using them unless they really want a braze-on front derailleur.
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Old 11-03-21, 08:51 AM
  #48  
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Nice! All the modification equipment, angled shim, concave washer/other vintage derailleur, and round file are already ordered so I'm going to try hard to make it work with those, was considering the removal altogether as a last resort alternative if that didn't work. Will think twice though Thanks for input!
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Old 11-07-21, 06:48 AM
  #49  
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Saw this while searching for something else; might help.

https://www.amazon.com/microSHIFT-Fr...289213&sr=8-64

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Old 11-07-21, 10:27 AM
  #50  
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You can make a concave washer out of a £2 aluminium spacer with a round file. No need to get rid of the braze on.
If you make the concave washer yourself it can be tailored to suit your braze on.
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