Bent front derailleur?
04-24-15 | 03:07 PM
#1
Thread Starter
Junior Member
Joined: Jul 2007
Posts: 145
Likes: 2
From: Pittsburgh, PA
Bikes: 1996 Marinoni Leggero, 1978 Bianchi Superleggera, 1972 Peugeot PX-10, 2007 Specialized Rockhopper
Bent front derailleur?
I am having a heck of a hard time trying to install this braze-on Campy Record front derailleur. After spending some time on it I realized that the derailleur tail does not follow the curve of the chainring. (see 1st photo) Also, when trying to get the hi limit screw (the one that controls how far inward the derailleur should travel) set, I am turning it again and again but don't get consistent results (I set it up but after I use it the FD doesn't always stop where it should). Upon further inspection, after taken it apart I realized (see photos 2 and 3) that there is a gap where the hi limit screw would end up. I took it apart and put it back together but the gap is still there, resulting in the hi limit screw falling in the gap. Is it bent? Is this FD toast?
Any advice would be appreciated.
Any advice would be appreciated.
Last edited by aggst1; 04-24-15 at 03:08 PM. Reason: typo
04-24-15 | 03:31 PM
#3
Senior Member
Joined: Apr 2009
Posts: 39,897
Likes: 3,865
From: New Rochelle, NY
Bikes: too many bikes from 1967 10s (5x2)Frejus to a Sumitomo Ti/Chorus aluminum 10s (10x2), plus one non-susp mtn bike I use as my commuter
A few possibilities here. I'll do the normal checkoffs first then your specific FD.
The angle of the cage is based on a 53t chainring, with the braze on at the right position and angle, typically on a seat tube of about 73°. If the Chainrings are smaller, or the seat tube steeper you can get the effect you're seeing. Likewise if the builder mounted the braze on at the wrong angle.
You may have a different issue. Looking at photo, the braze on does seem to be forward of the right spot on the frame, but that's impossible to know from the photo. Also the front of the derailleur where it meets the braze on seems to be worn or filed as if someone were trying to correct an angle issue. That may be an illusion so again, I can't be sure.
Start by checking the Braze-on's angle. A straight edge against it should pass through the center of the BB, or within a few MM's to either side, but no more. If you set a straight edge against yours and it passes well behind the center of the BB, you know the issue and can stop there.
In any case, the fix might be to straighten a bend braze-on, or to file the front of the FD to compensate so it sits where you want it.
The angle of the cage is based on a 53t chainring, with the braze on at the right position and angle, typically on a seat tube of about 73°. If the Chainrings are smaller, or the seat tube steeper you can get the effect you're seeing. Likewise if the builder mounted the braze on at the wrong angle.
You may have a different issue. Looking at photo, the braze on does seem to be forward of the right spot on the frame, but that's impossible to know from the photo. Also the front of the derailleur where it meets the braze on seems to be worn or filed as if someone were trying to correct an angle issue. That may be an illusion so again, I can't be sure.
Start by checking the Braze-on's angle. A straight edge against it should pass through the center of the BB, or within a few MM's to either side, but no more. If you set a straight edge against yours and it passes well behind the center of the BB, you know the issue and can stop there.
In any case, the fix might be to straighten a bend braze-on, or to file the front of the FD to compensate so it sits where you want it.
__________________
FB
Chain-L site
An ounce of diagnosis is worth a pound of cure.
Just because I'm tired of arguing, doesn't mean you're right.
“One accurate measurement is worth a thousand expert opinions” - Adm Grace Murray Hopper - USN
WARNING, I'm from New York. Thin skinned people should maintain safe distance.
FB
Chain-L site
An ounce of diagnosis is worth a pound of cure.
Just because I'm tired of arguing, doesn't mean you're right.
“One accurate measurement is worth a thousand expert opinions” - Adm Grace Murray Hopper - USN
WARNING, I'm from New York. Thin skinned people should maintain safe distance.
Last edited by FBinNY; 04-24-15 at 03:36 PM.
04-24-15 | 03:33 PM
#4
Banned
Joined: Jun 2010
Posts: 43,586
Likes: 1,380
From: NW,Oregon Coast
Bikes: 8
You may be able to fabricate a block to go between the FD and the Frame mount, to rotate and reposition the FD to be where you want it to sit.
Last edited by fietsbob; 04-24-15 at 03:36 PM.
04-24-15 | 04:49 PM
#5
Really Old Senior Member
Joined: Feb 2007
Posts: 14,649
Likes: 1,890
From: Mid Willamette Valley, Orygun
Bikes: 87 RockHopper,2008 Specialized Globe. Both upgraded to 9 speeds. 2019 Giant Explore E+3
The H limit screw controls how far OUT the FDER travels, not how far in!
04-24-15 | 04:54 PM
#6
Senior Member
Joined: Oct 2004
Posts: 3,248
Likes: 4
From: Seattle
Bikes: Kuota Ksano. Litespeed T5 gravel - brilliant!
A few possibilities here. I'll do the normal checkoffs first then your specific FD.
The angle of the cage is based on a 53t chainring, with the braze on at the right position and angle, typically on a seat tube of about 73°. If the Chainrings are smaller, or the seat tube steeper you can get the effect you're seeing. Likewise if the builder mounted the braze on at the wrong angle.
You may have a different issue. Looking at photo, the braze on does seem to be forward of the right spot on the frame, but that's impossible to know from the photo. Also the front of the derailleur where it meets the braze on seems to be worn or filed as if someone were trying to correct an angle issue. That may be an illusion so again, I can't be sure.
Start by checking the Braze-on's angle. A straight edge against it should pass through the center of the BB, or within a few MM's to either side, but no more. If you set a straight edge against yours and it passes well behind the center of the BB, you know the issue and can stop there.
In any case, the fix might be to straighten a bend braze-on, or to file the front of the FD to compensate so it sits where you want it.
The angle of the cage is based on a 53t chainring, with the braze on at the right position and angle, typically on a seat tube of about 73°. If the Chainrings are smaller, or the seat tube steeper you can get the effect you're seeing. Likewise if the builder mounted the braze on at the wrong angle.
You may have a different issue. Looking at photo, the braze on does seem to be forward of the right spot on the frame, but that's impossible to know from the photo. Also the front of the derailleur where it meets the braze on seems to be worn or filed as if someone were trying to correct an angle issue. That may be an illusion so again, I can't be sure.
Start by checking the Braze-on's angle. A straight edge against it should pass through the center of the BB, or within a few MM's to either side, but no more. If you set a straight edge against yours and it passes well behind the center of the BB, you know the issue and can stop there.
In any case, the fix might be to straighten a bend braze-on, or to file the front of the FD to compensate so it sits where you want it.
04-24-15 | 04:58 PM
#7
Senior Member
Joined: Apr 2009
Posts: 39,897
Likes: 3,865
From: New Rochelle, NY
Bikes: too many bikes from 1967 10s (5x2)Frejus to a Sumitomo Ti/Chorus aluminum 10s (10x2), plus one non-susp mtn bike I use as my commuter
Mea Culpa.
I should have read the entire post, and looked closely at the photo's besides the one showing the mismatched curvature issue.
Your problem is that you don't have this derailleur put together correctly. The two arms have to go ALL THE WAY onto the pins, down to the body. That way the limit screws (both) will engage the cam rather than pass behind the arm.
If you can't get the arms in all the way, back both limits out of the way, and work the assembly back and forth against the spring until the arms bottom. Then it takes either a circlip or screw into the post to hold them in place.
Once you have it put together right, then you can recheck the angle issues, and deal with if necessary.
I should have read the entire post, and looked closely at the photo's besides the one showing the mismatched curvature issue.
Your problem is that you don't have this derailleur put together correctly. The two arms have to go ALL THE WAY onto the pins, down to the body. That way the limit screws (both) will engage the cam rather than pass behind the arm.
If you can't get the arms in all the way, back both limits out of the way, and work the assembly back and forth against the spring until the arms bottom. Then it takes either a circlip or screw into the post to hold them in place.
Once you have it put together right, then you can recheck the angle issues, and deal with if necessary.
__________________
FB
Chain-L site
An ounce of diagnosis is worth a pound of cure.
Just because I'm tired of arguing, doesn't mean you're right.
“One accurate measurement is worth a thousand expert opinions” - Adm Grace Murray Hopper - USN
WARNING, I'm from New York. Thin skinned people should maintain safe distance.
FB
Chain-L site
An ounce of diagnosis is worth a pound of cure.
Just because I'm tired of arguing, doesn't mean you're right.
“One accurate measurement is worth a thousand expert opinions” - Adm Grace Murray Hopper - USN
WARNING, I'm from New York. Thin skinned people should maintain safe distance.
Last edited by FBinNY; 04-24-15 at 05:52 PM.
04-24-15 | 05:43 PM
#8
Thread Starter
Junior Member
Joined: Jul 2007
Posts: 145
Likes: 2
From: Pittsburgh, PA
Bikes: 1996 Marinoni Leggero, 1978 Bianchi Superleggera, 1972 Peugeot PX-10, 2007 Specialized Rockhopper
Mes Culpa.
I should have read the entire post, and looked closely at the photo's besides the one showing the mismatched curvature issue.
Your problem is that you don't have this derailleur put together correctly. The two arms have to go ALL THE WAY onto the pins, down to the body. That way the limit screws (both) will engage the cam rather than pass behind the arm.
If you can't get the arms in all the way, back both limits out of the way, and work the assembly back and forth against the spring until the arms bottom. Then it takes either a circlip or screw into the post to hold them in place.
Once you have it put together right, then you can recheck the angle issues, and deal with if necessary.
I should have read the entire post, and looked closely at the photo's besides the one showing the mismatched curvature issue.
Your problem is that you don't have this derailleur put together correctly. The two arms have to go ALL THE WAY onto the pins, down to the body. That way the limit screws (both) will engage the cam rather than pass behind the arm.
If you can't get the arms in all the way, back both limits out of the way, and work the assembly back and forth against the spring until the arms bottom. Then it takes either a circlip or screw into the post to hold them in place.
Once you have it put together right, then you can recheck the angle issues, and deal with if necessary.
Thread
Thread Starter
Forum
Replies
Last Post
th2dge
Bicycle Mechanics
7
03-27-11 12:11 PM
