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Old 08-13-09, 05:30 PM   #1
haighter
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How to attach this front derailleur?

I recently bought a Shimano Tiagra clamp-on front derailleur. It's a 31.8mm size and fits fine on the seat tube. However, the old FD was bolted on the two holes seen in the pictures below.

Will I be able to put the new FD either below or above these bolt-holes or am I going to need to figure out a way to take the bolt-holes off the bike? Maybe something else I'm not thinking of?

(Images won't embed for some reason)

http://img199.imageshack.us/i/boltonfdfullsmall.jpg/
http://img142.imageshack.us/i/boltonfdclosesmall.jpg/
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Old 08-13-09, 07:37 PM   #2
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Originally Posted by haighter View Post
Will I be able to put the new FD either below or above these bolt-holes or am I going to need to figure out a way to take the bolt-holes off the bike? Maybe something else I'm not thinking of?
Well, answer is "it depends". If you can get the clearance to the chainring that the new derailer requires without the derailer clamp being where the holes are then you're probably good. Was the original derailer mounted to a bracket that was bolted to the holes on the frame? Those look like holes for a bracket to use a braze-on derailer to me.

-R
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Old 08-14-09, 11:29 AM   #3
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Originally Posted by CCrew View Post
Well, answer is "it depends". If you can get the clearance to the chainring that the new derailer requires without the derailer clamp being where the holes are then you're probably good. Was the original derailer mounted to a bracket that was bolted to the holes on the frame? Those look like holes for a bracket to use a braze-on derailer to me.

-R
The original derailleur was mounted on a bracket, which then attached to the holes on the frame.

How can I tell what the required/preferred clearance is to the chainring?
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Old 08-14-09, 11:51 AM   #4
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The original derailleur was mounted on a bracket, which then attached to the holes on the frame.

How can I tell what the required/preferred clearance is to the chainring?
In most cases it's 1mm or two. Without knowing the exact model # of the shimano derailer you have, here would be a good place to start for the install instructions:

http://techdocs.shimano.com

If you need more install instructions, Park Tools site is very informative with their "how to's"
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Old 08-14-09, 06:14 PM   #5
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To avoid the possibility of incompatibility with your frame, why don't you just get a braze-on front derailleur to mount on the bracket that is supposed be on the frame? You can buy a decent front derailleur for less than $30 and save yourself the hassle of trying to get one to fit and line up correctly in the space where the holes are.

-j
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Old 08-14-09, 09:03 PM   #6
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Originally Posted by haighter View Post
(Images won't embed for some reason)

http://img199.imageshack.us/i/boltonfdfullsmall.jpg/
http://img142.imageshack.us/i/boltonfdclosesmall.jpg/
First the URL has to return an image. Although the link ends in .jpg, the URL is interpreted by imageshack and imagshack "returns" a webpage not an image. This will not work between the [ img ] [ /img] tags. What's between the tags has to return an image.

You need the exact Address (URL) of the image itself thus bypassing imageshacks auto page making response. The only link that worked on the imageshack page was http://img199.imageshack.us/i/boltonfdfullsmall.jpg/.
For some reason the img142 link doesn't find anything at imageshack.

After this page loads, right click the image and select Properties. Select/copy the Address (URL) information for the image.
img199's URL is h ttp://img199.imageshack.us/img199/3630/boltonfdfullsmall.jpg (space inserted in http to prevent BF forum from using URL tags) and it looks like this when inserted between [ img] [ /img] tags:


Last edited by tippy; 08-14-09 at 09:12 PM.
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Old 08-14-09, 09:28 PM   #7
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Haighter, can you post a picture of your derailleur?

Often, the derailleur will bolt on to the clamp in the same way it will bolt on to the bracket. If that's the case, then you'll just need to purchase a bracket that will fit on your frame correctly, unbolt the derailleur from the clamp and bolt it to the bracket.

Walt
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Old 08-14-09, 09:47 PM   #8
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Looks like the holes for the mountaing bracket on a braze-on front derailleur. You need the bracket for that...
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Old 08-16-09, 05:47 PM   #9
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Haighter, can you post a picture of your derailleur?

Often, the derailleur will bolt on to the clamp in the same way it will bolt on to the bracket. If that's the case, then you'll just need to purchase a bracket that will fit on your frame correctly, unbolt the derailleur from the clamp and bolt it to the bracket.

Walt


Here is a picture of the old one.





And the new one:





So, it's my understanding that if I get a dereailleur billed as "braze-on" that I can take the mounting bracket off of this old one and use it with the new one? FWIW, I was thinking 105 FD.

Last edited by haighter; 08-16-09 at 10:52 PM.
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Old 08-17-09, 02:04 AM   #10
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Yes, you want a "braze-on" front-derailleur. The mounting-bracket should be considered a part of the frame, not the derailleur. They are very, very specific to each and every single frame. Some have different types of mounting holes. The curvature is different depending upon the size of the seat-tube... etc. Always keep the bracket with the frame at all times. If you are getting the frame-painted, tape the bracket inside the BB-shell so it doesn't get lost. if you lose it, chances are very good that you won't be able to find another one and the frame is worthless.
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