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Front derailleur braze on is too low?

Old 10-15-16, 06:38 PM
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Front derailleur braze on is too low?

I'm building a Scapin frame up and had a Campy triple set from a donor bike, but the front derailleur braze on at it's highest point is too low and the derailleur hits the 52t chainring while shifting. I'm assuming a double would hit too as the chainrings are usually 52 as well. What am I missing? I could file the braze on up, but that seems drastic! Thanks
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Old 10-15-16, 06:46 PM
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fit a 50-40-30 triple instead, that will cure that. Maybe the frame company had a 50-34 double in mind. not a 53-39?
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Old 10-15-16, 06:54 PM
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There was a short period (I believe in the mid seventies) where Campy lowered the mounting bolt on Record front derailleurs. It's possible that the frame was made in that era and the braze-on was lowered accordingly
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Old 10-16-16, 05:52 AM
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I'm with FB on this one. I think the bike is made for a compact crankset.
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Old 10-16-16, 06:38 AM
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Drill and retap hole in FD mount block possible?
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Old 10-16-16, 09:52 AM
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Originally Posted by blakcloud View Post
I'm with FB on this one. I think the bike is made for a compact crankset.
Well, I tossed a Shimano double FD on there and it sails right over the 52 and would need to brought way down to work, of course it does not have enough travel for a triple, were bike frames built to be double only?

Never though about it, or not been able to turn a double into a triple. Thanks!
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Old 10-16-16, 10:06 AM
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I doubt the frame was built with a compact crankset in mind (likely time period of frame's manufacture is the main reason I say this). Could even be a manufacturing "flaw", brazed-on items on hand brazed frames aren't always in exactly the right place.

FWIW, it's not difficult for a frame builder to position a FD braze-on mount that, with the normal vertical adjustability of the mount using almost any braze-on FD, has the capability to run large chainrings ranging from about 53t to 49t. This one obviously misses that mark.
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Old 10-16-16, 10:25 AM
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Originally Posted by Mbrgr1 View Post
Well, I tossed a Shimano double FD on there and it sails right over the 52 and would need to brought way down to work, of course it does not have enough travel for a triple, were bike frames built to be double only?

Never though about it, or not been able to turn a double into a triple. Thanks!
Are you sure that Shimano FD can't handle a triple? Try adjusting the limit screws and you may be surprised how far it can swing.
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Old 10-16-16, 10:40 AM
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Originally Posted by HillRider View Post
Are you sure that Shimano FD can't handle a triple? Try adjusting the limit screws and you may be surprised how far it can swing.
It probably would, unfortunately for me, I decided to build an all Italian bike with all campy parts.

I'm convinced there must be a campy FD with a shorter stature, in the following pics there is a huge 10mm difference between the top pivot and the closest edge on the outer guide, it looks like the relationship between mounting bolt and top pivot is the same on both.


10mm would put me right where I want to be, I only need a few mm to clear now, so the hunt is on for a shorty campy!
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Old 10-16-16, 10:48 AM
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I'm quite happy with my 50-40-24 triple (replaced the 30) 'race triple' .. and I only have a 13t top cog..
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Old 10-16-16, 12:58 PM
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Is it possible that your frame was designed and built for the Junior Category of racing and thuse was made to fit the smaller chainrings mandated by the ICU?

Cheers
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Old 10-16-16, 01:40 PM
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Originally Posted by Miele Man View Post
Is it possible that your frame was designed and built for the Junior Category of racing and thuse was made to fit the smaller chainrings mandated by the ICU?

Cheers

Well, junior would be a pretty big boy, 63cm frame

I appreciate the thoughts and help though!
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Old 10-16-16, 01:46 PM
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Maybe it's time to take Admiral Hopper's advice and measure the height of he braze-on to confirm if the problem is the braze-on or derailleur.
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Old 10-16-16, 02:05 PM
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A Change to the 1 By will definitely cure the issue..

the innermost of a triple is a lot closer to the Center line of the Bike than the smaller one of a double ..

I used their 111 long Cartridge BB spindle on my Frame and the crank arms got close enough to the end of the BB out side cup face
that an O ring was able to seal the gap around the spindle and form an extra seal..




'/,

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Old 10-16-16, 02:09 PM
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Originally Posted by Mbrgr1 View Post
Well, junior would be a pretty big boy, 63cm frame

I appreciate the thoughts and help though!
I didn't see any mention of the frame size in any of the posts I saw before I replied. VBG LOL

Cheers
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Old 10-16-16, 02:12 PM
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Originally Posted by FBinNY View Post
Maybe it's time to take Admiral Hopper's advice and measure the height of he braze-on to confirm if the problem is the braze-on or derailleur.

The braze on "bottom" is approximately the same height from the top of the BB as it was on the donor bike, it is however a quarter inch shorter overall, which is what I need to make this derailleur work, so it is the braze on's fault!

I could go to a double, but it would mean buying a different group etc, I am hoping to find a solution with this group.

It may come down to a different frame for this group I have, but I'll dig around see what I can find.

Thanks for all the help. M
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Old 10-16-16, 02:17 PM
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Originally Posted by fietsbob View Post
fit a 50-40-30 triple instead, that will cure that. Maybe the frame company had a 50-34 double in mind. not a 53-39?
I guessed that this wouldn't be enough, but a 50 chainring would be 4mm shorter in radius, which might actually work.
Table of radius values ( in inches, from center of axle to center of chain pin.)
50 tooth = 3.981 inches = 101.1 mm
52 tooth = 4.140 inches = 105.2 mm

Originally Posted by HillRider View Post
Are you sure that Shimano FD can't handle a triple? Try adjusting the limit screws and you may be surprised how far it can swing.
Triple front derailleurs usually have a cage shaped to help shift the middle and small chainrings, it's not just the amount of travel.

Originally Posted by Miele Man View Post
Is it possible that your frame was designed and built for the Junior Category of racing and thuse was made to fit the smaller chainrings mandated by the ICU?
Cheers
Junior racing bikes use larger cassette cogs, not a small front chainring.
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Old 10-16-16, 02:19 PM
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Originally Posted by punkncat View Post
Drill and retap hole in FD mount block possible?
I looked at that for a project. It looks like it should be possible, but most of the derailleurs have other attachments and hinges attached to the lower half of the mounting block, so it would require a significant modification.

If it is only 1mm, perhaps grind down the lower edge of the derailleur cage. Or, track down a 51T chainring.
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Old 10-16-16, 02:28 PM
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Originally Posted by Mbrgr1 View Post
The braze on "bottom" is approximately the same height from the top of the BB as it was on the donor bike, it is however a quarter inch shorter overall, which is what I need to make this derailleur work, so it is the braze on's fault!

I could go to a double, but it would mean buying a different group etc, I am hoping to find a solution with this group.

It may come down to a different frame for this group I have, but I'll dig around see what I can find.

Thanks for all the help. M
At least now you know the situation. Going to a double with this same FD won't do you any good, since the outer ring will be in the same place, or maybe inboard a bit which would only make it worse. I can't point you to any specific model, except for that vintage Record version with the low mounting bolt. FWIW, a few weeks ago we had someone who had one of those and had the opposite issue, not being able to get it low enough. Maybe you can track him down and talk swap.

Otherwise, in your shoes, I'd be looking closely at the option of filing the braze-on's slot a bit higher.
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Old 10-16-16, 02:39 PM
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Originally Posted by FBinNY View Post
At least now you know the situation. Going to a double with this same FD won't do you any good, since the outer ring will be in the same place, or maybe inboard a bit which would only make it worse. I can't point you to any specific model, except for that vintage Record version with the low mounting bolt. FWIW, a few weeks ago we had someone who had one of those and had the opposite issue, not being able to get it low enough. Maybe you can track him down and talk swap.

Otherwise, in your shoes, I'd be looking closely at the option of filing the braze-on's slot a bit higher.
Thanks, the way a double would work is that the double FD would be considerably shorter from the pivot down to the leading edge of the guide, that is why my Shimano double sailed right over the 52t and would need to come down some to work cleanly. I'm sure a double with a double FD would work fine and be midway in the braze on adjustment area, that's why I was leaning towards and asking about a double specific frame. I could file up on the braze on, but something tells me it would weaken it too much, there is only about 6mm of steel there.

Thanks again!
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Old 10-16-16, 02:52 PM
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Originally Posted by Mbrgr1 View Post
Thanks, the way a double would work is that the double FD would be considerably shorter from the pivot down to the leading edge of the guide, ...... I could file up on the braze on, but something tells me it would weaken it too much, there is only about 6mm of steel there.
Sorry about that. I thought you were speaking about a double crank. I'm not sure there's a rigid standard on FD cage height vs mounting bolt, so you might find another Campy triple FD which might work.

As far as filing goes, that's always a judgement call. But FWIW, I'd be comfortable filing the slot up until the top connection is about 3mm, or even a bit less. The curved washer on the bolt would help hold things together, so the stress on the end of the slot isn't all that high.

I suspect that this will boil down to a philosophical differences. I date back to an era where stuff wasn't plug and play, so I'm used to and comfortable with using hammers and files to make stuff work.
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Old 10-16-16, 03:43 PM
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I just have a old Triomphe Leisure FD , its triple by having a wider back Plate to Push up the chain from the Granny to the larger chainrings.

The Triomphe had a smaller BCD than the Record so the wider step doubles were possible.

It obviously is dated and so Nothing Buyers all wanting it to 'Go to 11' want.





'/,

Last edited by fietsbob; 10-16-16 at 04:22 PM.
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