Front Derailleur Clamp Overtightened

Wayne

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Mar 10, 2011, 1:05:14 PM3/10/11

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Just bought a used steel frame with slight indentation on seat tube
resulting from prior owner overtightening the front derailleur clamp.
The tube has an indentation about .5-1.0 mm deep all around the tube
in the shape of the clamp.

Is there a problem with continuing to clamp a FD in the same spot? I
am having some other work done on the frame. Should I have a sleeve
brazed over the tube?

Thanks, Wayne

AMuzi

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Mar 10, 2011, 3:50:59 PM3/10/11

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What frame is it?
On a 753 or an EL I might be concerned but on an SP or
similar, surely not. It may also be paint deformation and
not a dent.

At any rate it won't harm you if it does crack [1] and the
only suitable repair is a new seat tube. On most frames I'd
ignore it, on delicate materials I'd inspect often and ride
it anyway until or unless a crack appears.

[1] may have to walk home but you won't land on your nose.

--
Andrew Muzi
<www.yellowjersey.org/>
Open every day since 1 April, 1971

kolldata

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Mar 10, 2011, 5:36:06 PM3/10/11

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quality duct tape from HD at $11 roll.

Nate Nagel

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Mar 10, 2011, 7:16:37 PM3/10/11

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is the seat tube straight or butted? if straight, I'd be tempted to try
to work the dent out with a dowel, or a socket on a locking extension.
However, I'm not a bike wrench, so I don't know if that's actually a
good idea or not.

nate

--
replace "roosters" with "cox" to reply.
http://members.cox.net/njnagel

AMuzi

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Mar 10, 2011, 7:46:29 PM3/10/11

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Nate Nagel wrote:
> On 03/10/2011 01:05 PM, Wayne wrote:
>> Just bought a used steel frame with slight indentation on seat tube
>> resulting from prior owner overtightening the front derailleur clamp.
>> The tube has an indentation about .5-1.0 mm deep all around the tube
>> in the shape of the clamp.
>>
>> Is there a problem with continuing to clamp a FD in the same spot? I
>> am having some other work done on the frame. Should I have a sleeve
>> brazed over the tube?
>>
>> Thanks, Wayne
>
> is the seat tube straight or butted? if straight, I'd be tempted to try
> to work the dent out with a dowel, or a socket on a locking extension.
> However, I'm not a bike wrench, so I don't know if that's actually a
> good idea or not.

If indeed it is dented (paint deformation is common there),
the butt of a butted tube is below the FD clamp area.

If it's crimped from a derailleur clamp and is then formed
back out smooth (mandrel and hammer or mandrel and rolled in
steel blocks) before clamping the same part over the same
spot I don't see where you necessarily come out ahead. If
anything that may aggravate the situation. Depends.

As I wrote earlier, it may well be simply paint deformation
and we still don't know the material. With 1.6mm mild steel
tube you can work most any machinations you like with
impunity. On a tempered 0.3mm tube, not so much.

Wayne

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Mar 10, 2011, 10:05:32 PM3/10/11

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>On Mar 10, 6:46 pm, AMuzi <a...@yellowjersey.org> wrote:
> As I wrote earlier, it may well be simply paint deformation
> and we still don't know the material. With 1.6mm mild steel
> tube you can work most any machinations you like with
> impunity. On a tempered 0.3mm tube, not so much.
> --
> Andrew Muzi
> <www.yellowjersey.org/>
> Open every day since 1 April, 1971
>

The bike is an early 2000 Santana Arriva. Tube set is supposed to be
Columbus 8/5/8. Can't be sure, but my ear tells me it is butted well
below the clamp area.

Removal of paint in the deformed area confirmed it was paint
deformation. I never would have guessed that because the paint was
not cracked or split and very hard. It took some effort to scratch
through the paint but after removing the paint I discovered an
unblemished seat tube.,

Thanks for the great information. There is no substitute for
experience. I appreciate the contributions of shop owners like you
that share thier knowledge. I have in the past and will continue to
support your shop with phone orders and encourage others to do so.

Wayne Sulak

thirty-six

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Mar 10, 2011, 10:26:26 PM3/10/11

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I used to be a bit cack-handed with my early racing bikes and I'm sure
I'd have done it if was possible. I'd guess a braze-on boss has been
removed and the band on derailleur was fitted whith the paint still
soft. I've had exactly this work done, quickly, but have never moved
the clamp. I'd expect an indentation to be there.

Whatever it is, rub back the paint and use a filler before rubbing
back again and finishing with a colour coat. You need to be able to
move your derailleur height depending upon the outer chainring.

Zarniwoop

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Mar 11, 2011, 2:37:19 AM3/11/11

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buy a series of big ball bearings, to press the dent out from the
inside.

8/5/8 doesnt apply to seat tubes. butt is only the bottom,
wall thickness,is straight at the top for seat post fitting.