Colnago C50 Rear Brake

Discuss light weight issues concerning road bikes & parts.
Briscoelab
Posts: 1730
Joined: Thu Jan 26, 2006 6:01 pm

by Briscoelab

Sometimes you need to guts to use a hammer. :) Spray some silicon lube or penetrating oil around the nut from both sides, thread a bolt in from the back and hit it.

I know you've done this... but I think it just needs a bit more persuasion (ie force). It's a bit disconcerting to hit your carbon bike with a hammer, at first. But it should really come out. If you don't get it out... it's only going to get worse. galvanic corrosion and scaling could even split or crack the carbon in that area if you don't get it out and cleaned up.

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SWijland
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Location: The Netherlands
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by SWijland

Briscoelab wrote:Sometimes you need to guts to use a hammer. :) Spray some silicon lube or penetrating oil around the nut from both sides, thread a bolt in from the back and hit it.

I know you've done this... but I think it just needs a bit more persuasion (ie force).


I agree. Just give it a couple of strong taps with a rubber hammer and keep on going until it comes loose.

philhul
Posts: 129
Joined: Sat Apr 30, 2011 1:08 pm
Location: Newcastle, UK

by philhul

Believe me I've given it a few hard hits, I've lost my temper a times through frustration! It literally will not budge. It's had numerous applications of the oil but it doesn't seem like it is even close to moving. Extremely frustrating. I want to go to Italy in May to ride some mountains and to see the Giro and Mille Miglia so desperately want to start training!!

Svetty
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Joined: Thu Mar 26, 2009 11:06 pm
Location: Yorkshire - God's Own Country

by Svetty

If you can place a supporting object (block of wood?)with a small hole in ( for the nut to hopefully shoot through!)against the surface of the fork it would ensure that the carbon was supported and the hammering force applied to the nut. Might enable a firmer blow to dislodge it?

Otherwise drill out the nut being careful not to drill the carbon...

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Rumsas
Posts: 554
Joined: Thu Oct 23, 2008 7:25 pm

by Rumsas

I would soak the brake bolt in Coca cola all night. then i would Screw in a good new steel allen bolt from the out side, all the way in. then use a long allen key, and just keep turning the bastard.
If it still is stuck, then i think it's glued in.
Hammering, wd40 and heat is no good imo
Good luck

philhul
Posts: 129
Joined: Sat Apr 30, 2011 1:08 pm
Location: Newcastle, UK

by philhul

Well I have a rear brake fitted. The bolt itself still wouldn't come out and anything else we tried would probably have ended up damaging the frame:

Image

In the end I just had to screw the brake in and use a spacer so that it ended up the right way round. Hopefully this will work, it is screwed tightly in.

Image
Image

bontie
Posts: 146
Joined: Fri Feb 18, 2011 8:33 am

by bontie

Phil, have you considered just drilling it out? It's not as if here is thread to damage.

ghisallo2003
Posts: 595
Joined: Mon Jan 02, 2006 7:10 pm

by ghisallo2003

Glad to see you have a solution, and if you happy, then that is great.

I suspect it would irritate me that this was not right, particularly on this frame, with those wheels and the obvious level of detail you are aiming at. Even the invisible bits on a bike should be right !

The bolt is free to move along its channel, but just not leave the frame - that is what appears by comparing your recent picture from earlier ones. Is that right? In this case, I think there it is just an abnormally tight fit.

I can understand why you would be nervous to whack too hard, and to chip paint away around the brake mount hole. It is also not the easiest place to drill. If you can access it though, I would certainly give it a go; Once the central core is drilled out, there is always the tendency for the remaining metal to peel away.

BobSantini
Posts: 292
Joined: Sun Jul 10, 2011 9:03 am

by BobSantini

Just looked this up. The coefficient of thermal expansion for standard carbon composite is about 1/10 that of aluminum so cooling it should loosen it, not that it matters now. Those Px brakes look right at home on the C50.
r o y g b i v

philhul
Posts: 129
Joined: Sat Apr 30, 2011 1:08 pm
Location: Newcastle, UK

by philhul

To be honest I'm not fussed at the moment. I haven't ridden a bike since October and am just desperate to get out. You'll see in the pics that there are other issues such as around the bottle cage mounts so next winter I'm having the whole thing stripped of clear coat and paint and refinished as new. I'll try something else with the bolt then as from that point on I'd want it to be perfect but for now it will do.

The bolt still doesn't move at all. I wanted to try and attach a bolt from the down tube side to try to extract it. Although the hex bit was rounded the bolt still wouldn't fit so I drilled from the outside with a bit smaller than the diameter of the threads and 'wiggled it about a bit' to try to enlarge the hole sufficiently. That is why it looks such a mess in the latest pic but it still wasn't wide enough to get a bolt in.

I'm not sure about drilling it out. The down tube doesn't allow enough space to get in and if I went from the other side I'd have to drill part of the frame first.

How cold would it have to be to loosen the bolt?

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