Re: DeRosa Merak Rear Brake Problem

On 1/1/2025 7:20 PM, Frank Krygowski wrote:

On 1/1/2025 6:20 PM, cyclintom wrote:

On Wed Jan 1 16:14:05 2025 AMuzi  wrote:

On 1/1/2025 2:46 PM, cyclintom wrote:

I discovered why I got the Merak for nearly nothing.
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When it came time to install the rear brake I found a bolt somehow installed in the rear B-stay brake hole that has a 5 mm threaded hole in it. It is aluminum so the forward end of the device (between the B-stay and seat tube) which appears to be a normal brake lock, is stripped.
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Since the B-stay is carbon fiber I don't think that it is screwed in. I would think that it is a slight interference fit which would explain the stripped allen end. I suppose I could thread in the 5 mm allen bolt and using a puller, push the fitting out. Hopefully that would leave the original brake hole in original condition.
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I have never seen a rear brake attachment of this sort so I am asking if anyone has ever seen anything like this and if they have any comments on it and if they could suggest a removal technique that would leave the hole in original condition?

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There is something inside your rear brake mount?
And that is a bolt? Or a sleeve with a 5mm threaded bore?
What is a B stay?
What is a normal brake lock?
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Could it be a stuck/corroded brake mounting nut? That would
be M6 not M5.  An aluminum nut may well be corroded in
place. Clean as well as possible, examine in a good light
with a magnifier if needed to see what it is an dhow it's
held in place.

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1. https://www.ebay.com/itm/387414175414?_skw=B- stay&itmmeta=01JGJ1SMVC3X64P451Y7V26RDP&hash=item5a33af2eb6:g:ojsAAOSwapJm8SeY&itmprp=enc%3AAQAJAAAA4HoV3kP08IDx%2BKZ9MfhVJKkKk%2BT%2BCfPB1NFw1gIOhTDcX5INzW7ZyWXx6ymLMxxUkrjgqEbMjg7byxSVBbnUf1OSX%2Fvcil1p15XMnhKWGWTb3w6SI%2BSogBVxH8U3lJYJ9cCu1IHbjcweuReuInwNEbjWdSN0YS743SYts0ZqnTbaXTlvuKSY6sywZQureWu4x4wfDXgFkt0cutCbAuWgNrXUrAyZ0kHi9fGa9FDktoHBJ2Ou5RhYYeJpFZojnp7qCmg2u61ElYwc8ZHbrzANgaQ2bBquUYm9q0wd1ExtoN%2Bp%7Ctkp%3ABk9SR-bN5sGEZQ
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2.  https://www.ebay.com/itm/183751311056?_skw=Ultegra+rim+ +brake+fixing+nut&itmmeta=01JGJ1RGGSH2W5TD4WMQXC1WN8&hash=item2ac86e7ed0:g:SLAAAOSw5cNYbIi8&itmprp=enc%3AAQAJAAABAHoV3kP08IDx%2BKZ9MfhVJKmDXGrXXDIzZaBH8%2FV8tvPcg9OmXd%2BLSGTrZ0E3ttBzz91TsnLw5frOpgp5%2BaLgKnsVuajVdLQlissnahvLQ1s%2B8jjBW5Zwe9gx3ufmUqMQbR28s5kmllEA6TneV3nRuIyCrBZ3w2AHL8T%2Fum15FGCrgWW3lJa5poIsouZTt3cjjMZUTQ6ChkB5U0JDjSSF6K8J4s9R1YtMY9twloP2CvPnXPEA01h2at9kiWlAko%2BecP%2FnrsuiewDvsK2lC1HohuyheFliyzVpmmF1v9KImGbXMTdMZt7gyFMor%2B%2BtTLFBurUsXqzG0OeVxPKt3VXc9zg%3D%7Ctkp%3ABk9SR7yI4sGEZQ
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3 No chance at all. The threads start at juust below the surface of the brake hole.

 The answers to Andrew's questions are still not clear to me, except that a "B stay" seems to be a proprietary term for an odd frame configuration.

It's a marketing name for the piece, but not necessarily anything odd. The "B-stay" is a Colnago proprietary seat-stay assembly of a rear "wishbone design", except that it's a modular formed CF piece designed to insert into a seat lug receiver and studs on the rear dropouts. IOW, it's only a "B-stay" when it's made by Colnago. It's not a "b-stay" on a DErosa Merak unless Derosa sourced the piece from Colnago. I believe Columbus made a similar piece under the "Curve" moniker.

 I don't recall seeing any brake mounting hardware that took an M5 fastener. I think M6 is normal.

M6 is normal, the issue is that tommy is still under the impression that the screw size is defined by the drive tool, not the screw dimension (remember his insistence that the water bottle screws on his Basso were M4s).
I really can't say what a "normal brake lock" is. I suspect it's just the bolt, similar to how he called the cable clamp on the derailleur a "lock" recently.

 The photos of the bike are helpful, but can you post and link to a closeup photo of the object(s) you're asking about? That, and/or a good engineering drawing of the relevant part might allow some of us to help.
 

I'm going with Andrews supposition that it might simply be a stuck bolt, or that the hole got stripped out and the bolt was epoxied in place.
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