Re: RE: Re: RE: Re: DeRosa Merak Rear Brake Problem

On 1/3/2025 9:50 AM, cyclintom wrote:

On Thu Jan 2 10:36:19 2025 AMuzi  wrote:

On 1/2/2025 10:08 AM, cyclintom wrote:

On Thu Jan 2 09:46:17 2025 Zen Cycle  wrote:

>
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.

>
>
Proprietary? This is not an uncommon assembly. Though perhaps Colnago has rights to the name. I doubt that though since Trek made on before Colnago.
>
De Rosa Macro Aluminum Carbon Frame - Size: ST 50 TT 53 - Light Blue | eBay
>
Canyon road bike frame Air Road CF Team Omega Pharma-Lotto Model Carbon L Rare! | eBay
>
Giant TCR Advanced SL Medium Frameset (Trek Cervelo Specialized Colnago Merckx) | eBay
>
Trek 120 OCLV Carbon Road Bike Frameset 58mm Large Made in USA Blue 2004 | eBay
>
>

>
I did not know the term. We normally use "seatstay" or
"seatstays".
>
For purposes of mounting a caliper, the monostay top portion
makes no difference. Zip. Nada. None.
>
I wonder if it's "B-stay" to honor Keith Bontrager, who
developed and popularized that style in 1985?
>
Back to your question, try slipping a 5mm bolt into those
threads. If it falls through, you have an M6; likely just a
brake allen mounting nut possibly stuck in the brake
mounting hole.

    Yes, it is an M6 fitting.

I thought so; that makes more sense.
It is most probably an aluminum brake mounting nut.
Possibly corroded in place, possibly stuck in with Locktite or epoxy, possibly just jammed into a brake mount hole improperly formed or full of clear coat.  Hard to say which.
It's unlikely to be a fatal problem for your frame and a new nut is a couple of dollars.  Observe as carefully as you can and do not do anything destructive until/unless you know what it is.
I'd try running a bolt into it, warm the area and give it a sharp rap. (not a full swing with a big hammer)
--
Andrew Muzi
am@yellowjersey.org
Open every day since 1 April, 1971