Re: DeRosa Merak Rear Brake

On 1/3/2025 9:49 AM, Zen Cycle wrote:

On 1/2/2025 6:45 PM, AMuzi wrote:

On 1/2/2025 5:12 PM, Tom Kunich wrote:

I discovered why I got the DeRosa for nearly nothing. When it became time
to install the rear brake, there is an internally threaded aluminum bolt
in the hole. The outside of the (front facing) bolt has an allen head on
it but being aluminum, is stripped. The inside of the device is 5 mm and
threadding a screw in until it hits the end does not allow it to be
unscrewed and I don't want to force it since it is aluminum.
>
I have never seen a rear brake that attaches from the rear and an Ultegra
brake shaft is 5.75 mm. (thread depth on what's present) Now I could drill
a shaft size hole fron the back but this would leave about 28 mm on the
other side that needs a hole 8 mm in diameter with stop 10 mm in diameter.
I could also drill a hole 8 mm in diamerer and the normal connector would
hold it in the center if the present stop would allow me to tighten it
enough. Or I could use a steel washer 8 mm ID to spread the load of the
stop enough to allow me to tighten it enough to lock everything.
>
As I say, I've never seen anything like this before and it appears like
the this thing was either threaded in (unlikely into a carbon fiber rear B-
stay) or glued in (extremely poor judgement if so). It also could be
simply an slight interference fit into the original hole and that would
explain the reason the allen headed front facing fixture stripped. If this
were the case, I could thread this deep 5 mm bolt in to the rear id taping
with a hammer or pushing with a puller, pushing that thing out without any
damage to the original hole.
>
Now, has anyone else ever seen anything like this and do you have any
comments? Would you have any suggestions on what to do?
>

>
Your description sounds like a regular M6 brake mounting sleeve installed backwards.
>
(guys do install calipers behind the seat stays. No functional reason to do that. But no technical reason not to either. Looks dorky to me. There are setups where the slightly different brake reach matters, but that would be very rare.)
>
Unless there's something I don't know about this, I'd screw an M6 bolt into it, warm it with a heat gun (Not hot, warm. Carbon adhesives don't like hot) and give it a sharp rap.
>
I agree that any drilling, reaming, assault with the dreaded Dremel destruction device, or any material removal at all is a bad idea until or unless you understand the problem better.

 "until or unless you understand the problem better."
 That's a pretty tall request considering the intended recipient.
 

Well, yes.
Hard to offer definitive advice when the problem is poorly described.
--
Andrew Muzi
am@yellowjersey.org
Open every day since 1 April, 1971