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From: Frank Krygowski <frkrygow@sbcglobal.net>
Newsgroups: rec.bicycles.tech
Subject: Re: DeRosa Merak Rear Brake
Date: Fri, 3 Jan 2025 11:52:19 -0500
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On 1/3/2025 11:19 AM, AMuzi wrote:
> 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.

I too found the description to be poor. Again, I think if Tom gave some 
close up photos from different angles, plus (say) a decent engineering 
drawing or sketch of the troublesome insert, he'd have a better chance 
of getting some good advice.

-- 
- Frank Krygowski