unworthy1

I would advise "NO" to trying to drill or fit a recessed nut type to that rear brake bridge: it can't be safely modified for recessed, you have to stick with an external nut. However, I have done many a front fork whether with a flat or curved back surface for a recessed front nut. I like to enlarge the back hole (only) with a tapered reamer until just the same diameter as the drill bit you'll use (which is just the same diameter as the nut's main body, with a smidge more for clearance). That way the drill bit is only used for a little "clean out" and no chance or it wandering in the smaller original hole. You then have the shoulder of the nut stand proud of the crown and on a curved surface it makes less complete contact on the crown than if a flat-backed crown, but never been a problem in practice.

Savannahdan

Fork crowns are easy, no need to remove it from the frame, just clamp it and drill. Just take it carefully and press very lightly, so the bit only takes off small amounts of material. Oil will be fine as a cutting compound. Provided your bit is sharp you shouldn't have any paint issues, so I wouldn't worry about heating with a gun. drillinfo.com

mpetry912 

The problem with drilling the rear brake bridge, other than very limited clearance as has been pointed out above, is that many bikes just have a piece of tube with no "boss" for the brake bolt.

drilling that just removes metal, possibly beyond what gives a safe margin based on the loads applied. I'd be really careful about drilling a frame that I cared about (meaning I probably would not do it !)

Mark Petry
Coronado Island, CA

Bianchigirll 

Thank you for your input but this thread is 3 years old.

I think in general most of here are opposed to drilling and part of any frame.

repechage

I have done it this way- sometimes the coupling nut needs to be filed back or ground back- if so, then I chamfer it very slightly toward the front.
The beauty in this way is that the frame and fork is unmolested, a M6 Button head cap screw is all one sees from the back of the fork.
Styling.

cudak888 

Zombie thread it is...but to build on unworthy1's suggestion, it is possible to ream out the back of a curved brake bridge to fit a recessed bolt if it doesn't have an internal sleeve in it. The OP's bike does have a sleeve, and it'd be ill advised to drill it.

Admittedly, I have seen this type drilled all the way through successfully, if sloppily. My "Leo" Bottecchia was attacked this way by a PO and somehow survived the butchery (and now I've got to sleeve the side the brake fits on thanks to this hack).

Nevertheless, even though someone pulled it off on my Bottecchia and undoubtedly others have made it happen on other frames, it's not advisable. There's no way to know how thick the brazed-in sleeve is before drilling, and you could go straight through the sleeve walls. That's fine on a crappy bike that you don't mind taking a torch to if you screw it up, but chances are it isn't a crappy bike...yet. (Personally, I think drilling for recessed mounts is the first step to crapification given a decent enough frame that's equally unsuited. Not to mention that dual pivots come nutted these days).

However, brake bridges with no internal reinforcement - just a tube with a hole through it - are somewhat fair game, as there's no sleeve to damage. While someone might bring up the concern that the recessed bolt will crimp and damage the tube, I'll counter that a nutted brakeset can do the exact same thing. As such, I prefer to drill out a brake bridge conical washer to the recessed bolt's OD, and use that to spread the force of the bolt. Seems to work.







Also, given the clearance issues with the seattube, converting an unreinforced rear bridge is usually only possible using a Dremel with an angled grinding attachment (or a really short drill bit on a 90 degree adapter or angled drill - basically, nothing that's usually in the toolbox). This also means you have to work very carefully and check/re-check your work as you increase the size of the hole. One wrong move will result in a useless rear brake bridge with a wallowed out hole.

-Kurt