Talking about
http://ebay.com/
Aldo wrote:
> I imagine the center bolt is threaded into matching threads added to
> the spring anchor (what's the correct name for that part?).
> There must be a shoulder on the bolt which bottoms-out against the
> front surface of the spring anchor.
Well we can't know without taking it apart, but the ones I have made like this require only a larger hole in the brake arms, and a typical brake centerbolt shortened, with a typical brake centerbolt allen-head nut, of the type that usually goes in back of the crown. The nut is shortened a little at a time until it tightens against the spring anchor just as the slack is taken out of the brake action. (I think this is what Aldo is describing.) This needs to be done precisely but only needs to be done once. In theory you can't thereafter easily adjust for wear, but in reality the wear that occurs there is minuscule. I suppose you could grind some more off the back of the nut to adjust for wear. I haven't had to do this on my brakes, but I've only been riding them for 10,000 or 20,000 miles. I'm not saying that's a lot, I know it's not much compared to some people. I bet the typical bike that would get this treatment doesn't see major miles though.
I saw this brake treatment on (and copied it from) an '81 Pinarello that Battaglin rode in mountain stages of the Giro - lots of little weight-saving tricks like that (as well as some big weight saving tricks). The bike looked lightly used, I doubt if he put more than 1000 km on it.
http://bulgier.net/
I have made them both with the front arm counterbored like this one, and without counterboring where the cap of the bolt sits outside. The latter is easier of course and technically just as good, but not as trick looking. I was lucky to have a counterbore with the right size cutter and the right size pilot, which makes the job quite easy, even a good solid drillpress would do (with the right vise) - no CNC mill required.
Mark Bulgier
Seattle WA USA