Bicycle Mechanics - Broken cantilever stud
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01-19-10, 10:25 PM
So I was riding along, and I hear a loud snap, look down, and my front cantilever brake is all over the road and a spoke is broken, not sure what happened...
Anyways, I've been trying to figure the best way to attempt a repair and was wondering if anyone had some good advice :)
Here's the damage:
Half the stud has broken off, and I could buy a replacement stud but the broken bit makes that impossible. There's this thread http://www.bikeforums.net/showthread.php?547083-Canti-boss-repair-can-anybody-help&highlight=broken+cantilever+stud but that's a little confusing, and I think I have a different problem. In that thread they describe a repair kit, could that thing help me somehow? I tried to grab that tiny piece of metal sticking out with needlenose pliers, but that didn't work...
Any help would be greatly appreciated!
01-19-10, 10:35 PM
You need an EZout, aka a screw extractor
Notice the "backwards" threads
01-19-10, 10:39 PM
The studs screw in. An you're lucky that yours already has a hole in it so you can run down to the local hardware or tool store and buy a set of EZOuts. Use as directed to relieve the pain of stuck threads and then go buy a new brake stud to fit. You may need some heat to help out. These things are often loctite'd in. Heat the area until the paint almost scorches. Or if you have a soldering iron that will fit into the hole stick it in and heat the threading directly. Once hot take out the soldering iron and use the EZOut right away while it's hot.
Or if by some chance this is a one piece brazeon then you may have to drill and tap what is left to allow a threaded stud to fit.
01-20-10, 07:03 AM
That is actually a pretty easy repair...I do about 6 a year. There is a kit for this, I belive it is a "Problem solvers" brand. Any good bike shop will have one, I've even made the parts myself for this job. It is a simple repair for any good mechanic. I think that we do the job for about 20 bucks, plus the part. I hope that helps.
01-20-10, 12:32 PM
The studs screw in. An you're lucky that yours already has a hole in it so you can run down to the local hardware or tool store and buy a set of EZOuts.
This looks like an older steel frame, so the bosses are unlikely to thread into the mount. Rather, they are swaged in place:
It may be possible to drill out the remains of the old stud and just braze the boss onto the existing mount without damaging the paint too much.
N.B. I always braze the stud to the mount, and all the seams on the mount when I put these on a frame. That makes it much more solid than simply relying on the swaging to hold it in place, which appears to have been the case with the OP's bike.
01-20-10, 12:55 PM
In looking at the picture I thought it looked a little odd. That's why I stuck the last sentance on about "if it's a one piece". I suspect that you're right and it is one of the type you show. If that's the case there isn't enough metal to allow a strongly threaded mount for a thread in pin if the swaged in part is removed. But the lower bigger diameter part seems to still be there. The swaging held fine but the smaller portion snapped off.
EDIT- Never mind, I saw the info on the repair kit for this in that other thread. Looks like that's the way to go. The remaining portion of the post would still require tapping so the repair kit has threads to fit into but that is a fairly simple job.
01-20-10, 10:01 PM
Thanks for all the quick replies everyone :)
I think I figured that problem solvers kit out. Before, I was thinking that it would somehow replace the broken stud only. Now I realize that the screw is a replacement for the screw for the screw that keeps the cantilever on the boss. The replacement screw threads onto the remaining thread (which thankfully is still good in my case, and I think should be the same threading as the replacement screw) and the aluminum sleeve acts as the broken off stud (with the actual cantilever brake slipped onto the sleeve). Since the screw is now deeper into the boss, if it happens again the whole thing might get pulled off, but it definitely beats brazing a new one on!
And I thought I was going to have fun with torches and crazy drill bits! But then I would have a bigger problem when my house burns down...
Thanks again everyone, cheers :D
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