Derailleur Hangar Repair?
 

I have an old 87 Cannondale Criterium with a broken derailleur hangar. It's broken at the threaded hole that would normally accept the derailleur bolt about half way through. Is there any way to repair this?

Might be a little crude but it seemed easier than replacing the entire dropout. I cut and filed off the broken piece so it was parallel with the horizontal dropout slot, then cut off the same part from a donor frame, cutting it so it matched the entire piece of metal removed, eyeballed the alignment, held it in place with vice gripes and brazed it on. Cleaned it up(marginally) will a little filing and done. Its plenty strong for the load the derailleur puts on it. Surprisingly it didn't need any alignment, but an adjustable open end could have easily done it. Frame is a 85' Pug urban express, a freebie because of the broken dropout, now a city/grocery bike for a friend.

Might be worth a try to adapt a replaceable (bolt-on) hanger to the broken dropout so that any future damage can also be easily fixed. If appearance is not a big concern, you could also use a steel "claw" derailler hangar from a older cheap bike that fits over the axel, sandwiched between quick release nut and the frame.

If there is no bolt-on solution, brazing-on a replacement wont really work for aluminim but you would likely be OK to have a replacement hangar TIG welded on without going through subsequent heat treatment of the entire frame that is needed for tubing or full dropout repair of aluminum bikes.

Sorry, I didn't notice the aluminum aspect, pretty obvious since its a C'dale.

No need to apologize. That was a pretty nice repair. Thanks for the pics.

It's got a bolt on adapter now but because it's bolted to the outside of the dropout the chain alignment is off and I get some rub on the big front chain ring when I'm on the small one.

THis site list over 300 different replacement hangars;
http://www.derailleurhanger.com/alld...eurhangers.htm

Look for one that has is thinned where it overlaps the dropout and thickens wider for the hangar hole so it is less offsett.

Wow, excellent site. I may be able to salvage this yet. Thanks

That is a bit unexpected - where are all the other sites devoted to only one frame part?

If you ultimately end up with offset, presumably there is a site selling only the BB axles that will allow you to customize the chain position for a straight run.

Did you check with cannondale or a cannondale dealer? At one time cdale did offer a hanger repair kit for their older frames that did not have the replaceable hanger. It required some drilling and tapping but might be worth investigating.

If you can find a damaged frame, you can cut off part of the dropout above the hole and have it TIG welded back on. I did that to my 1987 Cannondale after crashing in a race. Made a straight cut further up where there's more metal, got another dropout and made a matching cut. Beveled the edges, ran a TIG bead all around, ground it down a bit, rattle can paint .... off to the races ... still going strong.

Stopping by a dealer is probably a good idea. But it seems like the Cannondale dealers are all about new bikes, people start rolling eyes when I start talking about old bikes. I'll probably see if it's possible to call Cannondale as well. I thought about welding, I'm keeping that in my back pocket as a last resort.

I agree that a dealer is not likely to be much help, unless they have a damaged frame they can give you to use for dropout fixing material.

There is no need to cut off the derailleur hanger. You could use a helicoil repair kit for rear derailleur (10x1mm).

I've used helicoils. I was thinking about trying to find a small kit to re-thread a front derailleur high adjustment bore I cross threaded. The thing is if I drill above the old derailleur hole it's going to be too high.

Ala #7, maybe you can machine [router like cut down] the face, of those Non replaceable dropouts
to accept a replaceable dropout ..

If you can make a jig to hold your frame under the drill press ,
as a fixed rotating tool , machine ,
and supported by the jig , say made out of plywood,
so as to move the frame smoothly under the tool.
you might get a good parallel face..

or maybe, just wing it, freehand, with a dremel tool..