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Old 11-16-11, 03:14 PM   #1
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Tweaked Derailleur Hanger with Elongation at the Threads -- Repairable?

Slightly twisted might be a better way to describe it. Seems to have a barely discernable vertical S-curve from the lower part of the dropout to the tip of the hanger when viewed from the rear. The mounting hole is visibly ovalized and the derailleur won't start threading in.

I'd like to avoid using a dropout saver to fix it if possible. Is this something best left to a local framebuilder for repair? Anyone here done it? Based on my description, how much should I expect to pay someone to get the dropout & hanger back to normal?

This is on a mid-1980s Trek with a Reynolds 531 frame.
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Old 11-16-11, 03:29 PM   #2
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based on that description I think the best approach is to have a fresh hanger portion grafted on. This is not a uncommon fix, but not seen so often these days: it the repair guy doesn't have a Campy bit to braze or TiG on, he can cut one off a donor dropout. I think this is easier (and less paint damage) than brazing in a whole new DO. Cost depends on location and what frame builder/repair guys are available to you in F.F., MN. Ed Litton did one for me many years ago and cost was lumped in with other braze-ons and paint...guessing that in today's $$ might be $40-$65.
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Old 11-16-11, 03:31 PM   #3
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The S-curve itself isn't an issue. It's only when the plane of the mounting hole is out of alignment relative to the plane of the freewheel. This is a critical issue on indexed derailleur systems, so fortunately they've invented a tool to expedite the process of aligning the hanger. Depending on the shop, it will cost from nothing to about $10, as it's typically a 5 to 10 minute job.

As for the ovalization of the hole, it all depends on oval it is. It might be a simple job of chasing the theads. Sometimes threads get distorted only on the one end. Did you try removing the wheel and threading the derailleur bolt in from the backside? If you can start it from the back, dropouts are quite ductile on purpose and you may be able to sufficiently chase the thread with the bolt. Also, make sure the problem isn't with the bolt itself. Visibly inspect the threads and if possible, try another derailleur bolt.
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Old 11-16-11, 03:39 PM   #4
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I would first try puting it on an anvil and use a BFH to straighten the S curve out. If not too terribly ovalized, use a tap to chase the threads so the derailler will thread in. Once it is reasonably strait and threads are chased, you should take it to a shop with a derailler hangar alignment tool and have them bend to final aligned position.
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Old 11-16-11, 04:42 PM   #5
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I like this thread. So to speak.
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Old 11-16-11, 04:52 PM   #6
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My drop-out wasn't twisted or ovalized, but the threads on the outside were screwed up. Livermore Cyclery, my go-to place for things vintage, were able to retap the threads and make sure they were good and installed the rear derailleur for $15. It took about 10 minutes.

On another bike, I had them realign a rear drop-out & hanger. That took maybe 15 minutes and the cost was around $15, if I remember correctly. It certainly was not a large sum.

T-Mar's suggestion is spot-on. See if you can thread the RD into the backside of the hanger. If so, it is almost certain that a good shop can get you back in business quickly and fairly cheaply.
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Old 11-16-11, 04:53 PM   #7
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...barely discernable vertical S-curve from the lower part of the dropout to the tip of the hanger when viewed from the rear. The mounting hole is visibly ovalized and the derailleur won't start threading in....
Any reason not to run a tap through it and mount a derailliuer, see how the deraillieur mounts? If it's off use an alignment tool?
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Old 11-16-11, 05:13 PM   #8
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Thanks guys.

Eyeballing it more closely, the plane of the mounting hole appears to be curved outward at the front and inward at the rear. Lowered the dropout into a bench vise sandwiched between 2 thick plates of flat steel and carefully cranked it down to flatten the curve; didn't seem to change it much.

I also tried threading 2 separate derailleur bolts in from the back--no start. There's enough distortion to see a sliver of daylight around part of the bolt when trying to start it from either side.

This is the first time I've seen an elongated derailleur mounting hole and it has me a little spooked. I'm more inclined to try a Dropout Saver before going radical with a graft, which could be the next progression step.

Most bike shops in my area either can't be trusted with this kind of work or won't even try it. Got an email reply from a very experienced Minneapolis framebuilder who thinks straightening and rethreading the hanger at his shop might work based on my description. If it looks doable, it would cost $25. He isn't far away. What do you guys think?
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Old 11-16-11, 05:23 PM   #9
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Helicoil.
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Old 11-16-11, 06:19 PM   #10
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Helicoil.
except they don't make one in that size (10M x 1mm) and it you start running taps in it make sure you have that extra-fine thread as it is NOT a typical 10M size. Actually it might even be 26tpi if it's Italian, but 10M x 1 is "close enough" and what most LBS use. i agree it's best to exhaust all the less radical means before you opt for the graft-on surgery, but...when I needed it, it worked for me.
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Old 11-16-11, 06:52 PM   #11
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Depending on what the bike is. I'd use a crescent wrench to straighten it. Run the tap through it and get the threads good. Screw in a bolt and try tapping on the hanger with a hammer around the bolt (with the bolt still in it) to reround it as best I could and pull out the bolt and retap again. After I thought it was OK, have the hanger/dropout aligned.
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Old 11-16-11, 07:15 PM   #12
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except they don't make one in that size (10M x 1mm) and it you start running taps in it make sure you have that extra-fine thread as it is NOT a typical 10M size. Actually it might even be 26tpi if it's Italian, but 10M x 1 is "close enough" and what most LBS use. i agree it's best to exhaust all the less radical means before you opt for the graft-on surgery, but...when I needed it, it worked for me.
Absolutely correct, my faulty memory. What the OP needs is a Wheels Mfg Dropout Saver:

http://wheelsmfg.com/content/view/502/44/
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Old 11-16-11, 07:24 PM   #13
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...Got an email reply from a very experienced Minneapolis framebuilder who thinks straightening and rethreading the hanger at his shop might work based on my description. If it looks doable, it would cost $25. He isn't far away. What do you guys think?
Do it.
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Old 11-16-11, 11:50 PM   #14
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Thanks again. Lot of interesting ideas here.

There's a LBS that will do a Helicoil install and align the hanger for $35. I've brought work there before and the results have been mixed. With a 50-50 chance of getting a lasting repair, I won't be comfortable trusting them with this project.

Although I haven't met the framebuilder yet, he's pretty well-known and respected. $25 seems reasonable to me. However, if the cost starts escalating after I get to his shop I may try the fix myself. I'd probably start along the lines of what dedhed has suggested and escalate to a Dropout Saver if necessary.

Has anyone here successfully re-formed an ovalized derailleur mount or see it done?
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Old 11-17-11, 01:08 AM   #15
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If you're handy and equipped enough to do it, I'd take dedhed's approach too.
Nothing to lose, doesn't work....replace the dropout or use a claw.

If the frame is valuable enough to be saved, then $25 for a framebuilder is small potatos.
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Old 11-17-11, 05:20 AM   #16
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The S-curve itself isn't an issue. It's only when the plane of the mounting hole is out of alignment relative to the plane of the freewheel. This is a critical issue on indexed derailleur systems, so fortunately they've invented a tool to expedite the process of aligning the hanger. Depending on the shop, it will cost from nothing to about $10, as it's typically a 5 to 10 minute job.

As for the ovalization of the hole, it all depends on oval it is. It might be a simple job of chasing the theads. Sometimes threads get distorted only on the one end. Did you try removing the wheel and threading the derailleur bolt in from the backside? If you can start it from the back, dropouts are quite ductile on purpose and you may be able to sufficiently chase the thread with the bolt. Also, make sure the problem isn't with the bolt itself. Visibly inspect the threads and if possible, try another derailleur bolt.
+1. Nicely said.
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Old 11-17-11, 02:38 PM   #17
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If the frame is valuable enough to be saved, then $25 for a framebuilder is small potatos.
+1. Go see the builder.
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Old 11-18-11, 01:28 AM   #18
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Met the framebuilder at his shop today. Real nice guy. Looked over my dropout and hanger and came up with a plan of action in about 15 seconds.

Clamped the BB shell into a padded bench vise and ran a long elaborate-looking tap through the hanger hole a couple of times to get the threads clean, then moved on to aligning the hanger & dropouts. After asking me what the wheel spacing was, he set a 2-piece alignment tool into both dropouts and applied a fair amount of levering force to get the right side aligned with the left. Followed this by mounting a nice old racing wheel, installing an alignment gauge, and tweaking the hanger a few times to get it straight. Finished the job by chasing the threads one more time with the tap, then gave me his final assessment.

Neither of us detected any cracks or weakness. Although he felt the hanger threads were still kinda "chewed up", if it was his bike he would feel comfortable threading in the derailleur, snugging it down good and tight, and riding it as-is. If for any reason I thought it still wasn't right later on, I could bring the bike back to him, get a little weld added to the inside of the hanger hole, and have it re-tapped.

By this time another customer was en route to his place with a more seriously damaged frame. After asking if I might use his services again, I thanked him for his time and headed home. Paid $20 for the work. Glanced at my watch on my way back to the car and was surprised to see I had only been in the shop for about 10 minutes.

Took a closer look at the Trek when I got back. The dropout and hanger twisting is still visible, but less pronounced. Mounted my rear wheel and derailleur: the alignments look pretty straight. Seems I'm ready to continue with the overhaul on this bike.

I learned a lot from the responses here. Gives me confidence to try more challenging stuff in the future. Thanks for your support.

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Old 11-18-11, 10:14 AM   #19
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a happy ending and a cheap one, too. It's always good to get the follow-up since so many of these threads just evaporate: thanks for closing the circle.
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Old 11-18-11, 10:43 AM   #20
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Took a closer look at the Trek when I got back. The dropout and hanger twisting is still visible, but less pronounced. Mounted my rear wheel and derailleur: the alignments look pretty straight.
If he did everything you say he did I wouldnt worry about how it looks...sometimes hangers just look off even when they're perfectly alighned. He did exactly what I would have done if you brought into the shop I worked at. Tightnen your derailleur down, run it through the gears and double check the tightness, if its still tight ride a little and double check. If it ever loosens up regardless of the amount you'll need to either weld/tap as suggested or drill and use a framesaver. I prefer the framesaver method.
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