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Mangled

Old 01-21-23, 05:33 AM
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delbiker1 
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Mangled

A first for me, I blew up my rear derailleur yesterday afternoon. Not sure, but I think the Connex quick link had not been seated properly, and popped off. I had just changed back to that chain and the cassette it was matched with. I set the limit screws and made sure the derailleur would not move too far, and took a quick spin in my neighborhood, It seemed to just fine. More concerning than the dr, the hanger was really mangled, twisted and bent, outward and backward down, on a Lemond Poprad. The axle insert area was significantly widened. I did not see all this damage until I got home and took a good look at all. I then knew that I was either going to take it somewhere to get it fixed, or I was going to have to attempt it myself. I chose the latter, with vise grips, and, from different angles, I was able to get the slot closed up, and got the twist and bend pretty much straight when eyeballing it. I put a 6500 dr on it, but still bent outward. After more finagling with the grips, remounting the dr showed it was close to being lined up. A couple more tweaks by hand, then I put it all back together and went for a ride. The shifting is good, as well as the rest of the fix. I am using 6400 bar end levers, set on friction. I am not going to try indexed, at least not now. I have been using either 10 or 11 speed cassettes with this set up. I have no reason to go to 8 speed. I suspect indexed shifting would not be quite right without more aligning being done.

In the end, the worse damage is the hanger. It is a bit mangled, but cannot be seen when everything is mounted. The drive side stays have a couple new scratches, no big deal, the rear fender stays are broken, the wheel is way out of true, the 4600 gs derailleur is beyond worth trying to repair. It could have been a lot worse. I really surprised myself when, an 1 1/2 later, I was back on the bike, everything operating as it should. I left the 6500 dr on the bike, it is handling the 46/38 front, and 11-34 back just fine.
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Old 01-21-23, 08:46 AM
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Similar thing happened to me once. You can do an internet search for a DIY derailleur hanger alignment tool. As far as the index shifting. If it rides and works in friction mode, there’s no reason the indexing shouldn’t work. It is what it is, and is adjusted with the barrel adjusters at the derailleur or in-line.

Dan
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Old 01-21-23, 09:39 AM
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It sounds like the der got caught up in the wheel. When this happens the der gets pulled way back and up, following the spokes' path and can both bend the hanger inward (towards the wheel) as well as pry open the axle slot. If this happened there can be secondary damage to the axle or spokes. Have you checked them too?

It also sounds like the chain was un connecting linked, as in that link became undone. Is this also true?

Common reasons why a der can be damaged by the rotating wheel (that's kept rotating by the riders forward momentum) are: a previously bent hanger which means the der's low limit is now past that cog, something got caught in the rotating spokes and grabbed the der pulling it inwards further, a chain issue like coming apart and flaying about then enough to grab the der and rotating wheel. There are other reasons but these are the usual.

Think about the amount of force it took to realign the hanger. This is indicative of the amount of force that acted on the der/hanger when the incident happened. Now try to figure out how this force could be applied to the der. Dropping a chain due to an opening connecting link usually results in the chain just being ridden off the cogs/rings and falling to the road/ground. But if that link wasn't fully set you would have felt that "less than 1/2" pitch" of that link not seating in the cog teeth and usually feeling like a skip (much like a worn out chain does but only once per chain rotation, not rhythmic with the pedal position). In fact how one sets the connecting link is by loading the chain (as though one was stomping on the pedals).

I, too, have had this stuff happen to me a few times over the years and seen the results many times a season when I was still wrenching full time. Andy
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Old 01-21-23, 11:43 AM
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Originally Posted by delbiker1
In the end, the worse damage is the hanger. It is a bit mangled, but cannot be seen when everything is mounted. It could have been a lot worse. I really surprised myself when, an 1 1/2 later, I was back on the bike, everything operating as it should.
I was given a frame that a customer had done this to - the horizontal dropout opened up to 90 degrees. His insurance replaced it with a new frame and didn't want the old one returned. I stuck it in the vice and had it straightened and aligned in ten minutes, then built it up and rode it for several years. Forged frame ends seem to be pretty tough (replacing them is easy but it's more work to make it look nice).
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Old 01-21-23, 02:59 PM
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Originally Posted by grumpus
I was given a frame that a customer had done this to - the horizontal dropout opened up to 90 degrees. His insurance replaced it with a new frame and didn't want the old one returned. I stuck it in the vice and had it straightened and aligned in ten minutes, then built it up and rode it for several years. Forged frame ends seem to be pretty tough (replacing them is easy but it's more work to make it look nice).
Forged dropouts are generally made from fairly mild steel, and can tolerate a fair amount of bending/re-bending. Fancy cast dropouts can be a different matter.
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Old 01-21-23, 04:10 PM
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Great pics.
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Old 01-21-23, 05:30 PM
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I did not have my phone with me when it happened. I had to detach the derailleur and fender, and unwrap the chain to walk the bike home. Probably, most people on BF have seen numerous pictures of blown up dr's, including a mangled hanger, or, had their own experience with it. I'll just say it looked like the pictures I have seen.
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Old 01-21-23, 08:56 PM
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What photos can show is details about the situation that lay people don't initially think about. Often it's not what the photo taker sees, and is trying to capture, that I find interesting. Andy
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