RoadTire 

Should I disassemble everything to straighten this or what?

exeo

You need a special tool to bend it back to the correct position. Either buy the $60 tool and do it yourself or, I would suggest you take it to the bike shop and have them do it.

https://www.amazon.com/Park-Tool-Dera...ailleur+hanger

dddd

Nothing too serious here.
The frame's dropout AND the derailer cage both look bent to my eye, but is this causing any noticable problem?

I would be careful about applying too much force and over-doing it, but since this is a friction-shift derailer, I would gently twist the cage back toward a more-normal angle using my gloved hands and call it a day after re-adjusting the derailer's limit screws and re-torquing the mounting bolt and pulley bolts.

PS, don't over-tighten the cage pivot bolt. I've seen the bolt strip the threads in the pulley cage plate on this series of Shimano derailers.

dsbrantjr

It is interesting that it is bent outwards, they usually go the other way. Is this a botched repair?

FBinNY 

+1, Looking closely at the photo, both the RD and hanger look reasonably OK, but the RD upper body is at an angle to the hanger, and I suspect that the mounting bolt may be cross-threaded.

It's hard to tel from a photo, but I suggest the OP give this a close look, especially if he recently mounted the RD.

BTW- hangers bending outward is very rare, the vast bulk of bent hangers bend inward.

RoadTire 

Not yet.

I'll doublecheck that I didn't cross thread the mount and be careful about stripping threads. Should I take the cage off the the rest of the derailleur before trying to straighten it?

The chain is jumping on middle (an prob other) rear cogs when I stand and push hard. Chain length is good, 12" spot on, and brand new freewheel. After my last crash that put gouges in the derailleur, I woulda thought it bent inward too, but my guess is that I bent it outward when transporting in the back seat of my car w/o the rear tire. I would place it derailleur up, and it was probably resting on something. Noooo idea how log it's been that way, but it's been skipping for a couple years. Ooops.

I did see the special tool to align the hanger if bent, so ya, that's a run to the shop, but first I'm going to try to straighten the cage.

fietsbob

If the shifting is weird, doing the derailleur hanger alignment check
is where I'd start.

once you eliminate that possibility, it's all replaceable parts..

while RD is dangling from the housed cable,
see if the shifting[moving sideways] seems smooth and easy..

ultraman6970

YOu dont even need a tool for that, just stick the allen tool you used to bolt the derailleur in the drop out and wiggle it little by little until the rd is almost right.

dddd

The main symptom of a bent hanger is that the rear derailer positioning changes when the front derailer moves the chain from ring to another.

This is because the rear derailer and cage rotate off-axis with the axle when the hanger isn't straight, so the rotating cage (taking up chain slack) causes some lateral movement of the top pulley.

Kimmo

Are you sure it's bent and not just wear? Perhaps the parallelogram is sloppy and its spring is what's holding it in this position.

I'm quite sure the mounting bolt isn't cross-threaded. It doesn't look as if the hanger is bent either, but I'm less sure about that... although if I was going to do any tweaking on this derailleur, I'd certainly remove it. You could clamp it by the mounting bolt between some wood in a vise.

cyccommute 

Check for a cross threaded derailer first before you start bending the derailer hanger. If you look at your second picture you'll see that the derailer should sit flat on the hanger but yours isn't. There's a gap at the bottom between the hanger and the derailer. Carefully remove the derailer and chase the threads from the back side of the hanger then reinstall the derailer. You should never have to force the derailer bolt into the hanger. If it's tight, you've probably cross threaded it.

Kimmo

That's odd; it looks perfectly fine to me. It's obscured by the loop of housing on the rear view, but I'm sure it'd look just the same; that black bit isn't a gap, it's a circlip.



I see no gap.

cny-bikeman

On a friction shift if the hanger is bent in/out but not twisted straightening is not a great challenge, but I don't like the odds of figuring exactly how a derailleur is bent and where to "straighten it." I'd give it one shot and if still problematic just replace it.

RoadTire 

Thank you for that Kimmo. I didn't get a chance to upload what you just did. It does look ok to me.

In the picture from the back, looks like the bottom part where the cage is screwed on looks angled downward, (3 pm position to 8:30 pm position, only not that drastic.) while the cage is angled outward and twisted. Can you folks see that when you expand the picture?

Closed Office

I've aligned a few used ones to the chain with my specialty tool, channel lock pliers. No diss assembly required, and it lines up closely enough just by having your eyes open.

You do want to avoid bending the frame and having the wheel bolted in helps with that. Just grab a part that will only result in the derailleur hanger being twisted back in the right direction.

I'm not big on finesse, and apologize if this is too crude. Words I like to live by, 'close enough.'

d.vader123

Let me get this straight. Is the rear dropout bent on this frame or is it just the derailleur hanger? Sorry, but as someone who's still learning about all this I want to make sure that dropout is part of the frame while derailleur or hanger is that part of the derailleur that the chain goes through and that holds the pullys. The hanger is often something that can easily get bent upon impact. Is that correct?

Kimmo

Yeah, and since the upper pivot seems lined up okay (I think the outside is a bit tapered), it looks like you have really worn pivots in the parallelogram. What happens if you try to pull the derailleur cage into position?

Dan The Man

There is a much cheaper solution than taking it to a shop or getting a tool, and more accurate than an allen wrench. Get yourself another rear wheel, off a bike you have kicking around. Thread the axle into the derailleur hanger, and you have yourself a torque arm and a gauge. It's very easy to tell if the second wheel is not parallel with the first wheel in either axis.

Kimmo

Make sure it's the right thread pitch, though...

Dan The Man

Most axles are standard 10 mm and have the same thread as pretty much every modern rear derailleur. I would be surprised if you had some weird European mix and didn't know it. You will also find out very quickly that it is difficult to thread.

RoadTire 

Right now I'm on the assumption the dropout and hanger are ok, or at least not the biggest problem. But I'm going to try the wheel trick on the hanger that Dan suggested. I'm focused on the derailleur cage because it's "eyeballable."


Addendum:NATCH - the hanger is bent. See later posts

RoadTire 

Who woulda thunk? Give the man a cigar.

The back of the wheel is 1.0 (.993) inch farther apart than the front of the wheel.
The top of the wheel is .09 (point-zero-nine) inch farther apart than the bottom of the wheel.
At 27 in dia, that makes roughly 2.1 deg front to back. (Roughly, not exactly)

I think Park Tool recommends max of 4 mm diff.

This still doesn't explain the outward bend of the hanger to the degree it is, does it? Any idea how much I can ride this yet without damage to the drivetrain?


I took 3 sets measurements at the valve step of both wheels, 1 set with a dial caliper, 2 sets using a plastic ruler, indexed off one edge. I also double checked for cross threading on both the derailleur to the hanger and the cage to the other part of the derailleur. We are assuming the rear wheel is perfectly aligned in the frame I guess.

RoadTire 

Just got back from my local REI - they have a couple great mech's there - to have the hanger, rear drops, frame and rear derailleur checked out. They re-alligned my drops, because I have 126 mm spacing with 130 mm rear hub, and straightened the hanger. It was about 4 mm off. Then the mech actually took it for a test ride in the parking lot. How cool is that? Neither he or I could get the chain to jump the rear cogs.

The RD is definately worn and has play so that would contribute to some shifting issues so I'll have to replace it when I can. Not bad for a bike purchased in '75.

I'll try to get out for a ride a little later after it cools down, but for sure I'm up for a good ride tomorrow early.