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PostPosted: Thu Aug 09, 2018 8:04 am 
Devout Dirtbag
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Joined: Tue Jun 24, 2014 1:13 pm
Posts: 101
Location: London
Hi everyone,

I'm having some problems aligning the rear derailleur. The bottom cog never seem to be in line with the other ones.
No amount of fiddling with screws fixes that:

Image

I noticed there is a washer between the derailleur itself and the frame. Should it be there? Or is this the likely culprit?

Image

Thanks


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PostPosted: Thu Aug 09, 2018 8:12 am 
King of the Skip Monkeys
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Joined: Wed Nov 07, 2007 4:34 pm
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Location: in the shed
The washer is in the wrong place but that shouldn't really affect the travel of the mech over the cogs.


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 Post subject: Re:
PostPosted: Thu Aug 09, 2018 8:38 am 
retrobike rider / Gold Trader
retrobike rider / Gold Trader
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Location: In the Woods. . .
I think that washer is cocking the mech away from being vertical, so yes, before you get onto the biggest cog, your mech cage is probably trying to do a dance with the spokes.

Alternatively, either the mech or the hanger are bent, and need pulling back into line.
Or the cage and pivots are so worn and sloppy that it no longer hangs vertically.

Good luck!


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 Post subject: Re:
PostPosted: Thu Aug 09, 2018 9:36 am 
Devout Dirtbag
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Joined: Tue Jun 24, 2014 1:13 pm
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Location: London
Ah, I knew it!

Thank you guys.
The previous owner must have put the washer on the wrong side. In fact on the other side there is nothing between the nut and the frame.

Another question, still related to the same problem.
The derailleur has three adjusting screws. The bottom one is the L screw, middle one the H screw...and the top one, which seems to be acting directly on the derailleur mount. What does that screw do?


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PostPosted: Thu Aug 09, 2018 9:41 am 
King of the Skip Monkeys
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Location: in the shed
Thats the 'body adjustment screw' or B tension screw - adjusts for the clearance for biggest cog on the back/ smallest at the front

something like that


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PostPosted: Thu Aug 09, 2018 9:46 am 
Devout Dirtbag
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Joined: Tue Jun 24, 2014 1:13 pm
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Location: London
Thanks.
Not sure I get it, I will need a more exhaustive explanation. But now that I know what it is called I'll look it up


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 Post subject: Re:
PostPosted: Sun Aug 12, 2018 11:42 am 
Devout Dirtbag
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Joined: Tue Jun 24, 2014 1:13 pm
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Location: London
I'm sorry to say this (and I do mean it because I'm really sorry I just wasted my time) but you were both mistaken about the washer.

Turns out it works as a spacer onto which the svrew that hold the derailleur at the correct angle is fastened to.
I tried removing it but all I obtained was to tangle the derailleur into the chain, only to have to put it back as it was.

So it looks like my alignment problem might be a result of the bent arm of the derailleur


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PostPosted: Sun Aug 12, 2018 11:46 am 
Old School Grand Master
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Location: Cumbria
The mech is really pointing way far forward, maybe the tension in the chain is twisting the mech / cage.?


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 Post subject: Re:
PostPosted: Sun Aug 12, 2018 12:18 pm 
Devout Dirtbag
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Joined: Tue Jun 24, 2014 1:13 pm
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Location: London
Interesting observation.
But unless a shorter-than-normal chain was fitted, what could cause the excess tension?


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 Post subject: Re: Re:
PostPosted: Mon Aug 13, 2018 2:26 am 
MacRetro rider
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Location: A Fifer furth o' the Kingdom
Ugo51 wrote:
I'm sorry to say this (and I do mean it because I'm really sorry I just wasted my time) but you were both mistaken about the washer.

Turns out it works as a spacer onto which the svrew that hold the derailleur at the correct angle is fastened to.
I tried removing it but all I obtained was to tangle the derailleur into the chain, only to have to put it back as it was.

So it looks like my alignment problem might be a result of the bent arm of the derailleur


Sorry but that washer should not be there. The mech hanger should fit flush to the dropout but it doesn't. Why? Because the washer is there, when you tighten the axle nut onto mech hanger it is pulling it onto dropout closing the "space" created by washer, the mech hanger is now at an angle to dropout meaning the mech is not parallel to dropout or cassette. You can see this in your first pic and that is why bottom jockey wheel doesn't line up with the top one. Because the mech is not mounted in line with dropout it won't function as it should.

Don't know what you mean by "tangle the derailleur into chain"Image but after putting it all together correctly without the washer being in wrong place you will need to adjust the travel limit screws on mech because it's position will have changed due to hanger being lined up parallel. It is possible the mech may be bent but you won't be able to tell till it is mounted as it should be. I would also check mech hanger isn't bent where it has had the axle nut tightened against it, there is also the risk wheel may not be as secure as you think since axle nut and washer are not being tightened on to flat surface.


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