Dumb gear question

[swee'pea99]

I'm embarrassed to ask - I've been maintaining all my own bikes for decades - but I'm stumped by what is I'm sure a very basic & obvious problem.

I fitted a new derailleur to my daughter's bike. She tells me she got about a mile before 'there were some horrible sort of grindy noises and it sort of jammed up', since when she's been riding it single speed.

Obviously something is horribly wrong with the gear setup. In big front & rear, it almost doesn't look ridiculous:

But on anything else, the mech starts folding back, until on small front + small rear it ends up at:

I feel like I need to take 8" out of the chain before it even begins to make sense, but that can't be the answer.

What have I done wrong?

Thanks in anticipation for any help/suggestions.

 

[DCLane]

It looks like the chain is only threaded round the bottom derailleur jockey wheel, when it should be round the top, then the bottom.

 

[raleighnut]

It looks like the chain is only threaded round the bottom derailleur jockey wheel, when it should be round the top, then the bottom.

Nah you can see it over the top jockey.

As for the set up. well I don't think the rear mech has the required capacity (needs to be a 'GS' version) and the chain is too long.

 

[Sea of vapours]

Is the mech in the right position on the mech hanger? I don't know what that mech is, so don't know what it should look like, but it could be that the 'top' part of the mech should be about 90 degrees further back / clockwise. Failing that, it's lack of mech capacity as well as a substantially over-long chain.
EDIT: I meant to say that there is a lug on the top bit of the mech, sitting at about 3 o'clock in the top image, which has moved in the lower image. Is there nothing on the mech hanger which that lug can sit against, keeping the top bit of the mech further clockwise when under tension?

 

[swee'pea99]

Thanks for all your replies. Yes, the route the chain takes is fine. It's something to do with the mech and/or the way it's mounted on the frame.

I'm pretty sure the mech is correctly positioned on the hanger:

The screw/lug says to me that has to be right.

Whether the hanger is correctly mounted on the frame....?

But even some not-quite-rightness there surely wouldn't account for that amount of slack?

Proper baffled, me. Thanks again. I'm stopping for tonight, it's doing my head in and the light is at last beginning to fail.

Happy solstice!

 

[Ajax Bay]

The chain is a one inch link too long.
The derailleur is short cage and I estimate the chainset is a 53-39t and the cassette is (maybe - you can tell us) a 11-32.
This is massively out of spec: the RD cage can not wrap the amount of chain you need as soon as she drops to the inner ring.
In addition I suspect that the guide pulley is interacting with some of the sprockets.
Finally, the loop of outer cable from the stop on the chainstay to the RD is far too short. I suggest you need to replace it with one a couple of inches longer so it enters the RD 'in line'. This image shows good practice (images are not uploading for me):
https://www.killasgarage.bike/wp-content/uploads/2016/06/Derailleur-cable-loop.jpg
Q1: chain ring sizes
Q2: cassette small-large tooth number
Q3: distance in mm between axes of the guide and tension pulley wheels

 

[swee'pea99]

The chain is a one inch link too long.
The derailleur is short cage and I estimate the chainset is a 53-39t and the cassette is (maybe - you can tell us) a 11-32.
This is massively out of spec: the RD cage can not wrap the amount of chain you need as soon as she drops to the inner ring.
In addition I suspect that the guide pulley is interacting with some of the sprockets.
Finally, the loop of outer cable from the stop on the chainstay to the RD is far too short. I suggest you need to replace it with one a couple of inches longer so it enters the RD 'in line'. This image shows good practice (images are not uploading for me):
https://www.killasgarage.bike/wp-content/uploads/2016/06/Derailleur-cable-loop.jpg
Q1: chain ring sizes
Q2: cassette small-large tooth number
Q3: distance in mm between axes of the guide and tension pulley wheels

Thanks very much for that detailed and helpful reply. The message I'm getting loud & clear is that I've bought the wrong mech - it's fundamentally too short-cage for those gear ratios (I haven't counted, but I think your guesstimates are on the money, give or take). A longer cable housing I can handle, but by the sounds of things I'm going to need a new longer-cage mech too - correct? Thanks again for your help.

 

[wafter]

Also, looks like the chainrings are pretty worn (esp. the smaller) - perhaps this and excessive chain length caused the jam through chain suck?

Have you checked the chain for elongation / wear?

 

[Poacher]

@Ajax Bay and @wafter have pretty much nailed it; I'm only posting 'cos I'm intrigued by the frame.
Is it a Falcon Olympic?

 

[Ajax Bay]

clear is that I've bought the wrong mech - it's fundamentally too short-cage for those gear ratios (I haven't counted, but I think your guesstimates are on the money, give or take).

With those figures, 53-39 and 11-32 you need a wrap capacity of 35 - long cage. I need 50-30 and 11-28 and my long cage deals with that, complaining/telling me if in small and 14/13/12/11 sprockets.
You may improve the RD's capability to deal with the 32t sprocket (out of spec) by some 'b' screw screwing.
Till any changes, your daughter can probably ride with gears if she promises not to use the inner chainring.
While replacing the cable outer, I'd replace the section bypassing the bottom bracket as well - and perforce you'll need a new cable.

 

[swee'pea99]

@Ajax Bay and @wafter have pretty much nailed it; I'm only posting 'cos I'm intrigued by the frame.
Is it a Falcon Olympic?

Nope. C'est un Le Jeune. AKA The Bane of My Life. Most recently when I bought a new stem, only to discover later (after wasting grease + skinning a knuckle) that rather than adopt le spec Anglais, with was it turns out 7/8", or 22.2mm give or take, les bleedin' French decided to go with 22mm. What's 0.2mm between amis, innit.

But for all that a lovely bike, and she do love it.

 

[swee'pea99]

With those figures, 53-39 and 11-32 you need a wrap capacity of 35 - long cage. I need 50-28 and 11-28 and my long cage deals with that, complaining/telling me if in small and 14/13/12/11 sprockets.
You may improve the RD's capability to deal with the 32t sprocket (out of spec) by some 'b' screw screwing.
Till any changes, your daughter can probably ride with gears if she promises not to use the inner chainring.
While replacing the cable outer, I'd replace the section bypassing the bottom bracket as well - and perforce you'll need a new cable.

Thanks, that all makes sense. I'm in discussions as we speak...