Shifting into the small chainring throws off chain at RD

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istigatrice
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Joined: Sat May 12, 2012 8:32 am
Location: Australia

by istigatrice

Hi guys,

Having a few technical difficulties with my bike. When I shift into the little ring from the big ring the chain is thrown off the jockey wheel on the rear derailleur. I'm trying to work out why it's doing this. So far I've adjusted limit screws, straightened the mech hanger and neither of these have fixed the problem.

I was wondering if anyone else had a similar problem, and what their remedy was? I am tempted to try new jockey wheels, or a new derailleur cage/ new derailleur.

Here are some pictures:

RD jockey wheel - is it worn out?
Image

Chain thrown off:
Image

Sorry for the bad photos - does anyone have any ideas?
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bikerjulio
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by bikerjulio

How did you check the hanger? With a proper alignment tool?

If it needed straightening and it's a cast alloy looking thing, then replace it.

Yes the jockey wheel looks worn. Does it rotate freely?

Wear on chain? Correct chain length?
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One.

So let's just say I'm drivin' this buggy...
and if you fix your attitude you can ride along with me.

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istigatrice
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Joined: Sat May 12, 2012 8:32 am
Location: Australia

by istigatrice

Thanks for the reply,

I straightened/checked hanger with a Proper alignment tool - was easily straightened after checking with the manufacturer that it could be straightened (was only a little bit off to begin with though).

Jockey wheel does freely rotate, I think the wear is from having the chain thrown off - the groupset is less than 2500km old...

As above, groupset is less than 2500km old. Thought it was chain length but had a shop verify my chain length (they were happy with it).

I'm inclined to think it was a faulty RD, but just trying to eliminate the other options first.
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bikerjulio
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Location: Welland, Ontario

by bikerjulio

Bent RD?

Was chain checked for wear?

Other than that I'm out of ideas for now. Personally never had anything like this.
There's sometimes a buggy.
How many drivers does a buggy have?

One.

So let's just say I'm drivin' this buggy...
and if you fix your attitude you can ride along with me.

http://www.youtube.com/watch?v=GekiIMh4ZkM

mattr
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Joined: Fri May 25, 2007 6:43 pm
Location: The Grim North.

by mattr

I've had it when the spring housing in the rear mech is full of shit/grease/road grime. The cage doesn't spring back fast enough, so you loose the chain.

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bikerjulio
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Location: Welland, Ontario

by bikerjulio

mattr wrote:I've had it when the spring housing in the rear mech is full of shit/grease/road grime. The cage doesn't spring back fast enough, so you loose the chain.


This sounds better than my ideas
There's sometimes a buggy.
How many drivers does a buggy have?

One.

So let's just say I'm drivin' this buggy...
and if you fix your attitude you can ride along with me.

http://www.youtube.com/watch?v=GekiIMh4ZkM

istigatrice
Posts: 849
Joined: Sat May 12, 2012 8:32 am
Location: Australia

by istigatrice

I suspect bent rd. Will check chain for wear, if it is worn that's going to be the shortest a chain has ever lasted me...

Not sure if its an issue with springing back since its getting caught on the side. But will give it a good wash too. Any other things to check?

I'm thinking if the above fails I'll just replace it with another rd
I write the weightweenies blog, hope you like it :)

Disclosure: I'm sponsored by Velocite, but I do give my honest opinion about them (I'm endorsed to race their bikes, not say nice things about them)

spud
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Joined: Sat Feb 07, 2009 5:52 am

by spud

if you are considering changing out the RD, I would first try bending the cage. Set chain on big ring, then position the RD so that the cage/jockey wheel mounting bolts are vertical. Use a channel lock or adjustable wrench to twist the lower jockey wheel, in effect steering it in the appropriate direction to bring the chain back into the center. Be gentle with it, doesn't take that much to twist the cage.

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Calnago
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by Calnago

What kind of derailleur is it (which groupset)? Does the chain derail on the inside of the lower pulley?
The teeth do look a little worn but that shouldn't be the case after only 2500 miles unless maybe there's something causing it, which there may be. I'm interested because I've been working a similar issue recently.
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Calnago
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by Calnago

spud wrote:...Use a channel lock or adjustable wrench to twist the lower jockey wheel, in effect steering it in the appropriate direction to bring the chain back into the center. Be gentle with it, doesn't take that much to twist the cage.

Ouch! If you want to try bending it to force it to work, at least remove it from the derailleur hanger first. Doesn't take that much to bend the hanger either. But unless you've crashed it or have reason to believe that some other event may have bent your cage, I'd be contacting the manufacturer. If it is bent I would think it should be warrantied.
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Calnago
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by Calnago

... Double post
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xena
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by xena

Have you checked your other jockey wheel? Is that worn as well, Try swapping jockey wheels .

Is your chain worn?

I would replace jockey wheels and chain and see how that works .

Does it matter what cog you are in at the rear i.e. does it work ok when the chain is less slack?
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spud
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by spud

Ouch! If you want to try bending it to force it to work, at least remove it from the derailleur hanger first. Doesn't take that much to bend the hanger either. But unless you've crashed it or have reason to believe that some other event may have bent your cage, I'd be contacting the manufacturer. If it is bent I would think it should be warrantied.[/quote]

Less than 2500km on it, there's no way his stuff is worn enough to cause that issue. I suppose he could try to warranty it, but this thing is not the space shuttle, it can stand a little adjustment. I've seen pro mechanics get A LOT more physical adjusting equipment to function correctly.

And yes, I've made this adjustment on a derailleur in the past. Worked just fine for years afterwards.

highdraw

by highdraw

bikerjulio wrote:Bent RD?

Was chain checked for wear?

Other than that I'm out of ideas for now. Personally never had anything like this.

Two good ones above.
One more...chain length is wrong. Jockey wheels worn.

sungod
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by sungod

if this is only 2500km 'old', i do not see how it can be wear, you can ride that in a month, and unless there's some seriously abrasive conditions, it is not going to wear a groupset to the point this stuff happens

if the rd is aligned ok and there's no sign of the cage wobbling/twisting, then i'd look at...

i) lack of tension or binding of the cage, so that it's slow to take up the chain
ii) chain too long
iii) chain clogged up/contaminated so links are binding/stiff

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