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Old 01-25-09, 04:57 PM   #1
gerald_g 
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Shimano LX rear derailleur question

I am working on cleaning and such on a Stump Jumper. The rear derailleur is a Shimano LX.

When I took the idler wheels out, I missed noticing that they are not identical, and which one came from which position.

I've posted pics below. As you can see one wheel has a steel insert and the other not.
Which wheel goes in which position when re-assembling ?




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Old 01-25-09, 05:11 PM   #2
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As usual - Sheldon has some help. From his online glossary....

Jockey pulley

The upper pulley on a rear derailer. This is the pulley that actually guides the chain from one sprocket to another. Shimano jockey pulleys are designed with a "Centeron®" mechanism that allows a small amount of sidewards motion to compensate for imprecise index adjustment.

Since the pulley with the steel insert is slightly narrower than the bushing, which would leave some room for "sideways motion", I gather, that the pulley with the steel insert is the jockey pulley, and should be installed in the upper position.

An hence the other pulley is the tension pulley, and should be installed in the lower position.

Anyone like to confirm this ? I'd appreciate the input.
Thanks
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Old 01-25-09, 05:38 PM   #3
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I have an XT derailleur sitting here on the table and the upper pulley can indeed be moved backandforth sideways a little. So I think your analysis is correct. On the XT, the top one says "sealed ceramic bush pulley," while the bottom says "sealed bearing pulley". I can't read the writing in your picture, but perhaps your pulleys also have bush vs. bearing labelling on them? Bushing one goes up top.
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Old 01-25-09, 06:00 PM   #4
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easy. the way you have them in the pict is basically the way they go. the ideler wheel with the metal insert goes at the top of the derailleur, closest to the cassette. the other idler wheel, the tensioner, goes on the bottom of the derailleur. only the first wheel has the extra metal insert in it and the tensioner doesn't need but only the one bearing in it. a little lube on those beariings before you put them all together is a good idea.
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Old 01-25-09, 06:31 PM   #5
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Guide pulley
Tension Pulley
No horses/humans involved
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Old 01-25-09, 07:27 PM   #6
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If one is thicker than the other, the thicker wheel would be the top one. Do look if it says 'ceramic' on one.
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Old 01-25-09, 07:46 PM   #7
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One says "Centeron G-Pulley" The other says nothing more than Simano.

The one that says G-Pully is the thinner one with the metal inset.
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Old 01-25-09, 07:51 PM   #8
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G pulley=guide pulley=top.
It guides the chain while the other tensions it...
Bill Kapaun is on it.
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Old 01-25-09, 07:55 PM   #9
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thanks all - that's the conclusion I was coming to.
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Old 01-25-09, 08:08 PM   #10
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Good news! You're well on your way and I learned something new - have a good overhaul.

Happy Trails!
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Old 01-25-09, 08:12 PM   #11
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Quote:
Originally Posted by gerald_g View Post
I am working on cleaning and such on a Stump Jumper. The rear derailleur is a Shimano LX.
Is it the steel one?
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Old 01-25-09, 08:49 PM   #12
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Quote:
Originally Posted by gerald_g View Post
One says "Centeron G-Pulley" The other says nothing more than Simano.

The one that says G-Pully is the thinner one with the metal inset.
The "Centeron" means that pulley can "float" sideways a bit and that's the top pulley.
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