Bicycle Mechanics - 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 ?

http://i207.photobucket.com/albums/bb60/gerald_g/stump_jump/stump_jump_derail_01.jpg

http://i207.photobucket.com/albums/bb60/gerald_g/stump_jump/stump_jump_derail_02.jpg

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

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.

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.

Guide pulley
Tension Pulley
No horses/humans involved

If one is thicker than the other, the thicker wheel would be the top one. Do look if it says 'ceramic' on one.

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.

G pulley=guide pulley=top.
It guides the chain while the other tensions it...
Bill Kapaun is on it.

thanks all - that's the conclusion I was coming to.

Good news! You're well on your way and I learned something new - have a good overhaul.

Happy Trails!

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



Is it the steel one?

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.