Spire

I just need to know which of the 2 jockey wheels is the one that floats. Th one nearer or farther away from the rear derailler itself?

The guy at the shop said that one floats, but in the package of 2 he gave me, they look visually identical.

Cheers!

slider

Well they are both mounted to the derailler so I'm not sure which one is closest, however, it is the one closest to the cluster that floats so that the chain can move from cog to cog. It is also called the G (guide) pulley and is lower profile when looked at horizontally.

-s

Spire

Thanks, that answers my question! (I've just mounted them backwards!)

John E

Slider is correct. This is the fundamental enabling technology for indexed shifting. (We retrogrouches don't have this problem!)

prestonjb

Technically the "jockey pulley" always is the one that floats.

The "jockey pulley" is the top pulley (closest to the gears).

The bottom pulley is the "tension pulley".

Shimano jockeys have side-to-side play to help with index shifting. The tension pulley only takes up the slack and doesn't neex the side-to-side play.

sakarias

I have never heard of any difference between the two pulleys except for the names -- Jockey pulley for the one closest to the the cogs and Idler pulley for the one furthest away.

I think your eyes give you the installation answer -- it does not matter which goes where.

Maybe the guy at your shop can explain what a "floating" derailleur pulley is. I'm curious.

Cheers

John E

I suppose some indexed systems could successfully use two identical floating/sliding pulleys.

Historical sidenote: Some derailleurs of the 1940s and 1950s, such as the Simplex Tour de France which graced the first-generation Schwinn Varsinentals, had upside-down cages, with the UPPER pulley taking up the tension. On all others, "jockey on the top and tension" is consistent with what I have always heard.




---- I ride a REAL Schwinn. (1988 Project KOM-10 mountain bike, made in Greenville MS.)

greywolf

JohnE is right the top guide wheel has to have the float otherwise the indexing won't work very well , thats why its a good idea to remove the pulley wheels every now & again to clean out all the gunk & lightly grease ,I do it on my (nearly retro.) Exage changer every time I remove the chain to clean it .

Portis

Which way would be more effected? Shifting to outermost pulley or innermost pulley? If the guide pulley is gummed up and needs, cleaned/lubed. Also can you describe how to do this?

prestonjb

I dunno about using two floating pulleys.

I think that there may be some problem with keeping the chain to feed into the cage properly if the bottom one floated.

Esp if you were at one extreme or the other of the gears... For example if you were in the small ring and small cog the bottom pully would be pulled inward by chain deflection. If the index is off so the top pulley should float outward it may not be able because the chain and bottom pully may pull it inward. And VVS if bing ring and big cog and index is off toward the inside.

I think the bottom (tension) pulley must be fixed and the jockey pulley floats to help with the slight misalignment in the chain line between the tension pulley and the cog.

Don Cook

I respectfully disagree with the notion that the jockey wheel has side to side float. And until an authoritative source explains it differently, I'll continue to disagree. I have removed and installed a number of Shimano Ultegra and Dura Ace derailleurs. Aside from installation and removal, I've performed maintenance on both. I've never detected more than the very slightest lateral float in either the jockey or the tension pulley. It also strikes me as something that would just about ruin any prospects of adjusting the rear derailleur shifting so that it is precise and quick. Each time you shift, the lateral float would have to be overcome by the shift cable before the chain would begin moving. And when moving in the opposite direction, the return spring would encounter the same float before it began to move the derailleur.

Float: I'll believe it when someone demonstrates it's true. Then I'll salt and pepper the crow (for I'll be eating it).

Dave Stohler

FWIW, the float is not lateral, but rather it is axial. This gives the pedal angular compliance without 'flopping around'.

Don Cook

Dave, I think the premise that started this thread was that the "jockey" pulley wheel on the rear derailleur has side to side or lateral float or movement designed into it. More so than any "float" designed into the tension pulley wheel. If I'm not mistaken, your reply is in reference to peddle float and not rear derailleur pulley wheel float. Holler back if If mistaken.

Avalanche325

I put both of mine into a glass of water last night. Neither one floats!!!!

Dave Stohler

No, I am referring to the jockey wheel (notice in my profile: I am an engineer). The jockey wheel has a bit of axial compliance, not lateral. If you don't know the difference, drop me a line and I'll 'splain it to ya!

DieselDan

It's the jockey pulley. I just had to pull mine apart and grease it. It sounded like mice copulating when I upshifted.

sculptor

Here's the info from the Shimano (Europe) General FAQ on pulleys:

https://www.shimano-europe.com/cycling/
The upper pulley
Is called guide-pulley or G-pulley. Some G-pulleys have this marking on the pulley itsself.


[function]: The G-pulley should guide the chain into this position, that it is straight under the cassettesprocket. The G-pulley should run very smooth and efficient for good transportation towards the cassettesprocket.

Adjustment: Suppose if the rearderailleur is not adjusted perfect by cabletension, then the G-pulley can correct it. The reason is that all G-pulleys have some sideplay. In this case the G-pulley will go automatically to the best possible position under the cassettesprocket. Small differences in cable-adjustment can be corrected by the G-pulley, big differences can never be corrected.

Smooth turning: All G-pulleys have a small chamfer-pro[File] on the each tooth (see red circle in picture). This pro[File] looks a little bit like the Hyperglide-pro[File] which you can see on the our HG-cassettesprockets. This chamfer- pro[File] increases smooth turning.


The lower pulley

Is called tension-pulley or T-pulley.

[function]: The T-pulley holds the chain under tension.
Tips

Never mix T-puleys with G-pulleys. The above explanation helps you to seperate them.

miamijim

I'll see if I can explain this in a simplified manner. Grab hold of the lower pulley wheel, most often refered to as the 'tension' pully. TEST 1: Place your thumb on one tooth and your index finger on the tooth opposite it. Push down with your thumb while pulling up with your index finger. 'Rock' the pully back forth. There should be no movement or a miniscul amount of movement. STEP 2: Now push down with both your thumb and index finger and then pull back. The pulley wheel should not move or there should be a miniscul amount of movemet.

Lets move to 'upper' or 'G' or 'guide' pulley wheel. This wheel should behave the same as the lower wheel with the exception of the STEP 2. When pushed/pulled it should move in and out. It should not 'rock' as in step 1.

Once any pulley wheel, regardless of whether its the upper or lower 'rocks' it should be replaced.

Avalanche325

I would imagine that the chain would wear it to the point that it has pointy teeth first. That is what I have seen.

Miamijim. Do you play online poker? I play a bit and have seen a Miamijim there.

prestonjb

Another thing to note about the G and T pulleys is the G tends to use ceramic bearings with a little less "free-wheeling" than the T pulley.

I suspect this is to help get the chain to bite into the first teeth encountered.

The T pulley does not need this "slowdown" effect. It simply uses the spring to take up the slack (keeps tension on the chain).

FLYBYU

Since I just tore my rear derailer (shimano 105) apart I can tell you that the G-pulley is the one closest to the cassette. It also usually has better bearings in it then the jockey wheel. It also has quite a bit of side-to-side play in it, if you grab on you can move it back and forth quite a bit.