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Jockey wheels and shifting

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Jockey wheels and shifting

Old 09-03-21, 08:48 AM
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gauvins
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Jockey wheels and shifting

[I've had shifting problems this past summer, after riding a few rainy days on forest roads (loose sandy gravel laced with "calcium" to reduce the amount of dust -- at one point my derailleur stopped working). At first I thought that the mud buildup had forced the derailleur's cage out of alignment, but back home a thorough clean-up of the jockey wheels seems to have fixed the problem.]

This is on a 3x10 XT Shimano trekking drivetrain.

Quite a few times the chain would slip between the tension wheel (jockey wheel at the bottom of the cage) and the derailleur cage. This would be almost systematic when riding on the middle chainring and the top 2 sprockets. Which is why I thought that the problem was caused by a mis-alignment of the cage, leaning towards the wheel for some reason... I now think that this could be the result of a massive crud build-up on the jockey wheels, or because I've inadvertently mixed the guide and tension wheels (not clear to me which is which and what is the proper side -- I assumed that the wheel with the arrow is the tension wheel, and that the arrow should point in the direction of the motion...)

In essence, I've never paid much attention to the jockey wheels. Certainly never thought that they could have a material impact on shifting. I am now reconsidering.

Questions are: (1) how important are these contraptions wrt to the quality of shifting? and (2) is there any meaningful reason to install aftermarket jockey wheels? (this is for low performance touring)
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Old 09-03-21, 09:12 AM
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No impact on shifting? Why do you think they call it a jockey wheel. It is to jockey the chain into position when you shift. The wheel furthest away is just known as the pulley wheel which is also the less specific way to describe the jockey wheel.

I really don't understand how what you are describing can happen. Are your pulley wheels those that don't have hardly any tooth shape to them? I almost want to say that you've routed your chain wrong through them and it's rubbing the little tab, but then you'd hear that noise all the time.

For aftermarket wheels to be a benefit, you'd really need to figure out why the current wheels are a problem. Normally the after market stuff is for those needing that extra .01 watt to beat someone at in a technical discussion of what might be faster.
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Old 09-03-21, 09:47 AM
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Originally Posted by Iride01
I really don't understand how what you are describing can happen.
Me neither, which I why I raise the issue here. Now, there is material online. Just wanted to hear from this community as well. (FWIW, I know a thing or two about bikes)
Originally Posted by Iride01
Are your pulley wheels those that don't have hardly any tooth shape to them?
Stock XT coming with XT RD-T780-SGS. Plenty of cogs

Originally Posted by Iride01
[...] you'd really need to figure out why the current wheels are a problem. Normally the after market stuff is for those needing that extra .01 watt to beat someone at in a technical discussion of what might be faster.
The ceramic bearing in one jockey wheel was damaged. This + crud could have created the problem. But again, I am only speculating. For the record, I had replaced chain+cassette+chainring at the beginning of my trip. Could be that the cogs on the wheels didn't provide a good match for the new chain, and that additional riding has fixed this (I assume that it doesn't take thousands of kms for a chain to alter the tooth profile of a small plastic sprocket).
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Old 09-03-21, 09:57 AM
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Well of course you need to replace it if the bearing is damaged. When you said "aftermarket jockey wheel" I thought you were looking at those cages that come with extra large pulley wheels or something.

Replace them both with either Shimano or someone that makes a direct replacement version of them.

Telling us the bearings were damaged in the OP might have been an important detail to include. But are you sure they are ceramic bearings?

As to yours going bad so quick, that's more a fluke. Not so much the conditions you ride in.

Last edited by Iride01; 09-03-21 at 10:01 AM.
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Old 09-03-21, 10:46 AM
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Many mid level Shimano rear der pulleys have a ceramic bushing in the guide pulley (a more descriptive term then jockey pulley) AND also have a small amount of end play to allow better pulley/cog centering and accommodate manufacturing tolerance and cable wear. Once the guide pulley's play becomes a rocking/canting slop (besides the end play that retains the pulley's vertical relationship) the shifting can degrade. Much like a lot of cable friction results in. The lower cost ders have a steel bushing and don't last as long. Both levels typically have a steel bushing (with minimal end play) for the tension pulley (the lower one). All these versions can have tooth profile wear over time and also bearing wear/clogging with grime build/mud up. It's surprising how much friction a chain der. system can attain if not cared for.

Of course with the tighter tolerances and smaller dimensions that a 10 speed system has (compared to 7,8,9) less system wear and/or inattentiveness results in greater problems and sooner too. Andy
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Old 09-03-21, 11:15 AM
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With the 8 speed Acera RD pulleys on my hybrid, the guide pulley is unmarked, and the tension pulley is only marked with an arrow indicating the direction of rotation. On my 11 speed road bike with a 105 RD, both the original and the upgraded Ultegra pulleys are additionally labeled "Guide" and "Tension" to further distinguish between the two pulleys. The guide pulley usually has a little lateral (i.e., along its axis of rotation) movement range (as Andrew R Stewart mentioned) to (as Iride01 mentioned) guide the chain between cogs. The tension pulley at the bottom end of the cage is what allows the cage to maintain the tension of the chain. If the chain slides off this pulley, it may be because the teeth of this pulley are worn, as Iride01 suggested, but you apparently misunderstood because you replied "plenty of cogs." I suggest:

1. Examine wear on existing pulleys by comparing them to pictures of brand new ones online. If the teeth of the existing pulleys are worn, buy new ones.
2. If the teeth of the existing pulleys are not worn, disassemble them to clean all components, apply lubricant on all metal parts (Amazon.com : DuPont Non-Stick Value Pack : Sports & Outdoors) and reassemble.
3. If #2 does not solve the problem, buy new ones. You can upgrade to the next higher Shimano tier, but no point to buy the aftermarket ones for touring.
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Old 09-03-21, 01:02 PM
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Originally Posted by SoSmellyAir
. If the chain slides off this pulley, it may be because the teeth of this pulley are worn, as Iride01 suggested, but you apparently misunderstood because you replied "plenty of cogs."
hmm... cog is how a sprocket tooth is called , although many people use cog and sprocket (or gear) to designate the same thing, and tooth to designate a cog. What I meant is that the jockey wheel's teeth (cogs) are still very much present and not that much different from a new one, but I also know that diagnosing visually a worn set of cogs is very difficult (shark teeth etc.)

Originally Posted by SoSmellyAir
[...]
2. If the teeth of the existing pulleys are not worn, disassemble them to clean all components, apply lubricant on all metal parts (Amazon.com : DuPont Non-Stick Value Pack : Sports & Outdoors) and reassemble.
3. If #2 does not solve the problem, buy new ones. You can upgrade to the next higher Shimano tier, but no point to buy the aftermarket ones for touring.
I've cleaned the jockey wheels and it appears to have solved the problem. But perhaps not. Time might tell. OTOH, I've ordered a replacement set of XT jockey wheels (quite up there in terms of Shimano's MTB hierarchy, similar to Ultegra for road). I'll switch the jockey wheels and see if I still get shifting issues.

Regarding aftermarket jockey wheels, there are plenty, other than the very expensive ones made by Ceramic Speed and such. Amazon has plenty of aluminium+ceramic jockey wheels in various sizes at prices that are comparable if not lower than those of XT wheels. Reviews that I saw are inconclusive. I was wondering about them as well
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Old 09-03-21, 01:23 PM
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Originally Posted by gauvins
hmm... cog is how a sprocket tooth is called , although many people use cog and sprocket (or gear) to designate the same thing, and tooth to designate a cog. What I meant is that the jockey wheel's teeth (cogs) are still very much present and not that much different from a new one, but I also know that diagnosing visually a worn set of cogs is very difficult (shark teeth etc.)
Sorry, in that case I misunderstood what you were getting by "plenty of cogs." I thought you were referring to the number of teeth rather than the shape or remaining profile thereof.

Originally Posted by gauvins
I've cleaned the jockey wheels and it appears to have solved the problem. But perhaps not. Time might tell. OTOH, I've ordered a replacement set of XT jockey wheels (quite up there in terms of Shimano's MTB hierarchy, similar to Ultegra for road). I'll switch the jockey wheels and see if I still get shifting issues.
Hope that does it. Pulleys are relatively cheap so having a spare set is good.
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Old 09-03-21, 07:11 PM
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Shimano derailleur pulleys are top- and bottom-specific. The top ones have a bit of play built into them, to allow indexing to still work when the cable tension isn't quite right. The bottom pulleys don't float. If you swap them, which is easy to do since they look almost identical, shifting can get finicky and weird.

--Shannon

PS: Unless you're using an SIS derailleur in friction, especially with more than 8 cogs. In that specific case, they actually shift better with the non-floating pulley on top.
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