I was cleaning the bike, and see that my 2012 SRAM Force x10 RD Jockey wheel has a radial crack.



I can't tell any performance impact, but what would cause this? What's a good replacement -- I see many different options out there. Is alloy really better? (Never had alloy, but never replaced jockey/idler pulleys either).

scott s.
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Can't tell you the cause but it's not terribly common. Usually jockey wheels will last seemingly forever. I've played around with jockey wheel of different materials, nothing seemed to be as good and as quiet as stock equipment.

Likewise I've no comment on why it cracked it does not seem to be otherwise damaged or chipped where something could have caught it, the dolly wheel profile looks very good, I've never had one crack or seen one cracked, worn out yes, they last forever, not certain with SRAM but the Shinamo ones all have a internal metal bush that basically amongst other things stops the screw being over tightened which could have contributed to to it being squeezed.

I would personally replace it with the same material as fitted.

Lots of pulleys have (and will) crack. SunTour sealed bearing ones were especially prone to this. Campy NR, Simplex are other pulleys which have cracked more then others.

I think that the pulleys which have no inset bushing/bearing are less likely to crack. Perhaps the inserted metal changes the plastic's outer section ability to shrink after molding and the stress is relieved by cracking sometime later.

How does this effect the function? not much as far as shifting goes but after this radial crack happens the pulley now has one point that has a larger pitch then the chain's. So when the crack comes around and the chain tries to engage this wider pitch and the chain won't settle on both pulley teeth at the same time. Often there will be a noise as the chain shifts from one tooth to the other tooth (on either side of the crack). Kind of a nock nock nock with a rapid cycle.

The solution is easy. Replace the pulley. I don't like the aftermarket ones made of machined AL (and usually with a sealed cartridge bearing). They tend to run loud as the chain is riding on metal, not plastic. Additionally the upper pulley really likes to have some end play to handle indexing and chain/cog tolerances. Many of these aftermarket pulleys don't have this feature. I always suggest using the OEM pulleys if at all possible. Andy.

Have an Ultegra 6500 RD idler pulley with an identical crack (between the teeth) occurring years ago and it is still on the bike doing fine. The Shimano material apparently is flexible enough that it is not self destructing at lease to this point and I suspect that idler pulley loads probably are low compared to the guide pulley. I know I should change it out but now it is a curiosity to me and if it is costing me 1/100 of a watt I don't care.
I have a couple of alloy sets which perform fine and while they must be a little louder being metal to metal my old ears can not hear it.

The nice thing about sealed cartridge pulleys...they aren't garbage collection points like bushings in stock pulleys, that end up draggy and full of crud.

Odds are the noise will only be noticed if you have a strong tailwind. Even with CatEars on my helmet, I barely hear metal/metal pulley noise unless I have a tailwind.

I had a Sun tour sealed bearing pulley's plastic teeth crack , I presume the piece was at the end of the Branch

( having made plastic models in my youth) thats how the mold a lot of parts at once.
if the plastic cools just a little the flow into the Mold may not be fully a single volume as it solidifies, but have a seam ..

Wish you could see some of the Ultegra and XT lower pulleys that I've had to clean and lube... Andy

I remember the first time I pulled a jockey apart and saw the collected cesspool inside after a lone season of riding. The first words in my head were something like "WTF, who thought making these things bushings and not sealed bearings was a good idea???!!!"

Granted nitrile gloves are cheap....but for an equivalent mechanical function (and IME it is pretty darn equivalen), I'll take non-OEM sealed-bearing pulleys so I don't need to clean them again.

I service bikes weekly which the rider thought that spending extra money would allow not maintaining the bike. My wallet says keep thinking the way you do. My other side says you are not understanding how things really work out for all.

But this is America and we both can coexist. Andy.

I road with a set of cracked pulleys on my campy super record for 2 years they never got worse

Another data point: I ride for 6mo with a cracked pulley and no ill effect

HAHAHAHA

You're all right, man.

I rode for years with a set of suntour pulleys that had "seams" before someone mentioned that they were cracks

I could never ride with a broken wheel like that.

What if someone points it out in front of a girl?

Thanks for all the replies. After finding the crack I did a supported 100k ride yesterday. Couldn't tell any problem. I went ahead and ordered a set of SRAM Apex/Rival/Force pulleys. The ones I'm seeing online don't seem identical (mine have "AeroGlide" stamped on them but I'm only seeing the Red ceramic ones which are like $100 - yikes named that). Probably just marketing. They're all 11 tooth, don't know if the width / axle diameter varies at all. I guess guess try it and see. This is a WiFli RD but doubt that makes a difference. SRAM part catalog just shows 11.7515.060.000 as a part no.

scott s.
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The effect of a cracked pully wheel is you will hear a click sound when you pedal under heavy load, like when hill climbing. The click is cause as the pully wheel flexes due to the crack.

I have SRAM red and twice the pully wheels have cracked.

I had one split in half. It was along walk home.

To be technically correct, only the top one is a jockey pulley.

1988, I bought a Tacx pulley set on the road , in the NL on a Bicycle tour.

But Sram was not yet a player, back then.. (no proprietary pulleys)

I replaced the broken one back in April and the new set I got are identical to the ones that came with the DR.

scott s.
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