What Would Cause This Jockey Wheel Failure?

[Cameron]

After completing the Festive 500 my All City Mr Pink was pretty filthy and nasty from all the rain riding all at once and being put away wet.

Pulled the chain off today to give it a good scrubbing and found both derailleur pullies cracked. It rode fine, didn't make any odd noises (yet) and it seems weird to me. Both pullies cracked in a similar manner. My theory is manufacturing/design flaw. Reason I say so is that it appears to me both cracks/splits propagated from the same area. If you look close you can see there are 3 evenly spaced casting marks around the inner perimeter of the wheel where it meets the outer race of the bearing. On both it split right at one of the casting marks and the corresponding split on the teeth of the wheel is directly above the center of the corresponding window in the pulley.

Am I off base here? Is something else going on? Derailleur is a SRAM Rival and only a couple years old with maybe a couple thousand miles on it. Bearing still rolled super smooth.

Giant pic:

http://i.imgur.com/hK5DRnL.jpg

[drsmile]

To me it looks like someone pressed bearings into a pulley that was too small. Did the pulleys come with those sealed bearings? I don't do SRAM but that seems odd if they did.

[Cameron]

To me it looks like someone pressed bearings into a pulley that was too small. Did the pulleys come with those sealed bearings? I don't do SRAM but that seems odd if they did.

That would make sense but seems weird someone would do that? I bought the derailleur used and both pullies were seemingly OK when I installed it, but admittedly I didn't inspect super close. Definitely didn't have the splits at the teeth when I installed it though. That was 1000-ish miles ago.

FWIW, the SRAM replacement set I bought today and installed also have sealed bearings, so I'd guess that is stock for these things. Only $16/pair too so makes it seem even more odd someone would bother going to the trouble of pressing in bearings.

Of note is that the replacement SRAM pulley set I got doesn't have the window cut outs like the old ones had. Maybe a design change to remedy the failure I found?

[illuminaught]

Seriously, looks like the bearing are quite a bit too big.
Seems like your fishing for a (blame SRAM)...

[El Chaba]

Sram....the groupset for which the less you use from it, the better it works......replace with some decent aftermarket pulleys and your upgrade will be complete.....

[oldpotatoe]

That would make sense but seems weird someone would do that? I bought the derailleur used and both pullies were seemingly OK when I installed it, but admittedly I didn't inspect super close. Definitely didn't have the splits at the teeth when I installed it though. That was 1000-ish miles ago.

FWIW, the SRAM replacement set I bought today and installed also have sealed bearings, so I'd guess that is stock for these things. Only $16/pair too so makes it seem even more odd someone would bother going to the trouble of pressing in bearings.

Of note is that the replacement SRAM pulley set I got doesn't have the window cut outs like the old ones had. Maybe a design change to remedy the failure I found?

Probably a running change after the beta testers(that would be you guys that use this stuff) found that they crack a lot. I think they are specific to sram too, cannot use say the really nice Tacx ones..because of ID but don't really know.

[Peter P.]

Is it possible the pulleys are aftermarket? I see no reason why SRAM would change the design and since this is the first and only time I've heard of this happening, I'm suspecting the pulleys aren't OEM.

[mod6]

The Jockey wheel on my Force RD imploded like that after about 5k. Good excuse to buy some Bling for the RD

[Wilkinson4]

>What Would Cause This Jockey Wheel Failure?

Watts!!! :) I have a white campy jockey from a early 80's SR rear der where the wheel cracked just like this... I read something about them cracking right on the molding line where the injected material formed and probably didn't bond very well.


Here…

http://www.ebay.com/gds/Campagnolo-Nuovo-Record-Derailleur-Pulleys-/10000000175201916/g.html

mIKE

[Cameron]

Seriously, looks like the bearing are quite a bit too big.
Seems like your fishing for a (blame SRAM)...

I'll agree it seems like the bearings are too big, but I dunno for sure. Don't need to fish for blame really, no biggie at all and they're already replaced. Just curious if anyone had seen anything similar and if so, if maybe there were external factors at play I didn't think of that I could avoid in the future.

Sram....the groupset for which the less you use from it, the better it works......replace with some decent aftermarket pulleys and your upgrade will be complete.....

:p Already replaced and put back together and riding on it.

Probably a running change after the beta testers(that would be you guys that use this stuff) found that they crack a lot. I think they are specific to sram too, cannot use say the really nice Tacx ones..because of ID but don't really know.

I dunno how specific they are to SRAM really. The replacements I bought are SRAM branded, but I did eyeball the really fancy KCNC ones on Fair Wheel's site and they state they fit SRAM and Shimano both so maybe it depends on the specific wheels.

Is it possible the pulleys are aftermarket? I see no reason why SRAM would change the design and since this is the first and only time I've heard of this happening, I'm suspecting the pulleys aren't OEM.

Could be. I bought the derailleur used so not sure if the previous owner swapped them. As I mentioned above the replacements I installed were SRAM so we'll see how they do.

The Jockey wheel on my Force RD imploded like that after about 5k. Good excuse to buy some Bling for the RD

I definitely considered the KCNC ones but at $35/each it seemed silly to install them on a Rival derailleur.

>What Would Cause This Jockey Wheel Failure?

Watts!!! :) I have a white campy jockey from a early 80's SR rear der where the wheel cracked just like this... I read something about them cracking right on the molding line where the injected material formed and probably didn't bond very well.


Here…

http://www.ebay.com/gds/Campagnolo-Nuovo-Record-Derailleur-Pulleys-/10000000175201916/g.html

mIKE

I like the watts answer best, but I doubt that's it ;)

Thanks for the link - cracking right on the injection molding line sounds exactly like what I see on these failed wheels.

Either way, not overly concerned since I already fixed it and it was less than $20 to do so. I just like understanding how and why things work.