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Locknut/ring failure


HomerSimpson
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A question for those that know about things mechanical:

On Sunday I was riding the Paarl funride, and I kept hearing a rattling noise whenever we went over rough road, and at first I thought my bottle cages were loose.  The noise disappeared when we hit smoother road and I forgot about it.  Then, about 30km from the end I swear I heard a pinging noise (sounded like a good quality metal part hitting the road and bouncing away) and shortly afterwards the rattle returned with a vengeance.  As I changed to a lighter gear to head up a little roller I noticed that all was not well.  Closer inspection revealed that my rear cluster was quite loose (had about 1 mm of play).  Not having any tools that would do any good at that stage, I selected the small ring in front and rode home just using the middle three or four gears of the (Shimano 105 10 speed) cluster.  When I got home I saw the lockring had completely unscrewed.  Now:

Has anybody experienced this before?

Why would this happen?  Surely the lockring cannot unscrew by itself?

Is there anything that could possible have fallen of in the process (the metal pinging sound refers)?  My logic tells me that nothing could have escaped (not anything intact, anyway)

Any thoughts (other than telling me this would not happen if I rode Campy)?

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Have had that happen on a MTB, damn nuisance. It's worth checking the lock-ring tension occasionally. Anything can come loose with the bike's vibration, on or off-road.

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Not the first time I have heard of this.

Infact, I have a mate who's cassette started wobbling as you described on our ride in Tokai last weekend.

 

It probably wasnt tightened hard enough and just took ages to come undone.
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I can't explain the pinging noise of expensive metal. Is yor Rolex still on?

 

I have seen this happen. One of the pro riders has his wheels built by me once came to me with a bunch of wheels that needed this and that. He helped me by removing and replacing cassettes whilst I did whatever it was I had to do on the wheels.

 

One of the cassettes clearly wasn't properly tightened and came loose during his race. He told me that he had good legs that day and he made a break of sorts with this rattling cassette.

 

I immediately asked him if he wasn't distracted by the noise. He said not, he focuses on other things. Was it me I would have stopped and fixed the noise or abandoned the race. That's what sets pro's apart from me.

 

Anyway, back to your lockring. They have to be incredibly tight - 40NM and for a reason. Sprockets move during use and I suspect threre is some precession in the freehub body around the smaller sprockets and over the lockring area and that can loosen the lockring.  

 

Make it real tight but not so tight....
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happened to me before as well. Had to take it to the lbs to fix, and bought me a lock ringspanner just incase it happened again.

Needless to say it didn't happen again after that.....
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Thanks folks....I just needed to check.  I think I know who the culprit in this whole saga is.  Problem is if I give him a smack upside the head it will hurt both my fist and my head....Ouch  I was just worried about the pinging noise.  Nothing seems to be missing on the bike.  I'll double-check the bike tonight.  I want to make sure nothing comes apart on the descent of Ou Kaaps on Sunday.

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I can't explain the pinging noise of expensive metal. Is yor Rolex still on?

 

I have seen this happen. One of the pro riders has his wheels built by me once came to me with a bunch of wheels that needed this and that. He helped me by removing and replacing cassettes whilst I did whatever it was I had to do on the wheels.

 

One of the cassettes clearly wasn't properly tightened and came loose during his race. He told me that he had good legs that day and he made a break of sorts with this rattling cassette.

 

I immediately asked him if he wasn't distracted by the noise. He said not' date=' he focuses on other things. Was it me I would have stopped and fixed the noise or abandoned the race. That's what sets pro's apart from me.

 

Anyway, back to your lockring. They have to be incredibly tight - 40NM and for a reason. Sprockets move during use and I suspect threre is some precession in the freehub body around the smaller sprockets and over the lockring area and that can loosen the lockring.  

 

Make it real tight but not so tight....
[/quote']

 

40Nm on Shimano locknut and 50Nm on Campag locknut. Check what is used on SRAM and other. Use a torque wrench.

 

If the surface is clean and you torque it correctly it should never ever come loose. If it does come loose it is almost 100% because it was not tightened to the correct torque.
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Mine did exactly the same thing.  Problem is most of the lock ring spanners (the less expensive ones) come with a handle attached so you can't use a torque wrench on them.  After finishing the Berge en Dale with a noisy cassette I came home, removed the handle from my spanner with an angle grinder, fitted a socket onto the spanner part and torqued correctly with a torque wrench - no problems since.  As mentioned above 40Nm is tight.

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