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Praxis Lock Ring

by Hirsute
Sun, Aug 13, 2023 13:57
4

Got home and looked down to see the drive side of the crank looked odd but I wasn't sure why. Then I got off to look closely to find the lock ring had partly unscrewed. Easy to do up (LH thread) with a cassette tool.

What don't understand is how it happened - I've not done anything, so I'm a bit puzzled to the how and if it might reoccur.

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If you're new please join in and if you have questions pop them below and the forum regulars will answer as best we can.

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Hirsute | 8 months ago
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Thanks for the replies.
Needs some sort of threadlok then being a LH thread but the crank always loosening it.

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Cugel replied to Hirsute | 8 months ago
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Hirsute wrote:

Thanks for the replies. Needs some sort of threadlok then being a LH thread but the crank always loosening it.

Yes, with Loctite 242 being the usual stuff.

https://www.loctiteproducts.com/en/know-how/build-things/threadlocker-re...

Loctite 242 remains quite putty-like when dry - with enough strength to stop a treated threaded item from loosening; but it can be easily broken by unscrewing (or screwing-in). It also cleans off the threads easily so you can put a new coating on them when re-installing summick.

You can wait 'til the loctite has dried-off on the threads before screwing the item back in. The loctite will deform but still grip. Or you can screw the item back in while the loctite is still "wet" then wait for it to dry in-situ (takes much longer as it needs air to dry-off).

Loctite 242 in a reasonable amount on the threads seems to keep enough of its stickiness to continue working even if a part is unscrewed then screwed back in a couple of times or so. Many adjuster bolts rely on this to allow the user to make quite a few adjustments before the thread-fit of the adjuster goes slack as the loctite degrades via several thread movements.

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Cugel | 8 months ago
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Me too - about 3 months ago. It happened after I undid the central bolt to remove the chainset during a maintenance operation. I obviously moved the outer ring when doing so and this broke the blue loctite bond holding it in place. It fell out during a ride and didnae notice until getting home.

After eventually finding the correct replacement (there are various thread pitches and diametres, internal & external) I installed the new outer ring with blue loctite all round the threads.

I've now learnt the lesson - when removing and replacing the chainset with this attachment arrangement, take off, clean and re-loctite the outer ring as well.

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ktache | 8 months ago
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Entropy mate.

There are an infinite number ways of it coming loose, most of them involving the lockring lying by the roadside, than the singular one of being nicely nipped up.

Probably something to do with the stresses caused by the pressure of pedaling, incremental undoings, and of course it's never going to want to get tighter.

Maybe a little dab of some threadlok when reinstalling.

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