Chainset loosening problem

[Alison]

I have an old M739 chainset on my son's Cannondale. This is the one where the spider and outer chainring are one and the same and you need to change both to change one.

I bought this chainset and since being fitted the bolt holding on the spider keeps loosening off, and if I forget to tighten it he ends up with a spinning chainset. I think that either a locking ring or clip is missing.

Does anyone have a solution to this or on old knackered chainset LX/XT that is basically scrap so I can take off what is missing please :?:

 

[Augustus]

Lock ring is important and it's probably this.

I may be wrong, but I seem to remember someone saying recently that Madison still have the lock rings for the M952 chainsets and they are the same?

Ask LTS Biker - he knows A LOT about Shimano.

 

[messiah]

Loctite has held my XTR one on for years :shock:

 

[Cloverleaf]

Yup, the XTR spider will be compatible. However, what I think you are missing is the little circular steel snap ring which should reside in a groove on the crank arm so that it sits on top of the lockring, preventing it loosening. If you are missing this then give the threads a good clean with degreaser etc and then apply a reasonable amount of threadlock to prevent it working it's way loose.