# ISO Bosch Performance CX chainring lock ring tool



## Sparticus (Dec 28, 1999)

My 2021 Trek Rail's chainring came loose after one ride.

The ring is held in place by an 8-notch lock ring, looks like this:








The lock ring simply backed off, leaving the chainring wobbly. It was oily & gunky so I cleaned it up with spray contact cleaner, applied blue LocTite liberally and tightened it up with a drift & hammer (delicately).

Obviously I'd prefer not to use the drift & hammer. Does anyone know the proper tool? I'd like to purchase one. Is this it? TIA.
=sParty


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## 2SLOFATASS (Mar 26, 2020)

Yes


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## wschruba (Apr 13, 2012)

Check your toolbox first. One of them requires the "Bosch specific--which I think is also Rotor/Rohloff-sized--tool, but the other newer ones seem to have smaller lockrings (which are the same size as the old 8-point Truvativ/FSA tools).

I don't recall the specified torque being blisteringly tight. If you have a hook spanner (Hozan, for example), it should fit well enough to tighten it in the interim.


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## John232629 (Oct 11, 2005)

on your first ride? take it to the shop you got it from!


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## Sparticus (Dec 28, 1999)

John232629 said:


> on your first ride? take it to the shop you got it from!


As a general rule I don't let bike shops touch my bikes.

Thanks to everyone that posted in this thread with help in finding the right tool &/or helpful information.
=sParty


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## Ilovedoods (Jun 22, 2020)

*Park Tool CWP-7 and Park Tool BBT-18, 36mm socket. The lock ring is left hand thread, torque to 25-30nm. *


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## dbaelvis (Dec 24, 2021)

Sparticus said:


> My 2021 Trek Rail's chainring came loose after one ride.
> 
> The ring is held in place by an 8-notch lock ring, looks like this:
> View attachment 1919549
> ...


I have the same bike and have the same issue I just got the tool in the mail and plan to do the same thing with the thredlocker did it do the trick for you?


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## Sparticus (Dec 28, 1999)

dbaelvis said:


> I have the same bike and have the same issue I just got the tool in the mail and plan to do the same thing with the thredlocker did it do the trick for you?


Yes -- worked a charm.
I got the right tool and the chainring hasn't backed off since locktiting it.
However I did have to retighten my NDS crank recently (I'd locktited that, too.)
Just have to keep an eye on these things, I guess.
=sParty


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## Cleared2land (Aug 31, 2012)

Sparticus said:


> As a general rule I don't let bike shops touch my bikes.


Roger that!


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## slomtbr (Oct 9, 2010)

So many fasteners were loose on my 2021 Rail 7, I loosened everything I had a socket for and torqued them to spec. As for the lockring, I torqued it and safety wired it. With the crank arms, I torqued them, and torqued them again after each of the next few rides (without loosening them). All's been well for 600+ miles.


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## Cleared2land (Aug 31, 2012)

^^^ Aviation?


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## slomtbr (Oct 9, 2010)

Cleared2land said:


> ^^^ Aviation?


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## Dave Si (4 mo ago)

Sparticus said:


> Yes -- worked a charm. I got the right tool and the chainring hasn't backed off since locktiting it. However I did have to retighten my NDS crank recently (I'd locktited that, too.) Just have to keep an eye on these things, I guess. =sParty


 Can I ask do you have to remove the circlip to remove the locking ring


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## Sparticus (Dec 28, 1999)

Dave Si said:


> Can I ask do you have to remove the circlip to remove the locking ring


Sorry I don’t remember and I’m currently on an adventure in the outback. Otherwise I’d go to the garage & check for you… all I can say atm is I don’t recall removing any circlip. Best of luck.
=sParty


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