Crank arm fell off. [thm clavicula]

Discuss light weight issues concerning road bikes & parts.
2old4this
Posts: 278
Joined: Mon Jan 13, 2014 7:26 am

by 2old4this

I didn't hear anything but the non-drive side felt wrong (the crank slid out something like .25".) I am not sure if retaining component alone would do the trick. It'll definitely help to keep the crank in place but something has to push it in...

by Weenie


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maverick_1
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by maverick_1

@KCookie,
Glad no serious accident nor injuries.

The same problem happened to me yesterday, albeit on a different crankset (Campy Over Torque Comp).
Will create a separate thread for discussion, hoping to hear comments from fellow Campy users.

KCookie
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by KCookie

Thanks Maverick,
Hope no injuries for you to, thought I was the only one with bad luck. !!

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maverick_1
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by maverick_1

@KCookie,
Thanks.
All fine here (thank goodness) except cosmetic damage/chips to the left crankarms :x

Nefarious86
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by Nefarious86

Does the NDS preload bolt not hold the arm on? Once the preload is set and the pinch bolt tightened would it not be wise to remove and loctite it in place with low strength retaining compound while also using medium strength compound on the pinch bolt? Not criticising just curious as to how it could all come appart if tourqed to spec and assembled correctly.
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KCookie
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by KCookie

maverick_1 wrote:@KCookie,
Thanks.
All fine here (thank goodness) except cosmetic damage/chips to the left crankarms :x

Exactly the same damage to mine, still gutted though. !!

RyanH
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by RyanH

The instructions are very specific and very detailed, so detailed that it's easy to skip some because it almost gets tiresome to read it all.

Loctite is specified. Off the top of my head: put carbon paste on the arm splines, put Loctite on the preload bolt and preload until bearing friction is introduced then back off. Put Loctite on the pinch bolt and torque to 10nm. Once torqued, go back to then preload bolt and torque down to___nm.

I'm having a hard time believing that if it was installed correctly, and there wasn't play in the system, that these arms are coming off by themselves. Sample size of one but I put over 10k miles on mine and never had an issue. I also followed my instructions to a T. Kcookie's shop on the other hand has already done stuff like install the Fibre Lyte's backwards as well as ship off a bike without making sure the FD works.
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AUOC1OC6
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by AUOC1OC6

Sorry but I have to agree with RyanH. Knowing KCookie's previous issues with his LBS. i will definitely take issue with his LBS first and will definitely change LBS if possible.

I suspect insufficient Locktite and Carbon Grip.
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2old4this
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by 2old4this

I generally avoid arguing on this board but the instructions are very specific on where to use thread lock (none on the adjusting bolt) and on throughly degreasing the axle and the crank. I am not saying the OP's LBS followed the instructions correctly. But I think I did (then again I apologize if I sound snobbish but yet missed the obvious instructions...)


http://www.thm-carbones.de/manuals_clav ... 281%29.pdf

Page 10:
Adjusting Bolt: Greased
Crank clamping bolt: with thread lock

Page 18:
Throughly degrease the axle and crank multi-tooth segment.
...
Fit the left-hand crank to the multi-tooth segment of the axle.
...
Assemble the cover plate and the adjusting bolt.
...
Apply a medium strength thread-lock (Loctite or other similar substance to the thread of the clamping screw.

RyanH
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by RyanH

@2old4this, wrong manual. This is the correct manual for his (and mine was a M3):

http://www.thm-carbones.com/clavicula-m ... en_WEB.pdf

My recollection is correct (except for the carbon paste which is something I did on my own accord). Medium thread lock on both the adjusting screw and tightening screw as well as 10nm for both (pg 20). As I indicated before, the instructions are very detailed and almost tedious, which causes people to have trouble fully comprehending them. I am guilty of that as well with my first set of THM Fibulas, which I missed the torque specs for the brake bolts causing them to have trouble staying centered, causing me to think they were a POS.
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Current Stable. The Snob Machine
The Ex's. LS Siena: 6.21kg | Parlee Z5 SLi: 5.9kg | LS Xicon: 5.76kg | C59: 5.7kg | Cervelo R5ca: 5.09kg | Fuji Altamira SE - 6.2kg | Scott Foil - 6.2kg | Evo - 5.18kg | LS Classic - 6.7kg | The Crumpton - 5.9kg

leej88
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by leej88

I just took delivery of my brand new Clavicula SE cranks and they came with an additional plastic bag (2 set screws and an allen key) + instruction sheet stapled to the front page of the user manual.

According to the instruction sheet, the set screws are meant to be screwed on into any two holes (has to be opposite facing) on the preload cap to prevent it from unthreading itself after preload has been done.

I supposed this might be a new thing since I don't see any of the older production batch of clavicula SE cranks having that.

It could have been one of those minor rolling updates that THM have added to address the issue of preload caps loosening over time.

Of course, I suppose loctite would have worked just as well but having the two set screws interfering with the spindle's grooves seems like a more foolproof way of keeping things properly secured.

I've attached an illustration down below (pardon the awful sketch!).

Image

Nefarious86
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by Nefarious86

I'm going to go out on a limb here and say the set screws are a Lawyer tab type solution to people using the wrong installation instructions.

@2old what crank were you using? The SE or the original as shown in the instructions you linked?
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jimaizumi
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by jimaizumi

10nm for the clamping scew!? Holy cow!

I also enountered an issue with my 1st Gen Clavicuala when the cover plate and the adjustment bolt came undone, resulting in my left crankarm sliding off the spindle. Firstly, keep your aluminum plate... Do not, and I mean DO NOT go out and substitute it with those imitation carbon ones you can buy for $30. I did, think the carbon cap got soft, resulting in play with the adjustment bolt.

I searched high and low for the bolt (I had my aluminum cover back at home) but to no avail. It seems this bolt is specific to THM and can't really be sourced out at your local hardware store.

I contacted THM and they were kind enough to send me both the screw as well as the aluminum bolt. Awesome service from THM as usual. As per the installation, dry installed the arm into the star ratchet and bolted them down, I then dry installed the cover and bolt. I don't think that you need loctite but it will certainly be a insurance policy to avoid a repeat freak accident. Also note, this is for a 1st Gen crankset so things may have changed with your SE... Best of luck and better get in contact with THM ahead of having to complain to your LBS.
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trimenc
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by trimenc

I have the SE cranks and I don't have the set screws shown above. I also have not had a problem with the preload cap coming off, but I did use some loctite on the bolt when I installed the cranks. I am a bit of a nerd and tend to read all instructions and follow them word for word.

spdntrxi
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by spdntrxi

must be a rolling update... I too don't have these set screws on my SE cranks.. but I got my SE awhile ago. Never felt the preload cap getting loose... and I remove mine often for cleaning purposes.

by Weenie


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