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Why would a headset keep coming loose?

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Why would a headset keep coming loose?

Old 03-20-15, 06:41 AM
  #1  
mlamb01
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Why would a headset keep coming loose?

I have a 2014 Giant TCR advanced(got it in December 2014), with full carbon fork and steerer tube. Stem is original, and not carbon. I have about 500 miles on the bike so far, and a few weeks ago I noticed the headset was loose as I took her off of the trainer. So I loosened the bolts on the stem, tightened the expander bolt to preload the bearings, then tightened the stem bolts, alternating the tightening up to 5 nm. A few outdoor rides later it is slightly loose again, loose enough where I can rotate the spacers easily with my fingers. I noticed the handlebars buzzing abit when going over recent chipseal roads... I've readjusted it twice now, about after 2 or 3 rides I find it loose again.

What would you guys do to keep it from slipping? I've read about the carbon paste, and that it is a bad idea on carbon steerers. Still considering it, and just putting a very very light coating on so it does not get on the spacers and abrade the steerer tube. Torque setting listed on the stem is 5.5 nm, really don't want to go that high, it does not say if that is the max torque or not.

Its under warranty and I am taking it in to the shop tomorrow, but I wanted to get some opinions on how to deal with something like this. I prefer to do my own work when I can.
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Old 03-20-15, 06:53 AM
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I recommend something like Tacx Carbon Assembly Compound. I had a problem with a CF seatpost sliding down inside a CF frame and the Tacx stuff fixed it. It's available on Amazon and there are other similar products out there.

https://www.amazon.com/Tacx-LU2400-P-.../dp/B009F8B8N6
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Old 03-20-15, 07:02 AM
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Originally Posted by mlamb01 View Post
I've read about the carbon paste, and that it is a bad idea on carbon steerers. Still considering it, and just putting a very very light coating on so it does not get on the spacers and abrade the steerer tube.
I am not sure where you got the idea that carbon paste was bad for carbon parts; it would be odd to call it "carbon" paste if it was not good for that. There will be no abrasion if there is no movement. I believe that the carbon compound actually has soft plastic particles as the friction element, not grit like valve grinding compound.

So I'd give the paste a try, I would be more concerned with damage caused by parts moving against each other than the paste damaging them.
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Old 03-20-15, 07:05 AM
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The plug your adjustment bolt screws into may be loose.
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Old 03-20-15, 07:13 AM
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Originally Posted by dsbrantjr View Post
I am not sure where you got the idea that carbon paste was bad for carbon parts; it would be odd to call it "carbon" paste if it was not good for that. There will be no abrasion if there is no movement. I believe that the carbon compound actually has soft plastic particles as the friction element, not grit like valve grinding compound.
.
Here's where I got the idea... The Golden Wrench: A tech bulletin from Trek regarding carbon assembly paste Theory seems to be that the paste eventually works it way down into the spacers, and since they are loose they shift around slightly. The paste between the spacer and steerer tube acts as an abrasive, and will notch the steerer tube. It is true? Who knows, but I guess it does seem plausible...
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Old 03-20-15, 07:16 AM
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I thought about the plug adjustment bolt being loose. But each time I readjusted it, I tightened the plug to get the pre-load I wanted, then the stem bolts, then checked the play. Once the stem bolts are tightened, the plug adjustment bolt is not needed.
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Old 03-20-15, 07:24 AM
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Some other info that might be relevant... The steerer tube has not been cut, and the stem is in the highest position. There is no spacer above the stem.
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Old 03-20-15, 07:26 AM
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Headtube faced? Or paint free? Do you use a head set cap in this setup? Spaced high enough?
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Old 03-20-15, 07:32 AM
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Check your manual to confirm max torque setting for the steerer tube... but sounds to me like you're not tightening the stem clamp bolts enough.
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Old 03-20-15, 07:34 AM
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If you have a tall frame, this may be the nature of the beast. As the fork flexes on bumps and when you brake the steerer bows slightly. This makes it shorter and it tries to pull down through the stem clamp (only place with any give).

You there are a number of things you can try. My first would be to use an expander plug that reaches down into the stem clamping area, to support the tube under the stem's clamping compression. This will give you a bit of upside room on the clamping force used. Be sure not to over tighten the expander plug, because it expands the steerer and causes stem clamping issues.

You can also use a non-abrasive traction paste to improve the grip without causing the issues Trek reported. Use it also on the expander plug so you don't need to overtighten it. If concerned about the traction paste, apply it only to the upper half of the stem area (apply to inside of stem, not to fork). Ths way any abrasion will be away from the critical area below the stem.
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Old 03-20-15, 08:36 AM
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Originally Posted by mlamb01 View Post
I have a 2014 Giant TCR advanced(got it in December 2014), with full carbon fork and steerer tube. Stem is original, and not carbon. I have about 500 miles on the bike so far, and a few weeks ago I noticed the headset was loose as I took her off of the trainer. So I loosened the bolts on the stem, tightened the expander bolt to preload the bearings, then tightened the stem bolts, alternating the tightening up to 5 nm. A few outdoor rides later it is slightly loose again, loose enough where I can rotate the spacers easily with my fingers. I noticed the handlebars buzzing abit when going over recent chipseal roads... I've readjusted it twice now, about after 2 or 3 rides I find it loose again.

What would you guys do to keep it from slipping? I've read about the carbon paste, and that it is a bad idea on carbon steerers. Still considering it, and just putting a very very light coating on so it does not get on the spacers and abrade the steerer tube. Torque setting listed on the stem is 5.5 nm, really don't want to go that high, it does not say if that is the max torque or not.

Its under warranty and I am taking it in to the shop tomorrow, but I wanted to get some opinions on how to deal with something like this. I prefer to do my own work when I can.
i would tighten it down to the recommended amount and see where that led me.

Last edited by hueyhoolihan; 03-20-15 at 08:47 AM.
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Old 03-20-15, 01:12 PM
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Originally Posted by mlamb01 View Post
I thought about the plug adjustment bolt being loose. But each time I readjusted it, I tightened the plug to get the pre-load I wanted, then the stem bolts, then checked the play. Once the stem bolts are tightened, the plug adjustment bolt is not needed.

This used to be true and I thought the same thing until a friend had problems with a carbon steerer on his mountain bike. No amount of tightening the stem bolts or carbon assembly paste would keep it tight. The plug would slip in the steerer and allow the stem to slip enough to have play in the headset. The solution in the end was to epoxy the plug into the steerer. A less radical solution would be to epoxy an aluminum tube into the steerer and use a regular star nut
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Old 03-20-15, 01:41 PM
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I am not sure the stem will keep the headset tight, loosening the stem just allows movement as you tighten it up, then you tighten the stem back up, or am I misundertanding how this all works.

Last edited by obed7; 03-20-15 at 01:45 PM.
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Old 03-20-15, 02:37 PM
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thats it, it holds the adjustment once the top cap pushes all the loose stuff under it down,

Either compression Nut inside slips up and you cant get the pre load right first, ? or stem slips outside and changes ..

I stick with a steel steerer fork myself (tour not race style cyclist) have 2 stems a locking spacer, and one of these in 1.1/8"
WC Seat Post, Size 27.2mm, Aluminum, Black ? WiseCracker

clamped around my steerer. now they just have it as a spacer addition WC LITE, 1-1/8", Aluminum, Black Anodized ? WiseCracker

Maybe fill the rest of the fork with More carbon Fiber Tube or solid Rod. , stiffen that thing up good ..

Last edited by fietsbob; 03-21-15 at 04:25 PM.
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Old 03-21-15, 03:48 PM
  #15  
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The star nut has nothing to do with it. Once the stem bolts are tightened, you can remove the top bolt and drive the star nut out for all the headset cares. Tighten your stem bolts with a torque wrench to spec. Use an expansion plug instead of a starnut to support the inside of your carbon steerer. Consult dealer for max torque.
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Old 03-21-15, 08:44 PM
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Since it's under warranty, definitely hold the dealer responsible for adjusting everything in case there is an internal defect. It should not work it's way look for several hundreds of miles or from riding on extremely rough surfaces.
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Old 03-22-15, 07:38 PM
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mlamb01
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Seems likely that it was the headset expander plug. I took it in, the mechanic tightened the plug, re-adjusted it, and it is still tight after a 46 mile ride. Said I probably was not getting everything as tight as I thought I was, since the plug was abit loose.
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