#1
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Top cap and spacers above stem keep coming loose?
Have a CK noThreadset setup with 10mm spacer under stem and another 10mm above it. Tightened the top cap bolt to set the headset bearing first before tightening the stem clamp bolts.
No obvious play in the headset when rocking the frontend of the bike, yet the after the stem bolts are tightened both the top cap and the spacers above the stem become loose, i.e. both rotate but the top cap bolt stays put. Any idea what may cause this and does it affect function or safety in any way? |
#2
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...the underside of ur top cap is likely bottoming out on your fork steertube. U need to add more spacers or trim ur steertube.
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#3
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once the stem bolts are tight the top cap loses its function. You can even take it completely off to save some weight. more than likely your spacer above the stem is too short and the cap is hitting the steerer.
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#4
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Please correct me if I get it wrong. |
#5
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Put a larger spacer and I would look at the expander aswell, it might be getting lose. Do you have a larger expander?? IME Depending on the fork sometimes you have to go with a longer expander because the regular short ones tend to move. It happened to me twice.
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#6
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A slipping expanding plug is likely. I quit using expanding plugs many years ago. Instead, I epoxy glue a 1 inch star nut, that's had the tips of the stars filed down a little so it slides into the steering tube. I've also used 6mm tee nuts, but those are tricky to align.
The result is a permanent, crush proof area that requires no spacer on top of the stem. My bikes have no spacer under the stem either, so any height increase would be done with a stem angle change. |
#7
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This is my bet as well. The expander might hold well enough when adjusting the headset bearings, but over time it could slip under the shock and vibrations of riding, loosening the preload on the top cap bolt. Try a different expander, one that grips the inside the steerer better.
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#8
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I’ve had this happen as well. What worked for me was switching to Park carbon paste. I think the park carbon paste had bigger particles which helped keep the stem secure to the steerer. I’ve heard specialized makes a very good expander plug.
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#9
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Wondering if the clamping force of the stem would be putting pressure on the blob of epoxy, or on the star nut (which may dig in to the carbon?) |
#10
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Of course the stem puts pressure on the steerer and the epoxy, but JB Weld epoxy has a tensile strength of 5000 psi. The star nut can't damage the steering tube, when it's totally encapsulated in epoxy. I have more detailed instructions that I can send. Here's a link to a drawing that someone made. See post #21. https://www.bikeforums.net/bicycle-m...n-steerer.html This picture shows that last steerer that I did, where I used a 6mm tee nut that's used to put metal threads into wood. The center of the epoxy has been countersunk for some additional clearance. Last edited by Dave; 02-17-2020 at 10:56 AM. |
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