Marked steering tube from stem clamp. Is the steering tube ok? Change the stem?
08-24-19, 01:13 AM
#1
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Marked steering tube from stem clamp. Is the steering tube ok? Change the stem?
I tightened the stem pinch bolts to 6 nm as recommend 5-7 nm. I had never ridden with it since the bike I am building has not even been completed. The inside of the stem where it contacts the steering tube to clamp has a hollowed out part that puts more pressure on the steering tube like a cookie cutter. Is the fork ok? Should I replace the stem with a different one? The stem was an Aluminum Uno 7 I got from Ebay, if anybody has experience with that stem?
08-24-19, 04:10 AM
#2
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That is a VERY common stem design. Don’t know If there are any ”solid” stems out there.
I’d worry about there being something wrong with the steerer, not properly cured etc.
I’d worry about there being something wrong with the steerer, not properly cured etc.
08-24-19, 07:14 AM
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The broken stub of a clamp bolt shown in your photo makes me think it was tighten WAY above 6 N-m.
08-24-19, 10:28 AM
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Call me old-fashioned, but it seems like there is always something or other to fret about with carbon fiber parts; I'll stick with metal, thanks.
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08-24-19, 11:14 AM
#6
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I first tightened the stem to 6 newton meters with a torque wrench and then removed the stem to take pictures of another thing that was actually just a cosmetic thing nothing bad. Before I had tightened it back, I had noticed those marks on the stem and someone had recommended me to do 5 nm so I put it back on and set it for 5 nm and I was tightening the stem when suddenly the bolt feels like it's stuck and suddenly snaps in half.
08-24-19, 11:18 AM
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08-24-19, 12:39 PM
#8
don't try this at home.
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Your broken bolt doesn't sound good. "bolt suddenly feels stuck, then snaps" Odd.
Bad bolt? bad torque wrench?
~~~~
Bianchi had a recall/advisory a few years ago when some of their bikes had been improperly assembled, and had steerer tube damage.
Here's some examples that they published back then. I included them in a post from another steerer thread.
The first image is what my steerer looks like. I can see the outline of the stem, but nothing is crushed.
Not damaged. There's a shiny outline of the stem, just on the surface of the steerer. Looks like a 5mm spacer was above the stem, I think.
A damaged steerer. All their damage photos show the bottom, fork end of the stem crushed the steerer.
More extreme damage! A loose stem clamp? And a huge amount of spacers above, so the plug was likely located too high? I wouldn't be surprised if they had more than 40mm of spacers below the stem, too.
Bad bolt? bad torque wrench?
~~~~
Bianchi had a recall/advisory a few years ago when some of their bikes had been improperly assembled, and had steerer tube damage.
Here's some examples that they published back then. I included them in a post from another steerer thread.
The first image is what my steerer looks like. I can see the outline of the stem, but nothing is crushed.
Not damaged. There's a shiny outline of the stem, just on the surface of the steerer. Looks like a 5mm spacer was above the stem, I think.
A damaged steerer. All their damage photos show the bottom, fork end of the stem crushed the steerer.
More extreme damage! A loose stem clamp? And a huge amount of spacers above, so the plug was likely located too high? I wouldn't be surprised if they had more than 40mm of spacers below the stem, too.
Last edited by rm -rf; 08-24-19 at 12:43 PM.
