Slammed stem uncut steerer tube dangers ? !
08-09-18, 09:36 PM
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Slammed stem uncut steerer tube dangers ? !
Saw this video today WARNING HALF NAKED GIRL IN THE LAST PART DONT WATCH BEYOND 1 MINUTE IF YOU ARE OFFENED BY FEMALES BEING DRESSED IN THONGS AND THIN TOPS I DO NOT HAVE ANYTHING TO ENDORSE HERE JUST SAW THIS VID ON MY CYCLE FEED AND IT GOT ME WORRIED !!!!!
https://youtu.be/3WpNnKhDWQg
but i dont get what he is talking about , can anyone break it down.
I ride a full carbon bike and i havent had the tube cut down yet. I have my stem slammed as they say with all the spacers on top ! Now im kind of worried im doing something wrong .
I could get it cut or move the big spacers below the stem and keep the 5mm spacer on top under the cap .
I searched around but cant find a clear description of the danger ..
https://youtu.be/3WpNnKhDWQg
but i dont get what he is talking about , can anyone break it down.
I ride a full carbon bike and i havent had the tube cut down yet. I have my stem slammed as they say with all the spacers on top ! Now im kind of worried im doing something wrong .
I could get it cut or move the big spacers below the stem and keep the 5mm spacer on top under the cap .
I searched around but cant find a clear description of the danger ..
08-09-18, 09:48 PM
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Don't worry about that guy. Read this, the directions and you'll be fine:
Art's Cyclery Blog » Ask a Mechanic | Using Steerer Tube Expanders with Carbon Forks
Art's Cyclery Blog » Ask a Mechanic | Using Steerer Tube Expanders with Carbon Forks
08-09-18, 10:26 PM
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Wow, three minutes to tell that? For the love of God I wish people would learn to write instead of doing idiotic videos, so I could read the "information" in ten seconds or so, instead of wasting time on videos. I just skimmed this video to see what you were talking about. Odd to say the least with the woman in the background. She would be the only reason for the video, and that is a stretch,
08-09-18, 10:30 PM
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Yeah he seems like the kinda guy that has a hard time explaining the point , i always worry if im doing things the wrong way ...
Is this plug required though . should i rush out and get one at once , my headset stem and bars are very solid and smooth .
I had that page open but im still confused about the danger ..
Is this plug required though . should i rush out and get one at once , my headset stem and bars are very solid and smooth .
I had that page open but im still confused about the danger ..
Last edited by Teamprovicycle; 08-09-18 at 10:34 PM.
08-10-18, 12:38 AM
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Yeah he seems like the kinda guy that has a hard time explaining the point , i always worry if im doing things the wrong way ...
Is this plug required though . should i rush out and get one at once , my headset stem and bars are very solid and smooth .
I had that page open but im still confused about the danger ..
Is this plug required though . should i rush out and get one at once , my headset stem and bars are very solid and smooth .
I had that page open but im still confused about the danger ..
IIRC the top cap/plug doesn't actually do much other than get things pre-loaded so that you can get the stem on right.
08-10-18, 06:50 AM
#9
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The point of the video is that if you slam the stem without cutting the steerer tube, the stem is lower on the steerer tube. If the expander plug is not long enough, it might not fill the inside of the steerer tube where the stem (now lower) clamps to the steerer tube. Tightening the stem clamp without something backing it could crack the CF steer tube since there is no solid plug/expander backing it up.
08-10-18, 07:21 AM
#10
Non omnino gravis
Depends entirely on the expander you have. Cervelo uses a glue-in sleeve about 3" long that goes in the top of the steerer. No worries about an expander plug not being directly inside the stem.
No other steerer material cares. Steel or aluminum, you can have the star nut wherever you want. Knock the nut down 6 " into the tube and use a top cap screw as long as your hand. Makes no difference. It's only there to set bearing preload.
No other steerer material cares. Steel or aluminum, you can have the star nut wherever you want. Knock the nut down 6 " into the tube and use a top cap screw as long as your hand. Makes no difference. It's only there to set bearing preload.
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08-10-18, 08:22 AM
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@AndrewJB is exactly correct in post number 9.
An uncut steerer with slammed stem potentially leaves part of the steerer unsupported. Clamping forces from the stem can crush the steerer if the expansion plug is not supporting the stem. That's the whole point.
-Tim-
An uncut steerer with slammed stem potentially leaves part of the steerer unsupported. Clamping forces from the stem can crush the steerer if the expansion plug is not supporting the stem. That's the whole point.
-Tim-
08-10-18, 08:28 AM
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08-10-18, 08:29 AM
#13
Non omnino gravis
But I've also seen a bike at the LBS that had to have the fork cut out of the frame-- the owner had slammed that stem, and the expander was actually below the stem, inside the headtube. He then proceeded to crank down on the expander, and the steerer "puffed up." Then it of course behaved as if the bearings had gone bad. It took a bit of time to extract it.
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08-10-18, 09:02 AM
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Guys got a hot girlfriend ready to go... and he's more interested in playing with his new expander plug.
08-10-18, 10:51 AM
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But I've also seen a bike at the LBS that had to have the fork cut out of the frame-- the owner had slammed that stem, and the expander was actually below the stem, inside the headtube. He then proceeded to crank down on the expander, and the steerer "puffed up." Then it of course behaved as if the bearings had gone bad. It took a bit of time to extract it.
All it takes is 1/8 to 1/4 turn with an allen wrench when installing the expansion plug to deform the steerer to the point where a spacer won't even slide over it. This is why expansion plugs come with torque specs and many have the spec stamped right on the top of the part. Someone who tightens an expansion plug to the point where it puffs up the steerer so the headset bearings bind is clearly ignoring the toque spec.
The same is true of in the opposite direction. Overtightening the stem even a little can impart crushing loads on the steerer. If the steerer isn't supported by an expansion plug on the inside then the it can easily be crushed.
Steerers are constructed with fibers running along the length of the part but little or no circumferential or 45 degree angle fibers around the tube. They resist bending loads well but not crushing loads. 2% elongation is all it takes to start cracking the fibers. Two percent isn't much margin for error.
-Tim-
08-10-18, 11:50 AM
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RIght, I'm pretty sure she's basically a like a product placement that is intentional yet trying to appear not just so he gets more clicks. *rolleyes*
08-10-18, 12:12 PM
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That dude is making the wrong sort of video.
08-10-18, 12:52 PM
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JK!
You're totally right, he's blathering on about some mundane crap (and poorly I might add) and then it's all "Hey dude, why don't you slam a stem in it and find out what's going on back there! Actually, why don't you exit stage left and down some vegan protein powder cuz there's something behind you I'd REALLY like to see!"
Does this guy end all his videos with him flexing for the camera??? Ok bro...
08-11-18, 09:02 PM
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