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Old 11-19-05, 10:30 AM   #1
TallRider
me have long head tube
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Here's a pretty straightforward question that I raised in this thread, but probably deserves its own discussion.
As detailed in other threads, I'm really tall and my bike frame isn't big enough, but I plan to hold off buying a new one for awhile. So in the meantime, I'm using an uber-size Nitto Technomic stem - 130mm extension and 225mm quill. The quill is inserted into the steerer tube about 5mm beyond the minimum insertion mark, so we're okay on that front. Here's a picture:

The potential problem comes with the amount of torque that is exerted on the steerer tube with a handlebar that is so far above and forward from the steerer tube, specifically when standing and sprinting.

My question: is it possible to damage the steerer tube of a threaded steel fork by torquing on the bars when standing out of the saddle, while using such a long quill?
Also, is there any danger to the headset? If so, would it help (the headset and fork) if I replaced the aluminum locknut from the Shimano LX threaded headset with a steel locknot?

My main question is about the possibility of damaging the steerer tube when lots and lots of force is applied through the quill stem. Thanks.
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Old 11-19-05, 01:35 PM   #2
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your picture is making me dizzy.
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Old 11-19-05, 01:51 PM   #3
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I'm no expert, but I would think that since the stem is alu and therefore softer than the steerer tube, a huge amount of torque would damage the stem before affecting the steerer. If anything, I'd be worried of cracking/snapping/breaking the stem before causing any problems with the fork/steerer.
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Old 11-19-05, 02:35 PM   #4
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That stem will probably break sooner or later, in which case both you and the bike may suffer damage. The headtube will be fine, though.
If you're heavy as well as tall, and you must leave the bar that high, try not to stand out of the saddle much, especially if the stem is not top quality.
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Old 11-19-05, 02:56 PM   #5
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That frame is too small for you....?
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Old 11-19-05, 03:52 PM   #6
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Yeah, the thread linked above tells about the frame size and stuff. It's too small for me, but has a long enough top tube. The stem is flexy, yes (also discussed in the above link), but I'm not too worried that it's gonna break. It's a Nitto, and they have a very good safety/quality reputation, and it's forged. I'm not heavy for my height - only 185#.
Despite Aluminum's being softer than steel, the stem is much thicker aluminum than the fork's headtube, so I think that torquing on the stem could damage the steerer tube. Do you have background experience/knowledge that this isn't something to worry about? (If so, great - but if based on the reasoning that aluminum is softer than steel, then maybe not so great.)
But it's not a huge worry one way or another, as I don't climb out of the saddle or stand up and sprint very often. But when I do I can generate substantial force, especially since I've got a 46cm bar.
I plan to spring for a custom steel bike in a year or two.
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Old 11-19-05, 05:32 PM   #7
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Quote:
Originally Posted by LóFarkas
That stem will probably break sooner or later, in which case both you and the bike may suffer damage. The headtube will be fine, though.
If you're heavy as well as tall, and you must leave the bar that high, try not to stand out of the saddle much, especially if the stem is not top quality.
The Technomic stem is top quality! There is nothing better that money can buy in this style of stem.

I've sold many hundreds of these wonderful stems, and use them on several of my personal bikes. I've never heard of one breaking.

http://harriscyclery.com/stems

One of the beauties of quill type stems is that even if you do manage to snap the aluminum quill, the stem won't fall apart because the wedge bolt will hold it together. If one of these stem quills were to break, you'd immediately notice that it would develop some play, but it wouldn't cause you to lose control or crash.

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Old 11-19-05, 06:18 PM   #8
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Quote:
Originally Posted by 531phile
your picture is making me dizzy.
It took me a moment to catch the meaning of your comment. Then I saw the poster... then the door frame... and finally the hooks over (or rather under) the wheels.
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Old 11-19-05, 08:10 PM   #9
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I have that exact same stem now for about 5 years and after about 25,000 miles still no problems. The only way torque would break that steerer tube is if you hit something headon! It might break (but probably just bend) the steerer tube also if you way over tighten the stem bolt, if the bolt or wedge didn't break first. Or it could break the steerer tube if you did over tighten the bolt and they but the stem in a vise and then take the frame and yank it as hard as you can in any direction. Any of those above scenerios is not something most sane people would do to their bikes...are you sane?
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Old 11-19-05, 09:55 PM   #10
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Sheldon and froze - thanks a lot for the input. I was never really worried about the Technomic breaking. My main worry was, and still is, possible deformation of the top of the steerer tube because of the torque exerted with such a long stem. Though it's a pretty small worry.

531phile and cuda2k - photos of my bike hanging upside-down have weirded people out before. Not only is the bike actually hanging upside-down, but the poster behind it is of Yosemite Valley, with 3,000-ft. cliffs. I've gotten dizzy looking up while going on runs through the valley - everything is so huge and so close, it has an exaggerated 3-D effect... kind of like an IMAX theater. (I initially spelled it iMax... terrible... the internet age is really getting to me.) Here's a link to more Yosemite pictures. I'm the bald one there. And here's a full-color photo of the bike hanging upside-down:
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Old 11-19-05, 10:26 PM   #11
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1. You're not talking about torque, but about plain old force. That long stem is acting like a lever, and is not applying twisting force (which is what torque is).

2. No. You're fine, it won't hurt the steerer tube. You CAN cause problems if you over-tighten the wedge bolt, though. So don't do that.

3. That is one trippy picture, yo.
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Old 11-19-05, 10:32 PM   #12
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Quote:
Originally Posted by grolby
1. You're not talking about torque, but about plain old force. That long stem is acting like a lever, and is not applying twisting force (which is what torque is).

2. No. You're fine, it won't hurt the steerer tube. You CAN cause problems if you over-tighten the wedge bolt, though. So don't do that.

3. That is one trippy picture, yo.

Good points, thanks for clarifying, grolby. I knew there was something that seemed off about my visualisation.
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Old 11-19-05, 11:08 PM   #13
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Quote:
Originally Posted by grolby
1. You're not talking about torque, but about plain old force. That long stem is acting like a lever, and is not applying twisting force (which is what torque is).
2. No. You're fine, it won't hurt the steerer tube. You CAN cause problems if you over-tighten the wedge bolt, though. So don't do that.
1. Right. The torque is from my hands applying force to the bars, both torsionally while sprinting out of the saddle and downward while leaning. This is translated into force at the head tube. Should have been more careful with my physics phrasing.
2. Thanks. This is what I was interested in knowing. And the caution on the wedge is a good one, too.
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