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How essential are spacers and/or a "floor" under your stem?

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How essential are spacers and/or a "floor" under your stem?

Old 05-24-15, 10:11 PM
  #1  
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How essential are spacers and/or a "floor" under your stem?

Hi,
I'm converting an old style Quill Stem Adapter to a more modern 1 & 1/8 inch Stem and I have bought a Soma Stem Adaptor which doesn't have a "floor", thus I am completely beholden on the two screws that attach the stem to it.

By contrast, this Dimension Stem Adaptor does have a floor that would stop the Stem from sliding down.

Do stems slide down after they have been tightened on?

I guess I am particularly concerned there could be problems if I was standing up and riding, with there then being a reasonable amount of force being directed vertically downwards.


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Old 05-24-15, 10:36 PM
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Clamped threadless stems have been holding headsets together for a few decades now. If the clamp alone weren't reliable, the entire design would be a fail.

BTW- seatposts with similar clamp design, except with only a single bolt, are able to support your entire body weight, are you planning to do handstands on your bars?
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Old 05-24-15, 10:38 PM
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Not to worry. As long as you tighten the pinch bolts on your stem securely, it won't slide down that stem adapter.
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Old 05-24-15, 11:01 PM
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Originally Posted by FBinNY View Post
Clamped threadless stems have been holding headsets together for a few decades now. If the clamp alone weren't reliable, the entire design would be a fail.

BTW- seatposts with similar clamp design, except with only a single bolt, are able to support your entire body weight, are you planning to do handstands on your bars?
Originally Posted by Retro Grouch View Post
Not to worry. As long as you tighten the pinch bolts on your stem securely, it won't slide down that stem adapter.
What you have said certainly makes sense and puts my mind at ease.

But let me ask you one more silly question then, why do so many people put spacers under their stem when the have the stem as high up as they can?

Is it just for cosmetic effect?
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Old 05-24-15, 11:06 PM
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Originally Posted by ColonelSanders View Post

But let me ask you one more silly question then, why do so many people put spacers under their stem when the have the stem as high up as they can?

Is it just for cosmetic effect?
If it's a conventional threadless headest, there has to be a continuous column running from the top cap to the compression ring of the headset, so tightening the cap screw can press the stack down and compress the headset bearing.
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Old 05-24-15, 11:11 PM
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Originally Posted by FBinNY View Post
If it's a conventional threadless headest, there has to be a continuous column running from the top cap to the compression ring of the headset, so tightening the cap screw can press the stack down and compress the headset bearing.
Thanks for that.

You gots information I was completely unaware of.
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Old 05-24-15, 11:21 PM
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Originally Posted by FBinNY View Post
If it's a conventional threadless headest, there has to be a continuous column running from the top cap to the compression ring of the headset, so tightening the cap screw can press the stack down and compress the headset bearing.
Adapters like that are rarely (never?) used with threadless headsets.
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Old 05-24-15, 11:26 PM
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Originally Posted by AnkleWork View Post
Adapters like that are rarely (never?) used with threadless headsets.
You're adding 1 & 2 and coming up with 4.

The OP has a threaded headset and asked a question about an adapter. (see OP). Afterward he asked an unrelated question about why threadless headset users use spacers below the stem.
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Old 05-24-15, 11:26 PM
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Originally Posted by AnkleWork View Post
Adapters like that are rarely (never?) used with threadless headsets.
Never. Never ever. Never ever ever ever...
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Old 05-24-15, 11:30 PM
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Originally Posted by FBinNY View Post
You're adding 1 & 2 and coming up with 4.

The OP has a threaded headset and asked a question about an adapter. (see OP). Afterward he asked an unrelated question about why threadless headset users use spacers below the stem.
Can't imagine why you are so defensive when someone adds a little factual info to your posts especially when you do the same so often. Isn't that how a forum like this is supposed to work?
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Old 05-24-15, 11:40 PM
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Originally Posted by AnkleWork View Post
Can't imagine why you are so defensive when someone adds a little factual info to your posts especially when you do the same so often. Isn't that how a forum like this is supposed to work?
I'm not being defensive, just helping the OP, who's already uncomfortable about his stem and headset, avoid being confused by your nonsequitur.
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Old 05-25-15, 01:23 AM
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In your situation, with the quill adapter to a bolt on, you do not need any spacers. your headset is secured by the threads and a nut. on a threadless stem I use one (atleast) below and 1 above the stem. the top cap then presses it all together before you tighten the 2 binding bolts.

people often have a large stack of spacers on their steertube to try to raise the handlebars a little without buying a new stem with a different angle. Or maybe because they dont have a hacksaw to cut it down.

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Old 05-25-15, 01:38 AM
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You can use a spacer between your locknut and stem, using the top cap bolt to clamp it down before tightening the stem's clamp (as if it was a threadless headset) to gain a beefier junction to add some stiffness.
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Old 05-25-15, 06:45 AM
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Another way to think of it. If a properly tightened stem were able to slide down, it could also slide up (and off) with far worse consequences.
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Old 05-25-15, 07:10 AM
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You also need spacers if you have cantilever brakes, so there's space to route the front brake cable into the stop below the handlebar
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Old 05-25-15, 07:29 AM
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post 12 is showing a threadless type fork ,taking the wrong fork in the road wont get to the same conclusion.


FWIW, BBB BHP 21 ** BHP-21 - Headset parts - BBB is a clever Stem Raiser that works with Threadless or threaded (convert to threadless stem) forks
The number 20 is a 7/8"(1") version of the same ..
the simple design uses a specially made bolt that internally threaded the hex that tightens the wedge inside the fork steerer..


I used one ** to restore the steerer height cut too short by a factory precut steerer tube, on my Koga Trekking Bike, for this over 60 touring cyclist.

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Old 05-25-15, 11:44 AM
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Originally Posted by Kimmo View Post
You can use a spacer between your locknut and stem, using the top cap bolt to clamp it down before tightening the stem's clamp (as if it was a threadless headset) to gain a beefier junction to add some stiffness.
That's a good plan, plus it will add the "floor" he wanted, and it'll look cleaner.
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Old 05-25-15, 12:07 PM
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FWIW Machine speak, Proper terminology/name is a Shoulder or Flange, rather than a Floor.
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