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stack height on stem with shim

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stack height on stem with shim

Old 04-19-19, 05:55 PM
  #1  
binarylegit
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stack height on stem with shim

I bought a Specialized Comp Multi Stem 17 degree for my fixie. It comes with three shims to adjust the angle of the stem. After installing it with the angled shim that I want I'm struggling to know if I have too little or too much clearance over the end of the steering tube, because the height over the steering tube changes from front to back, and the shim is lower than the top of the stem itself. If I compare the height of the shim to my old stem height they are the same.

If I measure the height of the shim and stem over the steering tube in front and back I get approximately the following:
Front:
* Shim - 6mm
* Stem - 8.5mm

Back:
* Shim - 4mm
* Stem - 7mm

Should I be paying attention to the stem height or the shim height? and should I look at the front or the back? Can anyone tell me if those heights are acceptable/safe?
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Old 04-19-19, 11:47 PM
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Sapperc
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Not quite sure what you’re asking. The multi-position stem and shim fit together as a set. There should be an even 3mm recess between the top of the steerer tube and the top of the stem to accommodate the top preload cap. The shim is inserted into the stem from the bottom. The bottom edge lip of the exposed shim will vary front to rear depending on whether you are using the 0, 2, or 4 degree shim and in which orientation, negative or positive (or neutral for the 0 degree stem). This stem also uses a special top preload cap that has an offset bolt which is oriented to correspond to the orientation of the shim.

Hope that helps. Here’s a link to the instruction guide:
https://media.specialized.com/suppor...G0383_revA.pdf
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Old 04-20-19, 07:09 AM
  #3  
easyupbug 
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If the excellent response from Sapperc does not work for you, do some posting to get your count to 10 and post photos as your question is unclear.
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Old 04-20-19, 10:56 AM
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binarylegit
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Sapperc, you definitely understand what I am referring to

The bottom edge lip of the exposed shim will vary front to rear depending on whether you are using the 0, 2, or 4 degree shim and in which orientation, negative or positive (or neutral for the 0 degree stem).
So where is the 3mm supposed to be? from the top of the steerer tube to the top of the shim, or the top of the stem? and should I measure in the front or in the back because as you said it varies from front to back (see my measurements above). Sorry, I'd post a picture or a link to a picture but I don't have 10 posts yet.
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Old 04-20-19, 10:33 PM
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Sapperc
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That instruction guide should help. The pictures are pretty clear.

If you measure the shims above the lip and measure the inside length of the stem opening, you’ll see that the shim sits about 3mm below the top edge of the stem when inserted. That gap should be constant no matter which shim is used or whether it is used as a negative or positive shim. The steerer tube should come to the top of the shim, which gives a gap of 3mm to the top of the stem.

However, depending on the head tube angle of your bike, washers or shims installed below the stem, and how the steerer tube was originally cut, it may or may not be quite flush with the top of the multi position stem shim. Keep in mind that this stem is an after market option on your bike. So, if the steerer tube is a little high you should still be able to use this stem as long as the top preload cap fits onto the stem correctly.

Be be sure to follow all of the precautions and warning in the guide. Expander plug position and torque setting are very important, especially if the steerer tube is carbon.

If you you have any doubts about the fit, you should really check with a reliable local bike mechanic.

Best of luck!
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