Cutting Carbon Steerer Tube: Spacers Above Stem?

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Cutting Carbon Steerer Tube: Spacers Above Stem?

Postby GreeneRob » April 29th, 2013, 8:12 am

I will be cutting (or having someone do it) a carbon steer tube in the next couple days. I am hoping that I can find a few answers here.

1.) Is there a standard maximum height of spacers that can be used between stem and headset?
2.) I have read in several places that you should use a spacer above the stem also, is this completely necessary? If so, is there a max or min?


In case it makes any difference.

Headtube - 105mm
Bottom stack - 15mm
Top stack - 9mm
Stem stack - 40mm

Any help is appreciated.
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Re: Cutting Carbon Steerer Tube: Spacers Above Stem?

Postby c0nsumer » April 29th, 2013, 9:07 am

1) Read your stem/fork instructions and they'll tell you to have 3mm - 5mm of spacer or steerer above the stem so there is room for the top cap screw to preload the bearings. You could do this with just the stem, but then you don't have as much clamping surface, which I dislike...
2) I personally don't like the idea of cutting a fork to the exact size, because then there isn't much room to adjust fit, and transferring the fork to another bike or selling it can get difficult because its so short.
3) I like to stem mount my bike computer, and having just enough stem to stick up to the same height as the computer makes me feel that it's a bit more protected.

As a result, I tend to cut steerers to be 10-15mm longer than need be and put spacers up top. The result tends to be something like this or this, which I've been quite happy with.
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Re: Cutting Carbon Steerer Tube: Spacers Above Stem?

Postby iamkickstand » April 29th, 2013, 9:12 am

same. I like to set my stem height with spacers, then put a single thicker spacer on top.
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Re: Cutting Carbon Steerer Tube: Spacers Above Stem?

Postby pfox90 » April 29th, 2013, 9:23 am

What consumer said. Even if its like a 5mm spacer you should always have something ontop. Cut it long for resale and fit options. What are you cutting it with? I would wear a mask when cutting carbon
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Re: Cutting Carbon Steerer Tube: Spacers Above Stem?

Postby GreeneRob » April 29th, 2013, 9:39 am

pfox90 wrote:What consumer said. Even if its like a 5mm spacer you should always have something ontop. Cut it long for resale and fit options. What are you cutting it with? I would wear a mask when cutting carbon


I am not 100% sure I am doing it myself since it is only about $10 to have performance bike do it. But with the lunch 10% off they have a guide for $18 so I will probably buy that to have it for the future and add it to the tool box. I have a 32t blade that I have used for cutting handlebars in the past. A little electric tape and a wet blade with slow easy strokes on the saw. Depending on the condition of the cut, maybe some emory cloth to clean it up.

Thats how I did my bars in the past (without the guide) and they turned out fine. Does that sound right?
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Re: Cutting Carbon Steerer Tube: Spacers Above Stem?

Postby bikerector » April 29th, 2013, 12:58 pm

The difficulties I've had with cutting carbon steerers, in regards to cutting them long as some suggest, is that the compression nut can only drop so far from the highest point of the steerer. One on my road bike actually sits on top of the cut steerer and has no height adjustment to drop further in like others I've used have. Enve, for instance, has the ability to drop the compression plug down to the stem clamp level, tighten that portion, and them tighten the top cap to that. They're two separate pieces as opposed to a one bolt type that pulls everything tight and compresses against the stem clamping forces with the same bolt, similar to a dry-wall anchor screw.

Your process sounds right, I've always used a fine file though for cleaning up the edges and making the fine tune adjustment of parts of a mm to make it all fit together.

The spacers on the top are important for the top cap to compress everything together because the stem should mount below the cut of the steerer and he top cap needs something to pull against to bring everything together. Pulling on the top of the steerer does nothing. From experience, check this after a few miles if your top spacer is close to the top of the steerer, sometimes things settle in and you may need another .5mm spacer or so to tighten it back up.

Here's the instruction video from Enve on how their plug is installed (what I called a 2-piece and what I think most compression plugs are designed like).

https://www.youtube.com/watch?v=cQe9TJJq1PE
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Re: Cutting Carbon Steerer Tube: Spacers Above Stem?

Postby GreeneRob » May 21st, 2013, 2:30 pm

Thanks for the help here. I worked perfectly without a hitch. There was just something about cutting into a carbon fork that gave me the heebie jeebies.
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