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I have a chimney of 3 spacers which I would like to remove (cosmetic reasons mostly). I am not sure about marking at 2-3mm under the stem's top and cutting there. A bit too much of eyeballing. I feel more confident with measuring the height of the spacers I will remove and cut this height off the steerer tube. Is this method flawed?

ps: I will do it with a 32tpi steel blade on a 6inches hacksaw with no cutting guide, following a masking tape line, I plan on doing it with light pressure and as many strokes as needed. Filing the burr with sandpaper. Does that seem right?

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Cutting off an amount of steerer equal to the spacers you are removing is faulty logic because it makes assumptions about how good the steerer gap (that 2-3mm distance) is now. When you have spacers above the stem, that gap number could be anything and it doesn't matter because the stem is making full contact with the steerer. But if you're not going to have spacers above the stem anymore, it must be correct.

A good method is to put the stem to the level you want it, leave it clamped on, remove everything above it, then mark the steerer with a fine-tip marker or scribe at the top of it. Then remove the fork and make another mark 2mm below the first mark. That is your cut line. If your plan for cutting favors having the line encircle the steerer, just temporarily clamp the stem to match the cut mark and mark around that way.

It's very easy for things to go wrong cutting a steerer freehand, especially a carbon or aluminum one since the material is soft and things can happen faster. Even a basic saw guide made out of a scrap of angle iron is much better, and since you have a hacksaw you have the means to make one.

A 32tpi blade can be fine on carbon. Use a lot of water to lubricate it and also keep the dust out of the air. I like to do the trick of turning the steerer 90 degrees or so in the guide when the cut is almost complete to help prevent tearing as you go through the wall.

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  • Thanks for all this info Nathan. I have found this discussion to understand why a 5mm spacer above the stem could be useful. I have given it some thought and I think I will not use one, I will trust my compression plug to be supportive enough to clamp the stem at that end of the steerer. I will try using some cutting guide, I think I have two old stems around which could do that job! Many thanks again! Commented Jun 16, 2023 at 9:11
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I'd cut it at 5 mm above the top of the stem just to allow for a bit of adjustability.

If this is a carbon steerer, you can get special carbon hacksaw blades, and you should seal the cut edge with nail polish. Whatever it's made of, you can use a hose clamp as a sort of cutting guide. I wouldn't try to cut it in situ myself.

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  • Thanks for the input. What do you mean by 5mm above the top? Keeping a small spacer above the top cap? Commented Jun 15, 2023 at 15:34
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    About the carbon fiber specific blade, it seems like a bit of faff, £10 for a single use blade when the hardware shop next door sells good blades for 1/10th of the price. A whiff of cycling tax if you ask me. Commented Jun 15, 2023 at 15:35
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    I recommend keeping a 5-mm spacer above the stem. Not above the top cap. As to the blade, it's your call. Just letting you know they exist.
    – Adam Rice
    Commented Jun 15, 2023 at 16:19
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    It's a good idea to keep a 5mm spacer above the stem. It gives the stem more material (more steerer tube) to clamp onto. It's safer like that, especially with carbon steerer tube.
    – Robert
    Commented Jun 15, 2023 at 16:39
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    Also see this, may be useful to you: bicycles.stackexchange.com/questions/76385/… for non-carbon tubes
    – Robert
    Commented Jun 15, 2023 at 16:44

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