Minimum safe length of carbon steerer tube

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Minimum safe length of carbon steerer tube

Postby mike95 » Thu Sep 06, 2012 10:23 am

I just purchased a used carbon frame / fork.

I was doing a bit of trial fit yesterday & noticed that the steerer tube is quite short & has only 30mm of clamp area when it comes thru the top of the headtube.
my stem is 40mm stack height so this leaves the steerer tube sitting 10mm below the top of the stem.
The stem is a 2 bolt stem & the top bolt isn't able to clamp onto the steerer tube at all because its so short.

To me this is far from ideal & i cannot see how even a shorter stack stem will work.
The frame uses a integrated headset.

besides getting a new fork, is there anything i can do?

Im thinking of returning the frame, but would like to keep it if I can.


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Re: Minimum safe length of carbon steerer tube

Postby Mulger bill » Thu Sep 06, 2012 10:47 am

No way I'd be using that fork. General consensus seems to be a 5mm spacer top and bottom of the stem for max reliability.
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Re: Minimum safe length of carbon steerer tube

Postby rustychisel » Thu Sep 06, 2012 10:53 am


the question, as you've correctly surmised, is more about the depth of the stem clamp area, and short of finding another stem with less height I would not build or ride that bike.

A stem should be about 3mm proud of the steerer, or as some manufacturers claim in their warranty docs, you should be able to use a 5mm spacer above the stem to ensure against crushing. With the second bolt of a two bolt stem being above the steerer you face unacceptable risk IMO.

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Re: Minimum safe length of carbon steerer tube

Postby Nobody » Thu Sep 06, 2012 11:21 am

If you go to the site below and click on the PDF, "Caring for the Carbon Steerer Tube on your Fork..." you'll see what Trek recommends for their carbon steerers.

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Re: Minimum safe length of carbon steerer tube

Postby jules21 » Sat Sep 08, 2012 9:11 pm

if the top stem bolt is above the top of the carbon steerer, then you've effectively got a 1-bolt stem. clamping the 2 bolt risks buckling the top of the carbon steerer. if the 1 good bolt fails you risk losing steering ability, which will probably hurt.

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Re: Minimum safe length of carbon steerer tube

Postby ozdavo » Sat Sep 08, 2012 10:19 pm

How high is the upper bearing cap? That is often in effect a spacer of 10-20mm.

This could be an option to gain some height:
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