# Updated Carbon Fork Installation Info from Trek



## addctd2adrnlne (May 6, 2010)

Heads up if you have a carbon steerer and want to cut it yourself.

I was looking through the forums over her on roadbikereview for the first time and came across a thread on someone asking for advice on cutting their steerer which reminded me of a tech bulletin on Trek's dealer site that I read recently while I was at work. The tech bulletin is from 04/29/10.

This bulletin is for all Trek, Bontrager, and Gary Fisher forks with CARBON steerers. Sorry for the amount of text, but I thought it would be wise to include all the info. Since its on the dealer website, I can't simply post a link for people to go. 

If there is a way to post a PDF on this forum, let me know and I will post the Trek PDF.


_Updated installation procedures for stems on carbon steerers

Modern bicycles use high-tech materials and designs that rely on correct maintenance, precision workmanship, and compatibility of the parts. Mechanics must continue to learn the new procedures and requirements of these new bicycles. Incorrect mechanical work on a bicycle could lead to damage or breakage of a part, which could cause a fall and lead to serious injury or death. This bulletin includes information from an August 2009 Bontrager service bulletin, the Trek and Fisher bicycle owner’s manuals, 2010 Madone and Cronus assembly manuals, and new information.

Below the stem on all steerers
Always place at least one 5mm spacer below the stem. This spacer is in addition to the bearing cover (Figure 1), which must be at least 5mm. If the stem rests against the bearing cover, a point load is created on the steerer that could eventually cause the steerer to break. 

Above the stem on carbon fiber steerers
With a carbon steerer, always place at least one 5mm spacer above the stem (Figure 2). A stem placed right at the top of the steerer can put too much force on the unsupported cut edge of the steerer, possibly crushing the steerer.

Tightening clamp bolts
When tightening clamp bolts on a carbon steerer or other carbon part, you must use a torque wrench. Gradually tighten each steerer clamp bolt, alternating back and forth in small increments, until both bolts are at the correct torque. Use a similar method wherever there are multiple clamp bolts. Do not tighten one all the way before tightening the other, and do not leave the bolts with unequal torque.

Compatibility with all steerers
Make sure the stem clamp is designed correctly and is free of burrs. Correct design requires that the clamp is circumferential (closes in a circle); never use a wedge-type clamp. Also make sure the clamp bolts are tangential to the steerer (Figure 3). Angled clamp bolts can cause a point load along the clamp. 

Clamp edges should be smooth and slightly rounded. If a stem has a sharp or burred edge, sliding it onto the steerer could scratch or cut the carbon fibers, which can weaken the steerer..

Compatibility with carbon steerers
With a carbon steerer, do not use a star-fangled nut; use only the compression nut assembly supplied with the fork. A star-fangled nut can scratch or cut carbon fibers, which can weaken the steerer.

With a carbon steerer, avoid any stem with cutaways or holes in the back of the steerer clamp (Figure 4). For contrast, the stem in Figure 5 does not have a cutaway. Also avoid any stem that has a lightening hole (Figure 5) that is less than 15mm from the top or the bottom of the stem. Inadequate clamping surface area can cause a point load, which can crush a carbon steerer. With a carbon steerer, never use a stem with clamp bolts that require more than 55 lb•in (6 Nm) torque. Excessive torque can crush a carbon steerer._


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## RacerOne (Aug 17, 2009)

I suspect this was in reply to my post.. thanks for the heads-up.. luckily, I did all of these things anyway.


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## zac (Aug 5, 2005)

If you want PM me and email the PDF, I can post it.

I was unaware of the spacer above the bearing cap spacer. I have a 15mm cap, so I will try to get a narrower cap and add a spacer above it. 

Thanks
zac


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