Bicycle Mechanics - Carbon steerer Forks is it different to put a stem on it?
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10-22-07, 08:14 AM
I am concerned of cracking the carbon steerer tube of my Specialized Tarmac full carbon fork. Is there any special consideration or a different tool or a different set up to do on a carbon steerer? Cheers!
10-22-07, 08:30 AM
There are a couple of important considerations with a full carbon steerer:
1. NEVER use a star nut. Use a stem compressor (FSA makes a good one) or the specific type of internal fitting supplied by the manufacturer. Read the fork's instruction sheet and see your LBS for what you need.
2. Do not over tighten the stem clamp bolts. There should be a torque spec on the stem, tyypically about 8 N-m. Also tighten the bolts evenly.
3. Use a stem that wraps around the steerer and tightens with two bolts. Do not use a stem with an internal clamp. By now, most stems are now designed to be compatible with carbon steerers so this isn't a major problem.
10-22-07, 08:33 AM
hey thanks for a quick reply. What is a star nut?
10-22-07, 08:41 AM
A star nut is a directionally flanged steel nut that's inserted (read pounded) into the steerer tube of a steel or aluminum steerer fork. The flanges are angled to allow the nut to be driven into and grip the internal walls of the steerer but resist being pulled out so it anchors the stem compression bolt.
You do NOT want to pound one of these into a carbon steerer as it will damage and weaken the tube.
Do NOT use the torque spec on the stem. Use the torque spec recommended by the fork manufacturer and if you cannot find that stop at 5 nm. Trust me on this, I broke a very expensive fork at 8 nm because I was using the spec shown on the stem. Some companies like Specialized recommend 5 nm for their carbon steer tubes.
Also carbon steerers [generally] have a lesser maximum number of spacers allowed. Check your specific specs but in general 1" steerer=25mm max spacers, 1 1/8" = 40mm max.
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