Bicycle Mechanics - Do Carbon steerer tubes require special tightening plug?

I just obtained a carbon fork for my bike and was going to use the threadless headset I used previously.

My question pertains to the HS tightening plug. A mechanic I know said the plug does two things: (1) tightens the HS so the bearings are properly pre-loaded; and (2) it provides internal support to the carbon steerer tube so when the stem is clamped the tube won't break.

I don't know if the internal support assertion is accurate. If it is, then I'd need a new plug as it doesn't provide support throughout the length of the steerer tube being subjected to the clamping load of the stem.

Any insight or advice?

Thanks much.

Steve

I know the Civia Hyland all carbon fork specifies use of a special included top plug and warns NOT to use a star nut or regular metal steerer top plug. I would expect the same for other forks with a carbon steerer tube.

Use expanding-style top caps with carbon steerers.

Use expanding-style top caps with carbon steerers.
Agree. Also invest in a torque wrench to apply the proper torque to clamping on Carbon.

Yes, carbon steerers require the use of an expander plug and must not be used with a regular starnut. FSA makes a readily available expander if one didn't come with your fork.

Yes, carbon steerers require the use of an expander plug and must not be used with a regular starnut. FSA makes a readily available expander if one didn't come with your fork.

Except for Cannondale which uses a regular starnut on their carbon forks.

What do you do when the expander plug keeps slipping up the steerer before the right torque is reached?

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What do you do when the expander plug keeps slipping up the steerer before the right torque is reached?

Have you tightened the expander plug?

My question pertains to the HS tightening plug. A mechanic I know said the plug does two things: (1) tightens the HS so the bearings are properly pre-loaded; and (2) it provides internal support to the carbon steerer tube so when the stem is clamped the tube won't break.


Your mechanic is correct.
The FSA expansion plug is easy to use but the one I had did not offer enough support behind the stem (not long enough to reinforce the steer tube behind the stem clamp).
To avoid cracking the steer tube I recommend that you not exceed 5 nm when torquing the stem clamp.

Al

Have you tightened the expander plug?

The expander plug does not have a separate tightening screw. I think it just tightens when adjusting the headset. Maybe I need to get a plug with a separate tightening screw.

Your mechanic is correct.
The FSA expansion plug is easy to use but the one I had did not offer enough support behind the stem (not long enough to reinforce the steer tube behind the stem clamp).
To avoid cracking the steer tube I recommend that you not exceed 5 nm when torquing the stem clamp.

Al

Is there an expansion plug available providing full support to the steerer tube when clamping the stem?

I looked at the FSA expansion plug and see what you mean by it not being long enough to offer full support. Here's a picture of it from the FSA website:

http://webstore.fullspeedahead.com/fly.aspx?layout=estoreproduct&taxid=267&pid=423

Or, if none are available on the market, is the only safeguard to insure proper torque settings?

Steve

Full support over the entire length of the stem clamp is not needed. The FSA expansion plug works fine, as long as the ID of your steerer is the within the plug's expansion range.

As long as the stem clamp bolts are not over tightened, you should never crack the top of the steerer. Most 2-bolt clamps require 5Nm.

Anyone have any experience with these expansion plugs?

http://www.bikeparts.com/search_results.asp?ID=BPC121257

a little extra support is good.
http://www.universalcycles.com/images//products/medium/17005.jpghttp://www.cornercycle.com/insert2.jpg

Well I ran across the Alpha Q website. That's the company associated with Tru Temper and they make the carbon forks. The system they use is an aluminum insert tube epoxied into the carbon steerer tube. The insert tube has a fastener integrated into the center of it somehow. They claim it provides a good clamping surface internally, gives support to the steerer tube where it is clamped by the stem and lastly adds rigidity to the fork assembly.

I ordered one as they are sold separately for installation into your fork. This is what they have to say on their web site:

"Q: Do I need to use the Insert Kit supplied with the all-carbon forks? Will a compression plug work?
A: You must use the insert to comply with the warranty. A compression plug provides an anchor for the head set tension bolt. The insert does this and more. It also reinforces the steerer at the clamp area to support the clamping force of the stem better than any carbon tube with only a compression plug. Thirdly, the insert stiffens the top portion of the steerer for a more solid feel in the stem and handlebars where torque is generated. The insert provides the most solid connection possible and is well worth the time to install it."

http://www.alphaqfork.com/performance_tubing/faq.asp#FAQ5

I ordered one from Alfred e Bike. Best price.

http://www.alphaqfork.com/performance_tubing/faq.asp#FAQ5

Thanks for the help. I'll let you know how the install goes.

Steve

I suspect (but do not know for sure) that the main reason why most carbon-steerer forks must be used with an expansion plug is because a regular hammer-installed star nut will tear the hell out of the inside of the tube and seriously weaken the fork.

If the manufacturer of the fork you have says you must use a particular style of plug then use that plug and no other.

Except for Cannondale which uses a regular starnut on their carbon forks.

What do you do when the expander plug keeps slipping up the steerer before the right torque is reached?
I believe the Cannondale starnut is a specific propretary item and not the ordinary ones you use with steel or Al steerers. Also, Easton now machines threads into the interior of their carbon steerers and provides a special threaded insert that does the job of the expander/starnut.

All of the expanders I've used have two threaded parts, one to tighten the plug into the steerer and the second to hold the top cap/stem compressor bolt. The FSA's use a 6 mm hex wrench to tighten the expanedr and a 5 mm hex to torque the top cap.

Thanks for the help. I'll let you know how the install goes.


fyi- not all carbon steerers have the same internal diameter.

The Alpha-Q forks need that 125mm long support tube because the wall thickness is much less than other brands and the fibers run vertically, not cross woven. This tube not only protects the steerer from crush damage, it is supposed to extend slightly below the upper headset bearing to support the entire steering tube, about the headset bearing. Thes forks were recalled because a lot of people placed the support tube too high, due to poor instructions. I had one on an R3, but I did install mine correctly and used a large amount of JB Weld epoxy instead of the small glue packet provided with the fork.

This tube will NOT fit in the vast majority of other brands and is not needed for them either.

Is there an expansion plug available providing full support to the steerer tube when clamping the stem?


Yes, these are usually included with a new fork. If you do some digging you can probably find one.