Star Nut vs. Compression Plug ???

[DHallerman]

On the Competitive Cyclist site, in the copy for the Problem Solvers headset compression plug, it says: "As you know, you don't pound a star nut into a carbon steerer, rather you use what's known as a compression plug to hold the fork in the frame."

Problem Solvers Compression Plug (http://www.competitivecyclist.com/road-bikes/product-components/2008-problem-solvers-headset-compression-plug-1676_29_TRUE.html)

Is that true? I've seen star nuts in carbon steerers (at least one).

Or is it just that compression plugs work better?

Or do they work better?

While I'm an old hand with threaded headsets, I'm new to threadless headsets and to carbon steerer tubes.

So, any insight here would be appreciated.

Dave, who may still prefer the threaded headset and matching quill stem for aesthetic reasons is finally seeing the technical benefits of threadless

[MilanoTom]

I've seen plenty of things that shouldn't have been done...

My Peg Palosanto was the first bike I've had with a carbon steerer. Everybody I asked said not to use a star nut. In their headset instructions, Campagnolo's web site says, "The expandable adjusting nut supplied cannot be installed in forks with the headset tube manufactured out of carbon fiber since this may cause damage or breakage of the headset tube" (underlining was included in the instructions). Of course, they don't say what to use instead.

If you can use a compression plug, why take a chance with the star nut?

Regards.
Tom

[Chris]

Cannondale uses a starnut. I thought that was stupid and replaced it with a compression plug. Last week I replaced that frame, and as I was taking it apart I found where the compression plug had basically split the fork half way around. I suppose I was only weeks away from certain dental work. I would use the method that the fork manufacturer recommends... I sure am glad that my new fork has an aluminum steerer tube.

[weiwentg]

Cannondale uses a starnut. I thought that was stupid and replaced it with a compression plug. Last week I replaced that frame, and as I was taking it apart I found where the compression plug had basically split the fork half way around. I suppose I was only weeks away from certain dental work. I would use the method that the fork manufacturer recommends... I sure am glad that my new fork has an aluminum steerer tube.

carbon steerer forks do almost always use compression plugs. Alpha Q, however, puts a metal insert into the steerer and you use a starnut. it turns out that Canny forks use a special starnut.

[Dave]

As others noted, use what is supplied by the fork manufacturer whenever possible.

A standard star nut for a metal steering tube would be too large for a carbon fork, since the wall thickness is greater with carbon. The points digging into the carbon could certainly lead to failure.

Alpha-Q steering tubes are an oddball, with thinner walls and a long (100-125mm) aluminum support tube glued into place by the user. Inside the aluminum tube is a preinstalled star nut.

You do need to use some care when tightening a compression plug. The post is this thread is the first I've ever read of a compression plug splitting a steering tube. It does not require much torque on the clamp bolt to hold most plugs in place. They just have to resist the pull of the top cap bolt, used to preload the headset bearings.