Star nut in a carbon fork?
 

So I just took delivery of a new(to me) Merckx Team SC. Totally flabbergasted by the weight (or lack thereof).

But that's not the point of this post.

In the process of replacing the stem with one longer and lower, I noticed that someone had put a star nut in the carbon steerer instead of using the approved "expansion device". I know this is a MAJOR no-no, but it brings up a couple of questions:
1) Am I going to die a messy and embarrassing death when the fork inevitably and spectacularly fails?
2) Is there a relatively safe way to remove the star nut?
3) Assuming said removal could be accomplished, would the fork be safe to use?

Thanks
SP
OC, OR

What's done is done, and there's no benefit to removing the nut now. In fact removing will likely cause more harm, so leave it where it is.

In all likelihood, you're not facing sudden imminent death. The fork is marginally less safe than it as before, but IMO that doesn't make it unsafe. Unless there's very obvious and deep scoring, I'd ride the bike and inspect it from time by removing the top cap and looking in to the steerer for any hind of splitting along the scores.

Keep in mind that the star nut and damage are in the area where the stem clamp shores up the steerer, so I wouldn't expect an issue. OTOH do not push the nut deeper and extend the score lines.

1) Well, unless there is a metal sleeve bonded to the inside of the carbon steerer, the probability of it failing under load has definitely increased.
2) Nope.
3) Nope.

As far as I'm concerned, the shop that installed it has put you in danger and owes you a new fork. Check with the manufacturer of the fork and see what they have to say about it. NEVER EVER compromise when it comes to liability - especially with something as crucial and minimalist as a bike fork.

One could make an argument to remove the star nut and insert a bonded in (as in epoxied) compression sleeve that would both help fix the scoring the star nut made as well as provide the stem clamp compression resistance. But these bonded inserts tend to be fork specific.

I'd leave things as is and visit the steerer's condition periodicly. And take it up with the place that drove in the star nut. Andy.

The OPs reference to New (to me) implies that this was a bike bought used. So the person who installed the star nut was probably a prior owner, not a shop mechanic.

So, unless the OP wants to use this as a reason to return the bike for a refund, I doubt he has much recourse to anything.

BTW- if, despite my advice to the contrary, the OP decides he wants to remove the starnut, the best/safest way is to use a twist drill (probably 5/16th dia or so) to drill out the aluminum core, which will free the leaves which can be turned sideways and eased out with long nose pliers.

I'd disagree. With the star nut in there you can't use a compression sleeve style top cap which helps support the stem. When you adjust the top cap and as you ride the star nut is going to cut into the carbon steerer.

I'd get that star nut out, check for damage and then use a long compression sleeve style cap - you can get them around 2" long. If the steerer is open at the bottom then you may be able to support the star nut with a threaded rod while you drill or grind the center out.

A bit OT, but I like the idea of an epoxied in aluminum insert. I've searched a bit and not have found them to be generally available in a range of appropriate diameters and lengths. Is there a source?

An aluminum insert won't have the effect of reinforcing the carbon tube because it's strength and flex modulous are too mismatched for it to work in concert with the carbon steerer.

I'll try to explain by analogy. Imagine you're trying to lift a 200# man out of a hole. You have plenty of rope, and bungee material, but it's all rated to only 125#s. You can use 2 ropes, or two lengths of the bungee and get the man out. But if you use one rope and one bungee, the rope will reach it's limit and break long before the bungee has even begun to stretch, and once the rope breaks the bungee soon follows.

A steel insert of the right strength can work, not to prevent breakage of the steerer, but as a "safety net" to hold things together long enough for the rider to stop safely.

However, as far as the OP goes, he's best off living with it as is unless he's a strong sprinter or climber who really puts some stress into his handlebars.

If you can return the fork or whole shebang (if part of a larger purchase), do so. Why should this be your problem?

It seems to be a used bike, which may or may not be returnable. OTOH if it is returnable, the OP might want to keep it if it's safe, or can be made safe easily. I'm of the opinion that's reasonable safe (about as safe as bikes and carbon forks are generally) as is, but the OP has to make his own decision.

I have removed a star nut .. once you turn the stars on edge, after drilling out the center-rivet ring that holds the stars on.. they come out quite easily.

Aluminum steerer , carbon blades is another combination .. the the star nut isn't so bad..

In flex of the steerer I might agree, but to add strength against crushing where the stem clamps, and particularly if the stem/bars receive an impact, I believe an aluminum insert can be affective, which I believe is the reason that Cervelo uses them, at least on some of their bikes in the past, IDK about the most recent models. Some of the various expansion plugs are purported to do this, which is why manufacturers sometimes admonish against having the steerer extend too far above the stem so as to position the plug above rather than in line with the stem.

There are, of course, many examples of structures that combine the two materials by bonding and other joining techniques.

You're right that an insert might help prevent splitting from clamp stress, however an expansion plug at clamp depth does the same thing.

I suspect that Cervello used their system because they didn't trust people not to overtighten the expansion plugs and burst or bulge the steerer, which remains a common issue. If I remember right, their insert was steel and maybe they considered it would also serve as a safety net.

There's no single right answer, and I wasn't saying an aluminum insert couldn't help, --- if the engineering is right. OTOH, a poorly conceived on executed insert might create an illusion of safety without actually providing any.

1) Am I going to die a messy and embarrassing death when the fork inevitably and spectacularly fails?
2) Is there a relatively safe way to remove the star nut?
3) Assuming said removal could be accomplished, would the fork be safe to use?

I purchase a custom Marinoni Fango CX with a carbon fork about 10 years ago. I had ridden it about a month and I was climbing Mount Royal and had to stop part way up. When I restarted I stood on the pedals and pulled up on the bars and "Crack" I went over the back end of the bike and my legs got cut up by long carbon strands that extended from the sheared off steerer tube.

The tube contained a star nut. Marinoni did not assemble the bike and the shop that did swore that they did not put it there. I spoke to Marinoni and they installed a new fork and repainted the bike.

I've checked out every bike I've bought since that experience.

I've already offered (2) a couple posts above.. the way you get a star nut out, is destroy the star nut where it is.

3) hard to say anything about things I cannot see .. I'll go with .. Maybe..

I cannot predict the Future , so Number 1 answer is: "42" .

Sure, a good case can be made for going either way. I make enough mistakes of my own that I don't care to deal with other folks'. Seriously, I was reflecting my own personality. I know as a perfectionist that damn steerer tube would bother me every day. Others could deal with it fine.

George Hincapie went into a French Drainage ditch on his way to Roubaix.. It was an Aluminum steerer .

Shaving weight off with leading edge design, has its trade offs in that regard ..

After all of the input, I'm inclined to ride it as is (the bike is 10 years old and the steerer still appears to be sound) and inspect regularly. BTW, even at 6'3" and 185 lb on a good day, I'm not much of a "strong" anything so that may help mitigate things.

Thanks
SP
OC, OR
...hoping to get out for a ride this weekend on my 10 year "new" Merckx.