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Old 08-19-11, 11:41 PM   #1
DRietz
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Star Nut Already Installed In Carbon Steerer - Please Advise

I know Cannondale's carbon steerers come OEM with a star nut, but I'm unsure of what to do in this instance as it is an IRD Mosaic fork.

I just received a fork with a carbon steerer that has a star nut already installed. No visible damage from what I can see, but that's not saying much.

What are my options for safety? Leave the star nut? Cut the steerer below the star nut, sell the fork, and buy a new one? Remove the star nut?

Again, please advise. Thanks.

Last edited by DRietz; 08-20-11 at 12:21 AM.
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Old 08-20-11, 12:02 AM   #2
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Is this a Cannondale fork or not? if it is, and the Star nut is installed, what's the problem if they installed it at the factory? removing will do more damage than leaving in; if not, who installed it, what fork is it, does the fork need cutting to fit your frame?
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Old 08-20-11, 12:20 AM   #3
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Is this a Cannondale fork or not? if it is, and the Star nut is installed, what's the problem if they installed it at the factory? removing will do more damage than leaving in; if not, who installed it, what fork is it, does the fork need cutting to fit your frame?
Sorry, my post was unclear. I used Cannondale only as an example.

Anyway, a mechanic did install the star nut but not while at a shop (so no liability), and the fork doesn't need cutting to fit my frame. It is an IRD (Interloc Racing Design) Mosaic carbon fork.

I'm just curious because it is a used fork and if it hasn't failed yet, would the change really be that drastic that sudden? The steering was always torqued to specs as well.
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Old 08-20-11, 06:14 AM   #4
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Sorry for asking a silly question, but are you sure it's a carbon steer tube? I thought all Mosaic models had aluminum steer tubes (mine does), in which case a star nut is fine.
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Old 08-20-11, 07:50 AM   #5
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I would contact IRD man, some carbon forks come with star nut from the factory but in general they dont. Since the starnut was put by somebody else i would contact IRD to find out if a star nut does something bad to it. If not, leave it there forever unless u can can cut that thing in pieces to take it out and put a good compressor thing inside.

Good luck.
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Old 08-20-11, 08:35 AM   #6
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Re Star Nuts : the one I had there is an aluminum ring joining
the 2 steel plates, and the threads.
drilling out the aluminum , section releases the steel stars,
then you can turn them and pull them out edgeways.
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Old 08-20-11, 09:07 AM   #7
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...

I just received a fork with a carbon steerer that has a star nut already installed. No visible damage from what I can see, but that's not saying much.

What are my options for safety? Leave the star nut? Cut the steerer below the star nut, sell the fork, and buy a new one? Remove the star nut?

Again, please advise. Thanks.
What's done is done, leave it alone and enjoy the bike.

The issue with star nuts in carbon forks is the scoring that happens when installed. That's horse has already left the corral. The nut will dig in slightly more as the headset is tightened, but if it doesn't slide up, which it most likely won't, it won't be materially worse than where you are now.

Attempting to remove it without taking it apart within the fork (drill the nut out, and tip the leaves sideways) can do far more damage than would ever happen in use.

If you do notice any slippage as you tighten the headset, then you can either remove it, or push it deeper and use an expansion plug, but otherwise leave bad enough alone.
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Old 08-20-11, 09:21 AM   #8
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I don't like "not knowing" with carbon parts. The failure mode is often quite sudden. I think a call to the fork manufacturer is in order. If they say it's fine, great, but if they don't recommend it, I wouldn't ride it.
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Old 08-20-11, 09:43 AM   #9
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It is a carbon steerer. IRD, like any carbon fork manufacturer, does not recommend the use of a star nut.

I figure if it's been ridden hundreds of jarring miles already, might as well just keep packing 'em on...
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Old 08-20-11, 11:18 AM   #10
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I don't like "not knowing" with carbon parts. The failure mode is often quite sudden. I think a call to the fork manufacturer is in order. If they say it's fine, great, but if they don't recommend it, I wouldn't ride it.
This is good in theory, but unfortunately doesn't always work in practice.

First of all you don't know if the person responding is qualified to render an opinion.

Secondly you might get a "safe" answer. Meaning safe for the company from a potential lawsuit standpoint, as in no don't ride it. The company has little to gain, and exposes themselves to potential litigation if they give you reassurance, and anything goes wrong.

The reality is that you as the rider have to make a judgment call. If the inside of the fork isn't scored beyond a minor surface scratch, then the structure is OK, but if there are deep gouges, they should give you pause.

Also consider if any of the potentially damaged area is well buttressed within the stem, or is below the stem where the stresses are. Lastly consider how highly stressed the steerer will be, how strong or heavy are you, do you work the bars hard climbing and sprinting, how long is the extension, and how many spacers below the fork?

If you're expecting that this will be a highly stressed fork, then you might want to be more conservative than if you're a light rider with few spacers and a short stem.
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Old 08-20-11, 11:54 AM   #11
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This is good in theory, but unfortunately doesn't always work in practice.
Well......my hide, as well as my peace of mind is worth more to me than a few hundred bucks.

And, as if anyone here that hasn't laid eyes on this fork is more qualified than the manufacturer to render judgment?

If the instructions for the fork forbid insertion of a star nut, and one got installed, I wouldn't ride it.
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Old 08-20-11, 12:04 PM   #12
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Well......my hide, as well as my peace of mind is worth more to me than a few hundred bucks.
Absolutely, and that's entirely your decision.

But the OP asked for opinions, and not seeing the fork, I tried to give him factors that he could consider so he could make a judgment call for himself.

Mechanical strengh isn't black and white. What's fine for one rider, might be borderline for another, and totally unsafe for a third. This is true of every aspect of bike construction regardless of material, and is especially true of high performance bikes where assumptions were made about rider weight, strength, and riding style, then all excess weight and strength were carefully stripped away leaving little margin for riders beyond the design parameters.

I work in a town with lots of bridges and overpasses, many of these are rated for cars and light trucks only, others have higher weight limits. All are safe except in the event of an over-limit truck.

Likewise with the fork. Any loss of strength by virtue of the starnut damage, might not be an issue for most riders, but can be the straw that breaks the camel's back if highly stressed.
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Last edited by FBinNY; 08-20-11 at 12:09 PM.
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Old 08-20-11, 12:38 PM   #13
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But the OP asked for opinions, and not seeing the fork, I tried to give him factors that he could consider so he could make a judgment call for himself.
I get that! But neither you nor I are on the scene, and our esteemed OP is apparently not an expert in carbon fiber evaluation, but the manufacturer presumably is.

I know it's not black and white-that's why I said I wouldn't ride it until I felt I had enough information to proceed.

Even will all the talk of the various elements that might or might not be a factor it still comes down to "you nor I are there, and the OP isn't a carbon fiber expert.

You don't know if it's already been stressed to "straw that breaks camel's back status" as it sits this moment. You nor I know how hard it was to pound that thing in there!

So, I think a reasonable person might conclude it's not worth the risk.
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Old 08-20-11, 01:04 PM   #14
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BikeWise, if you are a carbon fiber expert, I can happily take pictures.

I do have a carbon repair guy locally - he developed the seatmast system used in Look frames. He'd know as well, I was just reaching out to the community for a general opinion.

This thread obviously shows the two sides to the opinion and both are quite logical. I'm a 130pound climbing machine and it's not like I'd put much stress on the fork at all, and seeing as how it was ridden by a heavier guy than me for thousands of miles without issue urges me in the direction of "I'll be fine."

But again, I'm no expert.

Pictures incoming.
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Old 08-20-11, 01:11 PM   #15
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It is a carbon steerer. IRD, like any carbon fork manufacturer, does not recommend the use of a star nut.

I figure if it's been ridden hundreds of jarring miles already, might as well just keep packing 'em on...
The other issue here is that carbon steer tubes are nearly always intended to be used with an internal expander plug that reinforces the steer tube from the interior, against both the compressive force of the stem and the "wilting" effect of forces from the handlebar (body weight, sprinting, pothole impact, etc). I advise not using the fork until you've contacted IRD about this.

Personally, I'd err on the side of caution and get a new fork. I'm attached to my face and it doesn't need to get any uglier than it already is
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Old 08-20-11, 01:20 PM   #16
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The star nut is well buttressed within the clamping area of the stem, so that's good.

These pictures are incredibly large. Open with caution...

http://img200.imageshack.us/img200/9573/img1487v.jpg
http://img803.imageshack.us/img803/3676/img1488b.jpg
http://img853.imageshack.us/img853/4653/img1489w.jpg
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Old 08-20-11, 01:33 PM   #17
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Everyone has to make their own decisions. I, for one, would have absolutely no more qualms then for CF forks in general about riding this fork, or letting my wife ride it (and I'm not looking to get rid of her....yet).
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Old 08-20-11, 01:46 PM   #18
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I'm a 130pound climbing machine and it's not like I'd put much stress on the fork at all, and seeing as how it was ridden by a heavier guy than me for thousands of miles without issue urges me in the direction of "I'll be fine."
Your OP said nothing of that fact! That certainly changes things. I thought the fork was purchased new by you and a friend installed a star nut.

Go ahead and ride it. You'll be the first to know if it breaks!
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Old 08-20-11, 02:08 PM   #19
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I'm unable to tell if that's serious, sarcastic, or a mix of herein.

Either way, I'll probably ride it.

Did I mention the lawyer lips on the dropouts are filed off too? This fork is my new favorite.
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Old 08-20-11, 02:47 PM   #20
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I'm unable to tell if that's serious, sarcastic, or a mix of herein.
Just a fact.

And a reminder that no matter what advice anyone may tender, it's still your flesh and bones at stake.

Oh, and, lawyer lips are the first thing that go when I get a new fork.
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Old 08-20-11, 09:25 PM   #21
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I know Cannondale's carbon steerers come OEM with a star nut...
Cannondale carbon steerer tube come OEM with an expander bolt/plug, not a star nut. Star nuts are OEM on their aluminum steerer tubes.

In any event, the Park Tool website suggests it may be possible to drill out the center and remove the pieces if you really had to get it out. Sounds like a risky project however. If it were me, I'd get a proper compression plug and push the star nut deeper until I had clearance for the plug and then not worry about the extra 2 oz.
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Old 08-21-11, 01:09 AM   #22
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How would pushing it deeper make it any safer? More scoring = more stress risers = larger chance of failure...
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Old 08-21-11, 01:36 AM   #23
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How would pushing it deeper make it any safer? More scoring = more stress risers = larger chance of failure...
Well, as it stands now, the steer tube has no internal reinforcement at all, so at least the expander would do that much. Granted, from the photos, it's quite thick. But so are OEM Specialized carbon steerers, and I've seen a couple of those cracked.
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Old 08-21-11, 03:10 PM   #24
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The star nut is well buttressed within the clamping area of the stem, so that's good.
Ouch that's nasty. I certainly wouldn't push the star any deeper. If it we me I'd attach the stem very firmly with the help of some friction paste, and then remove the compression bolt. I'd then reattach the top-cap with a very gentle glue, possibly with a very short bolt to fill the hole in the centre.

The idea is to prevent any force being transmitted to the star nut in the event of any unusual load or shock. Keep a normal bolt in your tool-kit.
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