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Old 06-15-12, 10:19 PM   #1
Hapsmo911
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Carbon steerer bulge where plug is seated?

Noticed some creeeking from my 2011 TCR SL. I removed the stem, and spacers, and noticed a vetical crack right below where the plug ends in the steerer, the crack is on the outside of the steerer. I then noticed another vertical hairline crack forming right above where the top of the plug sits. The steerer is noticeably bulging where the plug is. You can feel it if you run you fingers down the steerer, more noticeable when you try and slide a spacer down the tube, you have to nudge it past the bulge. Is this normal? Can plugs cause bulges in carbon? I use a torque wrench on my stem so I know its not cracked from over tightening. I just got this frame set from Giant under warranty, so its less than four months old.

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Old 06-15-12, 10:50 PM   #2
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I believe some of the TCR forks have been recalled. The 2001, 2009, 2012. Check Giants site here:

http://www.giant-bicycles.com/en-us/page/578/
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Old 06-16-12, 05:45 AM   #3
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Shouldn't bulge. Shouldn't crack. Needs warranty replacement (again). But you can't use a torque wrench on the top cap bolt. There is no specified torque for that. It is a very delicate adjustment related to the free turning of the fork on its bearings. It is ll by touch and feel. You may have cracked and bulged the steerer tube by overtightening the top cap. Top cap tightening is not supposed to provide structural support, it is only to temporarily fix everything in place until you can tighten the stem bolts. And as far as safety coming from using a torque wrench, I have had LBS mechanics tell me that the torgue listings are much higher than they normally use. Safe assembly and operation supposedly occurs at much lower torques. I cracked a very lightweight handlebar at the recomended torque. The shop mechanic showed me that the bar would have been secure at half the torque. Go figure.
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Old 06-16-12, 06:00 AM   #4
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I don't think the top cap tightening had anything to do with the crack. The expander plug body is capable of cracking the steerer if it is badly overtorqued so if you installed it and overdid it that may have been the cause. Or if you installed it properly and the steerer was defective, that's also a possibility. Overtightening the stem clamps would have distorted the steerer inward so that wasn't the cause either. You must replace the fork.

BTW, the topcap bolts on many cartridge bearing headsets do indeed have a torque spec. It's low, typically 4 to 20 inch-pounds, depending on the headset maker.
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Old 06-16-12, 07:10 AM   #5
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I don't think the top cap tightening had anything to do with the crack. The expander plug body is capable of cracking the steerer if it is badly overtorqued so if you installed it and overdid it that may have been the cause. Or if you installed it properly and the steerer was defective, that's also a possibility. Overtightening the stem clamps would have distorted the steerer inward so that wasn't the cause either. You must replace the fork.

BTW, the topcap bolts on many cartridge bearing headsets do indeed have a torque spec. It's low, typically 4 to 20 inch-pounds, depending on the headset maker.
+1 On the fork bulging or splitting because of top cap over-expansion. This has nothing to do and is a common enough user error that some makers have changed to a glued in steel sleeve and a star nut that eliminates user discretion there. You definitely need a new fork, lest the split steerer snaps off when you work the bars during a sprint or hill climb.

Unless your fork is on a recall list, you're at the mercy of Giant's generosity. IMO splitting of a steerer from top cap over expansion is a user error not a fork defect. You may try your luck with Giant, but don't blame them if they say no. However if they do say no, you may try for a hard luck discount. When I handled warranties, I always tried to find a way to give a break in cases where I couldn't (or wouldn't) warranty something. Usually it was an option to purchase a replacement at a deep discount.

BTW- while some makers specify a top nut torque, I'm not a fan of the concept. The optimum preload depends on the type of headset bearing and angle of contact. As noted it varies by a factor of 5 times depending on brand or model. No mechanic can remember that many specs, and there's too much between the top cap and bearing that can introduce variables for this to offer any degree of reliability.

Leave the torque wrench on the bench and tighten headsets sufficiently to remove all free play, measured by the front brake test. Cross check that the steering is free. If not sure check by walking bike holding the seat. The bike should steer easily with only slight changes in angle. Headsets need very little (if any) preload because all the flex in the system only tends to increase load anyway. They clearly announce looseness with vibration when braking, or with a knocking sound on rough roads, so an attentive rider can easily detect and correct a loose headset.
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Old 06-16-12, 07:28 AM   #6
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When I said I use a torque wrench, I meant on the stem bolts, not the top cap. I tighten the cap by hand, and have never got it so tight the steering was tight in the slightest. The plug was installed by the shop.

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Old 06-16-12, 09:28 AM   #7
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Wouldn't the inside of the stem prevent the steerer tube from expanding ?
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Old 06-16-12, 09:32 AM   #8
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Wouldn't the inside of the stem prevent the steerer tube from expanding ?
No, the plug is tightened and expanded well before the stem is fitted. Since the stem must be loosened for the headset to be adjusted you can't count on it for support against plug pressure.

In some cases I've seed steerers distorted enough that the stem even when tight rocks slightly and creaks when sprinting and climbing.
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Old 06-16-12, 12:34 PM   #9
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"In some cases I've seed steerers distorted enough that the stem even when tight rocks slightly and creaks when sprinting and climbing."


Funny you mention this. I started chasing a creaking noise when applying pressure on the bars, that's what lead me to finding the crack.
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Old 06-16-12, 12:35 PM   #10
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A clear case of your ears trying to preserve the space between them.
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