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installing a carbon steerer fork(8 posts)

installing a carbon steerer forkup_hiller
Oct 7, 2002 7:08 AM
How much force does it take to properly install a headset/carbonsteer tube combo? I have had some play in my headset every time I have put this thing in so far.

Now I think I know why: the "teeth" on the the blocks of the expanding plug are supposed to wedge into the steer tube. Once that happens, any futher tightening will create a compression force that will tighten the headset and snug everything up (the ultimate goal of the entire operation). Am I right here? That would mean getting pretty "big" with the hex wrench. I have never done this before, so I was afraid to man-handle it too much. I'd sure hate to break anything before I even get my bike put together.

Once the headset has been installed once, the dents from the plug will be in the tube forever. So, does that mean installing this thing is a one-time operation? Or can I put it on more than once? I'd like to give it a trial run before I cut the steerer tube.

I hope this makes sense. Thanks in advance.
Check this:Spoke Wrench
Oct 7, 2002 7:25 AM
Are you sure that your top cap isn't bottoming against the steer tube? If it is, and that's fairly common, you will never be able to get the play out of your headset. Try putting about a 2mm spacer under your stem and see what happens. As a comparison, the torque spec. for Diacompe Ahead threadless top caps is 22 in/lbs, or next to nothing.
If you have done this before, PLEASE HELP!!up_hiller
Oct 8, 2002 6:16 AM
Nope, that wasn't it. The bottom of the top cap is flat; it doesn't extend into the stem at all. Also, the recommended 3 mm space is left between top of steerer and top of stem.

"As a comparison, the torque spec. for Diacompe Ahead threadless top caps is 22 in/lbs, or next to nothing."
- Is this for a carbon steer tube, though? With an alloy steer tube, it makes sense not to need much torque because of the way the star-fangled nut mechanism works. I have dealt with that setup on my mountain bike, which like the roadie I am dealing with now, has an integrated headset. For this design I think it takes a lot more torque to force the expander plug to seat itself inthe wall of the steer tube.
BTW, S.W., I don't mean to imply...up_hiller
Oct 8, 2002 7:22 AM
that you don't know what you are talking about. I have done enough reading here to know that you do.
not enough info...C-40
Oct 8, 2002 8:30 AM
You don't mention the brand of fork. Every brand of expanding plug is different. Some have a separate hex socket that is turned to expand the plug to the proper tension, before the top cap bolt is installed (Colnago for example). Your description implies that the plug on your fork is expanded by the top cap bolt. Not the best design, IMO. Obviously the tension on the expanding plug must be sufficient to keep it from moving when the top cap is tightened.

The intergrated headset has nothing to do with the expanding plug or the amount of top cap torque required. All headsets need to have zero bearing clearance and a slight preload on the stem (from the top cap), before the steering tube clamp bolts on the stem are tightened.
some more info...up_hiller
Oct 8, 2002 10:27 AM
The fork is Fuji's own, but the top cap (and I assume also the plug assembly) is made by FSA. There is only one bolt in the entire plug. The top cap itself has threads that allow it to interface with the upper part of the plug, and the bolt of course runs through both upper and lower parts of the plug, but the bolt is not directly attached to the top cap. I wish I could at least post a link to a picture, but FSA's site is under construction.

Thanks for your help.
try this...C-40
Oct 8, 2002 4:20 PM
Since you only have one bolt to expand the plug and tighten the cap, you could place the bolt into the expanding plug, without the top cap and place the plug into the steering tube slightly deeper the normal. Try tightening the bolt without the top cap in place to see if it expands the plug to create a fairly tight fit in the steering tube. If it does, you may be able to remove the bolt, install the top can and then retighten. If the plug still moves up the steering tube with moderate bolt tension, I'm out of ideas.

I had a LOOK fork with a similar problem and the method above worked with the LOOK expanding plug. Once I got it expanded out at the proper location, I installed the cap and it tightened down properly.
thanks for your help.up_hiller
Oct 9, 2002 7:13 AM
I got it figured out last night, but thanks for taking the time and effort, just the same.

There is only one bolt because it only needs to expand the plug itself. The top cap has a hex head slot cut into the cap itself. It's one size larger than the bolt in the plug, so you tighten the plug w/ the 5 mm, then pull it out and tighten the cap (just the cap, not a bolt) with the 6 mm. Duh. Pretty ingenious little device.