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Carbon Steerer Question...(12 posts)

Carbon Steerer Question...asphalt assault
Mar 13, 2003 12:47 AM
I'm just finishing assembling my bike and haven't cut the steer tube yet. I have a bunch of spacers stacked ABOVE the stem so the "star nut substitute thingy" I'l call it, does not extend into the steer tube far enough to be "under" the stem clamp.

My question is this, is it necessary for the "star nut substitute thingy" to be extended under the stem clamp for support?
re: Carbon Steerer Question...jaybird
Mar 13, 2003 5:17 AM
No it doesn't have to be but it is recomended. How many mm of spacers do you have under your stem? I would put 25 or 30 mm under the stem and then do your cut. The reason is that you are not really supposed to have more than 25mm of spacers with a cf steerer. With That done you should still have plenty of room to move your stem as you see fit and as well, you will be working within the parameters of your cf steerer.
the instructions...C-40
Mar 13, 2003 5:40 AM
The manufacturer's instructions usually state that the plug is to be placed in stem clamping area, not above or below.

The expanding plug supplied with carbon steerers provides internal support to the steering tube so the stem clamping pressure does not damage the steering tube. The stem may also creak or fail to stay tightened if the plug is not properly positioned.

Recently my stem starting creaking. Tightening the stem only cured the problem for a short time. I traced the problem to the expanding plug that had loosened up a bit. Tightening the plug and the stem cured the problem.
What instructions?...asphalt assault
Mar 13, 2003 8:38 AM
I bought the fork from an online bicycle closeouts guy and it didn't come with instructions. It's a good thing he sent the expanding plug with the fork or I wouldn't have known the item existed. (heh, stupid mountainbikers;^)

Thanks for your insight!
Depends on manufacturer...PsyDoc
Mar 13, 2003 7:38 AM
as to how many spacers can be added under the stem. For example, an Ouzo Pro (1 1/8th) has a limit of 38mm of spacers.
re: Carbon Steerer Question...Live Steam
Mar 13, 2003 7:04 AM
Yes the expansion plug must be in the clamping range of the stem. This is very important to maintain the strength of the steerer and to limit the flex. Why do you have so many spacers above the stem? If you are just doing this temporarily to determine the stem height before cutting the steerer, just ride easily. You can leave 1cm max. above the stem after cutting it. Some people don't like the look of any spacers above the stem. I have no problem with it. This allows some flexibility in dialing in your ride. A tip for cutting is to use some tape on the steerer in the cut zone. I mark the steerer and then use clear Scotch tape. This helps to prevent the carbon fibers from separating on the cut area. The Scotch tape does not gum up the blade as much as thicker tapes such as masking tape or duct tape.
Pretty much as I figured...asphalt assault
Mar 13, 2003 8:52 AM
...It makes sense that you'd need the plug under the stem clamp to keep the steer tube from collapsing. Yes, this only a temporary setup til I determine my stem height.

I'm just going to pull the fork off today and have it cut. My local shop has a nice clamping tool for hacksawing tubing so I'l take it there to have the surgury done.

Star Nut? No!juanteal
Mar 13, 2003 8:04 AM
If you have a carbon steer tube, don't use a star-nut thingy, use a pressure-wedge thingy!!! I could be wrong, but I'm sure that the star-nut if for forks with alloy steerers. It'll damage and ruin a 100% carbon fork.
There are a few fork mfg's that say OKMR_GRUMPY
Mar 13, 2003 8:15 AM
Correct me if I'm wrong, but I think that Time is one of them.
"Star Nut Substitute Thingy". He's not using a star nut. nmBrooks
Mar 13, 2003 8:33 AM
Yuh, dat's it...a star nut SUBSTITUTE whachamahoozit...asphalt assault
Mar 13, 2003 9:00 AM
aka: an "expanding plug", by golly!
star nut no!!!! expanding yes!!!!!!CORONADO FLYER
Mar 14, 2003 9:35 PM