Bicycle Mechanics - Threadless headset woes...
Bikeforums.net is a forum about nothing but bikes. Our community can help you find information about hard-to-find and localized information like bicycle tours, specialties like where in your area to have your recumbent bike serviced, or what are the best bicycle tires and seats for the activities you use your bike for.
02-21-11, 12:33 PM
So my '06 Specialized Roubaix is having some headset issues. I kept trying to readjust it, but it would never get to a reasonably loose, yet tight point. Well, It turns out the expansion nut inside of my steering tube is slipping upwards as I'm trying to tighten down the headset.
I can make it go back down in the steering tube by slightly tapping it back in, but I can't get it to slip up and out to replace it/put some carbon paste on it. Even with the bolt taken all the way out, I can't seem to get it to budge or come apart.
So I'm looking for some tips to get this thing out of there. The bike is barely rideable with a loose headset.
02-21-11, 12:39 PM
Maybe you can drive out the poorly performing expander from the .. bottom.
If the fork is open at that end..
Do you have a carbon steerer? I would not attempt to drive it out from the bottom as the shape is made to exand when pulled up. That is intent to keep it from slipping. I would drive it down and out the bottom if it clear all the way through. See what it looks like at this site:
You dont want to drive it against base of the the cone shape but down along it.
02-21-11, 12:54 PM
Expanders in carbon is a different part than a star fangled nut..
restricted to steel steerers for safety .
(the link is to a star fangled nut with only the cap 'carbon'
I had a star fangled nut , [and a steel steer tube fork],
the threaded part is aluminum , joining the 2 dished steel stars,
the aluminum part breaks, when forced to ,
by using another stack of strong washers across the end of the tube,
and tightening the bolt, then once the aluminum piece yields ,
the stars turn on edge and come out, one at a time, easily.
Here the term compression plug is used to differentiate from star nuts
an example, amongst many from this retailer..
you, OP, need to know how to unscrew the expander, itself.
I think you just took out the bolt That pulls the cap down,
but have not touched the second set of hardware that causes the expander to expand.
Or unscrewed it to remove it
You can rarely pull out an assembled expander because as you lift the top it expands the wedge improving the hold, though not enough to do it's job. If you have strong fingers you can dis-assemble the expander unit, reach a finger through it and massage it up and out.
Otherwise you can make yourself an inexpensive expander puller with a hinged toggle bolt (http://en.wikipedia.org/wiki/Toggle_bolt)like the ones to the left in the picture and a long screw to fit. Get the largest that will fit through the expander, attach the bolt and push it through so it opens behind the expander and now you can pull it out.
02-21-11, 09:48 PM
Ok, to clarify what I have done, I understand there is one bolt that pulls the cap down and a second bolt inside of the expansion plug or whatever we'd like to call it (obviously not a star fangled nut). I have removed the cap and the bolt that keeps the cap down. I have removed the second bolt that fully inserts into the expansion plug and can see all the way through it. It will not, however, budge even with the second bolt fully removed. I can tap it back down a little to give some space for the top cap to tighten, but it keeps slipping up.
So does the second, larger bolt inside of the assembly actually do the tightening of the expansion plug or not? Do I need to be doing something differently to tighten the plug?
They very somewhat brand to brand, but the basics are usually the same. There's a split ring that's expanded by two cones wedging into it top and bottom. When you tighten the expander bolt - not the top cap screw - the ring expands and jams. Your problem is that it doesn't shrink back enough when the pressures off.
This isn't all that rare. See if you can find an "L" or "J" shaped piece of metal you can slide through the ring and hook behind it to give you a purchase to ease it up. I use an old screwdriver that I heated and bent the last 1/4" to a 90 angle. It's my mini pry bar and I use it to pull all sorts of parts up out of small holes.
If your fork has an open bottom you can reach through with a long rod and push the ring up. If not, and you can't find anything and don't want to bend a screwdriver, buy a toggle bolt as I suggested in my prior post. The ring will come up without much resistance, but you have to push it without expanding it.
02-22-11, 04:27 PM
post a pic of what type of expansion plug. i have had good luck tapping the bolt that expands the wedge with a hammer and pulling up at the same time for the trouble makers
02-23-11, 03:24 PM
Different types of expanders have different ways of removal and installation.
03-04-11, 11:56 PM
Just a quick update. Finally had time to mess with it again. long story short, I got the expansion plug out and will be replacing it. It was made from a very cheesy metal and a simple 4 pronged sleeve with a cone that went up inside of it. The outer surface of the expansion plug was totally smooth, mirror polish. And it was put in there dry with no carbon paste or anything. It got notched and sort of "stuck" and no amount of turning would tighten it properly. Attempting to muscle it into a tighter position only resulted in nearly stripping the larger bolt that was supposed to tighten the assembly.
So in other words, it was junk and I'll hit the local shop tomorrow to see about a replacement.
03-05-11, 01:05 AM
Measure the ID of that fork tube, because not all the expanders work fine, they have tolerances aswell.
Powered by vBulletin® Version 4.1.12 Copyright © 2014 vBulletin Solutions, Inc. All rights reserved.