Bicycle Mechanics - Quill stem keeps sliding out of steerer tube!
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10-22-08, 10:56 PM
So I have an interesting issue, and I have been trying to diagnose the problem. I have a 1" threaded fork that used to have a quill stem. Well, one day, the entire stem slipped out and it would fail to retighten (even at various insertion points). So I thought okay, I'll pick up a new quill stem.
I ended up getting a great deal on a 1" to 1 1/8" quill adapter and Salsa stem, and another issue arises - since my bike is tiny (48cm), the headtube is small and it seems as if the quill adapter doesn't fit in to the "Minimum Insertion Line," - it's about one inch over. However, I changed the wedge at the bottom to a smaller wedge from my old stem and it fit almost all the way in - about 1cm over the line.
However, it still became loose when it was inserted all the way in. So I used the fatter wedge, and now the stem is inserted 1 inch above the "Minimum Insertion Line." BUT, the stem doesn't seem to be moving, and I grabbed the front wheel between my legs and tried to turn the handlebars/stem, and it didn't budge. However, I don't know if this will last, and who knows if it'll just fall out again.
So what should I do? Take it to a LBS and have them take a look, and regrease? I'm aware that I shouldn't put the stem in TOO far, like in Sheldon Brown's advice. I'm wondering if that was the case when I had the stem inserted to the line, but it still came out.
10-22-08, 11:10 PM
Interesting problem. Check your headtube to ensure it has not been enlarged by excessive tightening of the quill stem. Check the wedge to ensure it is not so worn as to prevent "tightening" within said headtube. Check threading within wedge; is it stripped?
Re: min. insertion-you should never ride a bike with the stem above the min. insertion line as it may place undue pressure on the headtube, resulting in possible frame damage.
10-22-08, 11:28 PM
From what I can tell, the headtube/steerer tube area doesn't look to be damaged, enlarged, or any of that sort. But I am no expert in seeing what is damaged or not. I just don't see anything striking that would suggest it being larger around that area.
And from looking at the smaller wedge (the wedge that was able to put the quill adapter almost all the way to the line), it seems to be worn. I can't tell if the threading inside is still good or not, but nonetheless, it looks pretty old. The new and fatter wedge, which is in the bike now and has the quill adapter an inch above the line, looks to be fine. It does seem significantly bigger, though - it doesn't fall as far down the steerer tube as the other wedge.
So should I try finding a new wedge? It seems if I could find a wedge that was smaller than the one I am using now (allowing the quill adapter to go farther down the steerer tube), it might help or solve this problem.
10-22-08, 11:52 PM
Make sure the bolt that pulls up the wedge has sufficient threads so that the wedge doesn't bottom out on the threads. Tighten up the stem when it's out of the bike and you should be able to pull the wedge up so far that it sticks out sideways 1/4".
10-23-08, 04:56 PM
obviously the stem is the correct size for your bike (right?), so i'd replace the wedge nut and the lond tightening bolt it's attatched to. remember to lightly grease your threads and to use the correct stem bolt as to not run out of threads when you go to tighten it up. look in the steerer tube to make sure its clean and dry, too. if thread bottoming out is boarder line, a few slim washers between the stem and tightening bolt can help if the type of application you have will allow it.
10-23-08, 06:26 PM
well, i looked inside the steerer tube and it looks greasy in there - a filthy dark gray substance. I guess I will look for a new wedge, but exactly how far is the wedge supposed to go inside the steerer tube? when I have my adapter inserted with 1 inch below the minimum insertion line, it still looks like the wedge would connect to a non threaded part of the fork. my head tube is very small, too
10-23-08, 06:28 PM
You could have a quill to fit a steerer with an inner diameter of 21.1mm in a steerer with a 22.2mm inner diameter. This can cause the stem to come out as you described. The adapter is the correct size, and if it is bottoming out before reaching the minimum insertion line, then it is inserted far enoungh.
10-23-08, 08:15 PM
However, it still became loose when it was inserted all the way in. So I used the fatter wedge, and now the stem is inserted 1 inch above the "Minimum Insertion Line."
Keep running your stem this way and see if you like how your face looks when your stem fails. Minimum insertion markings are there for a reason.
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