On Wed, 11 May 2005 14:22:51 GMT, "soup" <[email hidden]>
Quoted message said:
I am pretty much a know-nothing when it comes to bike mechanics can
change wheels and adjust brakes/derailleurs but that is about it,
noticed a crack today on a nut on my steerer (?) is this the sort of job
you could tackle yourself (although not experienced with bike mechanics
I am not handless) or do I let the LBS replace it? All advice welcome,
if this is a non-event type job and I should tackle it myself could
someone give me a step by step account of how to change it or a link to
a page where this is discussed.
Pic of crack/nut etc at :-
http://www.sidtech.co.uk/iu/soup86307461862.JPG
Read this first:
http://sheldonbrown.com/handsup.html
(That's basically background about stems in general, but it's worth
reading since it explains how the stem mounting works.)
The job is easy. Mark the current installed depth of the stem using
some tape or nail polish or whatever you've got that will work.
Loosen the bolt in the middle of the stem a couple of turns (it's the
one that has the hex recess, right in the top of the vertical part of
the stem) and give it a smack straight down with a hammer or wrench;
this should make the stem and handlebars suddenly able to move without
turning the fork[1]. Pull the handlebar and stem assembly out of the
steerer tube. If the wire for the computer isn't long enough to allow
this, just undo the comp's bracket for now, letting it dangle, and put
it back on when you're done.
At this point, you can just unscrew the cracked nut and take it along
to the bike ship to get a replacement. If they're nice people, they
might scrounge one from the used parts pile and sell it to you cheap;
if they don't keep a used parts pile (or they're Profit Maximization
Oriented) they may tell you that the only way they can sell you one is
as part of a complete headset; it's up to you to decide if that's a
ripoff or not.
Having secured a new nut by whatever means, it just gets run down
against the stuff that's below it and tightened firmly in place. Huge
amounts of torque are not required. If everything's OK, there should
be no play in the steering bearing but you should be able to move the
fork freely with essentially no resistance. (A slight feeling of
non-smoothness is normal; these are generally not high-precision
bearings.) If there's drag, undo the nut a turn and unscrew the round
knurled part (below the nut) until there's no drag and just a teensy
bit of play, and then retighten the nut and check for play. Readjust
as needed so that when the nut is tight, there is neither slack nor
drag in the bearing.
If there's play in the headset bearing when the nut's tight (and there
probably will be until you adjust it, if that nut's been cracked for
very long), you'll need to screw that knurled round part (it's
actually part of the upper bearing) down a bit to take the slack out
of the bearing before tightening the nut. It is not uncommon to need
to leave just a tiny bit of slack in the bearing before you tighten
the nut in order to have no slack and no drag when the nut is tight.
Once you're happy with the adjustment of the headset with the nut back
on tight, slip the stem back into the steerer to the same depth that
it was before (you marked it, right?), snug the stem bolt a bit, check
the centering of the bars vs the front wheel, and when it looks right,
tighten the bolt to lock the bars in place. Recheck it after the
first couple of rides if you're not sure that you got it tight enough.
[1] If the bolt drops down flush when struck, but the stem is still
pretty much locked in place, unscrew the bolt a few more turns and
smack it again. That should get the stem loose.
--
Typoes are a feature, not a bug.
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