"dgk" <[email hidden]> wrote in message
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Quoted message said:I can't track it down, and it only happens sometimes. Trek 7100 ($300
hybrid, the low end, with 14,000 miles or so on it). It really sounds
just like one of those geiger counters in a bad scifi flick. Hmm.
Geiger is one of those words with e before i without a c. Must be
someone's name.
Anyway, I've tried putting my hand all over the bike trying to see
what would stop it, and it seems to be from the front fork. That
useless shock is pretty much frozen so perhaps it's coming from that.
I can't find any cracks in the frame, but I'm getting a bit afraid
that it's going to collapse under me.
Time to drag it to a LBS I think. Any ideas as to what it is?
Number of causes, some of these wont show up until weight is applied:
1. A bad bearing in the front hub. Spin the wheel and feel for roughness
or vibration.
2. A loose front spoke will click in the hub or spoke broken at the
nipple will click in the rim. Puck all of your spokes to make sure that
they are properly tensioned.
3. Something loose inside a box rim, perhaps an indication of imminent
failure or just a small stone.
4. A bent rim brushing the brake pad.
5. A loose headset. Lock the front brake while sitting stationary on the
bike. Try to rock the bike slightly backward and forward. If you feel a
click your headset may need to be adjusted. Cheap bikes used cheap
headsets that weren't hard enough to keep the ball bearings from
brinelling pits into the races. It's usually the bottom race where the
most thrust gets applied that goes first.
6. A cracked steering tube or a bad braze or weld at the crown. Danger -
if this is the problem replace the fork immediately. The treads in the
steering tube on older style forks were a perfect place for stress
risers to start. There's less than 1mm (.030-.040) of wall thickness in
the tube a the bottom of the threads. That's one reason why most newer
stems have minimum insertion makers so that you don't expand the wedge
in the threaded area.
Twice I had the joy of holding the disconnected handlebars when a
steering tube broke: once on one of my own bikes and once on a customers
bike that I was test riding. I was lucky that I was going slow enough to
safely stop the bikes both times. I also had an old cast aluminum stem
fail on me while riding.
Before I ride anyone else's bike, I always lift the front wheel a little
a rotate the bars back and forth and then I lock the front brakes and
rock it to make sure that the front end is solid. It only takes a few
seconds and most people don't even notice what I'm doing.
Good luck,
Chas.