Re: Death wobble in front bars!

kjparker wrote:
On Oct 21, 3:14�pm, jim beam <spamvor...@xxxxxxxxxxxxxxx> wrote:
kjparker wrote:
On Oct 21, 9:30 am, Jay Beattie <jbeat...@xxxxxxxxxxxxxxx> wrote:
On Oct 20, 2:35 pm, kjparker <keithjamespar...@xxxxxxxxx> wrote:
Hello,
I have an elderly (circa 1978) Raleigh Grand Prix road bike that I am
using for my daily commuter. It is in other wise fantastic
condition,
but just recently it has developed a wobble in the front end.
It manifests itselft when riding as for lack of a better description
a
wobble in the handle bars, with the wheel moving (slightly) side to
side.
If I were to tap with my palm on the side of the head tube, I can see
a slight bounce coming from the lower part of the headset, where the
fork goes through. I have dropped the fork, inspected the bearings,
re-packed them etc, yet the problem persists!
I also repeated the palm tapping just on the fork with the wheel
mounted, and it was solid.
Any advice on how I could resolve this? I really love this bike, and
would love to keep riding it!
Keith
Check your front wheel bearings -- and I assume you do not have any
broken frame tubes. When you get shimmy with a broken tube, the frame
is about to fail. If nothing has changed with your bike (and it
previously did not shimmy), then the shimmy might be rider induced. I
fell and broke some ribs on a descent a few years ago, and for a
period of about six weeks, I would get terrible shimmy any time I
descended more than about 40mph. It was a little PTSD and rib pain
from my fall that caused me to stiffen up through the shoulders while
descending. It went away. Any reason why you might be stiff through
the upper body? -- Jay Beattie.- Hide quoted text -
- Show quoted text -
The wheel has (as part of the trouble shooting process) had it's
bearings re-packed / replaced. �Axel is perfectly fine, not broken.
Wheel spins true.
I did turn it upside down and check the lugs, and I noticed that on
the underside of the bottom tube, there is a gap, about the thickness
of a hair in between the lug and the tube. �I assume that if this was
a "factory" gap, it would have been filled with paint, and not have
been a gap.
This makes me assume that there is a crack :(
What would be my options now? :(
paint can't stop cracks from opening and closing. �and if it's doing
that, the paint will crack also. �is the paint cracked or merely absent?

oh, wait, to sell you on my big tube frame theory, i need to tell you
yes! �the frame is cracked! �it needs to be replaced immediately!

alternatively, you can post a pic of what you describe so we can be more
sure.- Hide quoted text -

- Show quoted text -

I'm at work atm, so cant take a pic, but there is a bit of both.
Missing paint inside lugged area, and cracked paint.

Happy to buy a big tube frame, but my budget currently wont stretch
there, which is why i'm riding a 30 year old roadie! :)

understood. my commuter is built on one of these:

http://nashbar.com/profile.cfm?category=6000130&subcategory=60001176&brand=&sku=23451&storetype=&estoreid=&pagename=

zero frills but utterly stable. for a clydesdale that used to think shimmy was just a fact of life when i rode steel, this is the frame that changed my mind. and encouraged me to do some homework on the subject.

.

Relevant Pages

  • Re: Death wobble in front bars!
    ... I have an elderly Raleigh Grand Prix road bike that I am ... If I were to tap with my palm on the side of the head tube, ... When you get shimmy with a broken tube, the frame ... paint can't stop cracks from opening and closing. ...
    (rec.bicycles.tech)
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    ... tube, giving greater standover clearance. ... There are several paint chips on this frame. ... Please e-mail me with questions or picture requests: jpfaas at neb dot ...
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  • Re: Death wobble in front bars!
    ... I have an elderly Raleigh Grand Prix road bike that I am ... If I were to tap with my palm on the side of the head tube, ... previously did not shimmy), then the shimmy might be rider induced. ... paint can't stop cracks from opening and closing. ...
    (rec.bicycles.tech)
  • Re: Another shimmy question
    ... had a couple episodes of>40mph shimmy since the change. ... The bike will first feel a bit "loose," as if the front tire were underinflated. ... big tube frame. ...
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  • Re: Another shimmy question
    ... I think you'll find that adding a mass to the handlebar/stem junction will change the onset of shimmy if not get rid of it entirely. ... The bike will first feel a bit "loose," as if the front tire were underinflated. ... as jobst says, if you put a weight on the bar, it would probably tune it out, but i think it's better to address the root causes and tune out the resonances of the whole system of frame torsion combining with the lateral springiness of the rear wheel. ... big tube frame. ...
    (rec.bicycles.tech)