Conference noted::bicycle

     Just about any nuance to the bike could infuence its handling
     characteristics. Because you use the word "occasionally" I would
     look at something variable to be th cause, e.g. tire pressure,
     ingesting chocolate moose before the ride, etc...

    Not being as avid a bicyclist as many of the noters herein, I don't
    object to being corrected...  That said, I am a fairly avid
    Motorcyclist, (yes, I do respect peddlers).  On Motorcycles a wobble
    in the front, most frequently originates in the rear suspension or
    drivetrain and visa versa.  Other areas aside from -1 correctly states,
    tire pressure.   Check the steering head bearings for proper lube, 
    condition and torque.  Changing your center of gravity can cause some
    negative influences as well.  Does the problem occur regardless of
    soft-peddling, hard-peddling or coast???   
    
    good luck
    Frank

look in the cycles (as in motorcycles) notesfile under high speed wobble. 
it is a complicated problem involving frame geometry and fork geometry.  
motorcycles are heavy enough it can occur with your hands on and it is a 
frightening experience.  

i would look at your headset.  there has to be something different if it
never happened before and i don't think new bars would be enough.  but it 
can be intermittent.  anbother thing, i think it generally at a specific 
speed.

-craig

    My bike (road/touring bike, mainly used for commuting) does this, too.
    I am not all that happy with the frame stiffness, so I think there is
    some room for improvement (many women's bikes show this problem, too).
    I've not really resolved it, it's not too important for me - you are
    not supposed to ride hands-off anyway, and with the traffic we have on
    typical German roads, that's good advice.
    
    Anyway, from my observation, the wobbling seems to be excited by the
    rear wheel and gets worse when the weight distribution goes backwards
    (sitting upright, loading panniers etc.). Make sure that the rear wheel
    is running as true as possible.
    
    Also, I can imagine that the mass/inertia of the moving parts up front
    affect the resonance frequency (wheel, handlebar, stem and fork). Is
    the weight of the new handlebar significantly different from the old?
    Is there more mass further away from the turning axis (longer stem?)?
    
    Regards,
              Hartmut

    I'd second the suggestion to check the adjustment / condition of your
    headset, particularly where you said you recent replaced your
    handlebars. I've had similar problems (wobbling, or a pull to one side
    or the other when riding no-hands) that were ultimately proven to be
    related to a headset that needed to be replaced (or at least adjusted).
    
    	/Harry

Thanks for the suggestions. A ride at lunchtime today with a different front
wheel proved that the wobble isn't related to a particular wheel (unfortunately).
Wobble is more pronounced at higher speeds than lower speeds.

I'm going to try lowering the stem further into the forks - more areo anyway -
then I might try a shorter stem. I'm wondering if the weight of Ergo shifters
combined with a long stem is promoting this effect.


Rod

RE: <<< Note 2728.6 by JURA::MACFADYEN "no worries" >>>

>I'm going to try lowering the stem further into the forks - more areo anyway -
>then I might try a shorter stem.

Be careful about altering your position on the bike just to get rid of a hands-
off wobble. If the wobble is terrible and the fix is a minor position
adjustment, then what the heck. But I'd settle for some wobble hands-off and
a good position, rather than steady hands-off and poor position.
						-- Tom

>then I might try a shorter stem. I'm wondering if the weight of Ergo shifters
>combined with a long stem is promoting this effect.

weight of ergo shifters?  perhaps when installing the bars/shifters there is 
some cable tension or bias affecting the steering rotation?  -craig

    
    As I said in EURO_RANDONNEUR, I don't think that the wobble can be put
    down to a long stem. In the pro peleton, it's rare to go below 12cm,
    and Danish riders refuse to go below 13cm, even if it affects the
    position of the bike, and it's unlikely that they would put up with any
    wobble.
    
    As for cable tension, I'd be surprised. That would be more likely to
    pull the bars in one direction rather than wobble, and any affect would
    have no speed correlation.
    
    You say that they are new forks. Do they have the same rake as the ones
    they replaced or are they straighter? If they are straighter, then you
    may find that it could be that...
    
    Graham.

    you gonna let everybody in on the state of your wobble, Rod?  (He's
    told us in a few other files, I don't want to steal his thunder.)
    
    DougO

The whole discussion became academic last Wednesday when the down
tube on the frame broke at the gear lever mounts. It's cracked almost
all the way round. No crash: what happened was I got out the saddle 
to start a hill and the bike suddenly felt extremely wobbly and
strange. I was able to limp the thing home. It's an ex-frame now,
that frame is deceased. I theorise that crashing the bike last September
started a crack in the titanium tube that grew slowly until normal 
riding stresses could kill it off. Raleigh may do me a deal on a new
frame; we shall see.

I don't consider this as being related to the wobble effect discussed
in .0. The frame was rigid until it, well, wasn't.


Rod

    I think they could be related. The crack shouldn't have just happened
    suddenly, so the gradual softening may not have been noticed with
    looking  at it, but seen as a wobble...

     Congratulations and best of luck with your new steed! 
    
     Just remember, if you begin to ride in groups with other folks
     mounted on Ti frames you may cause severe atmospheric disturbances!
    
                                 :-)
    
     Enjoy!
    
     Chip