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Thread: Speed wobble question on VeloNews

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    Default Re: Speed wobble question on VeloNews

    Quote Originally Posted by Too Tall View Post
    Agree his answer is pretty good. The hardest speed wobble to solve is when the nut on the bike is loose.
    I like this!
     

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    Smile Re: Speed wobble question on VeloNews

    Q.Nick,
    I have experienced the dreaded “speed wobble” four times. Once on a pieced together early carbon bike and then three times on my Trek Discovery Channel Madone.

    Does this ever to happen to pro racers? If not, why? If so, what do they do about it? Are the newer carbon frames engineered to be less prone to speed wobble due to some harmonic damping or something? I never had a speed wobble on my steel frame Shogun from 1984. Any info would be great.
    — Robert Brudenell


    Foolish Robert. A Trek has been ridden to what, a few thousand TdF victories? The cycling mafia will be very upset about this ("I've never tested positive for a speed wobble") and poor old Robert is probably swimming with his concrete Nikes right about now...
     

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    Default Re: Speed wobble question on VeloNews

    Quote Originally Posted by Andrew R Stewart View Post
    Dazza- I'm glad that you haven't seen speed wobble in a race situation. Of course that only covers a very small amount of actual bike riding. And that's where wobbles are worse if for no other reason that the rider is often less capable of dealing with the resulting effects. One of the problems with this forum that I have is the race centric view that many seem to have. I ask how much of a rider's yearly mileage is of actual racing VS training or some other riding? In my limited experience even a dedicated racer will spend most of their riding in non race riding. Andy.
    maybe you miss my point

    refer to Too Tall's post.
    Cheers Dazza
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    Default Re: Speed wobble question on VeloNews

    let's call a spade a spade atmo.

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    Default Re: Speed wobble question on VeloNews

    In motorcycle terms, "The problem seems to be the thing connecting the seat to the handlebars."
     

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    Default Re: Speed wobble question on VeloNews

    This wobble is induced by lugs of questionable origin.
     

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    Default Re: Speed wobble question on VeloNews

    Daza- My responce to your post was that it did little to advance the discussion. When i hear the word "never" i question the speaker's reason to say such. The word is absolute, no further question can be asked. To me this position is not reasonible. I was trying to make the point that many riders that don't race read this forum and might have had the experience that you have "never" seen in racing. I didn't question your experience, just that others have had experiences that you haven't had. If you can explain how speed wobble happens and how, as a rider, to avoid it many will be greatful. Mypost (#14) was an atempt to do such. I don't mind being a lesser rider, strength or skill, then others. i do mind being dismissed as not a worthy concern. Andy.
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    Default Re: Speed wobble question on VeloNews

    AND I have had wobble crop up on bikes where riders rotate rear tires onto the front wheel. Don't do this. The tires wear differently and a flat worn rear tire up front will make your bike handle like poo.

    But yeah, it's likely usually a tall bar position and a short reach that will make it go.

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    Default Re: Speed wobble question on VeloNews

    I used to rotate tires, I wonder if that did cause some of my wobbles.
     

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    Default Re: Speed wobble question on VeloNews

    Quote Originally Posted by echelon_john View Post
    In motorcycle terms, "The problem seems to be the thing connecting the seat to the handlebars."
    Slap on a steering damper? :)

    But seriously pilot-induced oscillation seems to be common on all kinds of vehicles.
     

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    Default Re: Speed wobble question on VeloNews

    I experienced wobble this past fall although I think it was mainly the front wheel/fork and not a full bike death wobble. I didn't get a hard shimmy from the frame at all and I couldn't eliminate the wobble with a leg on the top tube, getting out of the saddle, shifting my weight, pedaling through it, etc. The only elimination was to bunny hop or turn. I'm setup pretty long and low and my shoulders, arms, grip, etc were all relaxed ... I definitely wasn't a nut on the bike and freaking out although I did slow down a few times because I became a little worried. I think it was just wind pushing my front wheel back and forth. I meant to swap out my front wheel with a friend to see if that was the cause but he was too scared to switch after seeing it happen. I was running new tires at 100psi. I'm going back to the mountains later this spring and going to see if it still happens. The only other thing I can think of is if my headset wasn't as tightened down as it needed to be which I've attempted to correct. Maybe the front tubular was glued off-center ... who knows. Maybe it was me and my muscular body.
     

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    Default Re: Speed wobble question on VeloNews

    Was looking through old threads regarding speed wobble and came across this one. I have been riding bikes for 38 years, decended countless alpine passes and never experienced speed wobble until riding more recent sloping compact frames. It happened several times overthe last 5 years or so. It happened yesterday while riding my Trek Madone 6.9 at 50mph on an exposed wide open decend with a bit of cross wind. Other bikes I've had it happen on were a Giant TCR, and Colnago CT2. Today I dusted off my 1992 Richard Sachs and headed out to the same decend to see if I could replacate it. Some people have said being uptight about decending can contribute to it. I have always been a fearless decender but admit today I was a bit on edge after yesterday. I accelarated going into it, put it in the biggest gear its got till I couldn't pedal anymore. It felt super solid even with a bit of cross wind. Got in a tuck and flew with not even a hint of wobble. My newer bikes are set up just the same as all my bikes ever were, long and low with no spacing under the stem. I am light at about 115 lbs. Maybe the extra 6, 7 lbs of the old Sachs makes the difference. Anyway just talking away the nerves from yesterday I guess. Thanks.
     

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    Default Re: Speed wobble question on VeloNews

    dt shifterz rule.
     

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    Default Re: Speed wobble question on VeloNews

    Quote Originally Posted by WadePatton View Post
    dt shifterz rule.
    Teaches you something about being loose on the bars, etc.
     

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    Default Re: Speed wobble question on VeloNews

    My worst wobble was on a Nottingham Raleigh 753 (black and red team bike). Fast descents meant a knee pressed into the top tube. I never figured it out, it only did it around 40 mph so it was ok for racing crits and road races. No wobbles since.
    I heart burnt bikes.

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    Default Re: Speed wobble question on VeloNews

    I would argue that getting in a shimmy has much to do with skill, getting out of it does.
    I've seen several bad ones when people raced the spinergy rev x ultralights (or someting like that) up front.
     

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    Default Re: Speed wobble question on VeloNews

    Update to my post the other day. As I mentioned in my prior post in 0ver 30 years, I never had speed wobble prior to newer carbon technology. I have decended well above 60 mph in the Rockies, Pyrenees, and many other smaller high speed hills in New England and never even heard of a speed wobble, let alone have one. Determined to resolve this speed wobble thing for myself I loaded three bikes and a bunch of wheels in my truck and headed for the hill it happened on the other day. First I took my Sachs. Hit the hill full gas, got into a tuck and just flew. Like being on rails, no hint of wobble. Next, I tokk my Giant TCR. Same result, no hint of wobble. Next I took my Trek Madone 6.9 Pro fit. Hit it full gas. Uncontrollable wobble started at about 40 mph. Pressing both legs against top tube, I was able to brake and come to a stop. I climbed back up the hill to try again. This time leaving both knees press against the top tube to try preventing it in the first place. Didn't work. Again wobble at about 40. This was with two 50 m carbon wheels with blades spokes. Next I put on a standard front wheel with round spokes. Hit the hill a full gas, no wobble. Next full gas again in a tuck, no wobble. So for me it was my choice of wheels. I'm thinking that at 115 lbs the bladed carbon wheel was causing some kind of lift effect making the front end light hence allowing the wobble. I didn't try putting the bladed carbon on one of the other bikes and figued I would leave well enough along and head home uninjured.
     

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    Default Re: Speed wobble question on VeloNews

    Try installing the suspect carbon wheel on your other two bikes to see if the problem follows the wheel.

    Some wheels can have a "heavy" splice inside the rim at the seem, causing an unbalanced condition that occurs at a "resonant" speed. Sometimes it's the computer magnet and not the rim splice. It could be a combination of the two i.e., one weight could counterbalance or exacerbate the problem.

    Now that realize it's a carbon rim, I don't know whether they even have splices as they're likely built in one piece. So, could it be an extra long valve stem with/without a computer magnet that's causing the problem? Sometimes just relocating the magnet can damp the oscillation. If there's no magnet on the wheel, perhaps placing one on the bike could cure the problem. And note that where along the length of the spoke you install the magnet will influence its effect on the wheel.

    I think it's brilliant you took the time to experiment as you did to try and locate the source of the wobble.
     

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    Default Re: Speed wobble question on VeloNews

    Thanks for the good advice Peter. The valve stem is very long to make it through the 50mm rim plus another inch or so sticking out, and there is no magnet on the wheel so perhaps placing one oposite the stem would balance it. I did think about putting the suspect wheel on one of the other bikes but felt sure that since I couldn't replacate the problem without the carbon wheel that it was the wheel causing the problem and didn't want to risk hurting myself. Thanks again.
     

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    Default Re: Speed wobble question on VeloNews

    I think it is the resonant frequency of the whole system (frame , wheels , rider on top) once you hit it at the right frequency, the darn bike turns into jello. Again my experience is that a deep dish carbon wheel that is not stiff, is bad for starting the whole cacophony.
    You must have some guts there, trying to repeat it, because I almost crapped in my pants after a bad shimmy in a descent in the Pyrennees at maybe 50 KPH.
     

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