what causes the hands free handlebar death wobble?- Mtbr.com
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  1. #1
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    what causes the hands free handlebar death wobble?

    I have had this issue on two bikes. It has started to happen on my good bike and I am just wondering iffin any of ya have any idears to what causes the "death wobble"?

    You know like when your trucks are loose on your skateboard and you are trucking down a big hill, or those fast motorcycle guys where it goes into an uncontrollable wobble and flings the guy.

    It happens when on decent pavement riding along no handed, it will start to wobble and gets worse till I grab back on.
    I am thinking it might be a loose headset, which I tightened but did not test.
    Possibly suspension fork or disc brake related (thinking cuz the tire is offset a bit to accommodate the disc.)

  2. #2
    Map Maker
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    it happens because you are riding no hands
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  3. #3

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    Is your front wheel true?

  4. #4
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    the physics of a bicycle. Your wheel turns just the slightest bit one direction, law of motion pushes your bike straight, out of the turn radius the wheel is making, also pushing the wheel to the other direction.The same thing happens. Your bike goes straight, pushing your wheel to the side again. This goes on and on until you can't controll it with no hands and go over. On a motorcycle, trying to fix it makes it worse along with weight going foward on the front wheel with all of this. On a bike, just grab on. On a motorcycle, loosen your grip and hit the gas.

    Had a pretty bad death wobble accident on my old dirtbike, sure makes you rethink how the steering works.

  5. #5
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    far as I can tell the rim is in pretty good shape (true). But that would make pretty good sense.

    And ya know what the front tire is a bit out of whack, as in maybe the bead is not set properly or it is not on perfectly. Noticed that last night after a ride. Being a 2.3 exiwolf there is a lot of rubber to try and get aligned.

    That has to be it, just switched out a tube a bit back.

    I was figuring it might have to do with some other thing like the angle of the fork to the ground, etc......

    Thanks for the virtual thump on the head.

  6. #6
    GAME ON!
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    use the handlebars as handlebars.

  7. #7
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    well after a long ride in the heat
    and you get back on the paved street
    you palms and fingers are beat
    sitting up and pedaling feels neat

  8. #8
    GAME ON!
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    true enough, but falling and getting road rash sucks balls.

  9. #9
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    Keep you hands on the bars

  10. #10

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    ...I took the brakes off my car to save some weight (and therefore gas $), but I'm having trouble trying to stop...

  11. #11
    Five is right out
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    Here is the real answer, which goes beyond the facetious "use the handlebars" answers you've beein getting so far.

    http://www.sheldonbrown.com/brandt/shimmy.html

  12. #12
    EastBaySteez
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    Its the vibrations that go through your bike. It happens to road bikes at high speeds. Thats why they hug their TT's with their knees. (silly roadies have to use their knees )

    It also has to do wit frame geo's
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  13. #13
    makin skid marks
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    I saw this happen to a guy on a Honda 550(or so)30 years ago. He had passed us, my dad told me & my bro to".. watch this guy." He got about 3-4 cars lengths ahead of our 64 Chevelle when the bike got the shakes- a bit more- more- OH MY... WHAP! Hands, chest & the front of his head SMACKED the pavement & ground to a halt from a good 70-80 mph. The poor basstid(who claimed to have raced MCs)never made any attempt to roll- just skidded to a stop on I-80. The man's meat-hooks were just that- meat.
    I saw something 50 feet behind where he stopped, went back & picked up his wallet. One corner of it had been torn clean off. Could've been his... well, you know.
    Actually I abhor cycling- I just like wearing tight shorts

  14. #14

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    With my old Canadian Tire Supercycle, I could ride with no handlebars for the longest times. It handledd great, I could even go over bumps and it was fantastic. My current bike replaced the 16 year old supercycle, but due to the geometry of the bike and possibly the wheel tread, I cannot ride without the handlebars. It is kind of annoying, because there are just sometimes, all I want to do is sit up straight and just coast with my hands free. Oh well, I guess even the supercycle had one good thing about it..

  15. #15
    A wheelist
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    Lennard Zizz of Zinn custom road frames and VeloNews tech writer fame has written much about this. Do a Google search to see if his stuff shows up. But his theories are more complicated that the "hold onto the &^%$ bars!" fix for you.

  16. #16
    chips & bier
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    As far as I know it's a combination of several things, such as frame stiffness, geo, fork trail, center of gravity, and so on.

    A couple of years back I had a bike that had a hideous shimmy. So bad I could let the handlebars go for a second and it would just scare the ***** out of the people riding next to me! Good fun.

    Anyway, it turned out the manufacturer had switched to a lighter weight tubeset compared to the previous year's model. If you turned a corned hard, the frame would flex and unload as you exited the corner... amazing! Flexiest frame I have ever ridden, and needless to say, they had a 100% failure rate AFAIK.

    I checked my wheels for trueness, switched tires a thousand times, and in the end figured out how to shift my weight so the shimmy was gone (while opening food packs during races). Just for fun I put a 1.5" shorter fork in the frame and that solved it as well. By that time the frame was already terminally ill, though.

  17. #17
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    Quote Originally Posted by womble
    Here is the real answer, which goes beyond the facetious "use the handlebars" answers you've beein getting so far.

    http://www.sheldonbrown.com/brandt/shimmy.html
    Interesting.. I can honestly say I dont recall ever having this problem... I ride no hands often when I am done a ride too, just to relax for a bit.
    2013 Cannondale F29 2
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  18. #18
    Big Boned
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    I think the short answer is, "physics."
    Never rub another man's rhubarb.

  19. #19
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    I think that the directional oscillation of the front wheel can get started by road irregularities, but more likely by wheel balance and rim / tire trueness.

  20. #20
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    Like others have said, natural resonance vibes from frame tire interaction.

    A worn tire, "incompatibility" of the tire with the bike or incorrect PSI. Try changing the pressure and see if it goes away.

  21. #21
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    yerp... physics... vibrations in particular; for roadies at faster speeds, hugging with their knees changes the damping on the bikes frame, and changes the damped natural frequency.

    the death wobble has so many different variables, but like people said before, it's got to do with road irregularities, frame geometry, wheel trueness... moment of inertia, etc...

  22. #22
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    what a coincidence! i saw some kid on a bmx crossing a busy intersection with his hands on the bars and he did a death wobble and fell right on top of his bike. he got up, pulled up his pants a bit and rode away hoping noone saw him...

  23. #23
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    resonance eh? makes sense....

    in my field (i do vibration analysis for SKF bearings), we see machines do this often. it's called a critical speed. if you can break through this critical speed, the resonance will disappear.

    you can also move this frequency around by adding mass (lowers the critical speed) or increasing stiffness (raises the critical speed).

    my first "mountain bike' was also a supercycle. I haven't had a bike since that I could ride any distance with no hands. I could even start no-handed. although my new bike is showing promise. it's a soul cycles hooligan with an mx comp eta 120mm fork and panaracer uff-da tires.......

  24. #24
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    Quote Originally Posted by mcfly
    resonance eh? makes sense....

    in my field (i do vibration analysis for SKF bearings), we see machines do this often. it's called a critical speed. if you can break through this critical speed, the resonance will disappear.

    you can also move this frequency around by adding mass (lowers the critical speed) or increasing stiffness (raises the critical speed).

    my first "mountain bike' was also a supercycle. I haven't had a bike since that I could ride any distance with no hands. I could even start no-handed. although my new bike is showing promise. it's a soul cycles hooligan with an mx comp eta 120mm fork and panaracer uff-da tires.......

    Hey McFly, are you a MechE?

  25. #25

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    Huh, last night I was riding no-handed, and I have done so before on my Giant Rainier. Does have a panaracers on it. I also have been able to pedal no-handed. I could definitely see how an offbalance bike could throw things off. What about a steep headtube angle? would this cause it to deflect easier over small bumps and such?

  26. #26
    Nervous Descender
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    Quote Originally Posted by beerorkid
    well after a long ride in the heat
    and you get back on the paved street
    you palms and fingers are beat
    sitting up and pedaling feels neat
    Word.
    Check out some of our local hills: CDRC (Capital District Road Climbs)

  27. #27
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    Quote Originally Posted by ppmtb
    ...I took the brakes off my car to save some weight (and therefore gas $), but I'm having trouble trying to stop...
    Convert to fixed gear.
    Check out some of our local hills: CDRC (Capital District Road Climbs)

  28. #28

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    Quote Originally Posted by Adirondack Blues
    Convert to fixed gear.
    *flashback to Dumb and Dumber*

    "WHAT GEAR ARE YOU IN?" (over the scream of an engine at redline)


    "GEAR?"

  29. #29
    friend of preston
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    for what its worth.

    Not a bad discussion if you remember your physics.

    http://en.wikipedia.org/wiki/Bicycle...cycle_dynamics
    He who makes a beast of himself, gets rid of the pain of being a man.- Dr. Samuel Johnson

  30. #30
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    Here's a Haiku:

    Handlebars help steer,
    Turn Left, Turn Right, Riding Straight
    No-hands makes you crash

  31. #31

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    Quote Originally Posted by fallen angel
    the physics of a bicycle. Your wheel turns just the slightest bit one direction, law of motion pushes your bike straight, out of the turn radius the wheel is making, also pushing the wheel to the other direction.The same thing happens. Your bike goes straight, pushing your wheel to the side again. This goes on and on until you can't controll it with no hands and go over. On a motorcycle, trying to fix it makes it worse along with weight going foward on the front wheel with all of this. On a bike, just grab on. On a motorcycle, loosen your grip and hit the gas.

    Had a pretty bad death wobble accident on my old dirtbike, sure makes you rethink how the steering works.
    Really? I was told that, on a motorcycle, you should actually SLOW DOWN. Or were you just messing around?

    I've actually had that "speed wobble" on my motorcycle. Was scared to death when it happened. I was SERIOUSLY ready to crash (on the freeway going 120+) but I just slowed down and it straightened itself out. Phew!

  32. #32
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    I had a Giant NRS that did this. I adjusted stuff, changed the front tire, changed the front wheel, nothing I tried had any effect. Then I bought a new fork, a Duke 100mm, and the wobble disappeared.

    A few months later I had to repair the Duke so I temporarily reinstalled the original fork. Wobble came back.

    After a couple weeks or so I reinstalled the Duke, wobble gone.

    The original fork was a Judy, 80mm as I recall. That fork always looked to me that the steerer tube was NOT parallel to the fork tubes. It looked like the fork tubes were more raked (slack) than the steerer. Can't prove it, though.

  33. #33
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    not on road bro, dirt bike. On a dirt bike if you don't hit the gas you aren't saving it. On the road I've never had it happen, I've seen it happen plenty of times and it doesn't look like fun.

  34. #34

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    Quote Originally Posted by fallen angel
    not on road bro, dirt bike. On a dirt bike if you don't hit the gas you aren't saving it. On the road I've never had it happen, I've seen it happen plenty of times and it doesn't look like fun.
    Yeah, if I sped up, it would only exacerbate the issue. Slowing down is the only remedy on a motorcycle.

    Never been on a dirt bike though.

  35. #35

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    Quote Originally Posted by elder_mtber
    I had a Giant NRS that did this. I adjusted stuff, changed the front tire, changed the front wheel, nothing I tried had any effect. Then I bought a new fork, a Duke 100mm, and the wobble disappeared.

    A few months later I had to repair the Duke so I temporarily reinstalled the original fork. Wobble came back.

    After a couple weeks or so I reinstalled the Duke, wobble gone.

    The original fork was a Judy, 80mm as I recall. That fork always looked to me that the steerer tube was NOT parallel to the fork tubes. It looked like the fork tubes were more raked (slack) than the steerer. Can't prove it, though.
    It sounds like it's the fork that's the culprit though. I wonder if it's Rock Shox that's the issue. I was SUPPOSED to have the Judy fork but the seller ended up equipping the bike with the Dart2 instead.

    I tried riding with no hands and it just seems so unstable. I could only do it for a split second. Unlike my motorcycle.

  36. #36
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    Quote Originally Posted by mattaphore
    Hey McFly, are you a MechE?
    Technologist. My job involves babysitting paper making equipment.

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