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Wobble

Discussion in 'Bicycle Mechanics and Repairs' started by velocipede2288, 26 Dec 2007.

  1. velocipede2288

    velocipede2288 New Member

    I have recently had a wobble escpecially when decending steep hills. I have checked the wheels for true and the axles. Everything seems to be right, but still the wobble.Can anyone suggest what the problem can be?
    It is an old Raleigh 1984 or there abouts.
     
  2. Monty Dog

    Monty Dog New Member

    Location:
    Fleet
    Do a google on 'speed wobble' - changing your forks might be a solution
     
  3. fossyant

    fossyant Ride It Like You Stole It!

    Location:
    South Manchester
    As monty says, it can be the fork but also frame geometry - it can happen on some frames and also motorbikes.

    Not an easy cure, especially if you don't want the expense of new forks. An old Raleigh of mine used to do it, but only when kitted with mudguards in the winter.
     
  4. Dave5N

    Dave5N Über Member

    Check the headset. Controversial but I know from experience a knackered headset can cause it to develop in a bike that was previously ok.

    If the bike has always had it, try putting your knee against the top tube.
     
  5. OP
    OP
    velocipede2288

    velocipede2288 New Member

    Well I have held the brakes fulll on and rocked the bike, but the headset seems fine. Thanks for all the advice, I will keep checking things.
     
  6. andygates

    andygates New Member

    How are you riding? Two tricks that can stop speed wobbles:

    1) Grip the toptube with your legs, or press one leg against the tube. Now, instead of shaking the light frame, it's got a big squidgy vibration damper attached.

    2) Instead of gripping the handlebars, push on *both* as if you're trying to stretch the bike away from you. Again this turns a rigid and shaky assembly (bars and arms) into a more dynamic yet damped one.
     
  7. OP
    OP
    velocipede2288

    velocipede2288 New Member

    Thanks for the advice guys, I will try the trick with the leg and shimmy instead of wobble :biggrin:
    Anybody want to buy an old raleigh ? :smile:
     
  8. Monty Dog

    Monty Dog New Member

    Location:
    Fleet
    Sadly, there are a lot of bikes out there that suffer from speed wobble and your first 40mph descent is typically the first time you find out. Whilst there are things you do to minimise the problem, it's due to a harmonic vibration of the complete bike and unless you change one of the major components e.g. frame or forks it's unlikely to go away - hence the recommendation to change to a different fork. Surprisingly there are still a few modern bikes that suffer from this too - but less common than it was with older steel frames.
     
  9. yenrod

    yenrod Guest

    It seems its down to ridgity :smile:

    I rode a 501 bike for a while and that was a bit flexible though no speed wobble.
     
  10. Fab Foodie

    Fab Foodie hanging-on in quiet desperation ...

    At the risk of being boring...

    All you need to know is here:
    http://www.sheldonbrown.com/brandt/shimmy.html

    Whenever this comes-up there are always anecdotes (which I simply don't believe) about this or that, but really Brandt says it all.
    Every bike I have had has exhibited speed wobble until I'd learnt to relax.
     
  11. Fab Foodie

    Fab Foodie hanging-on in quiet desperation ...

    Agreed, my old (1949 ish) Holdsworth is more flexible that a very flexy thing but can still be made to descend fast without shaking it's head.
     
  12. freakhatz

    freakhatz New Member

    None of my bikes do this thing.

    An old bike did, then I scrunched the front wheel, bought a new one and it never wobbled again. I reckon I taught it a lesson it never forgot:evil:
     
  13. andygates

    andygates New Member

    It's the resonant frequency of my flab... :tongue:
     
  14. OP
    OP
    velocipede2288

    velocipede2288 New Member

    Well this week end I stipped the headset, took off the forks and checked for allignment. Re- greased the top and bottom bearings. took off the bakc wheel, and freewheel, checked axle, and re-greased bearings. While I was about it, I fitted new cables and housing, and handlebar tape. re-greaed the hubs.
    As someon had suggested that the magnet on the wheel for the computer had casued wobble on their bike, I removed it also.
    Re-aligned the back drops as suggested by Sheldon Brown, see below. Seems drastic, but it works.
    http://sheldonbrown.com/frame-spacing.html
    Today I had a good ride. Still no idea what caused the wobble ..??
     
  15. OP
    OP
    velocipede2288

    velocipede2288 New Member

    Well this week end I stipped the headset, took off the forks and checked for allignment. Re- greased the top and bottom bearings. took off the bakc wheel, and freewheel, checked axle, and re-greased bearings. While I was about it, I fitted new cables and housing, and handlebar tape. re-greaed the hubs.
    As someon had suggested that the magnet on the wheel for the computer had casued wobble on their bike, I removed it also.
    Re-aligned the back drops as suggested by Sheldon Brown, see below. Seems drastic, but it works.
    http://sheldonbrown.com/frame-spacing.html
    Today I had a good ride. Still no idea what caused the wobble ..??