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Bike pulls to the left, why?

Discussion in 'Bicycle Mechanics and Repairs' started by Alcdrew, 29 Feb 2008.

  1. Alcdrew

    Alcdrew Senior Member

    Location:
    UK
    OK bit of back ground... I crashed my bike a couple of weeks ago, crumpled the front wheel and also caused the disc brake to warp, and a few brusies to me:sad: I have puchased a new wheel and disc, but now my bike has a pull to the left, bit like if your traking on your car is out.

    So my question is, what have I done? Is there some way of checking maybe the forks slightly bent? or the frame:ohmy: or something a lot more simpler? Problem is I'm a bit poor at the moment and can't really afford to take it to the LBS and have them fix it, so need to do it myself on the cheap!
     
  2. Twenty Inch

    Twenty Inch New Member

    Location:
    Behind a desk
    When this happened to me, it turned out that my forks were slightly bent. Try and get them facing dead ahead, and then see that the drop-outs are in line with each other.
     
  3. mr Mag00

    mr Mag00 rising member

    Location:
    Deepest Dorset
    Glad you are ok, jeez, if you did that damage to the front end i wouldnt be riding the bike at all until it was checked out completely. The forks may collapse the headset tube could be cracked, the energy from that crash had to go somewhere and to warp a disc brake !!!
    trying not to be alarmist but seriously get it checked out.
     
  4. Tynan

    Tynan Veteran

    Location:
    e4
    what magoo said

    if the frame is bent it might be a write off

    sorry
     
  5. TheDoctor

    TheDoctor Man-Machine

    Location:
    Stevenage
    You know how to check for a bent frame, yeah?
    String from rear dropout on one side, up round the head tube, back to the other drop out and measure distance from string to seat tube - should be identical on either side? Yeah, course you do.
    And obviously you've checked for crumples and flaking paint, often on the bottom of the down tube?

    Dunno why I mentioned it really.:biggrin:
     
  6. Danny

    Danny Legendary Member

    Location:
    York
    Will this really work? I presume Alcdrew would have spotted if his frame was seriously bent, so it seems to me that any bend is going to be pretty small(maybe mms). String is pretty floppy stuff so unless you have it perfectly evenly tensioned on both sides of the bike, there could be differences in length on either side would could be bigger than any bend in the frame.
     
  7. TheDoctor

    TheDoctor Man-Machine

    Location:
    Stevenage
    Yes it does work. Obviously the string needs to be tight, and given that it's running round a tube, the tension in each 'run' should be much the same. As long as the string is tight, it'll be straight. Then measure from the seat tube out to the string, and it should be as-near-as-dammit identical on each side. To clarify, I'm measuring seat-tube to string here, not the actual length of the string. It's tricky to explain without a diagram.
     
  8. 02GF74

    02GF74 Über Member

    the fact that you got dics brake implies you have mountain bike.

    and most likley to have suspension forks. these have an alloy crown with a steel tube pressed in - YOU MUST CHECK THIS IS NOT DAMAGED!

    get LBS or someone who knows a bit more about bikes to check it out,

    What is the point of having savied £ 30 when you are dead or in a wheelchair?
     
  9. Danny

    Danny Legendary Member

    Location:
    York
    Ah...that makes more sense. I thought you were measuring whether the lengths of string on either side were the same ;)
     
  10. fossyant

    fossyant Ride It Like You Stole It!

    Location:
    South Manchester
    Down to the LBS to get it checked - you don't say what the bike is made of - I'd advise it even if steel, as you've probably got something out of alignment - especially if it's not just the bars twisted out of straight.
     
  11. bianco

    bianco New Member

    You haven't broke your arm have you?
     
  12. RedBike

    RedBike New Member

    Location:
    Beside the road
    Sorry to ask, but are you sure your bars are aligned straight?
     
  13. hubgearfreak

    hubgearfreak Über Member

    string does give a straight line, of course.

    builders use it between corners when laying bricks.

    sheldon brown used it when checking coldset steel frames.

    http://www.sheldonbrown.com/frame-spacing.html

    if it was good enough for him;)

    you can use it on front forks aswell.

    what are they made of? does a magnet stick to them?
    if it does they're steel and a good framebuilder could get them perfect for you.

    if they're not steel, they're scrap, i'm afraid
     
  14. TheDoctor

    TheDoctor Man-Machine

    Location:
    Stevenage
    Damn, I should have known Sheldon would have a diagram!

    Bless him. What a guy. Sorely missed.
     
  15. hubgearfreak

    hubgearfreak Über Member