Wobbling Forks

jimmysplash
jimmysplash Posts: 30
edited February 2019 in MTB workshop & tech
Don't really take my XC bike out off road much, just roads.
However, i have noticed that a cracking sound would eminate from my forks when i would hit a speed bump or similar.
On inspection, and holding my front brake on mving the front wheel i noticed a bit of a wobble.
The screw was loose on the head stem. The screw that attaches to the forks (i think)
So i just tightened it up...but i thought why has it come loose?
Are the other screws involved?
Should i unscrew it all and then tighten it up the proper way of one at a time or summat?
I need advice please because i hear this scenario could potentially be dangerous
Thanks

Comments

  • jamski
    jamski Posts: 737
    Think I'm right is saying your stem should be loose when tightening up the headset. So loosen headset and stem, tighten headset, tighten stem.

    You can also get slight movement from brake pads moving in the calliper. Turn the bars 90 degrees, apply front brake, a rock forwards again. If the movement has gone it was the pads.
    Daddy, Husband, Designer, Biker, Gamer, Geek
    Bird Aeris 120 | Boardman Team 650b | Boardman Pro FS | Calibre Two.two
  • jamski
    jamski Posts: 737
    Tedbundy’sUndys wrote:
    JimmySplash wrote:
    Don't really take my XC bike out off road much, just roads.
    However, i have noticed that a cracking sound would eminate from my forks when i would hit a speed bump or similar.
    On inspection, and holding my front brake on mving the front wheel i noticed a bit of a wobble.
    The screw was loose on the head stem. The screw that attaches to the forks (i think)
    So i just tightened it up...but i thought why has it come loose?
    Are the other screws involved?
    Should i unscrew it all and then tighten it up the proper way of one at a time or summat?
    I need advice please because i hear this scenario could potentially be dangerous
    Thanks

    Release the stem bolts, tension the headset by tightening up the bolt in the middle of the top cap ( it only has to be finger tight) then tighten the stem bolts up to whatever torque is marked on them. Turn the bars 90 degrees and check for play.

    Isn't that what I said? :lol:
    Daddy, Husband, Designer, Biker, Gamer, Geek
    Bird Aeris 120 | Boardman Team 650b | Boardman Pro FS | Calibre Two.two
  • jimmysplash
    jimmysplash Posts: 30
    The stem screws 5.2Nm and the top screw is 4Nm.
    Not having a torque wrench i have no idea what amount of muscle to put in
  • steve_sordy
    steve_sordy Posts: 2,443
    One Newton of force is about the same as 4 ounces in weight and a metre is 3 feet (and then add 10% to be spot on)
    So Four Nm = Four x (4 ounces x 3 feet) = 16 ounces x 3ft. (By "x" I mean at a distance of)

    Or put it another way it's about 3 lbs @ one foot, or 6lbs @ 6", or 9lbs @ 4"

    So if you have a 4" Allen key, hang a 9lb weight off it to get the correct torque.

    Or use this:
    https://www.google.co.uk/search?source= ... tA9OE2KumE
  • Mad_Malx
    Mad_Malx Posts: 5,001
    Well that's cleared it up then
  • cooldad
    cooldad Posts: 32,599
    You don't need a torque wrench. Headcap bolt until there's no play and the forks are still nice and smooth, and stem bolts until they are tight without being a gorilla.
    I don't do smileys.

    There is no secret ingredient - Kung Fu Panda

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  • steve_sordy
    steve_sordy Posts: 2,443
    Mad_Malx wrote:
    Well that's cleared it up then

    Glad to be of service! :lol:
  • jimmysplash
    jimmysplash Posts: 30
    I have followed instructions and now there appears to be some friction when turning the wheel.
    I've not gone mad tightening the screws up.
    Something is rubbing and turning the wheel appears heavy even when riding.
    I did all of this without using a workstand.
    And i lifted the front wheel off the floor and discovered the resistance that way
    ...the wobble has gone though
  • cooldad
    cooldad Posts: 32,599
    So top cap bolt is too tight.
    cooldad wrote:
    You don't need a torque wrench. Headcap bolt until there's no play and the forks are still nice and smooth, and stem bolts until they are tight without being a gorilla.
    I don't do smileys.

    There is no secret ingredient - Kung Fu Panda

    London Calling on Facebook

    Parktools
  • The Rookie
    The Rookie Posts: 27,812
    All the top cap bolt does is preload the bearing, it does not hold ANYTHING together, you nip it up until the bearings run free and there is no play.

    You then tighten the stem bolts to lock the stem to steerer and that keeps the bearing preload where you set it, you could now remove the top cap and throw it away and ride the bike.

    You need to make an effort to understand what part does what here. You've probably got away with it but over preloading the bearings can wreck them straight away, it was described to you how to do it.
    Currently riding a Whyte T130C, X0 drivetrain, Magura Trail brakes converted to mixed wheel size (homebuilt wheels) with 140mm Fox 34 Rhythm and RP23 suspension. 12.2Kg.
  • larkim
    larkim Posts: 2,474
    Coming to it cold, it's an easy mistake to make to think that the topcap in some way is the bit stopping the forks falling out, especially if you come to it from other older bikes where the quill stem did get tightened up in that way.

    I even had to stop a roadie from messing things up with his bike a couple of years ago when his bars were swivelling around his stem and he was trying to cure it by applying as much force as possible to the top cap screw.
    2015 Canyon Nerve AL 6.0 (son #1's)
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