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Tyre judder

mark.oggmark.ogg Posts: 3
in MTB general
Noticed on my full suspension bike when braking heavy down hills the whole bike judders
The tyres grip but then slide really fast making whole bike judder
What tyres would any one recommend or it it any problem and not tyres
Thanks

Posts

  • robertpbrobertpb Posts: 1,866
    Lack of information to make any judgement beside learn to feather your brakes.
    Now where's that "Get Out of Crash Free Card"
  • JBAJBA Posts: 2,852
    edited December 2019
    By "The tyres grip but then slide really fast" do you mean you are skidding or that the brakes are failing to lock the wheels and the rotors are moving between the brake pads?

    More details are needed:
    What bike?
    What brakes?
    What tyres?

    “Life has been unfaithful
    And it all promised so so much”

    Giant Trance 2 27.5 2016 ¦ Sonder Broken Road 2021¦ Giant Revolt Advanced 2 2019 ¦ Giant Toughtroad SLR 1 2019 ¦ Giant Anthem 3 2015 ¦ Specialized Myka Comp FSR 2009
  • mark.oggmark.ogg Posts: 3
    It’s a Merida 120 full suspension
    On tarmac if you put brakes on hard bike will skid and lock wheels but as tyre grips it vibrants the frame
    Brakes are good
    Continental tyres are pretty new
    Not sure if I should change tyres but that might not help
  • oxomanoxoman Posts: 11,730
    Nothing wrong with it from the sounds of it. I suspect the problem is your expectations of braking. Hard on the levers on any bike will cause it to skid, the idea is to apply enough pressure for the bike to stop without losing friction with the surface. Staying sat on the saddle also helps thus process. When braking hard the forks will flex especially if they are of a smaller diameter suspension forks 28 / 30, even my fox 32s flex under heavy braking. It may be that have a warped disc or incorrectly adjusted pads if cable disc,s. If a warped disc you should be able to spot disc deflection when it's spun around. TBH even rim brakes can cause judder if not adjusted correctly.
    Too many bikes according to Mrs O.
  • david7mdavid7m Posts: 636
    Is your headset tight?
  • mark.oggmark.ogg Posts: 3
    Everything tight it’s all at the back end what shakes
  • david7mdavid7m Posts: 636
    Sounds like a regular skid to me :neutral:
  • JBAJBA Posts: 2,852
    Stop skidding is my advice.
    Skids are for kids!
    “Life has been unfaithful
    And it all promised so so much”

    Giant Trance 2 27.5 2016 ¦ Sonder Broken Road 2021¦ Giant Revolt Advanced 2 2019 ¦ Giant Toughtroad SLR 1 2019 ¦ Giant Anthem 3 2015 ¦ Specialized Myka Comp FSR 2009
  • thistle_thistle_ Posts: 6,976
    Is it definitely the tyre skidding, not the brakes losing grip on the rotor?

    If it's the tyre, I'd expect the skid marks on the road to be intermittent. Just break more gently (You'll probably stop faster if your tyre isn't sliding).
    If it's the brakes, there's something up with them. Possibly some contamination on the rotor or the pads are vibrating somehow or the caliper is loose. I've had this, but on really rubbish old brakes, with warped rotors and really old brake fluid (i.e. pub bike)
  • steve_sordysteve_sordy Posts: 2,438
    edited December 2019
    I don't know the OP, but I'm pretty sure he/she will be able to tell the difference between a skid and judder. On that assumption I would follow Oxoman's advice.

    If there is also any squealing or howling coming from the brakes, I would suspect contamination of the pad/disc interface. The contamination can come from oil on the road, it's not just from poor practice when lubing the bike.
  • Charlie_CrokerCharlie_Croker Posts: 1,660
    mark.ogg “…when braking heavy down hills… The tyres grip but then slide really fast making whole bike judder”
    mark.ogg “On tarmac if you put brakes on hard bike will skid and lock wheels but as tyre grips it vibrants the frame”

    This all sounds perfectly normal behaviour for a locked up rear wheel to me. Braking earlier, moving your body weight over the rear or further back and feathering the brakes if you lock a wheel all need to be practised to be perfected
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