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TT riders rear wheel wiggle when landing from a jump

Discussion in 'Racing, Motorsports, and Track Days' at netrider.net.au started by wokwon, Jun 19, 2012.

  1. Hard to say if this goes in here or in riding tips, mods please move if required.

    I was watching the IOM TT and noticed that when the guys come over the hills and leave the road for a bit, when they land, rear wheel first, the bike kind of does a rapid wiggle until it gets sorted. It seems to happen before the front wheel touches down but continues after that.

    I don't expect it to happen to me under normal riding conditions but I was just wondering why that happens

    Is it any of the following?
    - Bike is under large amounts of power when landing (i.e. throttle still open when in the air) so the rear tyre has to slow/scrabble a bit
    - Bike is under no power (throttle closed when in the air) so rear wheel needs to come back up to speed, scrabbles a bit
    - Suspension recoil/bounce or tyre deformation
    - Something else

    Search does not reveal anything.

  2. I would say you've nailed it with all of your points
  3. It might be something to do with the size of the nuts of the guys riding those kind of speeds around that track.
    • Like Like x 2
  4. My understanding is that their fuel tanks are specially shaped with a cutout to accomodate those attributes.
  5. Ah no cut out, if it's there it was man made :)
    You forgot flex, swing arm, frame.......
    Nah if you listen you will hear most spin up a bit after landing..if they can. By adding throttle it makes the landing a little softer.
    The ones that get into a real hippy shake, usually land closed throttle and try to open them up on landing. Usually starts in the front as that's where all the weight is going on a closed throttle landing. Once they open it up it just bounces between the front and rear wheel via the frame. Then it gets into the rider and it wont stop. How many times you see a guy in a big wobble and fall off, while the bike settles as soon as he is off and it wanders merrily up the track till it runs out of momentum.
    You have all sorts of energy coming from a lot of angles, and it has to go somewhere.
  6. Cheers bretto, that makes sense.
  7. Based on that explanation every rider that gets airborne must get into a big wobble after landing. Why didn't guys usually get the wobbles after getting air down Conrod Straight? Could it be the difference between landing straight compared to slightly crooked or is that just too simple?
  8. The wobble is from the rear wheel slowing down after spinning freely.
    They have to close the throttle a little, chop it and the front will smash down and bottom out the bike causing issues. Leave it wide open... The whole bikes weight is on the tyre that is spinning way faster than the bike is moving.
    Flip over backwards fast.
    The little wiggle is the riders keeping it just on the edge, because of their huge balls.
  9. What utter utter waffle. For there to be any "wobbling" there must have been a sideways directional component similar to developing a "tank slapper" after saving a high side. All forward and aft direction forces are absorbed in the suspension ie. the forks and swingarm, that's what they are designed to do.

    More waffle. The friction of the tyre would slow the tyre due to the greater mass going at a slower speed.
  10. i concur.
  11. and they don't land both wheels first to avoid high sides or other nasty business, having the rear down keeps their speed up, and enables them time to get the front where it is supposed to be after the jump. afaik.
  12. ill believe an answer when it comes from a TT rider ..

    and i suspect that their answer would be .. it just does, and it can be a bit hairy.

    I doubt they sit and theorise on a computer over it.
  13. I'm with Bazza. I think it has to do with not landing straight.

    But then watch this extreme example of Dan Keen, the front hasn't even touched down yet:

  14. I always figured it was comp lock from rolling out of it. That vid above is clearly wheelspin from holding WOT on the landing. Big balls indeed.
  15. and he kept going because he was able to hang on and straighten it up rather than a big crash

    thats one lucky rider
  16. Here are some slow mo jumps maybe it will help decide

  17. This happens to me sometimes when I hit speed bumps too fast. Bike gets a bit of air and comes down slightly crooked.

    Pretty certain it's because the inertia of the bike is trying to run slightly diagonally across the tyre, rather than along the tyre. Creates a wobble as it corrects itself and comes back in line. If the angle is bad enough, it'll just flick you off and give you a close personal view of drystone wall construction. ;)
    • Like Like x 1
  18. it's very simple.
    these tyres are all about grip. so very grippy ok.
    the rear is spinning very very fast under enormous power.
    they are very powerful and importantly also very light bikes.

    when the bike leaves the road and the the rear breaks traction with the road, the bike slows down but the rear tyre does not. it spins even faster now with no resistance.
    so then when it touches down again the bike has slowed but the rear has accelerated. then it just grabs. tyres like that don't slip. it's a super light bike. so it kinda spits the bike out in front of it.
    unless they were travelling dead upright and straight with a perfectly even distribution of weight, it will be unsettling.
    if front comes down on any measure of angle it's powering into that angle.

    these guys don't roll of the throttle. ever. they are ****ing mental. all they know is WOT and if the bike could do more, they would.
    the saves you see it these races are supernatural.
  19. It's got to be one of the best saves in motorcycling history. To see that bike over the crest like that, behave like that on just the back wheel, see the rider hanging on for his life and then hear him keep it going WOT out of shot is just absolutely amazing.
  20. they are not mortal beings