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Stopping fast and losing rear traction... but the rear always slides left?

Discussion in 'General Motorcycling Discussion' started by grue, Apr 3, 2010.

  1. Sort of a weird topic, but I've noticed this a few times. I'll be coming up to a light and it changes at an awkward time, or something happens in front of me, or wahtever (use your imagination), so I've gotta drop the anchors. Grab the front brake lever and get on the rear as well, and every so often I'll lock the rear for the last moment when allllmost at a stop (usually on greasy pavement)… but whenever I do it, it seems like the rear always tends to slide to my left. Not like huge amounts, just an inch or two at the most. Coincidence? Crown of the road? Something wrong with the bike?

    Bored and figured I'd ask the experts.
  2. could be weight transfer, due to whichever side you tuck it :LOL:

  3. Always to the left :eek:hno:
  4. Gyroscopic/centripetal effects like the old bicycle wheel and swivel chair trick?
  5. Road camber?
  6. ^^ WHS
    Also if you ease off the rear a little as you apply more front it won't lock.
    The technique, IF brakes lock, is to think the front is a hot iron i.e. let it go straight away, then reapply, and the at the back you've stood in dog doodoo, let it go slow eeeewwww. this'll keep you stable
  7. Your left butt cheek must be huge compared to the right one
  8. :rofl: Beat me to it.
  9. Oh, I have no problem handling a lockup, it's more just the fact that if I do lock it up (I think it's happened all of 3 times), it always goes left.
  10. Could be road camber, you might tense up and twist in your seat, maybe you lean on the bars when you grab handfuls of brake, rear wheel may be slightly off centre, maybe you sit slightly off centre in the seat or even pushing on the rear brake pedal off balances you...

    Could be a million things. Have you tried locking it up in a flat slippery carpark to see what happens? (all in the name of science of course) ;)
  11. Wheels not in line,
    when you corner, does it go round the corner smoothly one way and wobbles when go round the other way.
  12. I'll throw another one in there. Maybe you're not sitting central on the bike and have it leaning slightly to the right.
  13. My first bet would be Road Camber- try it on the other side of the crown... yeah I know, that's the wrong side of the road! Maybe you could find somewhere suitable on private property, a driveway or carpark, etc.

    If that doesn't sort it out, it could be the bike- check the wheel alignment. Have you had the bike since new? If not, it could even be a bent frame.
  14. Grue, it's a combination of things.

    A/ The spinning rear hoop gives your bike stability. When you stop it spinning, it stops providing stability and for all intents and purposes, the bike starts to fall over. The rear wheel will start to step out in relation to which way the bike is "falling". I think it's to the opposite side of the falling direction.

    B/Road camber. Sliding rear wheel slides down the camber - unless A or C tells it otherwise.

    C/Unbalanced load on bike. Sliding read slides away from the heavy unbalanced load.

    D/When your rear wheel is skidding, it's slowing down SLOWER than the front wheel. The speed differential ends up as a side ways step out, in a direction provided by A or C.

    You're talking about locking it when slowing to a stop. The important thing about this is it's much more dangerous when you're actually moving and panic brake at speed. If you lock your wheel at a decent speed and the rear steps out more than 15degrees or so (about a foot on most bikes) and you release the rear brake, that hoop will start to roll again, get traction and you will have just initiated a highside. If you're in a corner and stomp on the rear, it's bye bye charlie since you lose dynamic stability AND get to experience a Newtonian end to your ride.

    ...and folks wonder why I'm so uppity about misusing the rear brake...

    Ride safe.
  15. On my bmw the rear always slides to the right so road camber may not be the reason.
    The shaft drives the rear wheel from the right hand side so when I jam the rear it will slide to the right.
    On my Honda which the rear was driven by the chain on the left hand side the bike would lock and slide to the left.
    I think it may be more to do with which side of the wheel gets drive then it suddenly loses that drive. Physical forces and all that.
  16. Sounds like you need some training..... or training wheels. :p

    Grue, my first thought would be camber in the road. However, Rob and others have come up with stuff that seems to make sense.
  17. Yeah, I've been using fast stops as an opportunity to practice as well, experimenting with exactly how much rear brake my bike will allow me to use before it gets squirrelly.

    WHat's really interesting is that on the occasions where I've managed to get it to slide at the last moment like the ones that caused the topic, it's never left a mark or anything on the asphalt, which makes me think I might not actually be fully locking it, as much as it slipping a little bit because it's moving slower than the front wheel, much like when I'd left foot brake to initiate a drift in a front wheel drive car.

    Does that make sense?
  18. Ooooh, this is an interesting point. I hadn't considering it from that perspective.
  19. Nah, seems to be the Billie Jean King of bikes, it goes both ways pretty well.
  20. I still say its an unbalanced big arse problem :)