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tight u-turn question

Discussion in 'New Riders and Riding Tips' started by kyp, Dec 16, 2011.

  1. Hi guys,

    Today I've been practicing a u-turn on my GS500 and now can complete it within 5 meters which is normal length of one parking spot. I also noticed when I go wider then I need I add more throttle and more rear brake at the same time which enable me to fit the u-turn space. I'm wondering why it doesn't work just by playing with friction point as speed remains the same at all time.

  2. Reving the engine increases the centripetal force exerted by the mass in rotation within the engine which tends to hold the bike upright. its hard to manage the reving engine just with the clutch and the brake makes it easier.
  3. that makes sense but performing a u-turn(or just turn) I tend to lean the bike (to turn tight) rather than keep it upright. I see some contradiction why would I want to make it upright? more upright = goes wider, isn't it??? It just something isn't puzzling out in my brain.
  4. you lean bike one way but tilt your body the opposite way in a very slow manoeuvre it allows for tight cornering
  5. Exactly, that is what I do as well. So still the question why trying to make the bike upright helps. Am I asking stupid question?
  6. I would have thought for stability... but correct me if I'm wrong. As well as your weight over the other side counter leaning it the centrifugal force also wants to.
  7. Because at slow speeds if you lean the bike over it will fall down, as there is not enough momentum.
  8. I can't really imagine why but then my knowledge of physics is limited. (Reponse to original question not Smee's comment)

    Using some rear brake gives the bike some more stability at low speed. Could it simply be that because it feels more stable, you lean more without realising leading to a tighter turn?
  9. Not quite. Revving the engine holds the bike in lean better. It's to do with gyroscopic motion of the crank (effectively rotational inertia which is a function of the engines rotational velocity) and nothing to do with centripetal force - all that does is hold the flywheel and counterweights to the crank.
    You're right, holding it upright drastically increases turning radius. Revving just helps balance the bike for the lean it's on, making it more stable.
  10. The crank does have some righting affect. At slow speeds, but not much.
    Same goes for the wheels. They are you main righting mechanisms. But under thirty or so k's an hour they don't have much.
    Add some controllable righting affect from the REAR brake on the rear wheel and Bob's your uncle.
    Using that and some counterbalance from you and you should be able to spin anything, anywhere and at anytime.
    You main aid is having you eyes pointing back where you want to go before you start the turn.
  11. Bretto is right abt the gyro effects.

    U know, sometimes the physics doesn't matter. What works matters. Dragging the rear, dialing in some revs & slipping the clutch works - go with it. :)

    - - -
    Tapatalking loud, saying somethin'
  12. What do you do if you have a bike that has front bias on the rear brake? Genuine question.
  13. Heh. Of course.

    @drew. Pray. I would not want front at all engaged for slow tight turns. As rob said, whatever works matter so, use what you have got.
  14. :? You talking about linked brakes? Doesn't using the rear only activate two pots of the front brake? AFAIK If you don't dive on the rear brake when slow maneuvering, then the fronts should barely be noticeable. Happy to be corrected though.

    - - -
    Tapatalking loud, saying somethin'
  15. For example, the Yamaha FJR1300 when using the rear brake sends 20% bias to the front and 80% to the rear. I don't know any more of the technicalities than that.

    However I do know that if you ride the rear brake whilst riding one doing tight u-turns the front will bounce around as the front brakes comes on and off as you're rear braking and it also tries to make the bike stand up.

  16. Eeeesh!... I've never seen so much clumsiness in describing such a simple precess, in the one thread before! 8-/

    ...to expand a the subject a little...

    It's quite simple...
    1. You tilt the bike over, while counter leaning with your upper body.
    2. You use the throttle and clutch to set your revs by way of a suitable friction point.
    3. You use your rear brake to control the speed.

    As Rob said, the Physics, while present and in the background has little bearing on 'this' process.
    Just do it.

    OP, had you bothered to search you would have found this 3 step process, listed and explained, about a gazillion times.
    It is THE process to follow for all low speed control situations, regardless of whether you are turning or not. Below about 20k, the rear brake is your trusted friend and should always, be used.
    Above 20k or so, the rear becomes a danger and you switch to the front brake as your primary tool for braking.
  17. The op was asking why it works rather than how to do it. Sometimes it is good to understand why.

    The interesting thing with a lot of hows in motorcycling is that a lot of top riders do it all wrong. Wonder why tha works?
  18. Well, yes he did ask why, per the above, and the simple answer would be, that it does...but it's harder without the brake there to control ones speed. The brake is an important part of the recipe.
    Being able to do it without the brake is just a matter of overall balance, which takes more practice due to the extra difficulty.

    Physics is going on all the time in the background, but in this exercise, I don't believe it is much of a factor beyond the drag the brake provides to keep things controlled.
  19. I've had a bit of a look and couldn't find anything, do you know if there is anything on msgroup about rear brake use?
  20. Thanks everyone guys. Now it does make sense to me why it works this way. In a nut shell I want gyro effect to do the job of the bike stability(to compensate my oversteering maybe?) by revving and braking at the same time . Is that what you guys and FAQs call 'dragging rear brake'?