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Front brake low siding (or no siding)

Discussion in 'New Riders and Riding Tips' at netrider.net.au started by taiheung, Aug 7, 2007.

  1. I'm a big fan of watching youtube motorbike crashes and compilations to look at the "do's and don't do's" of riding. One thing I've noticed in a few videos where a guy is about to rear end something whether it be a car or wall or whatever is that they usually low side just before impact...

    I thought to myself that this was them trying to avoid a full on collision by hitting the dust first early. However then I read in General Discussion in the ABS braking thread about preventing front brake low siding and started to think that maybe that was what I was watching instead.

    Is this the case? How is front brake low siding caused? If I'm heading in a straight line and slam on the front brakes too hard shifting a lot of my weight forward, do I run the risk of low siding? or is it more likely I'll go head over heels first?

    Also, sometimes heavy under brakes I've had my rear try to overtake me - my mates have said that this is me applying too much rear brake. I've been lucky to control it so far by just holding the bike taught but I can see me flipping off one day if it catches the road abruptly.

    I'd really appreciate an answer to this as the more we can understand how it happens the better we can avoid it happening!


     
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  2. seriously it could result in either, i had a lowside cause by front brake lock up
     
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  3. If you put so much pressure on your front brakes that you lock it up, it will be a low side, however if you can brake so you can transfer enough weight forward, you will stoppie, and if you brake too hard mid stoppie, it will through you over the front.

    If your back end slides out in front, then your technique is a bit off, for qride we were taught to brake like so:
    1. Prepare both hand and foot.
    2. Apply back brake slightly before front brake
    3. While slowing down the weight will transfer to the front, so you need to apply more braking at the front, and less on the back
    4. Sometimes there will be next to no weight on the back wheel, thus the back brake is not doing anything and can cause the wheel to lock, so if you are braking that hard, release it if you start to feel a loss of traction
    5. as you are easing up on the front brake, use the back brake again.
     
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  4. You don't need to "lock up the front" to have a low side.



    A tyre/road combination only has "so much" traction.

    If you run hot into a corner, and you start braking while turning, you are now asking the available traction to both turn and slow you at the same time.

    Yes, the traction increases as the tyre loads up with the forward weight transfer, but there is a limit.

    Carrying lean menas you're not on the fattest part of the tyre and you're asking a lot from a smaller patch, plus the suspenders can't iron out the bumps as efficiently, plus since this is an emergency, you're likely to be stiff on the bars further reducing suspension efficiency...

    So, there you are, leaning, turning and slowing, demanding heaps from the front tyre... anything that reduces the available traction to something less than required (e.g. wet patch, sand, smooth surface, worn road aggregrate), or anything that demands more traction than available (e.g. brain fart on the brake lever, front lock up) - and the front will let go.

    Since you're leaned over, a low side is typical.


    www.msgroup.org has several articles about braking dynamics. They're worth reading.
     
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  5. p.s. you don't even need to be braking to have a low side in a corner. It happens to racers often - they are sooo leaned over and soooo on the traction limit, that a slight hesitation on the throttle loads up the front a frag and this instantaneoulsy exceeds the available traction... or a bump changes/reduces the traction picture for a millisecond... and down the bike goes.

    ...this is usually accompanied by excited commentators, "oh, he's just lost the front end!"...
     
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  6. thanks but what if your bike is up right and travelling forward? ie no lean?

    the lowside on a brake/throttle release through a corner is obvious - but what about in a straight line?
     
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  7. :?

    If you lowside a straight line braking manouevre, then you either lost it on diesel, or locked the front and got out of shape while still locked.

    You are not going to low side a strong front braking effort whilst the front wheel is turning and you're moving in a straight line.

    You could unexpectedly do a stoppie if the weight transfer is quick and uncontrolled though. That's why learner courses teach setup and squeeze.


    As to the rear stepping out under emergency braking, that's a recipe for a highside if the angle becomes too great by the time you let the rear brake off. Also, your spinning rear hoop provides a lot of stability which is lost if it's stopped and skidding. Learn to modulate your rear braking effort, OR under brakes, brace with your knees gripping the tank rather than putting input into the bars, and you SHOULD stay more in line.


    Like I said, go spend time on msgroup. It's worth while.
     
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  8. is what you are asking what will cause the bike to stoppie and what will cause the front to lock? i think this is what you are asking??

    well....

    alot goes into it.

    firstly, the type of bike. the hyo gt650r from what i hear from good friends who own it reckon it wont stoppie, im guessing the 250r would be similar. this is to do with center of gravity. the higher a bikes centre of gravity the more likely it is to stoppie instead of slide/lock (and low slide if you dont release in time). the other factor which affects this is suspension, the softer the front (ie the less preload) the more weight will transfere to the front quicker giving you more traction. the third factor is tyre compound, the softer the tyre, the more likely it is to grip, assuming the road and conditions are good of coarse.
    ive locked my front a few times on the 250, i went down once. and that was before i put braided lines in which will help the feel tremendously. i sometimes take the 250 to a park. on the grass i find is a good place to practise control of slides. if you can do it on the grass, you can do it on the road. it definatly paid off when i locked up the front on the brand new 1000 a week after i got it, i was able to release and regain control before i went down. i had braided lines in 3 days after that.
    it comes down to practise mate

    btw just thought id mention that ive got the VTR250 into a rolling stoppie before. no it wasnt intentional (was practising e braking) and yes i shat my self, then tried to do it again.
    :grin: :p

    cheers
    dom

    EDIT above response is not intended to be technical, just an anatomy students understanding of yr 11 and 12 physics :p
     
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  9. The reason people lose it when panic braking to stop in time is because they PANIC!
    No matter how dire it looks agead, bike upright, load up the front suspension with some front brake, and as the front suspension loads up, feed more and more front brake in smoothly, combined with as much rear brake as you can get away with. If the rear locks up, forget about it and keep the bike balanced and look where you are going.
    Don't forget if another option becomes available (like a gap) off the brakes and countersteer like a mofo.
    The key is proper braking and not to panic. The only way to do this is to practice emergency braking regularly so you know what both you and the bike will do. Only when it is something you can do safely and when you want to, will you not have to think about it.
    I believe proper knowledge/ability to carry out emergency braking is the most important skill to master on the road.
    I have locked the front a couple of times when braking hard(and in the rain too) and it is entirely survivable if you don't panic.

    Regards, Andrew.
     
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  10. thanks guys.

    I'll try to find the clip later...
    the guy is filming from the ute - the rider accidentally squeezes the throttle when reaching for the brake and begins to launch into the back of the ute. the rider panics, slams on the brakes, and lowsides before he even gets close to the ute. I was thinking he yanked the bike down himself or the front wheel gave way under him but I couldn't see how if he was maintaining a decent centre of gravity.

    on the topic of low siding:
    I was @ my mechanic the other day replacing a mirror I'd managed to slice off with the garage door (ha) and he saw that I had worn my front wheel down right to the edge. He said he was impressed considering most gt250r riders don't get close - it was at this point that I realised I was judging my lean via the wrong wheel! I had kept looking at the rear's wear rather than the front! He made me realise that I could still have some tread on the rear well after I've lost all grip on the front wheel. Now I'm scared shitless that I'll be riding along and see my front wheel just fling up into the sky. lol.
     
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  11. It's all to easy to lowside when you're learning this way, I did it 3 times before I figured it out.

    You're locking up the front, or getting it slow enough too fast causing the back wheel to try and overtake. I haven't had any more runins where i've needed to stop that fast until last night, where someone pulled out of an alley right into my path, luckily I jumped on the back brake and the front brake at the same time and didn't have an issue.
     
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