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post #51 of 57 (permalink) Old 06-21-2010, 06:14 PM
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Hi all,

Locking the front wheel = low side kind of accident. You will basically fall down towards the side you were leaning towards.

Locking the rear wheel and letting go of it on a good surface = high side kind of accident. The bike violently throws you off in the opposite direction that it was initially leaning.

Anti-lock brakes work to keep the wheel spinning once it's locked up. If you lock up your wheels while leaning in a turn you will fall down before the anti-lock brakes detect the skid and start working. Ever see a kid mark from a car that used its anti-lock brakes? The skid marks look like dashes not like a solid line. That was the anti-lock system pumping the brakes very quickly… after they were locked up.

Hard braking while leaning is generally a bad idea. That's why the MSF teaches the technique for doing quick-stops in turns as Straighten, Square and Stop -in a straight line because that's when you have the most traction for stopping. Of course if that's not an option for you due to circumstances (the possibility of going over a cliff for example) then trying to brake and straighten up the bike simultaneously to stop becomes more preferable than going over the cliff. You'd have to weigh your options with that one.

Braking while swerving is very bad for your health. So is accelerating abruptly while swerving. You want to maintain steady throttle to keep your tires within their limits of traction.

ATGATT, I'd rather sweat then bleed any day.

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post #52 of 57 (permalink) Old 06-21-2010, 08:47 PM
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Quote:
Originally Posted by Sloppyburpfest View Post

Locking the front wheel = low side kind of accident. You will basically fall down towards the side you were leaning towards.

Locking the rear wheel and letting go of it on a good surface = high side kind of accident. The bike violently throws you off in the opposite direction that it was initially leaning.
Just being picky here, but locking your front while leaned over usually will result in a high side. The front stops and the bike staightens up...violently.

Locking the rear will usually cause a low side , but as you mentioned, if the rear end has already lost traction and has broken loose, and you let go of the rear brake, real good chance it will highside.

You have to keep in mind there is a difference between skidding and sliding. The rear end can "slide" but the wheel is still turning and has forward traction. If the the wheel stops turning, or looses traction so it is no longer driving the bike forward, then it is a skid.

Modern ABS systems react in 1/10,000ths of a secound, Older ABS might have left "dashes" but the ones on bikes now release the wheel long before rubber gets laid.

"If you lock up your wheels while leaning in a turn you will fall down before the anti-lock brakes detect the skid and start working"

You may not have "locked" the wheel, because you can fall down because you simply over braked...not because the wheel ever locks up. If your going 35 mph through a turn and you slow the wheel down so it is only turning at 30 mph you can loose traction , low side or high side with out the wheel actually being "locked"...(not turning) ABS will not kick in because the bike itself has slowed down, which will still make you fall , or because the wheel has not locked up.

The point here is if you brake hard enough to even get close to "locking the wheel(s)" while leaned over in a turn, you are going to eat asphalt, but it not because the ABS did not have time to react, it is because you have upset the balance of the two forces working on the bike.(See my other post) and have sealed your fate..the bike will begin to fall or flip nano seconds before the wheel actually stops spinning, and that is why the ABS would be useless in a turn.

New ABS systems also can compare wheel speed of front and rear wheels to make sure they are the same when braking, and the same sensors are used in traction controll systems to make sure when you grab some throttle going through a turn you don't break the rear tire loose by opening it up too much (a possible problem with mega horsepower bikes) or to keep you in controll if you are " accelerating abruptly while swerving"...

KM

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Last edited by Knifemaker; 06-21-2010 at 08:52 PM.
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post #53 of 57 (permalink) Old 06-22-2010, 12:15 AM
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Quote:
Originally Posted by Knifemaker View Post
Just being picky here, but locking your front while leaned over usually will result in a high side. The front stops and the bike straightens up...violently.

Locking the rear will usually cause a low side
KM, you’ve got that backwards.

Watch the red one. He touches his front brake in the turn and low sides. http://www.youtube.com/watch?v=WNrp1Jzs7pg - Leaning left, falling left (low).

This other guy locks his rear brake and then lets go of it while leaning over on good pavement and high sides. http://www.youtube.com/watch?v=hR5GGmwbmNI - rider goes airborne, (high).

This next guy high sides and he doesn't even use his rear brake. He just loses traction and then backs off the throttle trying to save it. http://www.youtube.com/watch?v=rlMbFlPzS24 Engine braking is still braking and anti-lock brakes still wouldn't have saved him.

The danger with the high-side accident isn't locking the rear wheel, it's letting go of the rear brake on good pavement. As the Skidding / sliding rear wheel starts to spin again and gain traction it wants to snap back in line behind the front wheel's track. This snap causes the bike to throw you off the high side.

This isn't as scary for an experienced rider on a lose surface like gravel or sand since traction will be reduced and the snap won't be as violent. However many novice riders who accidentally lock their rear wheels hear the tire screech and instinctively let go and high-side as a result. Larger picture point being: Don’t brake in turns and if you accidentally lock the rear wheel when stopping in a straight line it’s safer to just keep it locked until you stop.

Quote:
Originally Posted by Knifemaker View Post
You may not have "locked" the wheel, because you can fall down because you simply over braked...not because the wheel ever locks up.

The point here is if you brake hard enough to even get close to "locking the wheel(s)" while leaned over in a turn, you are going to eat asphalt, but it not because the ABS did not have time to react,
KM
My point was that anti-lock brakes do not help you when you over-brake while leaned over in a turn. They are only useful when you over-brake in a straight line. If you've used that much brake while leaned over you're going to fall.

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Last edited by Sloppyburpfest; 06-22-2010 at 12:41 AM.
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post #54 of 57 (permalink) Old 06-22-2010, 01:04 AM
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Quote:
Originally Posted by Sloppyburpfest View Post
And while we’re at it, we can be thoroughly morbid and discuss rolling off the throttle while swerving resulting in “tank-slappers” (where your handlebars are slapping against the sides of your gas tank). http://www.youtube.com/watch?v=LZ1sr...eature=related

For the record, the only way to save those is to accelerate to lighten the load on the front wheel.

Anyway, all of these videos are good cases for ATGATT.

-Sloppy
They are also good arguments for walking every where you go too ,I am all for safety,but I am sorry people practice riding your bike ,getting the feel for the machine and Know it and your limits,wear the amount of safety gear that you feel comfortable with, and you can brake in turns but just not as hard ,sometimes it is the only option.If you are inexperienced ,a day at the track will help you learn things about your bike you never knew.and also a large well lit deserted parking lot will let you practice and learn about that balance that Knife told you about earlier between the forces that affect you and your bike and what happens when you brake while turning.Start slow and gradually build up to what you are comfy with on Braking and acceleration while leaned over and upright and read the link on pacing when riding in a group,it is a good informative article .There is no replacement for seat time and I am sure as some of these members who are pilots on here,They have to flu a minimum amount of flying with an instructor before flying solo.I think the MSF basic course is akin to that .So if you are a newb get some formal training from an experienced instructor.Riding a bike and riding it safely to your limits is something you are always learning as your skill level increases.That is one nice thing about being in control of your own machine, YOU set your own pace don't ride above your head or experience level ,if you friends are going faster than you, want let them go you'll get there in one piece that way.have fun stay safe and live to ride another day.




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post #55 of 57 (permalink) Old 06-22-2010, 01:36 AM
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Quote:
Originally Posted by Sloppyburpfest View Post
KM, you’ve got that backwards.

Watch the red one. He touches his front brake in the turn and low sides. http://www.youtube.com/watch?v=WNrp1Jzs7pg - Leaning left, falling left (low).
I'm not going to argue with you here. The reason the rider fell was because he braked only using his front brake and that caused the weight transfer to the front, and thus caused the rear end to let go..(see the rear end come around?)

At least that's how it looked to me...he could have hit a patch of gravel or tried to counter-steer the wrong way...or ran into a bat. I did not get to interview him after the crash to ask what he did.


The laws of physics seem to say you are more likely to high side locking the front wheel than the rear...(But as you say, letting go of the rear brake can cause a high side)

Also keep in mind a good rider knows how to avoid a highside....like turning the wheel as hard as you can into the inside of the turn ....much like what it looks like the fellow on the red bike did. He felt the rear give out and rather than risk a high side he rode the bike into the ground by turning the wheel hard to the left.

But hey I could be wrong, perhaps someone knows him and can ask him what he did.....

KM

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post #56 of 57 (permalink) Old 06-22-2010, 12:32 PM
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When leaned over in a turn, it is possible to use your brakes, but you have to remember that you only have a certain amount of braking traction available, since a lot of your available traction is being used to corner. Several of the better MC books cover this in great detail. Here is the diagram used to demonstarte the concept:


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post #57 of 57 (permalink) Old 06-22-2010, 07:46 PM
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Originally Posted by AJCruzin View Post
When leaned over in a turn, it is possible to use your brakes, but you have to remember that you only have a certain amount of braking traction available, since a lot of your available traction is being used to corner...
Yes, I can see how this can be confusing, but what they really mean when they say not to brake in a turn is "not to try and stop while the bike is turning".

(one should also read up on "Trail Braking")

There is a decreasing radius turn I run through here alot that does require me to brake while leaned over. The problem with falling really has to do with overbraking or locking a wheel.

And admitedly I may be confused myself as to the result of not using the rear brake and locking the front wheel in a turn.. mostly because I have never done so and lack that bit of first hand knowledge...

KM

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