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Discussion Starter · #1 ·
I'm still looking for an old article that explains how the neck of a bike works, but in the meantime, here is part of a great article about braking that does a good job as well.

Our crash course in braking begins at about 40 mph when you apply a handful of front brake. Unexpectedly, you ride over a small patch of gravel and the front wheel loses traction. With the wheel skidding, you've lost control, yet the motorcycle is still continuing straight. All is well-so far.

Unfortunately, a sliding tire is free to go any direction it wants. But with a firm grip on the bars and good balance, you've managed to stay upright to this point. The correct procedure from here is to release the brakes enough to get the wheels spinning again, and then re-apply them.

That's a lot easier said than done as you watch Grandma Jones' Buick hang a left in front of you. With your adrenaline pumping, you have a pretty healthy grip on the brakes, and easing off isn't part of your brain's game plan. Now there's a whole list of things that can go wrong.

Your biggest worry is the back half of the motorcycle-it's probably trying to pass the front. With the rear wheel partially unweighted and the steering neck turned into a huge hinge, it doesn't take a lot of effort for the rear to pivot and swing to the side. As if that's not enough to deal with, with the front wheel stopped you've lost the stabilizing gyroscopic force that smoothes out and slows steering inputs. With spinning wheels you can hit a six-inch pothole and the motorcycle will just about steer its own way out. With a locked wheel, any disturbance, no matter how small, can be disastrous.

Perhaps your undoing will be by way of some antifreeze or a small rock, or simply a tiny imperfection in the pavement. Whatever the cause, the wheel turns sideways (for discussion, let's assume the wheel turns to the left). If you're really quick, this is your last chance to release the brakes and regain control of the motorcycle. But more than likely you're past the point of no return. Once the tire changes direction, so does the contact patch. With a side thrust acting against the tire, the wheel suddenly turns full-lock against the steering stop violent enough in many cases to damage the metal stops.

As the right handgrip is ripped from your hand, the left grip is pushing your arm towards you. You react on instinct, reaching out for the missing handlebar, unknowingly shifting your weight outside and to the right. Now you're not only sliding, you're leaning to the right with the front wheel turned to the left. Congratulations. You just got tossed off your motorcycle.

From start to finish, our entire crash (not including sliding down the road) took about three seconds. Unfortunately, even in a controlled environment the idea of stopping by easing off the brakes is just not natural. The only way to really learn the technique is to practice (a risk in itself) until it becomes an automatic reaction. Then practice it again, and again.
 

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Good point, Steve. Does he mention rain? Or does he mention about four other reasons?
:biggrin:

well i was jus sayin...

the thread title says 'rain'
and this talks about hitting gravel.

it's a good and informative article, but i was hoping for some more proof for the nay-sayers that riding in the rain is not something to be scared about.
 

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Discussion Starter · #8 ·
Well, I can give some great proof that riding in the rain is nothing to be scared about (although one should slow down a bit and be a tad more cautious in the rain).

Go to a parking lot in the pouring rain and at ten miles per hour slam on the brakes. Notice that the bike doesn't skid or only skids a tiny tiny bit.

And then do it at 15 MPH.

Etc. etc.

When you get to fifty MPH and are weaving the bike and slamming on the brakes and you see how hard it is to get the bike to break traction, even in standing water, even as your leaning, and that when it does break traction (at the extreme end of the braking pressure or under extreme acceleration) and you simply back off the brake or throttle a hair and it grabs again, you will become a safer more confidant rider and rain rider.

And then you'll hit some painted surface or a manhole cover one day in the rain, at 50 MPH, and the bike will skid, and you'll heart will jump put of your chest for a split second... but then you'll adjust your brake or throttle and correct the skid. Easy as pie!

Riders should practice all the time in different conditions, and really they should practice every time they ride.

I've done this rain excersize in a parking lot and so have others that I know, and we all walked away completely amazed at how hard it is to lose traction in the rain.

This purpose of this is not win an argument, it's to make people safer riders so they don't panic in the rain, don't ride at 25 MPH in the rain (which could get them killed by a car trying to pass!), and so they have more fun on their bike.

Ride safe!

Dep
 

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....Your biggest worry is the back half of the motorcycle-it's probably trying to pass the front. With the rear wheel partially unweighted and the steering neck turned into a huge hinge, it doesn't take a lot of effort for the rear to pivot and swing to the side. As if that's not enough to deal with, with the front wheel stopped you've lost the stabilizing gyroscopic force that smoothes out and slows steering inputs. With spinning wheels you can hit a six-inch pothole and the motorcycle will just about steer its own way out. With a locked wheel, any disturbance, no matter how small, can be disastrous.
......
I'm calling bunk to this section. If your front tire locks and the rear does not, your rear tire will NOT (in my opinion) swing around to meet you. If the rear tire is not locked up, it will not skid. What will likely happen in the author's scenario is that the front tire will skid out and you'll go down on one side of the other. If you lock up the rear tire, THEN it will be swinging around to meet you.

He's right (again, my opinion) that releasing the brake is the correction, however, if done when the tire is cocked, it will cause a violent correction, likely a huge wobble, and down you'll go. Not always, of course, but the possibility exists. Same is true of the rear. it'll correct itself too if released.
 

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BACK ON TWO WHEELS
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low side vs high side....however once youve locked the rear tire in any situation, it is BEST to not let off until youre stopped,....
 

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on a sport or standard, it's a bit easier to deal with the rear lockup becuase you can use your legs and feet to control the rear end somewhat. It's harder to do on a cruiser because your feet are out in front of you more. It could be done, but I sure don't wanna be trying it! :D
 

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Discussion Starter · #14 ·
NCDAVE, my friend, I've been riding for a hell of a long time and have done a great deal of research about how bikes work and why and I don't have any experience with almost everything you've written. None. Zip. The things you say you've done or the things you say will happen are counter to every thing I know about motorcycling.

Not saying you're wrong, perhaps me and the pros are wrong, but it's just an interesting observation.

Ride safe!

Dep
 

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I'm your Huckleberry
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Dave's right about everything in his first post. If you lock the front and not the back, there is nothing that will cause the back to catch up to the front...it'll simply push the front until it falls over. Experienced that quite a bit in the dirt when I was first starting out :redface:

Also have experience locking up the front momentarily (both times in the past month :eek: ), and both times, it was accompanied by a fast wobble after I released the brake.

Not sure about being able to control a rear wheel skid better with mid or rear mounted pegs...but they offer better overall control, so I'd say that may very well be correct also.
 

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Discussion Starter · #16 ·
Dead wrong. Completely wrong. Not even close to being right. You guys must be kidding me. Where do you get your information? You just make it up as you go along? You think about it, and if it makes sense to you then it must be right?

The only thing that keeps the front end from slamming to one side or the other is the traction between the front tire and the road. Remove that, and the neck become a hinge that simply can't hold back the forward force of the rear tire. The front end will never go straight, it will instantly slam to one side or the other. It's not my opinion, it's physics. That's how a bike works.

Go take a racing class and tell the instructor he's wrong and that you know more than him. Tell Mike Kneebone, President of the IBA, and a guy who had one time held more long-distance motorcyle riding titles than anyone ever had that's he wrong. He wrote that article. And tell him you know more than he does about motorcycle riding.

And then tell the other motorcyling experts I've learned from that they're wrong. They all say the exact same thing. It's amongst the most basic parts of bike riding, but everyone has got it wrong except you two?

Amazing.

Ride safe!

Dep
 

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I'm your Huckleberry
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Again, there is nothing to move the rear tire...it still has all the gyroscopic forces keeping it moving straight, upright. The front wheel will tuck, and cause the bike to fall over long before the rear end slides out to try and catch the front. The same physics are at play when trail braking, only the bike is leaned over, and less traction is available for braking (making it easier to lock up). The most common type of accident in MotoGP is a lowside resulting from heavy trail braking...the front tire tucks under, the bike simply slides down...the rear doesn't try to catch the front.

Its simple physics...the rear cant pass the front unless the rear loses traction. Take your bike into your back yard, get up to second gear, and slam on the front brake. I guarantee the front wheel locks up, and the bike simply falls over. I can make that guarantee because I've done it!!! :lol:
 

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Discussion Starter · #18 ·
You're confusing a front wheel lockup with the principle of the "skidding tire always wants to pass the non-skidding tire". This is true. And you are very, very right when you say that the rear will not try to pass the front tire unless it's skidding. I agree one million percent. I apologize if that wasn't clear.

But no one said the back tire will try to pass the front tire. What he said, and what I agree with, is that the rear of the BIKE will try to catch the front of the bike. It will swing around... not SLIDE AROUND... swing around.

The front tire has lost traction... but not ALL traction! You're not riding a wheelie! It's still offering resistance to the rear of the bike, even as it's sliding on it's sidewall. But this resistance is no longer the counter-steering that we use when we steer the bike by the handlebars. Instead, it's a variation of the counter-steering we use and it's sending a bizarre message to the rear of the bike!

The neck is being pushed forward by the rear tire, and the rear tire WOULD go straight due to gyroscopic forces (you're correct about that) EXCEPT for the fact that it's being forced to swing around by the uneven resistance of a locked-up front tire. The neck has become a hinge and is actually steering the rear of the bike by resistance.

But I think what is confusing this subject is that when I say the rear swings around, you're thinking of a rear wheel skid. It's not like that at all. The rear swings around the same way it does when you turn the handlebars... although in that case, as soon as the rear starts to swing around, the bike leans and the swinging stops. IN our example, the bike can't lean, or it can't lean properly. (imagine doing a turn through wet paint. The rear wheel and the front wheel follow different tracks... for the purpose of this example, consider that "swinging around".)

Imagine pushing a plate around on the floor by using a broomstick. Unless the broomstick is perfectly centered on that plate (which is nearly impossible) the broomstick keeps shooting right or left or right or left. You must constantly manipulate the broomstick to get the plate going straight and most likely you will never get the plate sliding in a straight line.

Same principle here.

And your explanation of locking up the front wheel and seeing how the bike falls over is EXACTLY what we're saying will happen! The bike will fall over! That's the point! You can't just ride down the road with the front wheel locked and the rear wheel forcing the sliding wheel down the road. You will INSTANTLY fall over. It seems to me like you're saying that the gyroscopic forces will keep the rear wheel rolling... and they will... but it won't roll straight. It will try to pass the front of the bike.

I hope that explained it. I'm not sure that I did a good job.

And as punishment for all this grief I've been giving you guys, I came out of the restaurant tonight after dinner to find it was raining! And I was extra careful riding home because I said there is no way I'm gonna go on the Kawasaki board tonight and have to tell those fools I crashed my bike in the rain!!!

I kept it under 60.

Ride safe!

Dep
 

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Discussion Starter · #20 ·
Yea, I didn't realize that was the problem until I read your post and thought... he's exactly right!

Glad we figured that out!

Another way to explain it, I think, is the way a friend told me he was taught in a racing class. He said the instructor lifted the front end of the bike up with a jack and showed the class how the front end would not stay straight on it's own (unless it was perfectly balanced). He said that with one finger you could move the front end from side to side.... no resistance, easy as pie. (Or course, we all know that!)

But that's EXACTLY what happens when the front wheel locks up... it will easily float to one side or the other and there is no way to "manhandle it" back to center. (Although dirt riders often manhandle the bars to keep them straight, but it's not the same situation). The instructor's point was to release the front brake instantly if you lock it up, but it is also a good example to explain why hydroplaning a front tire on a bike is an instant crash... NO one can possibly hydroplane a bike for more than half a second (roughly) before the front end slams to one side or the other. Hydroplaning is instant crashing.

When you see videos of bikes "hydroplaning", or when NCDAVE said he was hydroplaning and moving the bars back and forth (at highway speed, no less) and the bike was tracking straight through standing water, what was really happening (I would bet) was the water was causing resistance and jarring the bars back and forth and back and forth.... a little left, a little right, a little left, a little right. The constant back and forth cancels each other out and the bike tracks straight. Sort of like riding a steel deck bridge, the way the front end goes back an forth in a wobble... this is TEN MILLION PERCENT SAFE, it just FEELS crazy weird. There is actually a name for this, but I haven't heard the word in years and I can't remember it.

Hydroplaning or locking up a front tire is the exactly the same as lifting the front of the bike with a jack. There is zero resistance to the front end... one finger will move it right or left, and obviously, with all that forward motion coming from the rear of the bike, once the front end goes a few degrees off center... it's all over! It's goin ALL the way till it hits the stops!

The "lightness" riders often describe in the rain is really their own very, very gentle steering inputs. They steer very lightly due to (understandably) their fear of the wet road. This light steering input responds just as well as normal steering input, and the riders gets the distinct impression the bike is sliding, or floating, or that the ground is "slick". Again,for you to tell the ground is sick there must be reduced traction... and this has instant consequences. One simply can't ride down the road with the bike slippin' and slidin' for very long before something bad happens.

Another way I thought of to make this clearer is this: YES... when you hit the brakes too hard or accelerate too quickly on wet surfaces YOU WILL BREAK TRACTION SOONER than on dry surfaces. No question. But my point all along has been, why would you do that? Learn how to ride your bike properly and this won't happen. DO you need 60 feet to stop in the rain instead of 40? Of course. Then, brake earlier or slow down.

Dep
 
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