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Cornering Practicing Techniques


Silvrluk
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This might be of no use to the more experienced riders, but I learned from it so another may also. Any suggestions or thoughts are welcome.

 

 

I read a bit of Twist of the Wrist II everynight before hit the hay, and Im rereading a part that talks about lean angle.

 

"A motorcycle in motion is a pretty stable unit if left alone by the rider. Put the bike into a slide to see if its true. Does the motorcycle feel stable to you when sliding? It should, if youre doing it right."

 

I wont lie, going into a slide scares me. I needed to test this out without killing myself. I always think of a car and how easy it is to push the limits with a four-wheeled machine. There is no fear of highsiding or flipping over, the car (if its decent) gives plenty of feedback before it starts to slide, and when it does slide, its pretty managable (just turn into the slide). I always wondered how I could accomplish the same testing of limits on my bike as the benefits are blatently obvious. More advice from Keith Code:

 

"How far you can lean (the maximum safe angle) is a question that is answered by experience with your machine, but on any sportbike, your knee can be down way before you've arrived at the maximum safe angle."

 

This also got me thinking, I barely drag knee when I ride the canyons, more for fear of: 1) sliding, consequently losing control and 2) how far can my bike lean over.

 

Now it gets interesting. I want to practice both these things in a controlled environment. A track would be good, but it costs money, there are other riders to worry about, and one might feel intimated testing how far you can lean over and practicing slides in front of other riders, not to mention the basic embarrassment of having others seeing you crash if you are so inclined.

 

So tonight, I zipped up in all my leathers, and headed to the local community college. There, a massive chunk of asphalt with adequate lighting awaited as my testing grounds.

 

I started off in first just going in circles, getting more and more lean in, when my knee touched, I just rode around on it for a while to get the feel. After a few laps, I did the other side. I practiced figure eights, trying to get maximum lean at both apex's, knee's sliding along as happily as can be.

 

I had no idea you could lean a production bike on street tires over as far as I did tonight. I feel as though I still havent reached the lean limit, but it felt good for a first time practice session of this kind and I didnt push it.

 

Finally, I practiced accelerating hard enough to get rear wheel spin coming out of my turns. The bike felt stable and kept tracking where it was pointed, and the biggest fault of bad riding, or what Keith refers to as a Survival Reaction of chopping the throttle, was the furthest thing from my mind. There was no fear about the slide, no fear about how far it was leaned over, and a exhilerating sense of accomplishment and comfort with my machine.

 

I am so excited about this I just wanted to pass it on so others could benefit from the experience.

 

On a sidenote, the campus police did stop by to see what the noise was. Once I told him I was only practicing cornering at low speeds, and I wasnt stunting, they had no problem with it and let me continue.

 

Disclaimer: I am not a professional motorcycle racer nor teacher. Any ideas or suggestions you may get from this article and then apply to your riding I do not take responsiblity for. Try this at your own risk!

 

 

Happy Riding!

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your tires actually NEED to slide a bit to get maximum traction. Is that true, and if so, why?

what they may have meant was to say that sometimes you can get more ACCELERATION (not traction) with a spinning tire coming out of a turn than you could on a perfectly hooked up one...

 

as far as cornering traction, though, i can't think of a way that less than total traction is more traction.

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I recently went into a rear wheel slide in a corner. It scared the dickens out of me. The bike leaned over, way over. The foot peg has a swivel, which swiveled up, putting the inside of the ball of my foot on the pavement. I had no idea that the bike could lean so far over (K1200RS with Dunlop 220's). Whew!

 

I thought my right leg was toast. My first instinct was to chop throttle. I felt the nerve implulses send the message to my wrist. Somehow, and I don't know how, I remembered what Keith had instructed about SRs... "don't chop that throttle."

 

I somehow managed to hold throttle. It happened all so fast, that i don't know if I could do it again. I certainly hope so, for if you do go down, it makes the difference between a low side and a high side.

 

But, to continue the story, the rear wheel slid, I kept the power on and the bike regained traction, picked itself up and completed the corner. As the bike picked up, I realized that I was turning the front wheel into the slide. But the pickup was smooth. It was all so very smooth. Scary, but smooth! I'm still amazed by what happened.

 

While I managed to contain the survival reaction of chopping throttle, I am still working with it. The whole event did shake my confidence in the traction I thought I had. It has effected my riding which I am trying to work through.

 

I refer to Kieth's books very frequently. There is so much there.

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I think you were lucky the cops left you alone. I have wanted to do the same thing for a while now. A buddy that taught me to ride told me it was the best way to get used to the lean angles needed for "real" riding. A few years back I was in Europe and picked up a biker mag. Can't remember which one. They had a story about trying to crash a bike on stock tires. These crazy Brits took a bike with OEM tires to an airport and rode around in a circle getting lower and lower until the bike crashed out. I was stunned to see how low the rider got. I am not talking knee dragging, but pulling the knee in to get even more clearance. Got to love the Bits!!! Could you imagine one of the American mags doing that as part of a camparo test with the new 2004 bikes?!! I think not.

Glad the test worked out for you.

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I'm pretty interested in this, as I have similar concerns but one thing that I was wondering about was a comment that I read on one of these BBs -- that your tires actually NEED to slide a bit to get maximum traction.  Is that true, and if so, why?

I can explain that, if you have a minute and some visualization skills.

 

Place any object on the table. Exert a sideways force on it, and you'll discover that it really likes to stay where it is. When motion first occurs, it is easier to keep the object moving than it was to start it moving.

 

This is not inertia at work - it is an example of the difference between two coefficients well-known to engineers: the coefficient of static friction and the coefficient of sliding friction.

 

On a minute level, any object in contact with another has a large number of surface contact points which intrude upon the other surface. The first phenomenon here is exactly like the action of a dirt-bike tire; tread blocks intrude into dirt to get grip. The tire's contact point, street and dirt tires alike, are intentionally built to offer the most friction - which is called traction when applied to motor vehicle propulsion.

 

A street tire works exactly backwards from the dirt tire. It has to let the road surface intrude upon it by conforming closely to pavement texture.

 

So, pause for a moment, and think about it. The tire's contact patch is completely stopped, isn't it, unless you are sliding the tire?

 

No. The tire is rubber, and it does not lock to the road like gear teeth. In rotating against forces of propulsion and braking, the tire "crawls" quite a bit. Perhaps you've heard about Daytona cases where the back wheel of a Superbike is actually spinning faster than the bike is going? This is simply a matter of tread elasticity, where, in order to exert a force, rubber must be stretched. At the contact patch, this means that as a point on the tire first touches the road, it has no load on it, and that as it rotates under and back, a point on the contact patch will assume and release load proportional to the rubber's elasticity.

 

But you aren't asking about that, directly. You want to know if a tire must slide for maximum traction. On motorcycles, that answer is yes.

 

Go back to the example of the difference between static and sliding coefficients of friction. If we were just trying to keep something from starting to slide, we would build a system that would bond very tightly to whatever it sat on. Glue is a good example of a substance that intrudes upon a surface in order to maximize the force needed to dislodge an object.

 

But we have to roll. We can't just put the tire contact patch in one place and leave it. We have to accelerate in all directions, and deal with weight transfer. So tires are built so that they first intrude upon the texture of the road surface, and then intentionally yield by allowing the road surface to abrade them. This costs a great deal of energy - one of the reasons you need less braking than you might think just in cornering - and energy is the product of force and time. The force appears, after conversion by the motorcycle chassis, as acceleration.

 

The energy which goes into heating the tire comes from the engine, the source of all your velocity. The tire's ablation converts kinetic energy into heat, exactly like your brake pads do, and disperses heat by shedding chunks of rubber, conduction to other parts of the tire/wheel, and convection to passing air.

 

You have probably seen the results of tire ablation. Those tatters hanging off the tire are evidence that this occurs even when gross (spectacular) sliding is not going on. When the tire gets hot, the rubber becomes self-lubricating; it cannot absorb any more (coincident) energy of ablation without liquefying.

 

Look back for a moment to where I mentioned "tread elasticity"; when a tire is actually sliding, all of the contact patch is loaded to its elastic limit, and is transferring the kinetic energy of your motion through several conversions into heat and force.

 

Does this help? There is a lot more to this...

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