Tuesday, March 13, 2007

Stopping quickly in a curve ( Part II )

The two “budget” accounts that figure predominantly are side forces and braking forces. To save me some typing I’m just going to call them Leaning and Braking.

Traction is defined as friction between the tires and the road surface. In any given situation there is a finite amount of traction available. The total traction available has to be shared between all the forces demanding their piece of the pie. In fact, the pie analogy is a good way to look at things. Each slice will vary in size depending upon the appetite of the consumers. However, the total of all the slices cannot exceed the overall size of the pie itself. We can change the size of the slices but when the pie's gone, it's gone! That’s when riders get into trouble. They try to get too many big slices out of the pie. It amounts to deficit spending, as it were.

Good money management is the key to financial success. In the same vein, successful riders do a great job of managing available traction.

I’m going to take a small side trip here. Bear with me. It will be pertinent to the discussion that follows. Managing speed in corners has a direct effect on traction management. It might surprise you to know how traction demands in a corner really work.

Setting a proper entry speed for a corner does more than see us safely through the curve. It also helps us to manage the available traction. We'll know if we have a proper entry speed because two things happen. Firstly, we make the corner! That's always a bonus. Secondly, we're able to maintain a steady or slightly increasing throttle. Not too long ago I wrote about not getting too aggressive with our throttle through corners. In that post I was talking about not having to waste traction by fighting to make the bike lean. Heavy throttle makes the bike want to stand up and go straight. Here's a little further explanation of what too much speed does to work against us.

Anytime we're in a corner on a bike, the cornering force is proportional to the square of the speed. Huh?

Think about taking a corner at 15 mph. I know, you're asleep already from riding so slowly. Bear with me. It's easier to talk to you if you're not whipping by so quickly. I'll put you out of your misery and allow you to go 30 mph this time through. A rider would think that if they doubled their speed the traction required would also double. Not so. The traction appetite has now quadrupled! That's what the statement above means. Ready to go faster? Now you can take the corner at 45 mph. What do you think the traction appetite is now compared to the first corner at 15 mph? We tripled the speed but the traction required is now nine times as much!

The most important tool for managing traction in corners is controlling our speed. Not that we shouldn't have fun. Heaven forbid. On the other hand, maintaining a useful traction reserve will go a long ways toward helping us survive those "Oh crap!! moments that arise once in a while.

Time to get back to the subject at hand. We have the bike deep into a corner. Here’s what our two accounts look like at this point.

LEANING A whole bunch of traction used here! tttttttttttttttttttttttt

BRAKING Not very much available here at all! ttt

Right now we’re really grooving in this awesome curve. We have a great head turn and we’re looking to the exit of our corner. (you do have great head turns, don’t you? ) Suddenly a body falls from the sky. D.B. Cooper has finally come to earth with his backpack full of money and a tattered parachute. My God, I’m really dating myself, aren’t I?

Looking at our traction statement above, it’s pretty obvious which account is eating up the most funds. This is especially true just before, during, and just after our apex. Unfortunately, circumstances require that we make a very rapid stop.

Here’s where our human instincts can work against us. When we’re startled our first reaction is to want to squeeze something. It’s called the “Human Grasp Reflex”. That’s why we ask new riders to cover the clutch during our classes. It’s also why we ask them to keep the fingers of the right hand around the throttle when they’re not using the front brake. We know they’re going to squeeze. Squeezing the clutch means they’re just coasting. No harm, no foul. Squeezing the front brake hard can have bad consequences.

Our first instinct is going to be to start braking hard. The squeeze thing, remember? Bad move. The leaning slice of the pie is really large. The braking slice is really small. If we apply the brakes hard while leaned over we face the possibility of low-siding. That’s the second least favorite way to leave a motorcycle. The rider and the bike will find themselves sliding in tandem down the blacktop. Ouch.

What really needs to happen is a very quick transfer of funds. Traction has to be quickly moved from the leaning account to the braking account. It will look like this.

LEANING There's a sudden need to pull a bunch of funds out of this account!

BRAKING This account needs a large deposit, like, yesterday!!!

You all know what position the bike needs to be in to allow for maximum braking. It has to be straight up and down. Easier said than done. Time and time again I see so called “experienced” riders reach for the brake way too early. What makes the situation even worse is that riders have a habit of covering the front brake all the time. This can be good or bad depending upon how we've trained ourselves. Even if they don’t fall down, the stopping distance is going to be longer. Every foot counts. It seems weird that we can stop more quickly by waiting to reach for the brakes. Nonetheless, it’s as true as if it were carved on a stone tablet. Maximum braking can only happen once the bike is totally upright. The traction advantage will make up for the slight delay in starting our braking. Repeated practice is going to instill the proper skills sequence. You knew I was going to come back to urging you to go out and practice, didn’t you? Build the habit. Habits are what we are going to fall back on during high-adrenaline situations. Make the habits ones that will work for us, not against us.

Here’s the sequence. What might surprise you is what needs to happen before anything else. The rider’s been looking through the turn. The very first thing the rider needs to do is to bring their head and eyes back so that they’re looking straight ahead. Remember the thing about the bike going where we look? Acquire a target that’s in line with the path we need the bike to follow. I know, you’ll be looking at a point that’s off the road. It can seem a little scary. The trick is to remember that you’re looking at the direction, not the destination! If done properly, the bike will stop before it runs off the pavement.

After acquiring the target, press on the outside handgrip. It’s a forward press. Remember countersteering? Remember how I urged everyone in a past post to practice it? We all do it but not all riders understand exactly how it works. Like I wrote before, countersteering needs to be a tool that we take out of our toolbox when we need it. Now would be a really good time to use this tool! Just in case there’s any confusion about “inside” and “outside”, “inside” is the direction we’re turning and “outside” is the opposite. If we’re in a curve to the left “outside” would be the right handgrip. If we’re in a curve to the right then the left handgrip is “outside”.

There’s the sequence. Look straight ahead. Press the outside handgrip. Once the bike is straight up and down, THEN apply good braking technique. At this point it’s become a matter of maximum braking in a straight line. The size of the pie slices have been successfully managed so that their total stays within the overall size of the pie tin.

Straighten and brake is the preferred method of stopping quickly in a curve. We can’t always use this method, though. It requires that there be sufficient room on the road for this to happen. Sometimes circumstances are such that we just don’t have the luxury of run-out space. Now what?

Miles and smiles,


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