Cornering

by Phil Floria

Cornering by the numbers. I have previously posted Braking Techniques and the explanation of counter steering . With some help from Keith Code and others, and my own experience I will attempt to explain the basics of cornering.

Every thing in this discussion is based on facts, and proven on the racecourses around the world. You may not want to race, you may not need or want to clean corners with your knee dragging…. True most of us are not interested in dragging our knees on the ground. But using the correct procedures and developing the skills may not only make you’re riding more fun; it could save your butt from a disaster.

To start out, a very short word about counter steering, we will assume you have gone out and figured it really works. You rode around a few corners and pushed on the inside handlebar and the bike fell into the turn just as described in the instructions. Now you’re ready for the next important skill to master Throttle Control.

Your throttle will do a lot more than make you bike go fast. In the corner it will set the attitude of the bike and carry it through the corner. Your throttle will adjust your suspension through the corner to provide max traction, or if you don’t master the fine control of the throttle you will find yourself in trouble either losing traction or not getting the bike to turn in and set for the corner.

Most of us understand that you want to have the throttle on in the corner and you can’t accelerate until the bike is upright. Abrupt throttle changes in a corner can upset traction. But correct throttle will not only set the bikes rear tire, it will improve traction on the rear wheel and provide better steering response.

“Throttle control is a very precise subject with it’s own rules and standards. The techniques of throttle control are directly descended from motorcycle engineering specifications and allow your bike to perform up to the level, which it was designed. Throttle control techniques list out like a manual of requirements any modern day bike demands of its rider.

When we talk about cornering we are talking about traction as the rider’s main concern. To determine an ideal scene for traction, machine wise we start by simply measuring the contact patches of the tires to discover what the basic distribution of loads should be while cornering. Roughly speaking, those measurements show that 40% of the total load should be up front, 60% at the rear. Bikes set up for racing and real GP machines carry more rear rubber, changing the useable load bias (possibly to as much as 70% on the rear) to favor hard acceleration coming off turns. Each bike’s exact ideal weight distribution may vary a bit from the basic 40/60 % rule. The rider’s task is to match the exact load specs of his machine with expert use of the throttle.

Considering that most machines in a static or constant speed situation have a 50/50 weight distribution (+ or – 5.0%) front to rear we begin to calculate the guidelines of correct acceleration through a turn. By the numbers we want to transfer 10 to 20% of the weight rearwards, using the throttle. Technically, this is 0.1 to 0.2 G of acceleration. Simply put it’s the force generated by a smooth fifth gear roll on in the 4000 to 6000 rpm range on pretty much anything over 600cc. That’s not much acceleration – but it does the job.

It seems riders often have difficulty sorting out this small amount of traction maintaining throttle through turns, instead trying for more dramatic acceleration. This is most easily seen in the common error of being too “greedy” with the throttle at roll on, which will make the bike run wide or slide and lead to a roll off.

Rule Number One: Once the throttle is cracked on, it is rolled on evenly, smoothly, and constantly throughout the remainder of the turn.

At the point where the correct transfer of weight is achieved by the rider (10 to 20 % rearward) by using the throttle, any big changes in that weight distribution reduce available traction. Once the bike is fully leaned into a turn, changes in tire load, either evenly (both wheels, most easily done in a crested road situation) or alternately (front to back, back to front, from throttle on /throttle off) must then either underweight or overweight the ideal load for that particular tire/bike combination.

The rider’s special skill in applying Rule Number One is in his understanding and sensing of the bike’s requirements and delivering them with his “by the book” use of the rule. Riders do not improve their bikes, they simply help their bikes to work correctly.”

Aside from throttle control and counter steering the other skill is braking. Used to set the motorcycle’s attitude or neutralize the suspension prior to entering the turn. Or as the instructors say adjust the speed of the motorcycle.

As we come up on a turn the first thing we have to do is see the whole corner, the entrance and the apex and the exit. If you can’t see the exit you have to enter the turn slower. Setting entrance speed is done with the brakes prior to putting the bike into it’s lean.

During braking you have to select the gear you need for the exit. Do you down shift once or twice? It depends on your bike and you. In the beginning until you get your confidence up and improve you ability to read the corners down shift at least one gear, which means you must reduce your speed to a point where your engine is not being used as a brake.

Select a point on a right turn to the extreme left of your lane (On a left turn select a point on the extreme right of your lane), this allows you to see farther into or through the turn. When braking and down shifting are done, you begin the steering input (remember Counter-Steering) to begin the lean or actual “turn in” to the corner, at the same time we turn up the throttle enough to adjust the bike’s suspension to put more weight on the rear tire making the front tire lighter. This will improve your steering control making it lighter and more responsive.

If you roll off the throttle the suspension will drop and make your steering heavy causing the bike to cut a tighter arc or pull tighter into the corner. Keep the throttle on. It will amaze you how much throttle you can carry in a lean. As you pass the apex you can now begin the steering input to bring the motorcycle back to it’s upright position and accelerate out of the exit.

None of the above is set in stone, on the racetrack each turn is designed to challenge the rider’s skill, on the road most turns are designed for the allowable conditions or follow the ground contours. Rough roads, and other hazards must always be in the forefront on the road; cross streets, animals, and traffic and of course the road and weather conditions.

Another method is the vanishing point method.

Judging your turn in point, braking, throttle control are all skills, which you have to practice. In the beginning always go for smoothness, make all of the things happen smoothly, speed will come as your skills develop. The vanishing point method will help you develop smooth entry and exit, it will also help in determining the speed at which you can enter the corner and how fast you can leave it.

Fast Version:

1. Observe where the center of the road appears to meet the right edge of the road (left edge for countries with traffic on the left) A long way away on a long, flat straight road, but a constantly changing point on most curves.
2. Never ride faster than you can stop in that distance.
3. Never ride faster than you can see, identify and avoid all obstacles within that area.

That's it.

Examples:

Constant radius corner

1. As you approach the corner from the long straight you are on, the Vanishing Point (VP) is essentially at the corner entrance (since you can't see around it), you slow down as you get closer to it, and it doesn't move.
2. As you get close, you can start to see around the corner, and the VP starts to move away from you. Adjust your speed so you are neither gaining on it, nor losing on it. \
3. As you go through the corner, the VP will be the same distance from you.
4. As you start to straighten out at the end, the VP will accelerate away from you, allowing you to do the same. The VP picks the point of acceleration, so you don't end up accelerating too early.

Increasing radius

1. corner As you approach the corner from the long straight you are on, the Vanishing Point (VP) is essentially at the corner entrance, you slow down as you get closer to it, and it doesn't move.
2. As you get close, you can start to see around the corner, and the VP moves away from you. You adjust your speed accordingly.
3. As you are in the corner, and the corner widens up, the VP starts to accelerate away from you. In the absence of road hazards, you can accelerate after it.
4. As you start to straighten out at the end, the VP will further accelerate away from you, allowing you to do the same.

Decreasing radius corner

1. As you approach the corner from the long straight you are on, the Vanishing Point (VP) is essentially at the corner entrance, you slow down as you get closer to it, and it doesn't move.
2. As you get close, you can start to see around the corner, and the VP moves away from you. You adjust your speed accordingly.
3. As you are in the corner, and the corner tightens up, the VP starts to decelerate towards from you. You slow down too. Remember, if you can't stop within what you see, you're asking for trouble.
4. As the corner finishes, and you start to straighten out at the end, the VP will accelerate away from you, allowing you to do the same.

This method allows you to deal with unknown varying radius corners with a minimal amount of fuss and hassle. A decreasing radius corner will never sneak up on you, since you've been continually adjusting your speed through it.

The beauty of it is that it automatically adjusts for hedges, parked cars, and other vision blockers. If you can't see the curb because a car is there, the VP will slow down, and so will you. It also dictates a different line through some corners. In order to go the fastest SAFELY through the corner you need to stay within your VP. So, the fastest way through the corner then, is to maximize the VP. This often means a different line than a traditional "racing line".

You DO need the skill of braking and accelerating while leaned over though. You need to at LEAST be able to brake as fast as the corner decreases. Practice this on a controlled area before riding to 100% of the VP on unfamiliar roads.

It is sometimes argued that available traction is reduced in a turn, and that slowing in a turn may cause a front-wheel slide as the wheel loading changes. Keep in mind that at all times, using this technique, you are traveling slowly enough that you can stop in a space you can see. If your braking technique in turns is such that a skid is likely, you need to reduce speed earlier, to eliminate this hazard. This is not the technique for maintaining the highest speed; this is the technique for maintaining the highest SAFE speed.

This method will protect you against visible stationary hazards in the road, by assuring that you always have the ability to stop before you reach the hazard. If you choose to ride at a speed so high that you can't stop between where you are and the point at which you can no longer identify a hazard, you have only yourself to blame if you suddenly find yourself trying to ride your bike through a pile of boulders or off a cliff or over an oil spill. Obviously if there is some fine loose gravel visually indistinguishable from the pavement, this approach will give you no additional protection. Oncoming vehicles may intrude into your path at higher speeds than you can respond to, and, of course, risks from hazards overtaking you from behind are not addressed. Be careful out there.

Vanishing Point Examples

For your further edification regarding Vanishing Points, here are a few examples (readers from places where traffic keeps to the left may wish to use mirror-image versions of these pictures).

The road is straight, climbing, with clean pavement. The vanishing point is a good ways off. We can keep plenty of speed at this point.

These are nice sweepers. The road is still climbing somewhat, so stopping distances are a bit shorter than they might be on level ground. If we were gaurenteed a clear road beyond the vanishing point, we could carry lots of speed, but we aren't so we don't. We note that the vanishing point is beyond the apex of the turn, so we anticipate that only moderate slowing will be needed in the turn, even if we should discover a hazard just beyond the obstruction.

This is a steeply descending turn, and the apex of the turn is beyond the vanishing point. We want to give up some speed early going into this situation. Someone from Kansas failed to do so a couple of years back, and collected upwards of a million dollars from the state of California, but I think he'd rather be on his motorcycle than confined to a wheelchair.

This is more like our first example. The road is straight and ascending, and it doesn't look like we have much to worry about in the way of cross-traffic. Check your 6 for the highway patrol and go!

Don't be fooled because you can see the road beyond the vanishing point. That rocky hillside suggests to me a high probability of loose gravel on the road, and there could be almost anything behind that tree. You know you're going to have to slow down for that oily-looking hairpin, so why not do it now and reduce your risk?

Here's another tricky one. You can see that the road is straight, and there's no traffic, and the pavement's good, right? Well, a low spot is a likely place for a washout. In another second or two, we'll be able to see over the ridge into this dip. Hold off on the accelleration until you're sure, and you'll likely finish the ride where you originally intended. Ignore the vanishing point, and you'll have nowhere to go when you meet a situation like this: Too Bad .

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