[Keith Code]

Holding Your Line

Predicting a Line

If you always knew precisely where the bike was going to be, as far up ahead as you could see in corners, what sort of impact would that have on your everyday riding, touring, track riding or racing?

Think of how easy it would be to have good throttle control if you always knew where you were going to be! Isn?t throttle control easy when you know your line is ?good??

This could easily lead you to believe that having a good line was the key to good throttle control but it?s not. In fact, it is the opposite: Good throttle control is the answer and opens the door to ?good? lines.

It is true, one of the great results of good, standard throttle control is the bike holding a predictable line in the corner; and all riders realize that having the ability to accurately predict the result of their line would result in a far more positive riding experience in any cornering situation. Would that be true for you?

The Purpose

I?d like you to take a look here at some data on this subject and at the end I?ve prepared an exercise you can do to gain better control of your line and more confidence in predicting it.

Throttle Control Virtues

At the Superbike School we spend a lot of time and put heavy emphasis on Throttle Control. From a technical perspective, all that goes right and most all of what can go wrong in a turn starts and ends with how well you conduct that precision control device on the right hand bar known as the throttle. A predictable line is one of the many positive results of controlling the throttle accurately.

It?s easy to communicate how easily good Throttle Control solves common problems and puts the rider in ?full? (the best it can be) control of the bike. We sing its praises and tout its many virtues--when we get it right.

Riders generally deplore their own shortcomings in being able to maintain it when fear and panic seize them. They understand its simplicity; they grasp its importance immediately and see areas where they could improve throttle control just from a classroom briefing on it.

Running Wide

Running wide is a major concern for all riders. Name a situation (other than in multiple radii turns) where running wide is a benefit. If you are at a loss to find one, I understand, no one ever has. How do you handle running wide?

This is a huge concern and it brings up such questions as: Should I just trust the tires? Should I just lean it over more thinking ?the bike can do it?? Should I stand it up and go for the brakes? What do you do?

Contrary Feelings

Let?s start out with our Survival Instincts and see how they may cause problems. When the bike is running wide the last thing your instinct tells you is: ?You need more gas here?. In fact, it is quite the opposite. It tells you that rolling on the gas will make it worse and you will crash. This is a Survival Reaction, we call them SRs for short.

This particular Survival Reaction (SR) may be based on the very first day you rode a bike at slow speed in a parking lot. Perhaps the bike felt like it was falling over and you gave it some gas and that stabilized it: that stopped the feeling that it was going to fall over. It may have even felt like it brought the bike up.

This second one is a false perception. The bike did not ?come up? but it did stabilize. If stopping the bike from falling inwards mistakenly becomes confused with ?coming up? your right hand on the throttle would have a very strong opinion about this in the future, i.e., gas on = bike comes up; as opposed to the truth of the matter which is: gas on = bike stabilizes its lean angle.

A related misconception that many riders have follows along this same line. Most riders say the bike comes up as they begin to roll the throttle on more aggressively towards the end of the turn. Contrary to that feeling, the bike does not ?come up? from throttle application when you are exiting a turn.

You Choke, You Lose

In running wide, even a momentary hesitation is enough to cause anxiety. Perhaps you find yourself in a turn running a bit wide (or at least you think you are) and that very brief hesitation, which is composed of you thinking it through and mind wrestling with the instinct to roll off, is enough to make it all go wrong?the throttle roll-on stops or even backslides towards OFF a bit and the bike does try to run wider.

By the way, this is another area of false perception that many riders have. They say the bike goes into the turn on a tighter line when they roll off the gas but, guess what, they are actually steering it inwards. Left to its own, the bike comes up and runs wide.

Back to the point. Even with terrific reflexes it takes time for you to subdue the Survival Reaction (SR) that created that hesitation and finally make the decision to roll it on. A half a second is short for this type of thing. In reality it takes more like a second or even two to regain your control. That is a lot of space, that is a lot of running wide, that is a lot of anxiety and that is most of any short turn.

Precision Control

Superlative Throttle Control is a precision activity. Easy for those who can do it and very confusing (probably based on the contrary evidence from false perception as above) for those who cannot.

Finding the right amount of gas to stabilize the bike and hold its line isn?t even vaguely easy, it is hard. Initially, you have to break through some pretty tough barriers just to maintain good throttle control to get the bike to hold a predictable line, especially as the speed increases. Unfortunately, even after you have done it successfully in one corner there is no guarantee it will be solved in other turns!

Throttle control must be looked at from the angle of a fluid and continuous maintenance of the bikes attitude in the turn, i.e., enough weight transferred off the front and onto the rear of the bike to maintain its best and most neutral handling attitude, not too much or too little. And more importantly, maintaining the suspension in its optimum stroke-range with the throttle. This requires a continuous roll-on.

The point is this: your ability to maintain good throttle control is an absolutely necessary and integral part of conquering the SRs connected to running wide.
Being able to judge your line has everything to do with your sense of confidence in any cornering situation.

Note: Throttle control is well covered in ?A Twist of the Wrist?, Volume II, as those of you who have read the book already know.

Any Solutions?

Not yet. Without first hand knowledge of how it feels and looks my words are not likely to make running wide disappear as a problem for you. Another thing I should mention, there is no iron clad, fits all situations type answer to it. But there are answers.

Here is a drill to improve your ability to predict your line.

1. Find yourself a curvy road. A familiar one is best. A calm track day would also be perfect.
2. Back off your speed enough so you are certain you won?t run wide. Set your speed that way for each turn you enter.
3. Get the bike fully turned into the corner so you are happy with where it is pointed.
4. Begin your roll-on as soon as possible after #3 is settled.
5. Estimate where exactly you think the bike is going to be at its widest point on the turn?s exit. Don?t choose blind turns to do it. You are trying to predict at what point ahead you will come the. closest to the center line (in right hand corners on the road) or the road?s edge (in left hand corners on the road). Your final and widest exit point.
6. Maintain a fluid, seamless and continuous roll-on throughout the corner.
7. Do not adjust the steering or lean angle of the bike (unless you really have to).
8. Evaluate your estimate from #5. How did you do? How close were you to the point you thought was going to be your exit?
9. Experiment with slower and/or more aggressive roll-ons until you get the feel for what it takes for that bike to hold a predictable line.

Run Wide Adjustments

Here are some classic errors and problems that counter your efforts to maintain a predictable line:

Throttle errors:
1. You roll on the gas too soon. Before it is fully leaned into the turn.
2. You roll on the gas too aggressively. This over-extends the forks and increases speed too much, both make it run wide.
3. You roll on a little bit and stop. That alters your line. This counter-steers the bike up (wide again) when weight transfers forward.
4. You go on and off the gas in the turn. That makes the line unpredictable and it widens it.
Line Errors
5. You start into the turn too early, forcing a wider line through it .
6. You start into the turn too far to the inside, again this forces a wider line through the middle and exit of the turn.
7. The turn is too much of a decreasing radius turn. Do it in constant or increasing radius turns until you get the hang of it.
The Usual Bike Setup Errors
8. You have an overly stiff a spring in the front of the bike. That holds the front up too high and makes it want to run wide.
9. You have too much compression damping in the front end of the bike holding the front up too high. This makes the bike want to run wide.
10. The rear ride height of the bike is too low. This rakes the front out and tends to make it run wide.
11. The tires are worn and you have to fight the bike a bit to hold it in the turn. This also makes it run wide.
12. Too much rebound in the rear and too little in the front. This holds the back down and the front up. Wide again.

As Good As It Gets

How many turns it will take to build confidence in yourself and, eventually, the bike I can?t tell you. I do know that it will all come down to achieving a high degree of good, solid control of the throttle.

It goes like this: you can?t trust the bike or the tires until you can trust yourself and your right hand to do the right thing. That?s as good as it gets. It is a tried and true route to confidence and accuracy in your lines.

Very best,

Keith


? Keith Code, 2006, all rights reserved. Do not reproduce in any form, in any way without permission from the author.

[mike the hike]

[ Unfortunately, even after you have done it successfully in one corner there is no guarantee it will be solved in other turns!

Keith,

Thanks for yet another great article. It clears up my understanding of and thinking about throttle-control.
One question though.

I think that the above quote refers to the fact that you'll be leant-over for a longer period of time in one corner then in the other? And that you'll have to smear-out your throttle-control over a greater distance,
demanding that the actual roll-on has to be even more precise then in the shorter turns?
Is this a correct assumption? Or am i missing the point here?

Please clearify.

Greetings,
Mike

[R Sole]

So am I correct in thinking that trail braking (gently so as not to cause sudden deceleration and hence breaking away of the front tyre) into a corner decreases the trail of a bike and helps it turn in, and then rolling on slowly and constantly (again no suddent acceleration/deceleration) to move the suspension to a balanced configuration between front and back wheels settles/stabilisies and optimises the suspension during cornering?

And getting your wight far over allows for the bike to stay as far upright as possible to enable its suspension to be used in the right directions for maximum traction.

I am an engineer, and I love getting technical about these things, because it makes more sense if I can see teh applied mathematics of it. I see the cornering forces as the balanceing of moments (or torque) on the rider and bike (when looking at teh bike from the front) about the wheel traction points (where tire meets road). One monet is the combined inward component of teh weight weight of the bike and rider and countersteering gyroscopic force acting inwardly. The other moment is the centripetal acceleration acting outwardly on the mass of bike and rider at the centre of gravity of bike and rider.

So increasing speed in the corner increases the pentripetal force and hence moment acting outwardly, and needs to be balanced by increased lean angle and/or lower body height. Assuming body height is as low as you can get it anyway, then lean angle must increase (for additional weight component acting inwardly), or the countersteering gyroscopic force must increase by using more countersteering. Does anyone need a force diagram?

[R Sole]

I am still not quite sure why sudden deceleration in a corner cause teh wheel to break away though? Angular velocity changes, as does angular acceleration, but why does it make the traction break away?

Is it because the change in trail cause the bike to turn in more suddenly, changing the radius of the turn too quickly and increasing the centripetal acceleration so quickly that the friction of the tire is overwhelemed? This makes sense, as it is only the front wheel that gives way.
Also, you dont get that highsiding effect on bicycles (that do not have a suspension set up, with a changing trail).

[Eirik]

You have less grip available for braking during cornering because somewhere between 0 and 100% of the available grip (depending on angle and speed) is used to counter centrifugal forces.

[R Sole]

Keith - This may or may not be on the same topic, but you explain why "chopping" the throttle mid-turn causes the front end to break away?
After all the same forces apply, but the speed is decreased, so the forces acting outwardly on the bike should decrease, not increase to them to cause them to overcome the friction of the front tyre?

I came up with a few theories:
1) Perhaps the weight shift to the front of the bike causes the forks to dip, and the steering geometry to change, causing a quick change in turn in (i..e a suddenly decreasing turn radius) that increases the cenripetal forces due to the sudden changes in radius? To my mind then, this effect would not be seen in bicycles with no suspension? maybe a cyclist can confirm this?

2) Is it because the sudden deceleration causes the front tyre to start skidding, and the dynamic friction afforded by a slipping front tyre is a lot less than the rolling friction? Although this does not make sense as there si noreason the tyre would not just continure to roll?

[Cobie Fair]

R-

Not a physics guy, but think of it in terms of load/weight. If you exceed the weight/load the tire can handle, it will push.

CF

[R Sole]

Cobie Fair, on Feb 16 2010, 12:06 PM, said:

R-

Not a physics guy, but think of it in terms of load/weight. If you exceed the weight/load the tire can handle, it will push.

CF

So the chopping of the throttle results in the riders weight moving forward onto the front wheel, This additional force downwards on the forks has a downwards component and an outwards component. The acceleration outwards causes the friction from the tire to be overcome, and it to lose grip. Makes sense I guess.

Although an increased weight at the front wheel should also increas the friction from that wheel (as friction is proportional to force downwards)

[Eirik]

I can only talk from personal experience, which is that I have never* (in 30 years of riding) suffered a front wheel washout when chopping the throttle midcorner, or even getting on the brakes. However, if I do have to slow midcorner, for whatever reason - be that fear, starting to slide or facing unexpected obstacles - I simultaneously pick the bike up if I'm already at or close to full lean. I can pick it up a lot and brake very hard before easing up and leaning in again at a slower pace, or just pick it up a little and use just a bit of slowing, depending on available room etc. There is, though, little doubt that loading up an already heavily loaded front tyre with deceleration can cause it to overstep the available traction - hence the picking-up-the-bike thing.

*It has actually happened twice; once at moderate lean when I hit a big bump that sent me skywards and made me land on a locked front wheel. The other time was when I was faced with two cars coming towards me on a narrow road - no room left for me - and I locked up the front and went down. I think. I have no recollection of the incident after stopping one of the cars with my face However, I digress as neither of those episodes can be considered usual occurences

[R Sole]

My understanding is that you can get washout in two ways on the front wheel on corner (assuming decent speed to start off with).

The one is the situation above with overloading of the front wheel by sudden deceleration, and the other is almost the exact opposite - where you accelelrate hard out of the corner while still at a lean, and the resultant speed increases the outward force, and the weight coming off the front wheel reduced the capacity for traction.

Is this correct?

[Bongo]

That's right mate, if you power out so hard as to lift the front while leaned, the front can go. You do get more of an idea of this though over losing the front under deceleration, because you can usually feel the bars start to wave and flap slightly. You know you're accelerating about as much as you can then without picking the front up and losing it.

[toly900]

Bongo, on Mar 16 2010, 05:30 PM, said:

That's right mate, if you power out so hard as to lift the front while leaned, the front can go. You do get more of an idea of this though over losing the front under deceleration, because you can usually feel the bars start to wave and flap slightly. You know you're accelerating about as much as you can then without picking the front up and losing it.

If the front wheel is in the air then where can it go?
All the force is being taken throught the rear tyre
Even if you opened the throttle fully at full lean the rear would spin out not the front
The only way you can really upset the front tyre after corner entry to mid turn is to push really hard by re-steering and in this case you wouldn't be on the gas as you have already made the mistake and trying to correct it.
Even fighting the steering (adding lean)on a fast corner with the throttle on hard will result in reducing the grip from the rear not the front
Anyway this is way off topic from what is being said.The crucial thing for me to hold a line is timing when I get back on the gas which is determind by turn in which itself is dictated by the shape of the corner

[YNOT]

Bongo, on Mar 16 2010, 01:30 PM, said:

That's right mate, if you power out so hard as to lift the front while leaned, the front can go. You do get more of an idea of this though over losing the front under deceleration, because you can usually feel the bars start to wave and flap slightly. You know you're accelerating about as much as you can then without picking the front up and losing it.

Once your bike is leaned over, I believe Keith stated that you can take your hands off the handle bars (assuming throttle control), your bike will continue leaned and on its line. I have seen Biaggi wheelie while leaned over and continue on the rear wheel leaned over. He had to drop the front quickly in order to change direction. I had a similar experience coming out of turn 1 at Lightning, NJ going over the crest at mid lean, front wheel coming up, and I'm still leaning over. Lessen your grip which will lessen your tank slapper.

[Eirik]

YNOT, on Apr 5 2010, 05:20 PM, said:

Once your bike is leaned over, I believe Keith stated that you can take your hands off the handle bars (assuming throttle control), your bike will continue leaned and on its line.

I just read an explanation on this. Before this can take place, you will have to have reached a "balanced" state where the centrifugal forces are equal to the forces trying to pull you towards the ground, usually when leaned over about 50 degrees (due to the width of the tyres). When the bike is leaned over less, let's say 20 degrees, you cannot expect to maintain your line if you let go of the handlebars.

[Cobie Fair]

Eirik, on Apr 6 2010, 08:22 AM, said:

YNOT, on Apr 5 2010, 05:20 PM, said:

Once your bike is leaned over, I believe Keith stated that you can take your hands off the handle bars (assuming throttle control), your bike will continue leaned and on its line.

I just read an explanation on this. Before this can take place, you will have to have reached a "balanced" state where the centrifugal forces are equal to the forces trying to pull you towards the ground, usually when leaned over about 50 degrees (due to the width of the tyres). When the bike is leaned over less, let's say 20 degrees, you cannot expect to maintain your line if you let go of the handlebars.

There is an interesting shot in the Twist 1 (yes 1) video/DVD, that shows Keith on a CBR 1000 I think on a skidpad and leaned over, holding the throttle with 2 fingers, thumb and forefinger I think--has anyone see this shot recently? Don't think he has much pressure on the bars at that point.

CF

[Eirik]

I haven't seen the video - I'd be interested to hear how far he's leaned over. I should dig out the article and run the full explanation by you, although it will require me translating it from German.

Note that these are things that I am not really qualified to comment on because I do not fully understand all the physical laws involved, so all I can do is repeat what others say/write and combine the information with my own findings. And my own fidnings suggests that most bikes will need some steering input in order to follow a certain trajectory around most corners - for me, at least. The amount required have varied from next to nothing to substantial depending on the machine ridden.

[YNOT]

Cobie Fair, on Apr 6 2010, 06:16 PM, said:

Eirik, on Apr 6 2010, 08:22 AM, said:

YNOT, on Apr 5 2010, 05:20 PM, said:

Once your bike is leaned over, I believe Keith stated that you can take your hands off the handle bars (assuming throttle control), your bike will continue leaned and on its line.

I just read an explanation on this. Before this can take place, you will have to have reached a "balanced" state where the centrifugal forces are equal to the forces trying to pull you towards the ground, usually when leaned over about 50 degrees (due to the width of the tyres). When the bike is leaned over less, let's say 20 degrees, you cannot expect to maintain your line if you let go of the handlebars.

There is an interesting shot in the Twist 1 (yes 1) video/DVD, that shows Keith on a CBR 1000 I think on a skidpad and leaned over, holding the throttle with 2 fingers, thumb and forefinger I think--has anyone see this shot recently? Don't think he has much pressure on the bars at that point.

CF

Nice plug Cobie. You just reminded me that I need to buy the DVD.

[Eirik]

From the MOTORRAD pamphlet, freely translated:

Leaned over 15 degrees, you would normally have to keep some pressure on the inside handlebar. Due to the tyre contact patch being off centre, the resulting force will try to turn the wheel further into the corner. Uncorrected, this will cause the bike to right itself.

Leaned over 50 degrees, very little steering torque steering remains and the centrifugal and gravity forces equal each other, hence little or no steering inputs are required to stay on the chose line. The reason this happens first around 50 degrees from vertical and not at 45 degrees is a result of the tyre width moving the patch of contact off the centre line.

[Cobie Fair]

Quote

Nice plug Cobie. You just reminded me that I need to buy the DVD.

I'm pretty shameless about plugging that stuff, aren't I?

It's been around, looks a little older, but it's not like the information isn't still applicable. I even worked in that video too--I remember diong one scene where I was supposed to miss a car on a curvy road. I was crowding the yellow line a little bit, and the car (driven by the director), was supposed to be a little over the yellow. Well, he was WAY over the yellow, and I really did darn near hit him! Not much acting needed in that scene

Best,
CF