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 To accelerate or remain constant, that is the question
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(Deleted or Lost)

Posted - 06/16/2011 :  8:23 PM
Change of tack.

What are the advantages of the roadcraft manual's approach to cornering (which I paraphrase as being):
  • Set a speed on approach to the corner, which allows you to stop within your lane and within the distance that's seen to be clear
  • Enter the corner and adjust throttle after/during tip-in to account for cornering losses and hence keep speed constant.
  • Track through the corner maintaining chosen speed and keeping a keen observation of the the road and limit point
  • Adjust speed if the limit point indicates to do so
  • On the exit side of the corner, start to bring the bike back to vertical and accelerate gently (if desired) if the limit point moves away - keep in mind the posted speed limit

It probably goes without saying that if the throttle position remains as is, the bike will naturally accelerate as it stands up on the exit phase of the corner.


When I look at the above listed cornering approach, the key advantage I see is that it gives the rider the time and space to stay fully appraised of the road, environment and traffic conditions. There are no assumptions about what's beyond the limit point and hence all control inputs are robust and safe.

A constant cornering speed is preferred to a decelerating scenario for a bunch of reasons - some of which are: a more balanced bike, less traction demand on the front wheel, traction demand remains constant if the trajectory remains constant...

One of the other advantages I suppose is the lack of the "woo hoo!" factor. A rider that is gently accelerating through a corner will be feeling the weight transfer, forces and speed increasing, which could distract them from the task at hand.

Any others?




quote:
James said:

Stability is not traction.

Stability is the tendency of your motorcycle to maintain both its course of travel and 'attitude' (lean angle, for example).
I agree. Many authors are not using the word stability in it's correct definition.

What term should one use to describe the increased "feeling" of "sure footedness" (for lack of a better word) between coasting through a corner, versus a constant speed through a corner, versus maintaining gentle acceleration through a corner? Each feels more "stable" than the one before.
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Arnold
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Santa Monica, CA
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Kawasaki

KZ1000

Posted - 06/16/2011 :  9:38 PM
Sorry to jump in here but I have a confusion about something. All things being equal, I can't understand why the tractions would not be LESS in a turn.

Picture in your brain a motorcycle driving in a straight line at a constant speed. Now imagine an incrementally increasing force pushing laterally on the motorcycle. (lets use wind as an example, although I am picturing in a my brain something that is just a constant lateral force) Eventually the force would become strong enough to break the traction on the rear tire and the motorcycle would start to skid/slide.

Now imagine a motorcycle driving in a constant speed around the circumference of a circle. would it not take a lesser lateral force to break the traction of the rear tire???? Even if there is more weight pushing down because of the gravity, then if there is more weight pushing down this will give you the traction?????

Thanks

Arnold
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James R. Davis
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Posted - 06/16/2011 :  10:20 PM Follow poster on Twitter  Join poster on Facebook as Friend  
Arnold,

Slow down and go a step at a time.

centrifugal force does NOT add traction,it adds traction demand and diminishes available or 'reserve' traction. Increased speed in a turn does not add traction, it increases traction demand and reduces the available or 'reserve' (unused) traction. Increasing speed (acceleration), whether going in a straight line or riding in a curve, increases rear wheel traction because of weight transfer.

A tire has a given "fixed" amount of traction for any roadway surface/tire combination and weight being carried. Add weight, the amount of traction increases.

A motorcycle traveling in a curve has centrifugal force (lateral acceleration) that essentially pushes sideways, but not downward. Thus, the weight carried by the tire does not change and therefore the amount of traction available does not change unless there is acceleration.

The rider feels heavier because his bike is always leaning in exactly the direction pointed to by the combined gravitational and inertial (lateral acceleration) demands. His shocks will compress and that is proof that weight is added IN THAT DIRECTION, but no weight is added in a vertical direction, therefore traction is neither increased nor decreased as a result of speed. There is a tiny difference that results from an increased slip angle a tire generates when it is moving in the same curved path with higher speed than with lower, but that trivial gain is lost as a result of increased traction demand that increased centrifugal force consumes.

(I think I stated all of that correctly < grin >.)

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(Deleted or Lost)

Posted - 06/16/2011 :  10:55 PM
quote:
Originally posted by James R. Davis



centrifugal force does NOT add traction,it adds traction demand and diminishes available or 'reserve' traction. Increased speed in a turn does not add traction, it increases traction demand and reduces the available or 'reserve' (unused) traction. Increasing speed (acceleration), whether going in a straight line or riding in a curve, increases rear wheel traction because of weight transfer.

A tire has a given "fixed" amount of traction for any roadway surface/tire combination and weight being carried. Add weight, the amount of traction increases.

A motorcycle traveling in a curve has centrifugal force (lateral acceleration) that essentially pushes sideways, but not downward. Thus, the weight carried by the tire does not change and therefore the amount of traction available does not change unless there is acceleration.

The rider feels heavier because his bike is always leaning in exactly the direction pointed to by the combined gravitational and inertial (lateral acceleration) demands. His shocks will compress and that is proof that weight is added IN THAT DIRECTION, but no weight is added in a vertical direction, therefore traction is neither increased nor decreased as a result of speed. There is a tiny difference that results from an increased slip angle a tire generates when it is moving in the same curved path with higher speed than with lower, but that trivial gain is lost as a result of increased traction demand that increased centrifugal force consumes.

(I think I stated all of that correctly < grin >.)


James, I'm assuming your statements are in reference to a curved path on a flat horizontal surface. How does the weight and therefore traction picture change for a positively cambered corner?
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(Deleted or Lost)

Posted - 06/17/2011 :  2:32 AM
...was just looking through the safety tips for another reason and Tip 39 leapt out at me. It would seem to be pertinent to the topic at hand. Tip 39, Handling in a curve. http://www.msgroup.org/Tip.aspx?Num=039

The tip is well worth a read - in fact, it should be read in it's entirety to get the full picture - I've repeated what I thought were the relevant parts as they relate to this thread.

I will presume that the tip answers my earlier question regarding an alternative word for stability - that word being "handling".

quote:

Handling Curves
A better line

By: James R. Davis


Taking curves is rather a personal choice in terms of selection of entry and exit points as well as speed, it seems to me.

...

...I stay to the outside edge well past the normal entry point, then turn much more sharply into it and hit the inside much beyond the normal apex.

...





...I TRY to overshoot my entry to a curve. Then I aggressively push-steer into it, and delay reaching the inside of the curve well past its apex. This also, incidentally, allows me to start an aggressive roll-on of my throttle sooner than when I am at the inside of the curve which gives me a better handling bike through the majority of it. I should add that this delayed entry approach requires that you get in the habit of not entering the curve too fast. Further, the right approach speed is one which requires NO BRAKING at entry.

[You should use MODEST throttle roll-on all the way through any curve. The 'roll-on point' that is shown in the graphic is where you can go after a higher exit speed if you happen to be aggressive with your bike.]

...

This method is just my preference, after all, and it seems to me is generally safer than the 'smoothest line' method usually described.



Is there a definition for "handling"?

What is it about the modest throttle roll-on approach to cornering that improves "handling"? Most riders would describe this sensation as "stability" in that the bike feels solid, stable and controlled, rather than stable in terms of it being more likely to maintain it's direction. Is this "sensation" purely a suspension position thing (as described by Lee Parks), or is it a traction increase and suspension position thing (as described by Keith Code)? Or a slip angle thing?? Or is it about extending the front forks so therefore adjusting steering geometry back to a more stable inducing configuration? Or unloading the front tyre? Or a combination of these factors? Or??


Seems like part of the answer is in Tip 128 "Braking in a curve" http://www.msgroup.org/Tip.aspx?Num=128 ...in part copied below for reference.


quote:

Braking In A Curve
(Of course you can)

By: James R. Davis

... he described a situation that he confronts every day which seems to defy what he was told in his MSF class - a long curve on a steeply declining slope.

... his instructor told him that he should establish his entry speed before he enters the curve and that he should gently accelerate all the way through the curve. He finds it impossible to do - safely - and asked for advice.

He is right! It is impossible to safely accelerate (using the throttle) all the way through a long steeply declining curve, and that is NOT what the MSF has tried to teach.

There are several intents of the MSF range exercise that the man refers to.
  • You should establish your entry speed BEFORE you enter the curve... while still traveling in a straight line and while the bike is vertical.

  • You should 'set' your suspension BEFORE you enter the curve. That is, you should NOT have to deal with a changing center of gravity that results from weight shifts that are caused by changes of acceleration or braking while in a curve. You should have already established your entry speed at this point so your springs/shocks are resting at normal riding positions. But because you want maximum control of your bike through the turn, you want your front tire to be able to handle modest bumps and surface distortions without destabilizing your bike so you want to shift some weight to the rear tire. That increases rear tire traction, loads the rear shocks/springs some what more than the front, and increases over-steer. And you want that attitude all the way through the curve so you maintain a modest acceleration all the way through it.

All of which sounds like you should accelerate all the way through a curve, I know. But, NOT IF YOU ARE ON A DECLINE!

To begin with, you know that you must lean the bike in order to make a turn. That the faster you go through a given turn, the greater the lean that must be used. Clearly you can accelerate to a speed that is beyond your ability to negotiate a turn. Thus, if you modestly accelerate all the way through a turn it must be that you established a low enough entry speed to allow it, and that you did not use excessive acceleration through the turn.

...

And, because you are on a decline, there is already more weight on the front tire than you can safely shift to the rear via acceleration to give you the handling stability that is sought from acceleration without exceeding your ability to negotiate the turn.

...


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James R. Davis
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Posted - 06/17/2011 :  3:54 AM Follow poster on Twitter  Join poster on Facebook as Friend  
Time out!

I respect that you have used my own words to more or less prove your point, but it is a matter of emphasis more than definition, and personal preference. I believe I made it clear when I described the late apex turn method that I happen to prefer it over a simple outside-inside-outside (single radius) method because it involves steeper lean angles which I crave when canyon carving.

For example, in the situation you last referenced in which I describe a late apex or late entry path of choice, I was trying to explain why *I* like to use that method over a simple outside-inside-outside (smoothest) line through a curve. The smoothest line is probably the safest line for most riders, but there are some decided advantages to using a late apex method that makes it right for the kind of riding I prefer (which is mildly aggressive).

Maintaining speed throughout a curve goes hand-in-hand with 'smoothest line throughout' - it is NOT mildly aggressive, it is easiest and probably the most stable. Nevertheless, I believe that the late apex method may be slightly safer, generally. (Unless your implementation of it is AGGRESSIVE instead of 'mildly aggressive' behavior. And here you see where I was coming from when I said that it is a matter of emphasis rather than definition. Used to maximize exit speed, a late apex method is VERY AGGRESSIVE (and not in any way 'safer'), but used to maximize sight lines it is merely mildly aggressive (and due to better sight lines, slightly safer) - though in either case it is a late apex.)

Choosing when to roll-on the throttle as described assumes that you HAD TO SLOW DOWN BEFORE ENTERING A CURVE. If you are riding along at 65 MPH and encounter a bend in the road that does not require any braking prior to entering, it sure doesn't require acceleration of any kind either during the bend or after.

'Stability' is not simply maintaining a path of travel. Stability includes 'attitude' as well as direction. In other words, constant yaw, pitch, roll, steering efficiency (under- and over-steer), response to perturbations (harmonic damping), and the all inclusive 'feel' of the motorcycle.

When teaching newbies, the single radius (outside-inside-outside) method is smoothest and easiest for them to perform, and the maintenance of a constant speed throughout is absolutely the safest method for them to handle a curve. There is nothing aggressive about it and 'stability' is maximized. You introduce late-apex methods to somewhat more experienced riders as a method to explore concepts that they might find valuable such as how to adjust sight lines and how to position a bike for the earliest possible point at which they can become more aggressive in the use of their throttle. 'Stability' is anything but maximized with this method, by definitions, as you have more than one radius to steer through the turn.

Different strokes for different folks.

All of this discussion in response to a statement that it is a myth to think that acceleration causes stability? It's like declaring that acceleration 'loads the rear shocks' as if there is ever a time (so long as the rear wheel is on the ground) that the rear shocks are not 'loaded'? Clarity requires understanding context, not just definitions.
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(Deleted or Lost)

Posted - 06/17/2011 :  9:41 PM
Thanks for your response James.

A noob who peruses your articles (as I did when I was a noob) could not be blamed for drawing the conclusion that there are clear benefits in accelerating throughout a curve, even if they didn't read tip 39 to find that it's only a preference.

This view would be and is reinforced by motorcycling literature, motorcycling website tip sections and motorcycling schools, all advocating the accelerating through the curve approach - all stating that it improves suspension compliance, bike control, stability, traction, handling, etc. or some combination of these factors.

The balance of conventional wisdom then is on the side of advocating modest acceleration through a corner. Like you I think it has some substantial safety benefits.


quote:
'Stability' is not simply maintaining a path of travel. Stability includes 'attitude' as well as direction. In other words, constant yaw, pitch, roll, steering efficiency (under- and over-steer), response to perturbations (harmonic damping), and the all inclusive 'feel' of the motorcycle.
So much about motorycling is "feel". But we all know that motorcycling dynamics is a true animal of physics and therefore definable and logical.


quote:
When teaching newbies, ... the maintenance of a constant speed throughout is absolutely the safest method for them to handle a curve. There is nothing aggressive about it and 'stability' is maximized.

So then we come to one of the fundamental questions of this thread. I'm confused by possibly conflicting statements: stability is maximised by a constant speed cornering approach and modest acceleration maximises "handling stability". Are these statements both correct and therefore can coexist? Could you please comment? What is maximised in either scenario?



quote:
All of this discussion in response to a statement that it is a myth to think that acceleration causes stability?
The myth is NOT that acceleration causes stability, but that it maximises "stability". Clearly it maximises "something" about motorcycling dynamics, otherwise it wouldn't be taught.


The roadcraft manual talks about stability and grip being maximised by constant speed cornering. It equates grip with stability and in doing so gives the impression that anything that maximises grip maximises stability. This tripped up my eye because it flies in the face of the bulk of conventional cornering wisdom... which caused me to talk my learned mate Rob and hence the creation of this thread...

Edited by - Robsalvv on 06/17/2011 10:15 PM
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James R. Davis
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Posted - 06/17/2011 :  10:37 PM Follow poster on Twitter  Join poster on Facebook as Friend  
No matter how hard I've tried to describe stability as consisting of a wide range of component measurements, some of which being extremely difficult even to define such as 'feel', and even though I've used the term 'attitude' on several occasions within this discussion, we come again to definitions of 'it' (remember the similar trouble with defining what 'is' is?).

A bike is absolutely stable if NOTHING changes about it as a result of your input. That bike would be PARKED, engine off, resting on its side-stand with you sitting in the saddle.

Suggesting that 'loading the rear shock' resulting from acceleration increases stability is contradictory on its face. Further, it implies that what happens to the rear-end of a motorcycle is somehow more important than what happens to the front-end - a contention that I do not agree with at all.

When you accelerate, the CG of a motorcycle raises and its wheelbase shortens. That increases its weight transfer ratio at the same time that it shifts weight from the front to the rear of the motorcycle. Who can claim that these things are 'increased stability'? Not me.

When you shift weight off the front tire, you reduce its traction. Who can argue that doing that increases stability? Not me.

When you accelerate, you increase speed. The faster you go, the lighter the front-end of a motorcycle becomes. Who can argue that that increases stability? Not me.

When you accelerate, you decompress the front shocks as you compress the rear shocks. Even if you argue that compressing the rear shocks increases stability, can you simply ignore the fact that the front shocks are decompressing? Not me.

The smoothest, most stable, path through a constant radius turn is the largest single radius path contained within that curve. If your acceleration through that turn is not constant, then you are constantly CHANGING the dynamics of the bike. Clearly that is not maximizing stability. But if you use constant acceleration, your bike's lean angle is CONSTANTLY CHANGING. That, too, is an example of changing stability - constantly.

Shocks are not perfectly compliant - else you would never feel any roadway perturbations. They are more compliant at some speeds as compared to others. Acceleration increases speed - ergo, the dynamics of the suspension changes. This is not an example of increased stability. Perfect example of that is riding a scooter over cobblestones. At slow speeds, you can manage quite well, but at higher speeds you loose control. Increased stability? Of course not.

Some bikes get 'twitchy' at particular speeds. That is, the front-end finds something harmonic in its response to perturbations in the roadway and exaggerates that response. When you accelerate you constantly change speed - and at the same time change how the shocks respond to those perturbations. Who can claim that because the rear shocks have less tendency to become 'twitchy' while the front ones have more tendency to become 'twitchy' that that is an increase in stability? Not me. (If anything needs to be 'stable', from this man's experience, it's the front-end. I've experienced a tank slapper, thank you very much, and I can assure you it wasn't the result of an unstable set of rear-shocks.)

Get the picture? The more CONSTANT you can make the environment that a motorcycle must deal with, the more 'stable' it is. Acceleration is the antithesis of making the environment constant.

By the way, I accept full responsibility for the fact that a newbie reading some of my 266 safety tip articles could easily end up getting mixed messages from those writings. They were written one at a time over a period longer than a decade and each had a different 'message' that I was trying to get across. They were presented in the order they were written rather than a logical order progressing from fundamental information and growing to more advanced information while relying on the assimilation of the prior material. - that is, they were disjointed.

Along the way I learned a few things and those new things ended up in the later articles - sometimes with a somewhat conflicting argument from earlier articles. Where I recognized that happening, I edited the articles. When an error was found in an article, it was corrected. Still, those articles have substantial merit individually (I hope) and cumulatively, even though they are disjointed in their presentation.

The book we just published (Motorcycle Safety and Dynamics) is certainly consistent within itself and is anything but disjointed in its presentation of information.

quote:
The myth is NOT that acceleration causes stability, but that it maximises "stability". Clearly it maximises "something" about motorcycling dynamics, otherwise it wouldn't be taught.


What is 'maximized' is a belief in the myth. It used to be taught by all learned men that the earth was flat.
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rayg50
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Shadow Spirit 750DC

Posted - 06/18/2011 :  7:39 AM
quote:
Like you I think it has some substantial safety benefits.

Robs, let me thank you for an interesting topic. I enjoy re-evaluating my personal thoughts/beliefs on any "topic" in life from time to time. For me it is a constant occurrence but I actually set one day aside with that specific task at the heart of it.

I have followed this one with 2 emotions one of great interest and the other of great discomfort. Let me expand a bit on the discomfort. The sources of my discomfort are the claim of increased safety benefits and the comparison to Roadcraft

Let us take the first, safety. When looking at any system all parts must be evaluated not just as individuals but as part of a whole in accomplishing a task. Let us assume that 2 riders enter a curve below the traction limit. Both will negotiate the curve regardless of maintaining or increasing speed. 2 riders that enter the curve above the traction limit will have the same result (failure to negotiate) regardless of methodology. Now comes the food for thought, 2 riders entering the turn barely below the traction limit. IMO the one that maintains his entry speed will negotiate the turn the one that accelerates will not. How can I personally possibly come to the conclusion that accelerating in a curve is the "safer" method?

On to my second source of discomfort, the comparison to Roadcraft. From my readings of authors such as KC I have come to the personal conclusion that they have some good thoughts however IMO much of their teachings have the subcontext of speed. They are not necessarily proposing the best way to do something to reduce risk IMO they are proposing the best way to do something to reduce risk in order to go fast. By way of example I expect a Roadcrafter (new word?) to advise me to slow from 40 to 25 before entering a curve with a posted advisory limit of 25. In short to be off the brakes before entering an area where poor brake use can be a bad thing. I would expect a KCer to tell me to brake later and enter it above the 25 and to still be on the brakes through the initial part of the curve (gradually releasing them of course) in order to get to the 25 while in the curve. Faster, yes, safer, IMO no.

While you can choose to pick a word or a concept and do a comparison I think it is apples and oranges. The context is completely different and therefore IMO makes the concepts very different in goal and philosophy. If you disagree please go to the track and tell the riders they must maintain a safe following distance.

Other than my discomfort with the above, the thread has given me a great opportunity to revisit, and in this instance reaffirm, certain concepts.

Ray

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(Deleted or Lost)

Posted - 06/18/2011 :  8:15 AM
quote:
Originally posted by James R. Davis


quote:
The myth is NOT that acceleration causes stability, but that it maximises "stability". Clearly it maximises "something" about motorcycling dynamics, otherwise it wouldn't be taught.


What is 'maximized' is a belief in the myth. It used to be taught by all learned men that the earth was flat.


I think that your point about stability has been well made. A constant acceleration requiring a constantly changing lean angle is anything but stable. Then could you please explain the comment in one of your tips, that modest acceleration in a curve maximises "handling stability". What does this mean?


266 tips condensed into an internally consistent book... that will worth a look. Good luck with it's success.

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James R. Davis
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Posted - 06/18/2011 :  8:30 AM Follow poster on Twitter  Join poster on Facebook as Friend  
It means that you use MODEST acceleration to maintain speed that is lost from the fact that you are in a turn. It would have been better for me to have said that you use a little more throttle through the curve than before or after it.
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(Deleted or Lost)

Posted - 06/18/2011 :  9:42 AM

quote:
Originally posted by James R. Davis

It means that you use MODEST acceleration to maintain speed that is lost from the fact that you are in a turn. It would have been better for me to have said that you use a little more throttle through the curve than before or after it.


?? I'm sorry James, but that answer confuses me.

You state that modest acceleration throughout a turn maximises "handling stability" and shifts weight rearward. Modest acceleration throughout the turn implies increasing speed throughout the turn - not just a replacement of otherwise lost speed, but an actual increase in speed. That seems at odds with your comment above.
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James R. Davis
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Posted - 06/18/2011 :  9:44 AM Follow poster on Twitter  Join poster on Facebook as Friend  
Yep, I'm simply unable to be clear with my writings. You got me. Congratulations.
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(Deleted or Lost)

Posted - 06/18/2011 :  10:02 AM
James, it's not about "getting" you, it's about understanding what's been said. Surely you see that?
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(Deleted or Lost)

Posted - 06/18/2011 :  10:04 AM
quote:
Originally posted by rayg50


Let us take the first, safety. When looking at any system all parts must be evaluated not just as individuals but as part of a whole in accomplishing a task. Let us assume that 2 riders enter a curve below the traction limit. Both will negotiate the curve regardless of maintaining or increasing speed. 2 riders that enter the curve above the traction limit will have the same result (failure to negotiate) regardless of methodology. Now comes the food for thought, 2 riders entering the turn barely below the traction limit. IMO the one that maintains his entry speed will negotiate the turn the one that accelerates will not. How can I personally possibly come to the conclusion that accelerating in a curve is the "safer" method?

Hi Ray, it goes without saying, and it's said in the tips, in order to use mild acceleration in a corner, you must first enter at a speed that gives you scope to accelerate.


When I was working through the CSBS levels, our instructors made the point that modest acceleration through a corner wasn't specifically about a track or racing technique. Modest acceleration works with the bike's design and gives a platform for the greatest bike control. That's not to say that the technique is the best technique to use on the road in all circumstances, but when coupled with a wide and late entry that maximises your sight lines, it has a lot going for it.

So those two riders of yours entering a corner at a near maximum available traction speed... well, they'd be going in pretty darn fast! I suspect they'll have a few other issues to deal with - accelerating through the turn will be their last priority!


quote:

On to my second source of discomfort, the comparison to Roadcraft. From my readings of authors such as KC I have come to the personal conclusion that they have some good thoughts however IMO much of their teachings have the subcontext of speed. They are not necessarily proposing the best way to do something to reduce risk IMO they are proposing the best way to do something to reduce risk in order to go fast.
I disagree. They propose a technique which is consistent with the design of the motorcycle. It's prime goal is not a track goal, it's a bike goal. Increasing traction of the rear tyre has positive benefits for getting through a corner. Taking some weight off the front tyre has some positive benefits for dealing with road irregularities. So you see, they are not focussed on getting around a track faster, though that might end up as an outcome.


quote:

By way of example I expect a Roadcrafter (new word?) to advise me to slow from 40 to 25 before entering a curve with a posted advisory limit of 25. In short to be off the brakes before entering an area where poor brake use can be a bad thing. I would expect a KCer to tell me to brake later and enter it above the 25 and to still be on the brakes through the initial part of the curve (gradually releasing them of course) in order to get to the 25 while in the curve. Faster, yes, safer, IMO no.
For riders working through the four levels of KC's CSBS cornering schools, braking is discussed as follows: A rider should set their speed early and be finished with their braking before they arrive at the entry point. This means the bike enters at a constant speed and in a balanced condition. Trail braking may be taught in their racing courses, but not in their cornering courses.

I'm happy to talk about how riders progress towards trail braking, but with respect, I must correct your assertion that this is a KC taught cornering technique.



quote:

While you can choose to pick a word or a concept and do a comparison I think it is apples and oranges. The context is completely different and therefore IMO makes the concepts very different in goal and philosophy. If you disagree please go to the track and tell the riders they must maintain a safe following distance.
Well in this case I chose to focus in on one particular aspect of motorcycling physics. The larger picture of cornering goal and philosophy was irrelevant. Roadcraft says constant speed = maximum grip and maximum stability. Most of the rest of the world says modest acceleration provides maximum traction or maximum stability (which I think means control/handling). One of them is right. It's that simple. This is not an apples and oranges thing. It's a science thing.



quote:
Other than my discomfort with the above, the thread has given me a great opportunity to revisit, and in this instance reaffirm, certain concepts.

Ray


Cheers Ray, just so long as your thought processes have placed the "opposing" technique in the right light! It's always good to test what you take forgranted and if that testing confirms it's validity, then all the better.
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James R. Davis
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Posted - 06/18/2011 :  10:13 AM Follow poster on Twitter  Join poster on Facebook as Friend  
Here's what I 'see' ... you want to prove a point using my words. You CERTAINLY understand the issues already presented as evidenced by your ability to zero in on any discrepancies in those words that tends to support your point of view. I applaud you for your tenacity, your understanding, your 'staying power', but I'll not now venture into another discussion of what 'feel' means and whether that is 'stability' or not. Suffice it to say that many if not most riders 'feel' that their bikes are better 'planted' in a turn when accelerating. Maybe that's good enough for those riders and is sufficient 'understanding' on their parts, but I thought we were trying to understand the dynamics, not define 'feel'. In any event, I'm apparently unable to do so with any degree of competence.

So, you win. Surely you see that?
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James R. Davis
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GoldWing 1500

Posted - 06/18/2011 :  10:21 AM Follow poster on Twitter  Join poster on Facebook as Friend  
When a discussion becomes a discussion of and critiques of the information presented by only one side of that discussion, where no new information is contributed, it is merely a critique. When you offer information in support of your opinion, I'll be happy to reengage.

Does maintaining constant speed or increasing speed result in the highest amount of 'stability' in a turn? Why?
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rayg50
Male Moderator
2082 Posts
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NYC, NY
USA

Honda

Shadow Spirit 750DC

Posted - 06/18/2011 :  4:42 PM
quote:
Cheers Ray, just so long as your thought processes have placed the "opposing" technique in the right light! It's always good to test what you take forgranted and if that testing confirms it's validity, then all the better.
Cheers Rob, I am hoping that you will help in putting the technique in the right light.

My current challenge centers on the claim of added safety. I gave you a scenario to which your response was
quote:
So those two riders of yours entering a corner at a near maximum available traction speed... well, they'd be going in pretty darn fast! I suspect they'll have a few other issues to deal with - accelerating through the turn will be their last priority!
Which I interpret as "they shouldn't do that". So I will pose my question differently. How can a technique that has a higher possibility of failure be the safer technique?


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Baggsy
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720 Posts
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Ottawa, Ontario
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Suzuki

09 Wee

Posted - 06/18/2011 :  10:43 PM
quote:
Originally posted by James R. Davis

When a discussion becomes a discussion of and critiques of the information presented by only one side of that discussion, where no new information is contributed, it is merely a critique. When you offer information in support of your opinion, I'll be happy to reengage.

Does maintaining constant speed or increasing speed result in the highest amount of 'stability' in a turn? Why?



Could that not be dependent on the bike/rider combination? i.e. a bike is designed to have it's optimum weight distribution between front and back during mild acceleration?

That's not to say that said weight distribution would not affect lateral stability in a negative way, or that said bike would be stable during deceleration. That's a wide open question.



Edited by - Baggsy on 06/18/2011 10:52 PM
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James R. Davis
Male Administrator
17292 Posts
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Houston, TX
USA

Honda

GoldWing 1500

Posted - 06/19/2011 :  5:35 AM Follow poster on Twitter  Join poster on Facebook as Friend  
quote:
Could that not be dependent on the bike/rider combination? i.e. a bike is designed to have it's optimum weight distribution between front and back during mild acceleration?

I have no idea what that means.

You think it's possible that Yamaha, for example, designs a bike to have a specific (optimum) weight distribution when it has a rider who weighs 173 lbs. in the saddle, half a tank of gasoline, and is accelerating at 0.15g's? Why would they do that?

What about if the rider eats a big meal first?

What about if he adds a passenger? Must he go on a diet for a year first?

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