Countersteering: Continual Or Once?

[Mapless]

Hey guys, I've searched all through the board and can't find clarification on this.

 

Here's what I PM'd Mr Code, maybe you guys could help shed some light on this as well (although considering the argument in question, anyone other than the author will likely be dismissed by my 'opponent').

 

I'm writing to you in order to ask for your assistance in clarifying a point in your book, 'a Twist of the Wrist II', in which you repeatedly state that 'One steering action per turn is perfect'.

 

I'm in a bit of a debate in an internet forum (hard to imagine a debate in one of those eh?) located at: http://forums.somethingawful.com/sh...hreadid=1893638

 

I take your statements to mean that in a steady-state corner, one could conceivably remove their hands from the bars (assuming you could still roll the throttle on throughout the turn while doing so) and a bike that's properly set up would continue to track throughout the radius of the turn.

 

My 'opposition' is of the opinion that upon taking the hands off the bars, the bike will stand up and run wide, that you MUST maintain a constant pressure on the bars in order to countersteer throughout the turn. He insists that your definition of 'one steering action' INCLUDES that constant pressure during the turn itself.

 

We're also at odds concerning your recommendation to 'get on the throttle as soon as possible' in a turn.

 

I take that to mean that one WOULD accelerate throught the course of a turn, verses merely cracking it open and holding the throttle at a steady rate, waiting to resume actual acceleration upon reaching the exit point.

 

So there it is. At this point I just want the guys on our board to get the right information, whether I'm right or wrong.

 

Thanks, you guys have an awesome community here.

[Woody]

One steering input is just that, one steering input (well, it's actually two, one to enter the corner and one to exit).

 

When you push on the bar to turn the bike, the front wheel points toward the outside of the corner and two things happen:

1/ the front wheel tries to move toward the outside of the corner, and

2/ the spinning wheel acts like a gyroscope and through some complicated physics, tries to turn through the third axis (lean).

Both of these effects cause the bike to lean into the corner (the effect of the first is far more potent than the second). With the bike leant over, when you release the pressure on the bars the front wheel then turns the other way and points into the corner, following the arc of the turn. This happens naturally and is caused by the steering geometry of the bike (ever leant a bicycle whilst holding onto the seat? Same thing happens, the front wheel points into the corner).

So yes, in order to steer through the corner, you must release pressure on the bars otherwise you'd keep leaning and eventually fall over.

 

Once you have turned the bike (leant it over) the line that the bike takes through the corner is also affected by the throttle (the speed of the bike). Keep the speed constant (throttle on slightly, giving the 60/40 weight distribution that Keith talks about in his books) and the bike tracks a constant radius. Wind on the throttle a little more and you will need more lean to keep turning at the same rate (there are exceptions of course, but I'm not talking about body position or rear wheel steering just yet ).

It is important to note that you should be looking to keep the bike at maximum lean for the shortest amount of time possible, after which time you will be exiting the corner.

A basic plan should be something like this:

1/ set your entry speed

2/ apply a steering input to turn (lean) the bike

3/ once the bike is leant, get on the throttle to stabilise the bike and keep the line constant

4/ when you start to exit, apply another steering input to start picking the bike up and apply more throttle as the bike starts to stand up.

The transition should be smooth and generally everything flows from one to the other very quickly.

 

 

Think that makes sense, but I'm sure someone will say if it doesn't...

[racer]

Hey there Mapless,

 

I take your statements to mean that in a steady-state corner, one could conceivably remove their hands from the bars (assuming you could still roll the throttle on throughout the turn while doing so) and a bike that's properly set up would continue to track throughout the radius of the turn.

 

I can't speak for Keith and I haven't read Twist II; but, I would tend to agree with this idea.

 

I believe one of the non-rider factors contributing to a motorcycle's tendency to stand up or continue to fall in once lean angle has been established is the construction and profile of the tires and the degree of wear which will also affect the shape, and hence, the profile.

 

If you view the crown of a tire from head on you will notice that some tires have a taller or shorter or rounder or sharper profile. Without getting into the differences in handling characteristics of different profiles or bias ply vs radial (do bias ply tires still exist or am I a dinosaur), it is my belief that one of the things that may be happening with bikes that want to stand up or fall in is that the shape of the tire has been significantly altered due to wear. Specifically, the pattern of wear which will reflect how the bike is ridden.

 

Imagine the average street rider who uses their motorcycle for general transportation and, perhaps, some weekend canyon carving. Even though they may use all of the tire in the canyons by getting leaned over all the way to the edge (no chicken strips), they probably aren't dragging footpegs around town. The majority of their riding is not done at full lean angle. Hence, the wear pattern of the tire will reflect that. Most of the time they will be leaning over to a point someplace before the edge to varying degrees. Wherever that point of usual lean is, the roundness of the tire will be worn a bit flat prior to that point and a discernible ridge or shoulder will develop over time. And since, no matter how many corners we take, the majority of most street riding is done on straight pieces of tarmac, the entire tire profile will tend to be worn kinda flat. Flatter than when the tire was new. And flatter and flatter the more the tire wears. The profile becomes "squared off" a bit.

 

Now, picture that "squared off" profile with a shoulder somewhere partway down the side of the tire and imagine trying to balance the bike on that ridge. It doesn't wanna do it. It wants to roll off that point, either toward the edge (falling in) or back toward the crown (standing up). Replacing worn street tires significanty changes the way that bike feels and handles. Restoring those confidence inspiring smooth and consistent transitions from one lean angle to another, it's like a brand new bike. (Insert Dunlop logo here.)

 

In any case, I think that is one reason why some street bikes may feel unstable at lean. There may be other mechanical reasons having to do with suspension or geometry, rake and trail, etc., or... rider inputs and instability on the bike.

 

Which leads to the next issue...

 

We're also at odds concerning your recommendation to 'get on the throttle as soon as possible' in a turn.

 

Your "opponent's" belief that getting back on the gas is not a priority might be leading him/her to, in fact, NOT GET BACK ON THE GAS. This would have major implications for mid-turn stability. Primarily, the tendency for the bike to run wide as it decelerates creating the need to push the bike down further to maintain turn radius, and, hence, the perception that the bike is standing up. (Because I keep having to push it down, it must be standing up.)

 

Perhaps you should suggest he/she try getting back on the gas and see if that cures the need for ongoing steering input. Or perhaps you might simply refer your "opponent" to Keith's books and the Superbike School and this website. It will probably save his/her life and, who knows, maybe we make a new friend out of an old "opponent" because, I have to agree with you... we DO have an awesome community here!

 

I take that to mean that one WOULD accelerate throught the course of a turn, verses merely cracking it open and holding the throttle at a steady rate, waiting to resume actual acceleration upon reaching the exit point.

 

I would agree with that statement as well.

 

I would be interested to know if Keith gave a different or conflicting reply to your PM. I don't want to 'steer' anyone wrong.

 

Good riding to you, dude.

 

And welcome to the community! Come back soon and bring all your friends!

 

CHEERS!

[racer]

Upon rereading my previous post, I think I missed something with my worn tire theory. Maybe this is better.

 

It would seem logical that a worn (flattened profile) motorcycle tire would be less inclined to lean over. Simply because the crown is no longer round. There is no longer a smooth arc to the side of the tire, no more "sweet spot" to corner with on the side. (A car tire at the extreme.) There is only a flattened base (very stable for riding in a straight line) and an abrupt transition to a radically steeper max lean angle. (Not very confidence inspiring.) It would seem that this tire would require more effort to initiate and perhaps even constant effort to maintain any lean angle if sufficiently worn. It seems to me that this might account for why some bikes seem to want to stand up in a corner. Or at least explains their lousy handling characteristics.

 

In any case, I'm sure there are other mechanical reasons for a bike not being stable in a corner. This just seemed the most likely. Otherwise, I'm goin with rider input or lack of acceleration.

 

G'day Woody!

 

I still feel that inertia, the tendency of the bike to continue in the direction it's going, is the main force behind the bike countersteering down or up. (A cornering bike at lean is actually trying to go straight toward the outside of the corner.)

 

I still feel gyro forces have some effect. But, not certain just what or how much.

 

That being said...a 60/40 (rear/front) weight distribution implies a little bit of acceleration in my mind.