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Throttle during turns and countersteering?

Finder

Finder

Snooge!
Joined
Mar 10, 2004
Location
Bay Area
Moto(s)
R1200GS
Name
Dan
I've been told through the MSF classes and other experienced riders that one should always roll on the throttle while turning. When asked why, they would usually come back with 'better stability, weight transfer, geometry, etc...'. However, I've never heard any one say that it would decrease the turn radius.

I've been wondering if this is the case for a while now. Think about applying the throttle on an upright motorcycle. This would generate a rotational effect on the complete motorcycle and cause the front wheel to come off the ground (eg. throttle wheelie). Another good example of this would be dirt bikes in midair using throttle or brake to control landing angle.

Now, what would happen if the bike was leaned? Wouldn't the same rotational effect from applying throttle cause the front of the bike to want to move towards the center of the turning radius (lateral) as well as off the ground (verticle)? Given that the front wheel will then correct for the new forces, wouldn't this sharpen the turn?

Just a thought. Am I crazy? Wait... Don't answer that! :teeth

I also have trouble believing the reasoning given by my MSF instructors on why countersteering works the way it does. They said it is caused by the gyroscopic effects of the wheels. Phooey. Gyroscopes resist rotational changes perpindicular to the spin axis right? This would then help an upright bike stay upright, as well as make turning the front wheel harder as you go faster, right? Hmm... I thought countersteering was caused by preservation of momentum in a straight line? You turn the wheel to the right, and the bike responds by going to the right 'initially'. Once the tires start aligning themselves to point to the right, momentum comes into play. The bike is pointed slightly to the right, but your momentum is still in the same direction as before the turn, which is straight. Well, since the tires are held by friction to the road, the bottom of the bike has nowhere to go. With the bottom anchored latterally, momentum would cause the top of the bike to tip over to the left. Thus, leaning left by steering right.

Once the desired lean angle is achieved, and provided you and your bike are perfectly balanced, there shouldn't be any pressure required on the bars to maintain that angle. Think about riding on a bicycle with no hands and turning at the same time (no handle bar pressure required at all!).


Crazy rantings? Am I wrong about this too? Sheesh! It's a good thing the weekend is here. :p

Cheers!
 
Damn, I want to chime in about this ... but I have to much to say about to type it all up now. I wish thispost had come up while I was at work :D
 
Okay, i will chime in a little.

Throttle roll helps;

traction, Idealy on 'most' bikes you want %40 of the weight on the front wheel, %60 on the back wheel through a turn. The back wheel has a larger contact patch. If you let off the gas mid turn you are shifting too much weight to the front wheel .. looking the grip of your rear patch some. If you get on the gas to hard your doing the opposite, transfering too much away from the front and on to the rear. A smoooth throttle through a turn idealy 40/60 will give you the best all around grip. Same thing with a slippery condition, if you drop the gas entirely you are transfering to much weight to just the front wheel (natural reaction to say gravel in the road) but this puta almost just your front tire in control of the grip through the slippery stuf, stay lightly on the gas and keep a good contact patch with both tires.

Suspension ;

the harder you twist the gas, the higher the rear tire and rear suspention rises. Most suspention setups are also designed to work best with a roughly 40/60 disrobution of weight.

as for turn radius are you talking about a decreasing radious turn, or a double apex turn? different situations come into play based on the type of turn it is.

The only way the roll throttle should not really apply is bumps mid turn, radious changes, or severe downhill.


much much more to chat about, but I gotta go chase some muff.


:laughing
 
My thoughts: As far as smaller turn radius; your rear end would wash out before you would have the rear wheel pulling the front of the bike up, or to whatever side you are turning into. But, if you were to go past that threshold your front end would be off the ground and the angle of the bike would determine the radius not the torque on the rear wheel.

Counter steering: I have a pretty good idea of how it works.. don't really wanna type it all out, but just to let you know; it is still real vague. There is no mathematical formula for why counter steering works. It is just theories justified by physics. If you actually start going really fast 300-1000+mph, counter steering will not apply at certain speeds depending on all the different aspects of the “bike.”
 
Read Twist of the Wrist 1&2(by Keith Code) then you will understand both subjects.
 
re:Gyroscopes resist rotational changes perpindicular to the spin axis right?
----------
Yes aka Gyroscopic procession

This would then help an upright bike stay upright,
----------
It would explain how a bike moving forward, would resist turning....the resistance is applied directly to the force trying to change the angle of the rotational axis.

as well as make turning the front wheel harder as you go faster, right?
-----------------
Yes.

Now on the topic of tightening turns.......
------------------
It has been my experience that when overshooting (or going into a turn too fast) you can tighten the turn by letting off the throttle, keep in mind you have to look where you want to go....

Keeping the throttle at a constant usually means you are entering or exiting the apex of the curve in which both tires have an almost equal coefficient of friction.

anyhow....gunning the throttle doesn't necesarily tighten the turn.

KC is a good riding/cornering instructor, definitely knows his stuff.
 
It's all about keeping the bike stable and against the road. Throttle gives you active input. It puts more force into the back wheels, and the front as well. You can actually steer and keep the bike level with the throttle. Throttle is your friend.
 
Keeping on the throttle also raises the suspesion, for better ground cleanence. More ground clearence allows for more lean angle for a tighter turn.
 
Finder said:

Crazy rantings? Am I wrong about this too? Sheesh! It's a good thing the weekend is here. :p
Click to expand...

I tell you ten times now, if you like this kind of intellectual masturbation, go buy Tony Foale's book Motorcycle Handling and Chassis Design: The Art and Science.

http://www.tonyfoale.com/book.htm



Sidewalk said:
Keeping on the throttle also raises the suspesion, for better ground cleanence. More ground clearence allows for more lean angle for a tighter turn.
Click to expand...
More to the point, that rear end jacking force on a chain drive motorcycle shortens both rake and trail up front, which typically means quicker steering.

I wonder if wheelbase also changes at the same time :confused
 
I wonder if wheelbase also changes at the same time :confused [/B][/QUOTE]

Yes, the wheelbase will change 'cause the swingarm moves in an arc.The the farther up the chassis moves, the shorter the wheelbase gets(that is unless the pivot is lower than the axle center)in wich case the wheelbase would get longer. Vise / versa
 
I say... go lean through some turns and you will feel it. No matter how much you read you have to feel the forces yourself and it will all click. In short... when you roll on through turns it flatens the profile of your tire and give you more contact patch... plus you go faster which puts a smile on your face. Something like that.
 
Finder said:
[CLIP]

I also have trouble believing the reasoning given by my MSF instructors on why countersteering works the way it does. They said it is caused by the gyroscopic effects of the wheels. Phooey. Gyroscopes resist rotational changes perpindicular to the spin axis right? This would then help an upright bike stay upright, as well as make turning the front wheel harder as you go faster, right? Hmm... I thought countersteering was caused by preservation of momentum in a straight line? You turn the wheel to the right, and the bike responds by going to the right 'initially'. Once the tires start aligning themselves to point to the right, momentum comes into play. The bike is pointed slightly to the right, but your momentum is still in the same direction as before the turn, which is straight. Well, since the tires are held by friction to the road, the bottom of the bike has nowhere to go. With the bottom anchored latterally, momentum would cause the top of the bike to tip over to the left. Thus, leaning left by steering right.

[CLIP]

Cheers!
Click to expand...

You almost got it...

First, imagine the roll axis of your bike, say in between the engine and gas tank. When you turn left, (turning the bars to the right), the "right" turn effort will make the lower part of the bike (below the roll axis) go to the right (the bike isn't "anchored", the contact patch will move to the right of the roll axis), the upper part will go to the left, to preserving the angular moment of inertia about the center of gravity. This can be seen on a video of at the start of a race while all the bikes are bunched together in a chicane.
 
i always figured countersteering worked because when you turn the bars left you're using the back of the right hand side of the front tire, and it's the tire profile that causes the turn. think about it. in devices where the tires are flat and stay level at all time (cars, atvs, bikes with sidecars, etc) countersteering simply does not work.
 
WAIT! epiphone! (spelling?) when you turn the bars left, the wheel ends up slightly to the left of where your center of gravity falls, causing you to "fall" right. think about head angle and trail. trail is the distance between a vertical line from your front axel to the ground, and a line parallel to the head tube that stops at the ground. the line from the head tube ends up a couple inches in front of the line vertical from the axel to the ground. thus, the front wheel is following the weight of the bike and you. yes that's right, your weight is in front of the front wheel. why do you think you can stay upright when riding no handed?
 
My mind is numb. I've given up on my thoughts of throttle induced reduced turn radius, but I'm still mulling countersteering. Perhaps I should clarify. The act of a bike moving around in a circular motion (ie. arcing around corner) while leaned over is caused by the geometry of the bike, round tires, etc...

Counter-steering however is the act of leaning the bike over to one side, by steering to the other. My questions is what causes this? Since the gyroscopic effect of the wheels resist these changes of attitude as the speed increases, that is why counter-steering breaks down at a certain speed. The forces of the gyroscopic effect overcomes the forces trying to tip the bike over. Your tires (gyroscopes) make the bike stay upright, thus; turning left makes your bike go left with no lean. This of course happens at insane speeds, but it should happen.

Ugg... Maybe I should just stick to riding and not think too much about it. I need my concentration anyways to countersteer my way around cages cutting me off. ;)

As always, it great hearing all your input!

Cheers!
 
Seems like something for Gary J. or Doc Wong but I'll bite....
My understanding is as follows:

Cornering a bike with countersteering is an act of balancing opposing forces. Countersteering input causes the bike to rotate along the long axis (fall into the turn). Throttle input causes the bike to standup and widen its arc. The strategic use of both countersteering and throttle results in a balance of forces that describes an arc through the turn that is the fastest possible way around.

Example:
Joe/Jane blow rider lines up an approaching turn. He/she countersteers into the turn. The bike drops into the turn. When the desired angle is acheived Joe/Jane Blow adds more countersteering input and throttle input as he/she guides the bike through the turn and out the other side. Joe/Jane used more countersteering prior to the apex and more throttle after the apex.

You almost got it...

First, imagine the roll axis of your bike, say in between the engine and gas tank. When you turn left, (turning the bars to the right), the "right" turn effort will make the lower part of the bike (below the roll axis) go to the right (the bike isn't "anchored", the contact patch will move to the right of the roll axis), the upper part will go to the left, to preserving the angular moment of inertia about the center of gravity. This can be seen on a video of at the start of a race while all the bikes are bunched together in a chicane.

Thats what I understand.....

Sidewalk said:
Keeping on the throttle also raises the suspesion, for better ground cleanence. More ground clearence allows for more lean angle for a tighter turn.
Click to expand...

Suspension ;

the harder you twist the gas, the higher the rear tire and rear suspention rises. Most suspention setups are also designed to work best with a roughly 40/60 disrobution of weight.


Not on a chain drive bike. Just the opposite. The rear suspension compresses with throttle. Shaft drive bikes rise in the rear when the throttle is applied.

Now, what would happen if the bike was leaned? Wouldn't the same rotational effect from applying throttle cause the front of the bike to want to move towards the center of the turning radius (lateral) as well as off the ground (verticle)? Given that the front wheel will then correct for the new forces, wouldn't this sharpen the turn?

It sounds like your asking if in a wheelie while leaned over does more throttle cause the bike to tighten its line. My experience is no. The bike is still leaned over and you're still applying throttle so the bike wants to widen its arc. When this happened to me I had to use a lot of body english and some throttle control to keep the bike from running wide. Yes a Hayabusa can pick up the front wheel while leaned over!

My thoughts: As far as smaller turn radius; your rear end would wash out before you would have the rear wheel pulling the front of the bike up, or to whatever side you are turning into. But, if you were to go past that threshold your front end would be off the ground and the angle of the bike would determine the radius not the torque on the rear wheel.

Yes a Hayabusa can pick up the front wheel while leaned over. Been there, done that!
 
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