Jump to content
Thielert

Pivot Steering

Recommended Posts

I've recently started using this technique and it really solves a problem I call Aero-steering for want of a better term. That is where a buildup of aerodynamic forces on the rider pushes him back I'n a high speed sweeper and eases up the countersteering pressure on the inside bar, I'n effect countersteering the bike out of the turn.

 

I noticed this effect on a couple of my favorite high speed sweepers, I had reached the false conclusion that I was taking the corner as fast as I could go and SR#1 kicks I'n and you ease off the throttle to finish the corner.

 

Pressing down on the outside footpeg creates an action-reaction pair that automatically

increases counter steer pressure on the inside bar and the line tightens up, you can't stop it! The net effect is you're back on the gas and taking the corner at a higher speed.

 

What I found cool was that pushing off on that outside peg requires no conscious effort to push forward on the inside bar and tighten up your line, it's almost like steering with your foot.

 

This is probably old news to most but a "eureka" moment for me.

Share this post


Link to post
Share on other sites

I've recently started using this technique and it really solves a problem I call Aero-steering for want of a better term. That is where a buildup of aerodynamic forces on the rider pushes him back I'n a high speed sweeper and eases up the countersteering pressure on the inside bar, I'n effect countersteering the bike out of the turn.

 

I noticed this effect on a couple of my favorite high speed sweepers, I had reached the false conclusion that I was taking the corner as fast as I could go and SR#1 kicks I'n and you ease off the throttle to finish the corner.

 

Pressing down on the outside footpeg creates an action-reaction pair that automatically

increases counter steer pressure on the inside bar and the line tightens up, you can't stop it! The net effect is you're back on the gas and taking the corner at a higher speed.

 

What I found cool was that pushing off on that outside peg requires no conscious effort to push forward on the inside bar and tighten up your line, it's almost like steering with your foot.

 

This is probably old news to most but a "eureka" moment for me.

Perhaps I'm misunderstanding this, it seems like you're describing adding lean and throttle at the same time.

 

Countersteering increases or decreases lean angle, not needed to maintain it. One possibility is subconsciously pressing on the outside grip then countering with pressure on the inside.

 

Example, T6 at Sears Point, once turned-in I will take my left hand completely off the grip to check my right arm/shoulder is relaxed.

Share this post


Link to post
Share on other sites

Hi Matt, now you have me really confused!

 

From Wikepedia:

 

"It is also important to distinguish the steering torque and steering angle necessary to establish the lean required for a given turn from the sustained steer torque and steer angle necessary to maintain a constant radius and lean angle until it is time to exit the turn. The initial steer torque and steer angle are both opposite the desired turn direction. The sustained steer angle is usually in the same direction as the turn, but may remain opposite to the direction of the turn, especially at high speeds.[5] The sustained steer torque required to maintain that steer angle is usually opposite the turn direction.[6] (See the graphs to the right.) The actual magnitude and orientation of both the sustained steer angle and sustained steer torque of a particular bike in a particular turn depend on forward speed, bike geometry, tire properties, and combined bike and rider mass distribution."

 

Please comment on their reference to "sustained steer torque" in a turn as this sounds exactly as what I am experiencing. Corner speed is above 125 mph I'n this particular turn where I am using countersteer torque.

Share this post


Link to post
Share on other sites

More info, the turn in question is crested, you are still going uphill at the turn in point and then the road begins to fall away. Entry speed is about 125 mph and there may be significant camber and radius changes throughout.

 

I know I'm hard on the gas throughout but that may be to counteract aerodynamic drag and rolling resistance. I'm no expert so I'm just trying to figure out why I'm having to maintain constant negative steering torque (countersteer) throughout to make the corner. If I ease off, I go wide.

Share this post


Link to post
Share on other sites

From James R. Davis "neutral steering fact or fancy"

 

"I have maintained that the rider MUST maintain some measure of negative torque throughout the turn in order to maintain it. That is, he must maintain a certain amount of forward pressure on the inside grip throughout the turn else the bike will, of its own accord, attempt to straighten itself out and abort the turn - ending up moving in a straight direction. However, there are 'tuning points' where a specific speed and turning radius can result in a motorcycle that requires no steering input to maintain its path."

Share this post


Link to post
Share on other sites

Something you could try is to consiously lift up the hand at the outside bar when you push the inside bar, you may be surprised by the result, I someday found out that although I had intended to be loose on the bars I was actually sabotaging my own steering impuls by holding on (too tight) to the outside bar.

 

Adding weight to the outside footpeg has a similar correcting effect (at least for me), as a result I put less weight on the outside bar,

 

Sure hope I'm making sense... my head is hurting too... didn't hurt last night though :lol:

Share this post


Link to post
Share on other sites

I'll try to really get loose on the bars next time out and see if I'm unintentionally countersteering my way out of the turn. Anyway, weighting the outside peg seemed to fix it.

Share this post


Link to post
Share on other sites

More info, the turn in question is crested, you are still going uphill at the turn in point and then the road begins to fall away. Entry speed is about 125 mph and there may be significant camber and radius changes throughout.

 

I know I'm hard on the gas throughout but that may be to counteract aerodynamic drag and rolling resistance. I'm no expert so I'm just trying to figure out why I'm having to maintain constant negative steering torque (countersteer) throughout to make the corner. If I ease off, I go wide.

If there are significant radius changes, then is it a decreasing radius or double-apex? Which track and turn are you describing?

Share this post


Link to post
Share on other sites

From James R. Davis "neutral steering fact or fancy."

 

"I have maintained that the rider MUST maintain some measure of negative torque throughout the turn in order to maintain it.

 

Sorry, but James R. Davis is wrong, as the following clip shows clearly. Just look at Flo's front wheel as she does the Intersection Drill. "Oh, but that's because she riding REALLY slow on a big cruiser!" I'm afraid not. Check it yourself. Glance down at your bars in a corner, after the lean angle is set, and you will see the bars--and so the front tire--are pointed INTO the curve. This is harder to see on big corners, but clearly visible on the tighter stuff. Unless you are running a car tire, you should not need inside bar pressure to keep the bike leaned over.

 

On the other hand, pushing off the outside footpeg can help you lock into the tank, relax your upper body and gain instantly better control over both gas and steering.

 

Share this post


Link to post
Share on other sites

you will see the bars--and so the front tire--are pointed INTO the curve. This is harder to see on big corners, but clearly visible on the tighter stuff.

Crash;

Maybe it's just me but it's my sense that the bike begins its transition to the opposite direction before the front wheel is pointed there...but I could be wrong.

Rain

Share this post


Link to post
Share on other sites
From Wikepedia:

 

"It is also important to distinguish the steering torque and steering angle necessary to establish the lean required for a given turn from the sustained steer torque and steer angle necessary to maintain a constant radius and lean angle until it is time to exit the turn. The initial steer torque and steer angle are both opposite the desired turn direction. The sustained steer angle is usually in the same direction as the turn, but may remain opposite to the direction of the turn, especially at high speeds.[5] The sustained steer torque required to maintain that steer angle is usually opposite the turn direction.[6] (See the graphs to the right.) The actual magnitude and orientation of both the sustained steer angle and sustained steer torque of a particular bike in a particular turn depend on forward speed, bike geometry, tire properties, and combined bike and rider mass distribution."

 

 

Please go back and read this excerpt from Wikepedia very carefully with reference to steering torque and steering angle. The direction the tire is pointed is steering angle, the force applied at the handlebars is the steering torque. The two may be in the same direction or in opposing directions as clearly stated in the article.

Share this post


Link to post
Share on other sites

you will see the bars--and so the front tire--are pointed INTO the curve. This is harder to see on big corners, but clearly visible on the tighter stuff.

Crash;

Maybe it's just me but it's my sense that the bike begins its transition to the opposite direction before the front wheel is pointed there...but I could be wrong.

Rain

 

I think this statement from the Wikipedia article confirms your senses are correct:

 

The initial steer torque and steer angle are both opposite the desired turn direction.

Share this post


Link to post
Share on other sites

yes this is the countersteering to produce the lean angle. Once the lean angle is set, the front wheel has to point into the turn to stablise the lean angle and cornering combo. If you have to apply pressure all the way round the corner, then you're partly straightening the front wheel up, but not turnign it outwards i.e. reducing the stabilisation so the bike tries to lean in a bit more - counteracting its desire to get back up again.

 

No idea who Davies is TBH but what he's saying is that the gemotry and tyres of a bike won't give you neutral steeering in every turn and speed. Not really news but I disagree that it's a rare situation on a modern sports bike.

Share this post


Link to post
Share on other sites

Pivot steering... just to make sure I'm on the same wavelength - is pivot steering where you apply pressure to the outside foot peg during the steering input?

 

I think I see what you're saying Centurion, as well as what the Wiki article is getting at. I noticed that alot changes in fast corners as well, I was trying to do the usual 'quick steer' into one and it was just really difficult. I mean it was physically difficult to put enough pressure on the 'bar and get it to turn quickly. (I was approaching the turn point at around... maybe 170-180km/h when I was trying this.) Rather than being confusing, this makes complete sense because of the much greater rotational force in the front wheel which is resisting your steering inputs. So I had to make my turn point alot earlier and the line turned into a big smooth arc. (Using the earlier turn point, I was more confident of making the turn and was able to arrive at the turn point doing about 200km/h, barely rolling off - it was definitely a faster way through there.)

 

Now I think what the Wikipedia article is saying, is that because there are much greater forces in play, the steering input will take longer. And so this will mean that the time you're pushing on the inside 'bar is longer than needed for a low speed corner where you can really 'quick steer'.

 

Faster corner = longer steering input (you will be pushing on the 'bar for a greater length of time.)

Slower corner = shorter steering input (you will be pushing on the 'bar for a much shorter length of time.)

 

Is that what everyone is getting from this?

 

I would think that the article is describing that sustained initial steering input rather than making an additional input mid-turn.

 

What Crash describes seems correct to me - a bike with a constant speed does not need steering input to maintain lean angle. But I think there's a bit of confusion over that Wiki article. And no offence to whoever wrote it, but that is not written in the most easily readable manner - looks like it was written by an engineering professor or something (sorry, no offence to engeineers or professors either.) If I can translate it into something that's actually easily comprehensible... it's not saying that a steering input is needed to hold the bike in the turn, it's saying that steering input it's needed to turn the bike (it's describing the initial steering input). This must be true, because I don't know of any instance that I've seen or experienced where the front tyre can be pointed towards the outside of a turn other than during steering inputs or when the rear wheel is sliding (dirt track, anyone?).

 

In the case of your corner with the crest, that's another problem to deal with. As the road 'falls away', will the will the forks spring into action (haha, I made a pun tongue.gif ), and will the forks actually extend? If the forks extend, will that change the geometry of the bike? If the geometry of the bike changes, will it maintain it's previous cornering line?

Share this post


Link to post
Share on other sites

... it's not saying that a steering input is needed to hold the bike in the turn, it's saying that steering input it's needed to turn the bike (it's describing the initial steering

once you've made your steering input, then when you're holding the bike in a corner, is your inside arm relaxed enough to do the chicken-flap?

Ago

Share this post


Link to post
Share on other sites

... it's not saying that a steering input is needed to hold the bike in the turn, it's saying that steering input it's needed to turn the bike (it's describing the initial steering

once you've made your steering input, then when you're holding the bike in a corner, is your inside arm relaxed enough to do the chicken-flap?

Ago

 

Coaches mostly use this as a reminder, not so easy to actually do (especially with the right arm) while rolling gas on.

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...

×
×
  • Create New...