Jump to content


  • Posts

  • Joined

  • Last visited

About Carl_T

  • Birthday 05/05/1946

Previous Fields

  • Have you attended a California Superbike School school?

Contact Methods

  • Website URL
  • ICQ

Profile Information

  • Gender
  • Location
  • Interests
    Cycles, Art.

Carl_T's Achievements

Cornering Enthusiast

Cornering Enthusiast (3/5)

  • First Post
  • Collaborator
  • Week One Done
  • One Month Later
  • One Year In

Recent Badges



  1. Same comment from a Bike Magazine interview of Rossi. It helped him brake better. The photo was of him with his right foot off the peg. Same interview he felt putting wieght on the bars until turn in helped him stop faster too. Also on acceleration he used ouside peg pressure to stabilize the bike with a bit of extra traction, and inside peg pressure to reduce traction as desired to help steer. That made me smile as a couple took me to task in the distant past for thinking the same thing of peg pressures. The magazine tried the foot thing and didn't feel they got much braking aid. Wayne Rainey and Mick Doohan had some comments to go with Rossi's. Short, nice read.
  2. As I said at this point I need more information at my disposal to understand the logic behind this accurately, and will come back to this thread when I have more from reasonably reliable sources. Just quick poking around it seems racer and I both are correct........ to a point....... and the truth may even be some combination of both of us. In the meantime, NOT as an authoritative source, but more as a look at the results of someone even more obsessed with pushing bicycles in the garage than either racer or I, take a look at all of this guys web pages and his conclusions on the subject. It's an interesting enough read with a couple of interesting experiments even though with bicycles. I've got a line on some better sources than this for sure related to motorcycles, that I'll go over in future including Tony Foale, but some of what this guy has come up with makes sense to me. His experiments with cones lashed together, bars wired straight on turning and "tracking" are important and they do bolster my front wheel most largely determines changes in lean angle and radius, while rear adds stability theory. They do not discount racers assertion the rear steers with conical steering and the front follows either, better sources will have to be used to settle that out. At the outset of my looking around it appears conical steering (most often labeled "camber thrust") tries to turn a tighter radius than I previously thought possible, and it seems slip (not slide) angles are involved as well. here's the website http://www.terrycolon.com/1features/bike1.html As to why lean angle changes with speed here is what the guy on the above website came up with, stated more simply than the way I tried. " Circular motion, including turning a bike, is from a combination of momentum and centripetal force, a force deflecting your forward motion to the side. This creates a centrifugal "effect" (my own note here: centrifugal effect coming from the bike trying to continue going straight) directly opposite the centripetal force (here I think he's wrong about directly opposite, more like at a right angle). Gravity is a constant. The centripetal force is determined by the angle the wheel is turned, the size of the circle you're turning in. The centrifugal effect is determined by your speed, i.e. momentum, plus the centripetal force. The faster you go, the tighter your turn, the greater this effect. That is why you must lean more the faster you're going for the same size turn. " (my note: if you lean more for the same size turn, you have a larger radius for the same lean angle with the increase in speed). I would use more words to clarify it better, but basically that's about right. Anyway I'll be back with whatever extra information I have found (however it turns out), but it will be likely be a long while, there are books to order and read, since I've gone as far as my own logic could take me with the limited information I have at my disposal right now.
  3. Hei Keith, that was your cue! ..Enter the guru himself.. (please??) Yeah, I've reached the end of my suppositions, surmises, and guestimations for now at least. Never know what tomorrow brings, but I would need additional information to go forward from here. I'll do some searching, but would be interested to know Keith's thoughts on the subject one way or another. Racer, It's an interesting discussion for sure, thanks for getting me thinking about it.
  4. We mostly agree here for sure, I only meant the rider does it through the bike. Also a riderless bike on it's own will sometimes correct itself and run on a long ways by itself until it slows enough to fall over so it does do some things "itself" due to forces acting on it and since the bike is riderless and no longer under throttle, it does them with the front wheel as well as the rear. So far, "I think" our difference is that you think the front wheel only trails along in the direction the rear points it due to the conical steering and forward momentum along a path of the rear. I think the front continues to play a significant part in the direction the bike takes, according to it's load, while receiving it's due influence from the rear. I may be mistaken, but it is my memory that at slower speeds when I lifted the front on a dirt bike in a turn the arc the rear dictated was not the same as the arc being traveled when the front was on the ground. Some adjustment in CG and or lean had to be made. The thing is I never did this as an experiment, so I only did it occasionally on exit that I remember. I'm thinking that the arc only remains the same during a wheelie at higher speeds where conical steering is doing a larger percentage of the steering. Again, perhaps I'm wrong, but I also think at times under good throttle when some slip angles develop at the back, the rear tries to move outside, pivoting as it pushes forward around the front steering pivot, which steers the bike on a tighter" path not a wider path. There may be some of this effect at all times under throttle, but in general I'm thinking if you purposely do not change lean angle, and you add throttle, that will increase speed, which will require a correspondingly larger radius to be run, or lean angle will have to alter. This can be a very small effect on radius and speed at small acceleration amounts like 10%, especially since the friction of cornering must be overcome with some acceleration. So, at 10% there may be no discernible change in speed and therefore radius. It DOES revert to the single radius dependent only on lean angle with the front off the ground. It couldn't tighten up because the front was doing it's part to run a bit tighter radius than conical steering of the rear alone would do when both wheels were on the ground. The higher the speed, the more likely only conical steering of both tires finally comes into play. The lower the speed the more likely you would see a change in path because the front was steering more sharply. I don't know that Keith really wanted his words to be taken quite the way you're interpreting them Racer (though maybe he did), I'm guessing he may have been referring more to the stability the rear wheel gives to the equation. Again I dunno though. Everyone is evolving in understanding of this stuff, a two wheel vehicle's ability to do what it does is NOT simple (at least for me) because SO MANY darn things are going on at once and contributing to the situation. What Keith may have thought a few years ago could be somewhat changed through new discovery today. Heck what I thought a few hours ago can change in a flash with new information and thinking. Perhaps again, I'm way off base, but I'm still standing fast until something comes to light that fits "better" for me. One thing that could change my mind is IF something happening at the contact patch could change it's amount of conical steering so radically it could explain the differences of radius at slow and high speed. I am doubting right now. That means that a wooden or steel wheeled bicycle would behave radically differently with respect to radius and speed. Again I'm doubting. This may be correct though the amount it alters it may not be radical enough as I just wrote. However perhaps this needs to be explored more (though I still, so far, say the front has more effect than you are giving it credit for). HOW do you think this works?
  5. Racer, you are jumping too far ahead for me, as trail was squatting in my brain. So I'm trying to get trail settled before I catch up to the things you have added. Also you robbed me of my Sat. morning beauty sleep. I wake up at 5AM going “I have it!” (in regards to trail Sorry about the length, this is mainly about the question of TRAIL and how the front wheel knows to point into the lean more or point in less, due to how fast the bike is going. We will see the front wheel is NOT JUST trailing along, but locked in a balance of forces similar to what we were already talking about. These forces POINT the front wheel at a specific angle depending upon the relationship of power/amount between the forces . They are side forces working at the contact patch, one turning the front wheel into the lean, the other turning the front wheel back to straight. How they balance when fighting each other, determines how far the wheel gets turned into the lean (removing rider input). We will see the amount of turn in does change with speed change, and we’ll see how that achieves a state of balance we talked about in earlier posts. As an aside, HAH! Racer, I’m up at 5am not being able to sleep again. Then I’m out in the garage at 5:30AM taking the front wheel off of my wife’s bicycle just to confirm leaning it to the right will turn it out to the left, it does. Further turning it to the left leans it to the right. This is familiar yes? Yes, turning the front to the left also steers the front axle out from under the headstock, leaning the bike to the right. That means the gyroscopic forces help at the front with countersteering. They can help you lean the bike in the air too, which had been my experience. THAT BEING SAID, I remember someone, somewhere, put reverse spinning discs on a two wheel vehicle to negate gyroscopic force and IT WAS STILL RIDABLE. Therefore, countersteering WILL WORK even without gyroscopic force, though it is aided by it. (PS I see you saw that somewhere too) End of aside, and back to trail. I’ve been trying to think how trail acts to steer the front wheel INTO the turn MORE going slow and less when the bike is going faster. I figured the front wheel could NOT just trail passively along behind conical steering force, in order for the bike to behave the way it does in the real world, so the answer had to lie in balancing forces at the contact patch. There had to be a force trying to turn the front wheel IN and a force trying to turn the front wheel OUT. These had to balance each other out in a way that helped describe the NEEDED path for balanced status quo of the bike in a turn. In order for the front to turn in the CORRECT amount, creating centripetal inward force, to work with forward momentum, in balancing gravity, I figured the 3 forces we identified must be doing something at the contact patch with trail then. I figured we should look at our original 3 forces first. That line of thinking bore fruit in my sleep. When you lean a motorcycle, the contact patch at the front wheel moves inside, off center. The pivot point for the front end is found thus; looking at the motorcycle from the side and drawing a line top to bottom through the headstock parallel with the forks, where that line contacts the ground is the pivot point. The actual contact patch of the tire is on the ground behind that, so It’s trailing behind the pivot point (trail). So, you lean the bike, with the wheel pointing straight, the trailing contact patch moves inside the center (as viewed from the top, diagrams would be helpful) AND IT’S BEHIND the pivot. Gravity (one of our original three force friends) exerts its force on the patch making the patch want to ROTATE BACK IN LINE CENTERED behind the pivot (instead of staying inside center). Due to gravity pressing on the patch through a lean angle, the contact patch does rotate to the outside of the lean, and since the pivot is ahead of the patch this turns the front wheel INTO the LEAN (a picture would show this real easy). It does this quite a bit, as when I put the bike on the kickstand at not that much lean, the front wheel wants to turn in, all the way till it hits the steering lock when friction at the patch is overcome. That happens at not all that much lean even, and would do so more strongly at a steeper lean. Important point, SO, GRAVITY is turning the front wheel strongly into the lean, due to trail and lean of wheel. You lean the bike, gravity wants to turn the front wheel sharply inward, the more you lean, the more strongly it wants to do that. In our old formula centripetal (inward) force combined or added with forward momentum (speed)force, to balance(equal out) gravity. Remember this as we go on here. Speed+radius= Gravity that is during a constant lean, constant arced turn. Once countersteering successfully has the bike leaning the amount the rider wants and he/she lets off pressure to the handlebar, the offset contact patch turns the front wheel into the turn from the force of gravity. Left to itself it would turn in TOO FAR to balance forces as the other two forces need to balance gravity for a status quo. Conical steering along with the front axle of the bike following the pointing direction of the front wheel, creates centripetal (inward) force which is the 2d of our forces. The TRAIL TRIES TO MAKE the wheel point in the direction the front axle is TRAVELING (trailing along), working AGAINST theEXTRA inward pointing of the wheel from GRAVITY (gravity would make it turn too far in on its own). The trail is using centripetal force to balance what gravity is doing at the contact patch. That’s so far just like stabilizing lean angle, only it’s acting on stabilizing where the tire is pointing due to trail. There is however a third force, forward momentum (speed). So does speed come in to add it’s force and help balance things at the patch to steer, just like it helps balance lean angle? Yes. The conical steering and turned front wheel are providing inward force. At the contact patch speed trying to go straight ahead AGAINST a TURNED IN TIRE pushes backwards against the contact patch as the CONTACT PATCH tries to GO straight FOWARD in a direction the tire is not pointing in, the pressure at the patch is back. The PATCH IS TRAILING the pivot point, SO the BACK pressure TRIES TO STRAIGHTEN the front wheel out more, FIGHTING the turn in from gravity ALONG WITH the centripetal inward force. THAT also FIGHTS GRAVITY which was turning the front tire in. SO, DUE TO TRAIL, at the contact patch you have CENTRIPETAL FORCE, AND SPEED (forward momentum) BALANCING out GRAVITY at the patch and telling the front tire where to point. SO, speed+centripetal force=gravity at the patch to steer the wheel due to the fact trail is built into the system AND the fact the bike leans and makes the contact patch move inside center and gravity is working at the patch through a leaning angle. DUE TO TRAIL, due to trail, due to trail: To understand the following REMEMBER, forward momentum (Speed) COMBINE with centripetal (inward force from following an arc or radius), needs to match or equal the force of gravity (lean angle). That MATCHING of the combined two forces to the third force, achieves a balanced status quo (constant arc/radius/lean angle). Said another way for a constant corner, you want speed AND turn in angle, to match the singular falling down force of lean angle. For steering at the contact patch you want speed AND turn in angle, to match the turning in pressure of gravity. If you increase the lean (gravity, which is trying to turn the tire in more) keeping speed the same, the tire WILL turn in more, increasing centripetal (inward) force to balance the extra gravity gained from more lean. If you decrease the lean (gravity, which is turning the tire in), keeping the speed the same, the tire will turn out more (gravity trying to turn it in, speed trying to turn it out). This lessens centripetal (inward force) to match the decrease in lean (gravity) If you increase the speed (speed trying to turn the tire out), keeping the lean (gravity) the same, the tire will straighten out more. That lessens centripetal force which combines with the extra speed to still retain balance with gravity (lean angle) in use. If you decrease the speed, keeping the lean the same , the tire will turn in more. Since speed is less you need the tighter turn to balance the same lean angle. The competing forces of gravity turning IN and speed turning OUT at the TRAILING contact patch, turn the tire the required amount to dial in the needed centripetal force for balanced status quo. I’m guessing there is a sweet spot for the amount of rake and trail needed to get this to work in a way that dials in the CORRECT amount of turn in, WITHOUT the rider having to do much, or without the rider having to do anything. So, It’s probably no accident rake and trail numbers are pretty similar on good handling bikes. Of course the bike goes through an unbalanced state to get to the next balanced state (whether rider induced or otherwise). With the right amount of trail it should seek balance on its own due to what I just described above. SO, THAT is my idea of how the trail knows how much to turn the front wheel into the turn given a lean angle and a speed. THE REASON YOU NEED A DIFFERENT RADIUS AT DIFFERENT SPEEDS for the SAME LEAN ANGLE, is that is necessary or the bike cannot keep either a constant arc or a constant lean angle. That is because speed and turn sharpness forces must combine to equal the force of the lean angle used. The ONLY way the bike can vary the radius is by following the direction the front tire is pointed in, and there is only ONE CONSTANT radius possible for any given speed and lean angle combination. It seems the front with its vertical hinge is VERY needed to change and achieve the status quo in turning at a wide variety of speeds. On the other hand it seems the rear with its horizontal hinge is VERY needed, when stability is important. I’m thinking as far as stability is concerned you can weight shift for one hinge or the other. However while the front is on the ground rolling free of large slip angles, the axle is going where the front wheel is rolling along and pointed, trying to haul the rest of the bike after it and so heavily involved in steering. That’s even if the rider is not touching the bars and the speed and gravity through trail is doing the steering instead. Got weekend stuff to do, then I'll come back and look at your other stuff.
  6. OK ok ok, so I'm aaalmost grasping the essence of what you're saying, but I'm still missing that final puzzle piece.. I'm with you on the whole gyro effect thing, I see how the rear will turn outwards if you apply a force to decrease lean angle (and vice versa). But how does this apply to real life riding? How would you apply that force to change the lean angle of the rear tyre? By countersteering the front wheel, or by changing BP or by throttle control...? Because you ARE talking about the REAR wheel all along..? Lets take the front wheel out of the quotation for a second: HOW would you "steer for the rear" if your front end was in the air as you exit a corner (GP style) ? ... BTW, I was just thinking about how this phenomenon also affects the FRONT wheel as you turn on the bars. Interestingly, it seems that the "gyro effect" will contribute to leaning the bike to the left when countersteering to the right. So the front wheel actually "helps" the top end of the bike to lean over to the left when the lower end is turning right. Kind of like a team work between inertia and gyro forces. PS. That gyro phenomenon only applies when the bike is "unstable" due to the rider giving steering inputs. It doesn't affect anything when the bike is trailing happily at perfect balance (straight forward or at a constant lean angle).. Lots to think about and not much time to do it yet. However I will mention from riding motocross. With the front wheel in the air on a left turn if I wanted to lean left more, I seem to remember turning the front wheel to the right, which made it easier to lean left more. Also during a jump if I wanted to lean the bike left in the air to land pointing left some instead of landing straight (for a left turn placed right at the landing spot), I would steer the front right as I applied body english. The bike would lean left and I'd land sliding into the left turn ( which allowed more speed over the jump). Gotta think about racer's questions and assertions this weekend.
  7. Or the inside peg until it slid away from him. :-)
  8. The BOTTOM of the bike will go where the front wheel is pointing always, regardless of whether the rider or the trail points it, unless it's not on the ground, or sliding. When it's in balance the top goes there too on a parallel path. However, the conical steering action of the front and back tires being leaned, will also be acting on radius. radius is the result of where the wheel is pointing AND the conical steering. Traveling a path on a radius produces centripetal (inward) force. Yes. If the front did not behave so, the bike would go into countersteering state instead of balanced status quo, and so eventually crash through the changing lean angle that unbalances the forces. If you instantly turned the front wheel in at 50mph like you do at 10mph the bike would lose front traction, slide away and lowside. If it could maintain front traction it would high side. If you turned the front wheel only the amount it turns at 50mph, but were going 10mph, the bike would continue going into a steeper and steeper lean until it fell over lowsiding. the three main forces would be out of balance. The bike would be acting continually as it acts in countersteering, changing lean angle. it would do that until disaster unless the forces were changed to re-balance themselves. Since traveling a radius produces centripetal force, I guess yes. lean angle NEEDED for balanced status quo, is determined by velocity and radius. Actually any lean angle is determined by velocity and radius as well as direction of turning (left/right). Radius NEEDED to achieve balanced status quo is yes. the velocity NEEDED to maintain the other two at an unchanging level and get balanced status quo is yes. If you are looking for a balanced state of these forces in the bike, yes. Because I'm stuck with using WAY too many words to try and explain myself. That's not a good thing by the way. Like I said before, I don't know from physics. I'm just trying to practically figure out the factors at play which are numerous and some of which haven't been addressed yet when it comes to the effects of trail and some other things I think. Such as, when you accelerate, the rear tries to pivot around the headstock/fork angle, where it contacts the ground when a line is drawn through the center of the forks top to bottom.Slip angles will complicate things too I'd guess. How the contact patch behaves may complicate them as well. Then again you have the chance that I am totally wrong :-D I just don't think I am yet.
  9. I'm too old a fart nowadays at 62, but back in the day I rode smooth dirt track, then advanced to semi pro motocross when it was very light two stroke bikes, family stuff stopped further progression. Yes it is for traction. It is also very largely for something else that has not been mentioned as of yet. When you get the bike sliding sideways as much as you can in the dirt, sitting on the high side of the bike lets the bike move a very long ways sideways underneath you before your chest/shoulder weight drags it down into a steeper lean from hanging to far off the inside (thus sliding out). That's WHEN you are planning on sliding good. That's not so clear is it, so maybe approach it another way. If you go in sitting up on the high side (outside corner of the seat), you push down with your knee on the tank (and countersteering in) leaning the bike under you (leaned more than your body). You've already got it sliding (brakes, then rear brake) and it will slide sideways a good bit now. If the bike slides a lot the bike moves SIDEWAYS under you as it slides, so maybe your shoulders are now lined up centered in line with the bike's lean (kind of like cops and road riders who don't like to hang off ride the street, in line with the lean). the bike is no longer pushed down under you but most of the pivot is done. You've pivoted in a short space, so you are now exiting. The front tire may or may not be on the ground much on exit as you pin the throttle and clutch heavy acceleration. You need more traction on heavy acceleration, so to help with that you shove the bars (not turn them, lift them up and shove them away from you) towards the outside of the turn to help stand the bike up a lot more for traction (you've also countersteered the bike to stand it up by aggressively turning the front wheel INSIDE more sharply during a part of the pivot). The bike stands up so much your shoulders are likely hanging inside the center line (like road racing hang off minus the arse) as you come out of the turn, most likely at full throttle or at the least on very heavy gas. That's a sharp square off style turn, not using a berm or a long sweeper. A motocross bike (especially when I raced) is very light and does respond to a rider's weight inputs more than a supersport would. If you rode the dirt bike into a sweeper where you planned on a rather large slip angle of sliding, and you started out hanging way off the inside road race style, you'd get the following. When you got your slide and the bike moved toward the outside of the turn on you a long ways, your contact with the bike would begin to pull on the bike trying to lean it further down into the turn because you were hanging off to begin with, so now you're hanging of a LOT more and pulling the bike down. That would be opposite of what's needed at that point. Especially at lower speeds, your body weight off to the inside pulling for a steeper lean as the bike moved away from you, would succeed in leaning the bike more, and result in a lowside. I've both watched and experienced this. By sitting towards the outside and pushing the bike down under you, you create a situation where the bike can move a relatively long ways to the outside before your chest/shoulders (where a man's center of gravity is) are hanging off the inside, and you aren't likely to hang to the inside enough to pull the bike down. You probably will only be centered and be able to use hanging to the inside to straighten the lean of the bike up even more yet for exit, when combined with countersteering. It gives you a lot more slide control. Even in big sweepers, you will notice, whether it be flat tracking or speedway, the fast guys usually end up hanging chest and shoulders to the inside on exit as they stand the bike up more for traction. That traction gain to be used for extra throttle. One of the negatives of hanging off on the inside on a supersport road bike, is less slide control, the positives outweigh it and you aren't looking to slide big on the blacktop mid turn, at high speeds anyway. In the dirt for square off turns though, mostly I used the front brake hard coming in straight, kept it on leaning a small amount on a slight or big radius curve coming in, and let it off as I entered close to the pivot area, while staying on the back brake to keep the rear sliding good before the pivot point. I'd be way up front, slide into the pivot on the rear brake, countersteer and throw (knee) it down, clutch it out on full throttle while turning into the turn real hard (which would help with standing the bike back up to catch the acceleration sliding) and exit. That was two stroke type power though and the progressive traction on dirt let you get away with it all. With that skinny little knobby up front you weighted the ###### out of it to dig the knobs down in and you were either on the brake or a reasonable helping of gas for most things. If you tried coasting at all you lost the front and ate it unless you were actually going too slow (and you still might lose the front going slow). Rule was brake or gas to keep the front. An unweighted rear tire spun up easier and you could straighten the lean up more without highsiding by having it spin heavily reducing ultimatel traction for just a bit as things progressively grabbed. Also that spinning rear added some gyroscopic stability at lower speeds. You could shift body weight rear when you stood the bike up and had it moving forward on exit and things were already beginning to hook up good sideways. Essentially you gave away ultimate mid corner speed to gain the advantage of better slide control and less time spent at risk at heavy lean (traction can go away fast at big lean on the dirt over rocks and bumps big enough for the back tire to lose contact with the ground). For the most part you were on a berm using it like a banked turn, or you ran a line that kept the turning part of the turn real tight and of very short duration minimizing what you gave away. The line in and out you straightened up more on larger radius to maximize traction for braking and gassing it out. The little bikes had to run more sweeping lines to some degree, but they used holding it wide open and clutching the bike in a higher gear to try and minimize needing wider radius mid corner lines. I've never run the new 4 stroke dirt bikes, so there will be some differences to a point. I did ride the bejeebus out of a friends old British Ariel 500 single (not a lot of power). The extra tractability of that motor let you hang the rear out speedway style in a farmers meadow like I couldn't believe, and still maintain control. I need another go round at life, sigh. The new bikes look like a blast. So supermoto, some guys seem to be going for the dirt bike body position style to utilize sliding it in like on dirt, while some others are going for less lean angle and less sliding to gain more mid turn speed like in supersport.
  10. I'm just going to pick on a couple of points. I do know that when the front suspension compresses rake steepens and trail shortens along with the wheelbase. The front wheel takes on more of the load of the bike's weight as well (amount depending on whether the brakes are applied or throttle off or not). If the bike is accelerating and a bump compresses the forks the rake, trail, wheelbase shorten but the front wheel may not take on more weight and could even be in a state of lessening weight due to acceleration shifting the bikes CG rearward. As to countersteering into the wind: The rider has to push the bars, countersteering to cancel the centripetal force of the wind, thus progressively leaning the bike into the wind, UNTIL THE CORRECT amount of lean is found. That's where gravity (lean angle) balances the centripetal force of the wind. AT THAT POINT, when a balance of gravity against the other forces is established and the bike describes a constant path at a constant lean, there is no more countersteering happening. Lean angle is constant, path is constant since things are in balance. It doesn't matter that the rider has to maintain a certain pressure to keep the forces balanced (feeling like countersteering to the rider). It doesn't matter that the bikes trail and gyroscopic effects can't do that on their own, due to the added centripetal (sideways or inward) component of wind. What matters is the bike is in a state of relatively balanced forces and so is not countersteering anymore. Status quo is found regardless of riders need to press the handlebar to keep it. As soon as some input (steering, path direction change, change in wind's centripetal force etc), as soon as one of the forces involved change enough to disrupt balance of forces the bike is AGAIN countersteering until the new balance is achieved, or things degrade far enough for a crash. So, if the forces of momentum, centripetal force, and gravity are in balance the bike is NOT countersteering. The lower portion of the bike is following the direction of the front wheel at the same rate as the axle. The top of the bike (headstock, tank, rider etc.) is on a parallel path to the bottom of the bike (axle lower frame etc.). That's true whether turning or going straight, whether pressing on the bar or not. It's true whether the bike's trail is keeping things in balance or the rider is doing it. If the forces of momentum, centripetal force, and gravity are OUT of balance, THEN the bike is in a state of countersteering (a state of unbalance) . This is regardless of what the rider has to do pressure wise on the bars (regardless if it is the trail doing the deed or the rider doing the deed of balance or unbalance). I say unbalance of forces on the bike is countersteering because in unbalance, the top of the bike (headstock) is NOT exactly following the bottom of the bike thus creating a lean angle/gravity change. When the bike is countersteering it is in an unbalanced state where the bottom of the bike is on one path and the top of the bike is on a non parallel path thus changing lean (the bike is countersteering). When the headstock does not exactly follow the direction of the axle's forward movement, lean angle changes (if the front axle and wheel moves to the right and the headstock lags behind moving right on a slower wider arc, then the bike leans left as an example). The front axle can be steered out from under the headstock, or back under it. This is done by pointing the front wheel in a new path. This is countersteering and reflects an unbalanced state of forces on the motorcycle. When the forces of momentum, centripital force, and gravity balance, the headstock follows a parallel path to the front axle, both moving in a direction at the same rate, and the bike is in balance (whether going straight of describing an unchanging arc). At that point NO COUNTERSTEERING is happening, and the bike travels a straight line or a constant arc at a constant lean angle. SO, it can be said, if the headstock exactly follows the direction the front axle is traveling in on a parallel path, at exactly the same rate of travel, the bike is in a state of balance of directional forces and is in balance. If the headstock is on any slightly different non parallel path than what the front axle is moving in, the bike is in a state of countersteering because the lean angle and ultimately the path of the bike will be changing. The balance between momentum, centripetal force, and gravity will also be altering (in flux or inbalance ). SO, balance of forces and constant path, there is no countersteering going on and everything top and bottom goes in the direction the front axle is moving (the direction the front tire is pointing) at a UNIFORM rate. Thats so even if the bike is leaning into the wind going straight, and the rider is pressing on the bars to keep the forces balanced. In an unbalanced state of the forces mentioned, the top of the bike (headstock tank rider etc.) is moving in the direction the front axle is pointed at some different rate and different path over time. The bike is changing lean angle not keeping it constant. Very important to getting a grasp on this is the fact that the axle and lower portion of the bike will ALWAYS HAVE TO follow the direction the front wheel is pointed, period (that is UNLESS the front tire is sliding or off the ground). It physically HAS to, things are bolted together and not made of rubber bands, and a rolling tire goes where it's pointed if it isn't sliding. Change where it's pointing, you change where the bottom of the bike is going. At a slower rate (due to momentum) you change where the top is going as well. The reason the bike's top can change direction of path slower than the bike's bottom, is the bike can lean, since there are two wheels not 4, and the top is not directly bolted to the wheel on a vertical plane like the front axle is. The rear wheel is ultimately connected to the front wheel and HAS TO trail along in some manner (UNLESS it is sliding). Now the rear under weight shift can INFLUENCE "the direction the front points" as the front directionally trails a balance of the forces acting on it. But, the direction the front is pointing matters much so long as it has traction. I have to mention that in reality, the bike is only "moments" in an actual state of balance as it "hunts" back and forth for balance. It gets a tad out this way, mildly over corrects, gets a tad out the other way, and does a constant slow weave even when going straight. It's so small you don't feel it but it's always "hunting for balance" even when it feels stable. It confuses the issue talking about it though as it adds further complexity to a complex subject. So, best to ignore this small unbalance hunting effect when trying to think of balance/unbalance of the bike when turning. In reality the bike is always countersteering itself a tiny amount when acting stabilized. That just makes things harder to grasp though so I'm ignoring it for the most part. Though it may lead to clarity of thought in discussion of how trail is trailing along, and how the bike finds balance of forces from that. The front trails along, and when you write that, it appears language wise, to imply it is passively following without exerting turning influence or force acting through it, that's not so though. When cornering, the forces of momentum, centripetal force, gravity, and forces due to trail are duking it out at that front contact patches well as at the rear. Beyond this I haven't thought through things with trail and trailing along yet. It seems to me the answer would lie in forces at the contact patch and how they balance or unbalance. However think about it, if the bottom of the bike did not HAVE TO follow the direction the front wheel is pointed in, then the rear and front wheels conical steering would wholly determine radius alone, countersteering WOULD NOT work, and turning the front wheel into the turn full lock would have no effect. The fact that putting pressure on the bars one way or another DOES countersteer a bike, proves the bottom of the bike HAS to follow the direction the front wheel is pointed period. The front always has an influence on direction until it is off the ground.
  11. Amen! Thanks leftlaner, I hope I am correct, which i think I am. Here's a quote from a guy currently on a trip to and around Alaska that I think relates to this thread and the need for a balance of forces. this also helps prove in my mind that you can steer the front wheel of the cycle in a direction and the rear and indeed the whole cycle will follow so long as gravity is balanced out correctly with any forces involved. the wind was in part the centripetal force in this case. He was leaning right and still able to countersteer, then steer left and turn left while leaning right into the wind. He was reducing the winds centripital (inward) force with lean angle (gravity) until the bike went straight, then he lessened the lean angle (gravity) pushing on the wind, so the centripital force would start moving the bike inward, and so the bike WOULD turn even though he was still leaning the wrong way. I'm saying the bike could not turn without the front whee being pointed into the turn some (the correct amount to balance out momentum, centripetal force, gravity to get the desired radius). In this ODD case wind AND wheel pointed in to desired radius was centripetal force.
  12. Just a few quick thoughts. Centripetal force is the force that is exerting it's influence/push TO THE INSIDE (center) of the turn. That's created through steering into the turnwith the front wheel AND conical turning influence of a leaned tire. Centrifugal force (to the outside) is a "felt" effect, not a force. It is what a person feels in a turn pressing them to the outside so it's given a name. HOWEVER that is the result of forward momentum trying to go straight WHILE centripetal force tries to push things to the inside creating a turn. The Centrifugal force is the felt combination of trying to go continue going straight and trying to turn inward at the same time. IT can be FORGOTTEN when thinking about a bike in a turn. It is instead the momentum forward speed, and inward centripetal force that must balance equally against gravity for a bike to have a constant lean and turn. To balance gravity, if the speed is low (force small), the inward turning centripetal force will have to be higher to add up to enough for balancing gravity. If the speed is higher (high force), the inward turning centripetal force will have to be correspondingly lower to balance the same gravity (same lean angle). A bike can have any amounts and combinations of forces going on that do not balance but it will be unstable then and left that way long enough without change, heading for a crash. That's how we initiate a turn, destabilize it to tip in, and re-stabilize it again in a leaning/turning attitude. There has to be that balance of forces for it to be stable in a turn where it carves a constant radius. Change any one thing and the others will have to do a corresponding change or stability will be gone. Stability is gone tipping in and straightening back up. Stability happens mid turn where you follow a constant radius. Decrease speed and you will have to change lean angle, and or turn in (centripital force=radius) to get balanced status quo again. (hard thing is that when you steer you have both countersteering (changing lean angle) AND the front going in the direction the wheel is pointed, with the rear following it, happening AT THE SAME TIME. Decrease radius (turn in, centripetal force) and your lean angle or speed will have to change. Decrease lean angle and your speed and or radius will have to change. That's in order for a balanced constant state to be achieved that is. You can't single things out much because EVERYTHING here is having it's input at the same time and has it's influence on balance of forces. It's all interrelated, change one thing and everything in the whole system has to also change to get balance again. Trail, happily when you lean the bike the contact patch moves inward causing the trail to steer the front wheel into the lean some (what turns out to be actually needed). Also the wheel tries to point in the direction the headstock/forks/axle are moving in. That's due to it's trailing along behind the rake of the forks/headstock angle. If I take my heavy two up bike out (Bandit) and run cones at slow speeds with it in a parking lot, the front IS NOT trailing along enough for the tight turns to be made with little steering input. I have to physically help turn the front wheel into the lean enough to make the tight turn. It turns in on it's own yes, but is too slow about it and the bike would fall over before the trail could catch up and turn the front inward enough. The rear wheel follows the front and the bike makes the tight radius. I then "over turn" the front wheel into the turn (turn too sharp), that countersteers the bike (front wheel turns in and axle moves to the inside faster than the headstock can follow), the bike stands up out of the lean, I "hold" the turn in (the trail does not do it) and the bike stands up straight and leans in the other direction (for a turn in the opposite direction now) as the wheel continues to move faster than the headstock can follow (the top of the bike cannot keep up with the bottom front wheel causing lean). At this point the trail tries to turn the wheel into the new turn in the other direction (doing cone weaves). HOWEVER, I need to hurry it up on that bike (help it). It is not a passive does it's own thing system at that slow speed. It tries but is heavy and slow about it. The bike feels heavy steering because I have to do a lot of steering myself with it at that particular slow speed maneuver. If I was willing to do less tight turns, I could wait for the trail and manage speed properly to not have to add my steering input I would think. My point being, the front does not always just trail along. Even when it does it is still doing a sizable portion of creating centripetal (radius following) force, WHILE it also can potentially be countersteering as well AT THE SAME TIME. If the front is turned in too much or too little to help speed balance gravity, THEN the bike undergoes countersteering. That's an important point. Even when the bike is countersteering, the whole machine does try and follow the direction of the front wheel. That's another important point. Countersteering happens when the top of the bike can't quite keep up with the bottom front wheel as it rolls out from under the bike to one side or another. When the bottom front wheel of the bike goes farther right than the top of the bike does, the bike leans more left. You could steer the wheel left then and steer so sharply it rolls the front back under the bike and straightens it up again. Both of those things are countersteering and the rider is the one who initiates it, leaning the bike into a turn and standing the bike back up coming out of a turn. The front axle and lower front part of the bike still ALWAYS follow the direction the front wheel is rolling. The difference is in what the top of the bike does, whether it follows along or not. In the balanced mid portion of the turn the top of the bike is following the front wheel along with the axle and the bottom of the bike AND the rear wheel is being brought along. That's so long as the front has some weight and traction.This is during mid turn status quo. I do maintain that weighting one wheel over the other correspondingly increases the influence of the weighted wheel. Hence you can have the hinged headstock influencing more, or the unhinged swing-arm stabilizing things more. Have someone sit on a bike and you kick the front wheel sideways. Then go kick the rear wheel sideways. The front will destabilize with ease causing the forks to turn. The rear just receives a bump from the same force kick. It's all because of the direction of the steering hinge. By the way, conical steering does work as you can lift the front end of a bike off the ground mid turn in a wheelie and continue to turn on the back wheel. You are however stuck with the singular radius that conical steering produces and so speed and lean have to be correct for it to work (as the front can no longer help by changing radius through steering or lean through countersteering). In a tight turn where the front wheel is needed to get the desired radius the turn would open up when you lifted the front off the ground. This follows in the real world. I maintain the conical turning of the leaned tire AND THE AMOUNT you or the trail steers the front into the turn creates the centripetal force that combines with speed to balance the falling gravity force of the lean. If you or the trail don't turn in enough for the speed there is no balance. If you or the trail turns in too much there is no balance. The amount of turn in needed depends on lean angle and speed.
  13. This is what I've been trying to say, even if poorly with too many words. I think I've stated the last half of this post more clearly than the first, but here's what I've come to. I've thought about this more. I feel I have a grasp on the basics. You have many things going on here at once. You have "conical steering" AND "car type steering" (where the rear wheel follows the front) , ALONG with "countersteering" (where the front wheel gets steered either 'out from under' or gets steered 'more underneath' the top of the bike and rider), and all these are happening at once. They are all used to establish a state of equilibrium between momentum, centripetal force, and gravity in a leaned state when cornering. Lest say you are leaning 35 degrees while going 10mph. At that slow speed, the amount of turning from conical tire turning forces is not adequate enough to balance gravity at a 35 degree lean angle. If the front does not turn into the turn and tighten the radius further, "car steer" in a sharp enough radius, the bike and rider will fall on their arse as gravity sucks the bike down further and further. Conical tire steering turns too large a radius over what is needed to overcome gravity at that lean, at that 10mph speed. Some additional radius tightening method is needed to strike a balance of forces. SO, the front tire turns into the turn and tightens the radius car steering style, enough to balance gravity against velocity at 35 degrees of lean at 10mph. This is a form of countersteering going on (steering the front back under the bike) at the SAME TIME that car steering is operating (rear wheel following where the front wheel is pointed) AND conical steering is doing what it can to contribute to the situation. I'm defining countersteering here as either A. steering the front wheel out from under the top of the bike and rider, thus initiating lean angle or leaning the bike in more. OR B. steering the front wheel BACK under the bike reducing lean angle, or standing the bike up more. THIS IS DONE with the front wheel (which does not say you can not wheelie and use rear wheel conical steering to corner IF you have the speed needed to balance gravity at a given lean. Since the rear wheel can only steer at lean through conical steering alone, I'd bet you dollars to donuts that in a wheelie lean angle DOES determine radius, regardless of speed. However we have two wheels and one can steer the front under or out from under as well as steer the whole machine in a direction. At any rate back to the 35 degree lean turn at 10mph. Let us say we are doing this turn as described now. The front wheel is turned in very sharply doing MOST of the actual turning in this low speed situation. It is turned sharply because the radius must be tight to balance gravity at that weak speed force. In order to make it easier to think about, let's say it is turned in to full lock, and the bike is doing a 25 foot radius at 10mph (arbitrary full lock, arbitrary radius numbers) and momentum and gravity is in balance and the bike will do this all day at this setup, 35 degree lean, full lock, 10mph speed. NOW, let's instantly accelerate the bike to 100mph keeping the lean angle at 35 degrees and the front wheel turned to full lock. In our make believe setup we'll say the tires can NOT slide. the bike WOULD still try and describe a 25 foot radius following the front wheel, conical steering effect would still be operating at a given effect regardless of speed. In this case the front wheel would still follow the 25 foot radius, but this would overwhelm gravity and bring COUNTERSTEERING (as I defined it) into play. The front would steer back under the top of the bike and rider standing it straight up and down (because the radius is the same, but the momentum was increased way past balancing gravity[lean angle]), it would further continue on the radius and after the bike got straight up and down it would lean the OTHER WAY... performing a massive high side. This is what would happen in the real world as well but sliding or losing traction would be involved (causing a front traction break lowside, if the front could hold the bike would highside). THAT"S WHY a bike's radius increases with speed. To successfully turn a bike, you have to BALANCE the forces with lean and radius (or centripetal force). We are using a changeable momentum (speed) and a changeable centripetal force (radius) in order to balance the constant force of gravity. At low momentum (10mph), for a given gravity (35degrees of lean), we need a higher centripetal force (tighter radius) to balance that gravity since the speed is low. At a high momentum (100mph), to balance that same force of gravity (35 degree lean angle) we can only use a very small centripital force (large radius) to add to momentum (speed) for balance of gravity (35 degrees of lean) to be struck, and a successful turn made. If we fix the gravity (35 degrees lean angle) We can either vary the speed (momentum), or the radius (centripital force). If we increase one, we must reduce the other. We increase the speed the radius must be expanded or balance goes away. If we lower the speed the radius must be tightened to make up for it to balance the constant force of gravity. How do we vary the radius on the bike for a given lean angle? The conical steering is constant. the only variable available to actually change radius is how much the front wheel is turned in or not (again car type steering principal) It matters not if the front wheel is trailing along. If it is turned in, unless it is sliding, it will roll in the direction of it's turn AND it will also be doing some conical steering as well. If it turns that way the forks follow. the headstock will try and lag until a status quo is set (countersteering). IF the forces are balanced, and ONLY if the forces are balanced will the bike hold it's lean. Otherwise it will be falling in or standing up. One can countersteer to "fix" the unblanced forces with a change in centripital force (radius) OR a change in speed (momentum) Gravity is the same for a given lean angle. The thing is ALL these things work in flux, in changing combinations. Gravity is the same until the lean angle changes, then it is different. SO, gravity (lean angle) is a constant for a given lean angle but changes as soon as the lean angle alters (the same gravity force acting through an angle). Conical steering force is constant and the same regardless of speed, for a given lean angle but will change radius with changing lean angles. Momentum (speed) can change. Centripetal force (radius) can change. Countersteering is always in operation until a balance of forces is found that sets the lean angle to constant, then no countersteering is taking place as long as the lean and forces stay the same. Car steering (front of bike goes in direction front wheel is pointed, rear follows along) is ALWAYS in play but is ALSO acting as countersteering UNLESS a balance of forces has been established that maintains lean angle. In countersteering the front wheel steers car style (the axle moves in the direction the front wheel is pointed), BUT the headstock lags behind, trying to continue it's former direction. This changes lean angle (either lean, more lean, less lean, or total change in which side you lean to). AS SOON as a balance of "momentum, centripetal force, gravity," IS established thus holding a constant unchanging lean angle, THEN BOTH conical steering AND car steering are in total play (so long as the front wheel contacts the ground). Countersteering isn't being used at all (unless the rider or other force makes a steering change upsetting things), and the axle AND the headstock BOTH DO follow the direction the front wheel is pointed in to the same degree. THIS is how a bike can describe a tight turn at slow speed with the front turned in sharply and a wide turn at high speed with the front barely turned in, or not turned in (totally relying on conical steering). The front can even turn out to balance a rear wheel slide car style IF the forces of momentum (speed), centripetal force (radius), and gravity (lean angle), remain in BALANCE. Again at slow speeds (weak momentum force) you need a tighter radius (front wheel turned in a lot to increase centripetal force) to balance the gravity of a 35 degree lean angle. At high speed (strong momentum force) the speed is doing a lot of the balancing of gravity (35 degree lean angle) so to keep forces balanced, you can only add a small amount of centripital force (open radius), making a large radius necessary for the same lean angle. Otherwise forces would be out of balance, countersteering would be active, and lean angles would be changing (as would all the things in play change until balance was established again or if not, then a crash occurred). To summarize, The radius only changes with speed due to the front wheel changing how much it is turned into the turn. If conical steering was relied on solely (at two wheel bike with welded headstock) lean WOULD determine radius regardless of speed. Of course you couldn't balance a bike with welded headstock because you could not steer the front wheel of a falling bike back under yourself fast enough (conical lean turning alone only turns very slowly, not fast enough to maintain balance). As to how trail comes into play with the set it and forget it thing I'll think on that some more.
  14. Interesting point, and I'll play a little again the next time I'm out, probably tomorrow. It's been a long time since I've messed around with footpeg pressures odd to my normal thing. I'll reserve opinionated comment until I play with it again. My memory says there still are differences to be found, could be wrong though. If I am wrong, there's no harm in my weighting the outside peg more anyway then. :-) Where are you holding on when you weight the inside peg? Are you "locked on" with outer leg? Is it possible that your body position (hence CoG) changes and could have some effect when weighting the inside peg? Or inadvertent handlebar inputs might be occuring? I haven't played with this much on or off the track and I have heard other road racers say that weighting the inside peg helps them to initiate a slide or weighting the outside peg helps them control a slide, but, Keith claims that weighting a peg in and of itself effectively does nothing. Now, I don't know that it holds true for dirtbikes as much, especially at low speeds, but, maybe you could think about these questions while riding tomorrow? Have fun! r Father's Day weekend, so the only riding I got in was two up with the Mrs. so no oddball peg playing got done, I'll do it during the week. This is my experience with it. and what I was thinking of when I said I disagreed just a little bit with the statement peg weighting does nothing (it may do nothing for turning, but I'm not talking about turning the bike with it). It may not steer, but weighting still does something. Again I'll reserve standing by that hard and fast until after a bit of play time just to double check a feeble old memory and make sure there's no question about it in my mind, given respectable opinion to the contrary. I've found in the past that inside peg weighting will get the bike to break traction for a slide sooner, outside peg weighting tends to stabilize things more and aid a small bit in maximizing traction. I don't try and steer with the pegs, that's what countersteering is for, so I don't find myself trying to weight the inside peg for anything in everyday circumstances (that's the original guy who posted who does that and I'm thinking it can't help his sliding situation). However I DO habitually outside leg toe raise, outside knee into the tank, weight the outside peg, and get weight off my hands so I have bar/grip/front-end feel, and no unwanted inputs. Anytime I need stability for anything with the bike the outside peg gets more weight, including in a slide. Just did this in the rain a few days ago with a throttle on rear wheel slide. Again, I'll experiment during the week to see if I "can" agree with "peg weight does nothing," but I'm thinking you need to get pretty near triple digits (or be on a super duper porker bike) before I would end up agreeing with that, given what I remember of my old time experiments. Also, I'm quite certain, with a dirt bike at speeds up to 70-80mph there is no question whatever that it does a great deal to help both bike and slide stability to have the outside peg weighted. It's just a fact of experience riding them. That would be one reason I'd personally avoid inside peg weighting entering a turn. I mean inside peg weighting on entry, it's OK, but a lot of leg work for no helpful return that I could find in the past (and even a negative return to my mind with easier sliding for no helpful reason). Whereas I can definitely tell you a 50mph rough patch of pavement on either of my road bikes mid turn, especially downhill, the bike AND your body will stabilize more through there with outside peg weighting. That's also so for sliding situations to my mind (though I'll check again). Again, I'll not stand fast until I experiment with current riding as I've been doing it my way for some years now without playing with alternates. Also again, I'm NOT talking about steering the bike, but how your body locks in, and how the machine and traction responds to sliding and rough areas with a bias to outside peg weighting. I lock in with some outside peg weighting before I ever initiate turn in. Then I maintain it to at least some degree (depending upon need) throughout the turn. I always have more weight on the outside peg than inside peg through a turn no matter my body position. It never hurts to "real world check out" and confirm or deny new input from others who know their stuff though. :-) I'll get to play sometime during the coming week.
  15. I would want to disagree just a tiny small bit with the statement as set forth. Understandably a dirt bike is lighter than a Supersport and so reacts more to body weight inputs, however the following principle still applies to at least some degree, I believe. Street bike wheels are comparatively heavy and create significant gyroscopic forces at speed which stabilize the machine such that weighting one footpeg over another is essentially meaningless. Not to mention the relatively low speed and near zero gyro forces created while negotiating your hypothetically steep and slippery switchback goat path. Interesting point, and I'll play a little again the next time I'm out, probably tomorrow. It's been a long time since I've messed around with footpeg pressures odd to my normal thing. I'll reserve opinionated comment until I play with it again. My memory says there still are differences to be found, could be wrong though. If I am wrong, there's no harm in my weighting the outside peg more anyway then. :-)
  • Create New...