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Lnewqban

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Lnewqban last won the day on July 13

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About Lnewqban

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  1. Steering Video No Bs Bike

    I was corroborating your statement, which I found to be correct. I agrre with your last post as well. Sorry about the confusion.
  2. Steer for the Rear - Ch13 of TOTWII

    1. The bikes want to follow a straight line, if they can, if not forced otherwise (remember the Newton's law we described priorly?). A sphere rolling on a flat surface can't make a curvilinear trajectory. A disc (like a coin or a tire) can, if rolling over the same flat surface off a vertical position (leaned). For keeping that leaned attitude, someone or something must have initiated the leaned rolling. The Newton's law manifests itself in the case of the rolling leaned disc, however, there is a force making the disc deviate from the straight trajectory, turn instead over a circle: a portion of its own weight constantly pulls the disc towards the center of that disc. Same force is what keeps the motorcycle leaned and turning in that out of-the-curve wheelie. If that centripetal force (portion of the weight) equals the centrifugal effect of the circular movement, the bike as well as the disc will keep describing the same circle over and over again. Yes, your wheeling bike will keep turning even after the end of the curve (you must put your front tire down and counter-steer to decisively straighten the trajectory up). If that centrifugal effect becomes bigger that the centripetal force (portion of the weight), then the bike tends to open the circle (to constantly increase its diameter). That is what makes a leaned bike that is excessively accelerated (greedy application of throttle) run wide and subsequently reduce the lean angle. That is also the reason that the leaned and turning bike in that wheelie will tend to return to a straight trajectory, if enough acceleration and time is provided. 2. You could accelerate harder than 0.2 g, let's say 0.9 g and achieve 10/90 weigth distribution. Consider that your rear contact patch will be loaded with harder longitudinal forces (exactly 90% the magnitude of the combined weight of your bike and your body, because F = mass x acceleration). If the rubber of your good racing tires is able to achieve traction of 1.1 g, then, your rear tire can only deal with around 0.3 g of cornering lateral force (around 20-degree lean). Then, you will be forced to slow down to prevent a slide (like riding on wet-dirty pavement). There it goes your excess of acceleration due to the need to moderate your speed. Even if you make the turn in those conditions, you will only have a fraction of the grip that you could have in the front contact patch (only 10% of the weight on there, remember?) for countersteering out of the turn. 3. Let's do some math: Sustained acceleration of around 1.0 g (32 ft per second or 22 mph of additional speed per each second in the curve) will give you a nice sustained wheelie. If the limit of available traction allows a maximum speed of 80 mph in that curve, that will be your leaving or exiting speed. If it takes 3 seconds to complete the curve in the described conditions of strong acceleration, your maximum entering speed must be 80 mph - (22 mph x 3 seconds) = 14 mph. Your average speed through the curve would be (80 + 18) / 2 = 49 mph. Another rider following the recommended 40/60 weigth distribution (acceleration of 0.1 g) would increase the speed at a rate of 2.2 mph per each second, which means same exit speed of 80 mph and entering speed of 80 - (2.2 x 2 seconds) = 75 mph, being his average speed of 77 mph. Note that he used 2 seconds while you used 3 seconds (gross approximation only). Hope those numbers help you see the dramatic difference. There is more than maximum available traction involved in this picture of moderate or recommended weight distribution: steering, suspension, tire performance, stability, as mentioned in my previous post. Practical considerations: You want to keep your steering tire loaded with a decent amount of weight or available traction. To force a speeding heavy bike in and out of a lean angle requires muscular effort and a solid fulcrum, which is a gripping front contact patch. That loaded front tire can save you in an emergency swerving and in a slide of the rear tire. Imaging going through a quick chicane with only 10% of the total weight on the front tire? Please, excuse my long post.
  3. Steer for the Rear - Ch13 of TOTWII

    I believe that the answer to your question can be found in the last section of that chapter: Stable suspension. Perhaps re-reading Chapter 3 could help you see the whole picture more clearly.
  4. Steer for the Rear - Ch13 of TOTWII

    We care the most about inducing the 40/60 weight distribution via throttle control when we need maximum performance from the tires and the suspension, when cornering on asphalt as fast as possible. If, while cornering like that, we put more weight on one tire, we compress that suspension and load that tire beyond the optimum state or conditions. The suspension becomes harder, the contact patch becomes a little bigger and the profile of the tire less pliable. Following the irregularities of the pavement is more difficult for the tire. The rubber becomes less elastic and it changes its shape more slowly. Once the weight carried by that tire while cornering hard reaches a crtical point, the available traction that the over-loaded tire can offer rapidly decreases. During a leaned wheelie, all the weight of the bike and the rider is on the rear tire and on the rear suspension. That tire would not be able to develop the traction demanded by the lateral forces of extreme cornering, which normally surpass the value of that weight. The wheelie always happens during the way out of the corner and at a lean angle that is much smaller than the max lean angle required by that turn. If the rider tries to wheelie the bike at that max lean angle, when the lateral forces of cornering on the contact patch are close to the max, the tire would slide. The tire would not slide only if the rear contact patch has been unloaded enough from lateral forces in a way that its performance can be reduced by the the extra weight.
  5. Steering Video No Bs Bike

    Using arm's force to countersteer and make any bike turn, we cancel the self-correcting property of the steering geometry. Motorcycles don't really need a rider to avoid cornering:
  6. Steering Video No Bs Bike

    First Newton's law of motion: In an inertial frame of reference, an object remains at rest or continues to move at a constant speed along a straight line path indefinitely, unless acted upon by a force.
  7. CORNERING VS. RPM INCREASE

    You are welcome The difficult part of your question is the 50% throttle: something hard to get precisely accurate. Full or partial throttle only means that the power delivery of your engine would be maximum or partial, leading to similar results than in the OP's case. The power plant of any bike delivers the necessary torque (rotational force) at the necessary rate (rpm's or torsional speed) to compensate for the forces that resist the acceleration and movement (internal friction, hills and aerodynamic drag mainly). At partial throttle, you are taming the engine to deliver exactly what you need to achieve certain final speed or rate of climbing or acceleration (a specific amount of resistive forces). At full throttle, you are full feeding the engine to generate maximum torque-rpm's combination (HP), which will be naturally resisted by certain amount of resistive forces (aerodynamic drag force grows with the square of the speed), which will result on maximum acceleration and speed on a level road. Electric motors have a delivery of power that is more or less linear with the "throttle opening". They will burn themselves trying to give you exactly what you ask. That is the reason for which electric bikes need few or no gear box to select gears. An internal combustion engine is a pneumatic machine that very much depends on "breathing" and over-the-piston pressure. That breathing is determined by intake, valving and exhaust and rpm's. That pressure is determined by the expansion of the gases due to the heat of the combustion. That makes them have a delivery of power (HP) and torque that is a curve rather than a line. For partial throttle, the amount of mix (air plus fuel) is artificially restricted (carb(s) or FI alike) via increasing intake resistance (butterfly damper(s)). For full throttle, the amount of mix is allowed to be has high as possible. After certain point along the range of rpm's, the breathing or mix intake gets compromised due to turbulences, needed time to expel the exhaust gases and valve floating (lack of time to fully close) and torque followed by HP begin to decrease. A good selection of the transmission steps and sprockets (the equivalent to manipulating the diameters of the wheels in the OP) tries to match max speed with the point of rpm's on the curve where the engine is stronger. That selection is always a compromise for tracks of different configurations (max acceleration out of curves (max torque) versus max speed on straight sections (max HP)), in order to complete the circuit as quickly as possible. If you wrongly select that 22-inch wheel for a track of few fast turns only and long straights, that other bike with a 27-inch will have an advantage over yours, reaching max speeds that are higher than yours. At full open throttle, the engine of your bike will reach its max HP about the same rpm's than the other engine, but it will not reach the max speed of the other bike with the bigger wheel. What happens is that your engine will deliver higher rearwards force onto the contact patch of the smaller rear wheel than needed to counteract the resistive forces generated by that speed (excess of rear wheel torque), but will restrict its own breathing or choke itself as soon as it tries to turn that smaller wheel faster to keep up with the other bike, resulting in less torque to fight the resistive forces (returning to the balance point). That is what happens when you extend a gear (second gear, for example) beyond the proper point of switching, the engine keeps screaming, but the bike does not move faster. When you switch to the next gear is the equivalent to replacing your rear wheel with a bigger one: you are simultaneously slowing down the rpm's of the engine and increasing the resistive torque, moving the operational point of the engine back over the curve of HP to a state in which it can deliver higher torque by breathing better. In extreme cases, when the engine is unloaded too much, even when the delivered torque cannot push that wheel (downhill, for example), it will reach the rpm's limiter, which is designed to prevent the auto-destruction of the engine due to excessive forces of its internal alternating parts, cutting the ignition and temporarily killing its strength. In essence, the proper diameter for your theorical wheel (sprocket and/or transmission selection in practical terms) should make your engine rotate at the optimum average rpm's (between top torque and top HP) demanded by the track conditions. https://m.youtube.com/watch?v=3idIpc0Bv_I
  8. CORNERING VS. RPM INCREASE

    Welcome, Kneedragger727 What the video shows is very close to be true. They show two different engine's rpm's (in and out) for the same speed of the bike. If you carefully watch between 3:33 and 4:00 times, you can detect an error: entering and leaving speed/engine rpm's ratios must be exactly the same when the bike is perfectly vertical. Why do the RPM increase without throttle input? Because Newton's first law of motion: "In an inertial frame of reference, an object either remains at rest or continues to move at a constant velocity, unless acted upon by a force." Because the masses of bike and rider try keeping a constant velocity, the engine "is forced" (see further explanation below) to spin faster by a smaller rear wheel that is forced to spin faster. Rear wheel and engine are solidly connected by a gear train (there is no relative slipping or jamming). In order to follow the constant speed or inertia of the bike, the leaned rear wheel must cover the same linear distance in the same period of time as when vertical, having now a smaller diameter and perimeter. The only way for the wheel to achieve that is by spinning faster (increasing its angular velocity) in the same proportion in which the diameter gets reduced (10% reduction in diameter induces 10% rpm's increase). Velocity of bike = Radius of wheel x Angular velocity of wheel Further explanation: When the throttle is full open, the engine is not really forced to spin faster. There is still enough pressure in the combustion chambers as for the engine keep pushing the rear wheel to rotate, although not at peak torque. The inertia phenomenon explained above unloads the engine (less torque applied over the rear wheel is needed), which performance point moves over the torque curve to a new state of lower delivered torque and higher rpm's. Nevertheless, if the leaned situation would last long enough, the speed of the bike and the rpm's of the engine will go down some. Because of all that, at the end of the curve the leaving speed is slightly lower than the entering speed of the bike. The whole story is that the engine and the gear train have their own rotational inertia and tend to conserve it due to the very same first law of motion........"unless acted upon by a force." A portion of that force is provided by the impulse or the change in momentum of the moving masses of bike and rider (the rest of the force is provided by a weaker engine off the peak torque). Impulsing the engine to spin faster plus the additional internal friction losses of engine and gear train cost energy. The kinetic energy (read speed) of the bike pays for that energy demanded by additional rpm's of the engine. If rather than moving at high speed, your bike with a wheel of smaller diameter (or a much bigger rear sprocket) would start from repose, the final speed of the bike and the the rpm's of the engine would end up being lower at full open throttle.
  9. Dirt vs Asphalt riding styles and technique

    Revisiting your #1 question, asphalt riders push the bike under them sometimes. Both types of riders are improving the agility of the bike to lean over the desired side when they "disconnect" the mass of their upper bodies from the mass of the bike. Yes, the result is an exaggerated final lean angle, but that could be beneficial on asphalt as well as the front tire turned at full lock will describe a smaller radius with a greater lean angle. The first five minutes of this video show the dramatic differences in steering inputs, accuracy of lines and available traction between dirt and asphalt: https://m.youtube.com/watch?v=BzF_q5ivlKE
  10. Dirt vs Asphalt riding styles and technique

    1) The traction is so marginal that the front tire cannot force the bike to turn as easily as tires on asphalt can. Sometimes, the rider tries digging the front tire into the loose surface in order to gain a traction that depends more on surface material building up over the sides of the tire than on pure friction. He/she achieves that by transferring the weight forward, by moving the body forward in the saddle and by extending one leg forward. When the described above is not sufficient to turn the bike as quickly as the next racer can, he/she increases lean angle which makes the rear tire step out of line. That achieves two things: the torque on the rear tires pushes the front tire to stay more or less in track by sliding less out of the turn and the material building up on the out side of the tire helps improve its traction. 2) Making the most from the marginal available traction is the priority. Those are their racing lines. Outside-inside-outside lines are for reducing the length of the curve and increasing the radius when traction is plenty and surface is firm enough to grant a precise line.
  11. Wet Vs Dry riding

    In that hook is the main advantage of the quick-flick technique: a rider can achieve a few degrees of change of direction (horizontal) during the relatively safe transition from vertical to full lean angle. That lean angle will be less dramatic than the resulting lean angle (and cornering forces) of a lazy entering steering. In every turn, we must change the direction of the motorcycle. There is always an angle between in and out directions (45, 90, 120, 180, etc. horizontal degrees). The racer who can "rotate the nose" of the bike sweeping the full horizontal angle in less time, without crashing, has an advantage. An important limit to that rapid change of direction is available traction. According to Sir Issac Newton, any body in movement will follow a straight line, unless forced to change direction. Steering and available traction are all we have to force the bike to turn. The faster the turn, the stronger the cornering force (proportionally to the square of forward velocity). The tighter the turn, the stronger the contact patches need to grip the asphalt (inversely proportional to the radius of the circle described by the bike at each moment). The angle of lean at each moment is a very accurate reference for us to learn how intense is the cornering force that is trying to break that grip of the contact patches and to help the bike resume the straight trajectory (which is the natural thing, rather than turning). Since the quick-flick gains some bonus degrees of horizontal rotation for us and reduces the magnitude of the final lean angle some degrees (meaning less cornering forces), we can increase the speed around the corner in order to use that little reserve of traction. The quick steering uses the abundant traction of the vertical front tire and simultaneously rotates and flicks the bike certain amount of degrees. Regarding the line or trajectory, it means that we are transitioning from a straight line into a curve of constant radius as quickly as possible. A lazy entering steering is what we normally do in a car, because it takes some time to rotate the front wheels. What our car describes is closer to a parabola than to a semi-circle, it looks and feels like a decreasing radius turn. Please, see: https://en.m.wikipedia.org/wiki/Euler_spiral#Track_transition_curve https://en.m.wikipedia.org/wiki/Racing_line The lazy entering steering produces the same effect: less lean angle at the beginning, which trades off for a extreme lean angle (and cornering forces) around the apex (or tip of the parabola) where the radius of turn becomes very small. That extreme lean angle becomes your bottleneck, regarding speed and traction, even if you trail-brake all the way until there. Sooner or later you must rotate the nose of the bike around, quick-flick allows you to do it sooner (and safer) than later. Quick-flick goes very well with the late apex approach and allows a line that straightens the geometric curve very much. Using more width of the track when/where possible can increase your speed and improve your line of sight. The direction of the following turn is important when choosing a wide or narrow line out. Remember, on dry or wet pavement, the best and safest trajectory is that one that allows you to use the throttle golden rule. More discussion about that "hook" and quick-flick in wet conditions can be found here: http://forums.superbikeschool.com/topic/4101-can-quick-turn-be-overdone/
  12. Wet Vs Dry riding

    4. Your visor doesn't let you see as well. 5. The rubber of your tires is cooled down and the internal pressure decreases. 6. The feel of your brakes may change, as the temperature of discs and pads is never as high. 7. The feel of your hands and fingers is different under wet leather.
  13. What happened- My Highside Crash

    Carefully observe the hand and steering inputs of the rider in this vid, as well as how the rear tire reacts to those inputs (or lack of them). Keeping traction of front tire and torque flowing onto rear allows command of rear tire regarding returning to proper alignment. Just like needed for proper braking, the transfer of weight towards the rear should happen prior the contact patch receives the additional torque from the engine. The transfer takes some time and it can only be initiated by moderate throttle, which can be increased progressively as rear traction improves. That smooth initial throttle is hard to achieve in bikes with fuel injection and lacking traction control aid. https://m.youtube.com/watch?v=H93kPnDQEqA
  14. What happened- My Highside Crash

    Sorry to see that happening. It is hard to tell from that point of view and sound only. The engine can put a lot of torque on the rear wheel while in third gear. Could it be that inadvertently you applied excessive throttle, which made the tire break loose?
  15. Lowering the body

    Because it is very complicated, the subject of friction between rolling rubber and pavement has been and will be debatable. It goes beyond the simple empirical determination of a coefficient between two sliding surfaces. Rubber is a material which properties change a lot under mechanical and thermal stresses. It acts like a viscous-elastic material and it suffers from elastic hysteresis. When the same area of rubber hits and partially slides over pavement, internal chock waves develop and the original softness of the rubber has less time to recover. It has been demonstrated that for stationary surfaces and for light pressures in the contact area between a tire and a road, the rubber will only make contact with about 5% of the road surface. As the contact pressure increases, the rubber gets squeezed into many of the smaller-sized cavities. The coefficient of friction is not constant for different conditions. Many universities have studies and papers explaining this. If interested, you can research "elastoplastic contact between randomly rough surfaces". https://en.wikipedia.org/wiki/Viscoelasticity https://en.wikipedia.org/wiki/Hysteresis#Elastic_hysteresis Nevertheless, let's assume that friction and area are more or less independent in this case. The useful range of traction of any tire depends on the pressure/temperature/stress over the contact patch. If that is true, then the rider needs to unload the front tire some, and overload the rear tire some, in proportion to the differences in the areas of both contact patches. If the rubber compound and manufacturer of both tires are the same, he/she wants to achieve the same pressure/temperature/stress on both contact patches while cornering. The whole idea of proper throttle control to achieve a proper weight distribution while cornering is based on that concept. "To determine an ideal scene for traction, machine-wise, we start by simply measuring the contact patches of the tires to discover what the basic distribution of loads should be while cornering. Roughly speaking, those measurements show that 40 percent of the total load should be up front, 60 percent at the rear.......... At the point where the correct transfer of weight is achieved by the rider (10 to 20 percent rearward) by using the throttle, any big changes in that weight distribution reduce available traction." - ATOTW-2
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