Jump to content

Leaderboard


Popular Content

Showing content with the highest reputation since 08/12/2019 in Posts

  1. 4 points
    This is a very broad question. The answer will depend on a variety of factors about the corner: radius (and whether it is increasing, decreasing, or staying the same), camber, surface (grip, bumps, etc.) so I am not sure what sort of answer you are hoping we can provide. If the radius of the corner is increasing, and the camber is either unchanging or getting more favorable, you should be able to accelerate through the corner, however if the radius is decreasing and/or the surface is going off-camber, you may have to be slower later in the corner instead of faster. A corner with a crest in it may, as you mentioned, lighten the bike as you go over it and may require a pause on the throttle to maintain traction. My recommendation would be get ahold of a copy of "The Soft Science of Road Racing Motorcycles" and have a look at Chapter 2, which includes info about how to sense traction for yourself, and Chapter 3, which talks about making a plan for how to ride a turn and how to adjust the plan to fine-tune it, and Chapters 9-10 that get into how to increase your speed through corners, and specific riding styles and how to make the best use of the strengths of your specific motorcycle and your own riding skills. There is a lot of information about how to handle certain types of turns, adjustments that can made to line or throttle and the effects those adjustments will have, and a ton of other information I am sure you will find very helpful.
  2. 4 points
    Whew, this thread has gone all over creation and back since the original posted question, and the OP seems to have checked out. So, I'm going to jump in here. I am a CSS coach. First let me note that Yakaru is a very competent rider, fast, has come to many schools, and is very knowledgeable on the material. Now, on to some of the info that is in question. 1) When a rider is in a corner, if the throttle is APRUPTLY shut off, the bike will INITIALLY stand up a bit and run wide. Sudden loading of the front tire creates drag on the inside of the contact patch which tries to turn the wheel into the turn which makes the bike stand up. This is the same phenomena that occurs when you pull the front brake in the middle of a corner, that makes the bike stand up and run wide. THEN, once the bike recovers from the initial weight shift and begins to slow down, the arc will tighten due to the bike slowing down. There is a GREAT CG animation of this in A Twist of the Wrist II DVD. 2) Rolling on the gas does not, BY ITSELF, cause the bike change lean angle. You must countersteer to stand the bike up. However, as the bike speeds up, the radius of the arc changes (widens), which can give people the impression the bike is standing up - especially if they unconsciously STEER it up! It's a rare rider that knows and understands that it is ONLY the handlebars that steer the bike up (not the throttle), most riders have been doing unconsciously since the first day they rode. I hope this helps clarify these points.
  3. 4 points
    Keith asked me to add a little more info about grip: The point on max grip is another many faceted process. Due to the slip angle tires never do have 100% mechanical grip, they actually are sliding. That is a prophylactic process as it cleans the spent rubber off the tire's surface but is ALWAYS happening, in every corner. It's sometimes overlooked in the traction arguments. In the end it's more to less, less to more SLIDE rather than more to less, less to more traction. Maybe that's just another way of looking at the same issue.
  4. 4 points
    This is a common enough question that lately Keith has put a new focus on the no-brakes drill with Level 4 students, having them re-do the drill to help increase their awareness of how much speed gets "scrubbed off" in a turn, and to make sure that concept is understood. There are, in fact, multiple Level 4 drills designed to increase the rider's awareness of this, and help the rider determine where, EXACTLY, one should have their entry speed set for a given corner. Dylan actually does cover this topic pretty thoroughly in the very first lecture in Level 1, Throttle Control, pointing out that the bike continues to slow down after the turn point, so trying to set your target corner speed AT the turn point can result in ending up too slow at the slowest part of the corner. However, I think for many riders who are new to track riding this speed-scrub aspect of throttle control may get lost; there is a lot to take in on that first day. And, of course, judging entry speed and speed scrub are the sort of thing that even the most advanced riders continue to work on, it does require focused observation and experimentation, and every turn is different so there is no "pat" answer that will work for every bike and every corner. Learning to observe the speed scrubbed after the turn point, and bringing up the entry speed gradually, is a good way to approach the problem - or make it a focus of your next Level 4 school day.
  5. 4 points
    It would be a rare 180 degree turn where you could roll on the gas as soon as you have your lean angle set (at the beginning of the turn) and be able to roll on continuously for the whole rest of the turn. If the turn was large, and U shaped (as an example) you would most often have to roll off (or at least go flat) on the gas in the middle of the turn, more or less treating it as TWO turns, the first part with one turn point and apex and the second part with its own turn point and apex. Depending on the shape of the turn, you may or may not need to make another steering input to change your lean angle at the second turn point (ie if the turn tightens up in the second part, you will likely have to make a steering input to change the lean angle for the second part of the turn). Alternatively, you could consider that your "real" turn point is somewhere in the middle of the 180 degree turn, a turn point that will line you up for the apex and exit you want. Everything before that would really just be pre-positioning to get to that turn point and you might very well be slowing down (off the gas and trail braking) ALL the way to the turn point which could be located near the middle of the 180 degree turn, or even later if it tightens up a lot at the end. You could try working backwards from the exit (if exit speed is the priority) to find the exit line you want, then find the apex and turn point (in the second half of the turn) that will line you up for that without any additional change in lean angle . That will be your "second turn point" (or real turn point if you are thinking of it as one turn) then work backwards from THERE to find an entry line from the first part of the turn that will get you top that second turn point. Does that make sense? If the turn is at the end of a fast straight and whatever comes after the 180 degree turn is slower, you may want to prioritize carrying the straightaway speed as long as possible and in that case you might choose a line that allows maximum trail braking as long and late as possible before you reach the second turn point, potentially sacrificing some speed in the latter part of the turn with a less optimum exit but a wide fast entry.
  6. 3 points
    Hanging off moves the combined center of gravity of bike and rider more to the inside which allows the bike itself to be leaned over less. With the bike more upright, the suspension works much more efficiently which improves traction by keeping more of the tire in contact with the road.
  7. 3 points
    Your collection of data and research shows you are barking up the right trees. Here's some more data regarding tires: Per the Dunlop engineers tires grip in 4 ways: 1) Adhesion--the temporary chemical bond between the tire and surface. 2) Keying--the tire deforming and filling in all the nooks and crannies of the asphalt or squishing into the depressions. 3) Abrasion--the tire tearing from itself or wearing away. 4) Hysteresis--the energy storage and return by the rubber and partial conversion to heat. The first two can be looked at as static properties and the last two dynamic properties in my opinion. I'm still learning on all this stuff and when talking to the tire engineers, they don't have all the answers either. Heck, aviation engineers still can't all agree on exactly how a plane flies through the air!
  8. 3 points
    It sounds to me as though you might not be taking into account how suspension affects tire grip. Are you, for example, assuming a completely rigid connection between the wheel and motorcycle, with no suspension action and a non-deformable tire? Are you assuming that the grip of tire to pavement is constant, and is at the theoretical maximum friction of rubber to asphalt? There is more grip available when the bike is upright because the suspension is more effective at keeping the tire consistently in contact with the pavement. There is a theoretical maximum friction that you can calculate but in real-world riding, the pavement is not perfectly flat or perfectly consistent so the theoretical grip (calculated from formulas, with assumptions and simplifications made - usually a LOT of them) is NOT the same as actual real-life grip. Does it make sense to you, in your actual riding experience, that you have more grip when the bike is more upright than when you are at maximum lean angle? If so, does it follow that as you stand the bike up, you HAVE more grip available, so that even though you were at the max (for that lean angle) a millisecond before, you now have MORE grip available because the bike is coming up, and any tiny slide that would have begun from the countersteering effort would be halted by that additional grip? One must be very careful when attempted to use physics formulas to calculate grip. There are MANY factors that are ignored, assumed constant, or simplified in order to make formulas or concepts easier to understand, but trying to apply theories that don't take into accounts the LARGE number of variables present in real-world riding can lead to some confusions. You can find numerous examples on this board.
  9. 3 points
    I do not understand this statement, can you restate it or explain it more? If I understand your question about how to exit a corner, you are talking about coming out of the corner onto a straight(er) part of track, and you are asking how to change the arc to put the bike in a straighter line, is that right? If so, then the answer is yes, you would counter steer to bring up the bike. The momentary instability caused by the countersteering effort is overcome right away by the increased grip afforded by getting the bike more upright (primarily due to your suspension being able to work more effectively). In other words even if the front tire DID slide a little, it would recover, and in fact that is often how riders recover when a tire starts to slide - by standing the bike up. (Sometimes they recover by just staying loose on the bars and the tires regain grip either because they reach better pavement - like a slide on a greasy spot in the road - or because the bike has slowed some.) Keep in mind, though, that the rider must make a reasonably controlled steering input - a death grip on the bars that restricts bar movement, or a rider pushing on BOTH bars, or an extremely rough bar input could indeed cause a fall.
  10. 3 points
    Interesting topic. Three things that came to mind while reading through the posts: 1. Many moons ago, Roberts sr had trouble going fast enough around Suzuka. Instead of continue circulating, he went back to the hotel and had a think. A few hours later he returned to the track and said he had found 2 seconds. Hei proved it by going 2 seconds faster. 2. Darren Binder, Moto3, says he has no braking points, he brakes when those around him does. He's fast, but cause a lot of havoc and crash frequently. 3. Rossi, and others, often try a fully new and untested setup before races when they haven't found a competitive setup during practice. At least in the case of Rossi, it seems to pay off more often than not.
  11. 3 points
    Practice till you can't get it wrong, I'd just heard this in another arena (pistol shooting), but like the idea!
  12. 3 points
  13. 3 points
    I see a second steering input also. Could be that the roll on was already starting as you leaned it that extra bit, or maybe you were already near the limit (for those tires) and the extra bit of lean was enough to break it loose. I can't hear it well enough on the video to tell for sure but that extra lean combined with some throttle application could definitely have caused the rear to slide without warning.
  14. 3 points
    Braking, with the front brake, while leaned over in a turn, can definitely cause the bike to stand up noticeably - assuming the braking is hard enough to shift significant weight to the front and NOT so hard that the wheel actually slides, the braking forces cause a friction drag of the contact patch against the pavement that makes the front wheel want to turn to the inside, which creates a countersteering effect and stands the bike up. So when braking while leaned over, the rider has to resist that turn of the front wheel by pushing on the opposite bar to counteract it, to keep the bike on line (i.e., if in a left hand corner the rider would have to push on the left bar to offset the countersteering effect of the braking). This can get tricky to manage, as the rider is restricting movement of the bars, and placing additional load on the front end, so braking TOO hard while leaned over can exceed the limits of traction of the front tire. If braking verrrrry gently the counter steering effect is so slight that the rider may not feel any tendency of the bike to stand up, and the fact that the bike is slowing down will eventually decrease the radius of the turn, so a rider who only brakes very gently while leaned over (or uses just rear brake - which can also be tricky) may not ever notice any tendency of the bike to stand up. But braking harder or more abruptly makes it much more noticeable. Or, a rider who has a lot of experience with using the front brake while leaned over may be so accustomed to automatically pressing on the opposite bar to counteract the countersteering effect may not be aware of the bike's tendency to stand up, and a rider like that would have to go out and consciously try to relax the arms and observe what happens if he or she ADDS front brake in a corner while leaned over.
  15. 3 points
    Let's touch on one thing: bike doesn't turn as well when the throttle is on, even just maintenance throttle. When off throttle, bike weight is forward, more on the front, steering angle is steeper, wheelbase is shorter--the bike turns better. Does anyone know a single turn where braking is done, then gas on, then bike turned,? As mentioned earlier by trueblue550 (Streets of Willow Springs) there are series of turns where the throttle is stopped for a moment to complete the steering (T 4-5), or where rolling it on puts the rider too wide for the next turn in point (T5-T6). These are situations where there is a series of turns, the following one dictating the exit of the previous turn.
  16. 3 points
    I'll take a swing as well. I may be misreading the question but I don't believe it is an "either or". I believe the answer is "yes" to both sides of the question. First, I think the vast majority of today's motorcycles are designed for their intended use. In the broadest sense think dedicated dirt bikes, trials bikes, track bikes, touring bikes, etc. Their frame and steering geometry, suspension set-up, basic rider ergonomics, engine choices, etc., are all designed with a purpose or specific rider use in mind. However they are also designed within the limitations of today's technology and materials science knowledge, plus the economic realities and limits of what consumers will pay for a given motorcycle's capabilities. With regard to "do we need to do something to keep a motorcycle in its operating envelop", my initial reaction is to say we do it every single time we ride when managing things like throttle and acceleration levels, braking force, lean angles and traction limits for the specific riding situation we happen to be in. And we all know what can happen when we exceed an operating envelop. Just an add-on thought to this. What I love about many of today's motorcycles is how technology (e.g. ABS, traction control, engine braking, wheelie control, slide control, various riding modes, etc.) is being leveraged to help us safely stay within a motorcycle's operating envelop, AND that we can adjust the parameters of the envelop for our various skills and capabilities. I can't even imagine where motorcycle tech will be in another 20 years, but I know it will be fantastic! I've heard people say we're in the golden age of tire tech, but we might even be able to say that about the software / sensors / ECU technologies of today's motorcycles. Dave
  17. 2 points
    I was so happy to find out, today, that A Twist of the Wrist II is available on Amazon Prime Video now! You can watch it instantly, here is a link to it on Amazon Video (or you can just put A Twist of the Wrist in the search box) : https://www.amazon.com/gp/video/detail/B089ZNVBW9/ref=atv_dp_share_cu_r And since we're talking about the movie, what was your favorite part? I can't wait to hear what y'all liked best. My favorite part is the CG animation and explanation of why using the front brake in a corner tends to make the bike stand up, it was BY FAR the clearest explanation I've ever seen for why that happens. (My second favorite part is near the beginning where it shows a rider going off the road due to SR's, and explains and shows each of the Survival Reactions individually.) How about the rest of you, what did you like seeing in the movie, or what helped you the most with your riding?
  18. 2 points
    I have the Kindle edition, here is a link for Twist II for Kindle: https://www.amazon.com/Twist-Wrist-II-High-Performance-Motorcycle-ebook/dp/B00F8IN5K6 and here is a link for A Twist of the Wrist (Twist I), it is available on Kindle also: https://www.amazon.com/Twist-Wrist-Motorcycle-Racers-Handbook-ebook/dp/B00BNFIU08/ref=tmm_kin_swatch_0?_encoding=UTF8&qid=1593622442&sr=1-2 I love having these, because I can search for a word of phrase electronically to go right to the info I want. And it's great to be able to pull up the books on my iPhone Kindle App, at the track or wherever I might be.
  19. 2 points
    Yes, riding the NO B/S Bike with Josh Galster behind me...outright terrifying. Let's the stage: Josh was a pretty solid AMA Pro, racing 600 Supersport at the time, good rider. We were on the NO B/S Bike, and came pretty close to the camera car (seemed way closer on the bike than it does in the video). At what seemed like the last possible moment Josh would reach down with his thumb and steer the bike away from the car. What you might not be able to see is how hard I was pressing on the NO B/S bars--surprised they didn't bend. Veins popping out of my neck, trying to steer the bike (was sure we were gonna hit the car) I felt totally out of control Really everyone should ride the NO B/S bike, at least once. The little fine-tuning adjustments riders make to keep the bike pointed exactly where one wants, not even aware that they are being made, become crystal clear when one rides that bike.
  20. 2 points
    That movie changed my life. I had been riding (commuting) about 5 or 6 months when I figured I was ready to ride some twisty roads. So I went out and scared myself pretty bad. The bike wouldn't turn, I was crossing the yellow repeatedly, my wrists hurt from my death grip on the bars, etc. Every corner was terrifying; a "mild panic" as they say in the movie. It was a bad day. Then I found TOTW2 and I felt like Keith had just watched me ride and was going over my mistakes, one by one. The entire movie was a series of "ah-ha!" moments. Everything was explained so well. Now I've done a bunch of schools and I mostly ride track days. It's a slippery slope. My favorite parts of the movie are the cheesiest parts. That's what makes it fun!
  21. 2 points
    Looks like good news:
  22. 2 points
    Sorry to hear about the down. I think Apollo has the core of it, and if your lecturer didn't say to obviously use the brakes if you needed then that does seem to be an oversight. I'll put a clip in at the end from the Superbike UK's level 1 presentation -- should jump to 18:16 -- which is the clearest explanation of 'how' and 'why' to do the drill (including using the brakes if you must). In my experience, the no-brake drill is best approached in a stepwise manner and helps tune entry speed and understanding of slowing from things other than the brakes (tire drag, lean angle, engine braking)... I can say I definitely cover the brakes but don't need to trail brake in for this drill (and a mild brake application mid turn can be done safely -- just be smooth and be open to needing to stand the bike up a bit, and definitely don't be adding brake while you're still trying to bend the bike over further).
  23. 2 points
    I'm pretty happy. Got to grow my trophy case a bit.
  24. 2 points
    Being a mediocre rider with a history of more brawn than brains, I have had to stand the bike up to slow down before continuing at a reduced pace countless times. Sometimes from running out of cornering clearance, sometimes just running out of courage. I have never planned for it or practiced it, it's just a result of my SR.
  25. 2 points
    Personally, I prefer a softer carcass and a more rounded profile for the tire. That's partly because I am a smaller rider and most bike's suspensions are too stiff for me anyway so the softer tire helps absorb some of that, but it is also because I like to feel the tire react - I like to feel the tire "set" in the corner, and feel it compress under acceleration. I do not like to feel rigidity or vibrations, or feel like the tire isn't reacting or won't compress, that sort of feedback tends to make me feel like the tire is cold or has too much air pressure and won't have adequate grip, so I am more tentative and don't load it enough for it to really work well. If I am SURE it is OK - like on warmed up Dunlop GPA tires, which have amazing grip, then I can push through that mental barrier and can appreciate the stability of the stiffer carcass under very hard braking and acceleration. But I prefer to ride with a smoother style so I don't miss it if the stiffness/stability is not there, I rarely brake/accelerate with that extreme force unless I am following someone who DOES ride with that sort of style and get (sort of) forced into it. What is it that makes you say "how soft MotoGP tires are"? Are you saying that because Michelins have a reputation for being softer than some others, or is that something that was said or written or published somewhere, that current MotoGP tire carcasses are softer right now than in the past?
  26. 2 points
    We are shooting for Barber, which is May 23-29. It's mostly booked up but there are about 10% seats available.
  27. 2 points
    We made it out, about 2 hours north of LA in the desert. Had a great time, daughter loved it--asking about going again this coming weekend!
  28. 2 points
    It definitely can be done (sliding an S1000rr in a controlled fashion) and you can watch high level racing and see it happen. The school also has an off-track tool called the Slide Bike that can be used by more advanced riders to find our what it feels like to slide the rear tire. (And, for that matter, there is the Brake Bike that can be used to find out how it feels to slide and recover the front, in a straight line on the brakes.) One thing to consider is that the tires are ALWAYS sliding, to some degree, it is a built in part of how they work. In any corner the tires are always scrubbing off some rubber. Yes Q3s will slide and it can be controlled, but technique must be good. What is tough to recover is a very sudden, abrupt slide, where the tires move sideways fast and then when they regain grip the slide is halted abruptly - such as a situation where there is a patch of oil on the road (in a corner) and the tires slide fast and then catch abruptly on good pavement on the other side. Another example would be a rider that leans the bike way over into a corner, then whacks the throttle on abruptly, delivering way too much power to the rear tire and initiating a slide at a steep lean angle, THEN gets scared and shuts the throttle off abruptly. The rear tire suddenly regains traction which stops the slide and the sideways momentum can make the bike rotate over into a highside. (Traction control on newer bikes helps prevent some of those too-much-throttle situations, delivering less power to the rear wheel at steep lean angles.) Those types of highsides are probably what the "slip, grip, and flip" comments are referring to, but those can be prevented with good throttle control and knowledge of how to manage rear tire grip, and we have a variety of classroom sessions and drills at the school that cover those topics.
  29. 2 points
  30. 2 points
    The brain is not typically wired to be bothered with words like "don't" and for most will only react to "fixate". If your kid has ice cream running down the chin and you tell the kid "do not look down", the child will definitely look down. If you instead say "look up", you can wipe the chin before the kid ruin the shirt.
  31. 2 points
    I love it when topics get resurrected, and especially when I have just discovered the technique, literally yesterday...it forces me to relate my newfound exuberance not only to the "what" but also the "why." I am not a proud author and I am seriously interested in all responders. Why? Because if what I know to be true as outlined below proves false - I need to know ASAP. First, kudos to the CSS Coaches who asked the poignant question and provided the illustrative example: i.e. Cobie's 'stirring the pot' getting the topic back on track, "Does it matter which peg is weighted?" and then HotFoot's barbell example. Nice tag team. The OP's question was "Why weight the outside peg vice the inside?" and then we got into locking the body, Newton's Laws and "vector mathematics." We do "things" on the bike - perform techniques - to aid our riding. So I reckon the better question might be what are the advantages to weighting the outside peg over the inside peg? 1. Many of you have written it helps you 'lock-on' to the bike with less fatigue than other techniques. 2. Others have written that it helps focus major muscle groups in the steering process - as per TOTW2, Keith mentions it is like 'power steering' yielding less fatigue. Also Keith tells us in TOTW2 that "pushing under the bike" is not a good technique for asphalt based motorcycles. 3. Others have advocated that it only serves to 'pickup the bike' upon the exit. 4. My experience from a one-day experimentation over 5 hours and 300 miles is that in the great "ballroom dance" that is elegance & finesse motorcycle riding, I am in a much better position to lead the bike around the dance floor when my "touch points" on my girl are correct AND effective. Those are 3 GREAT reasons (4 if you count mine) to weight the outside peg! Are there ANY disadvantages? I haven't read about one or personally found one yet. The comment about riders who are "inseam challenged" and lift their foot off the outside peg yet still win races doesn't mean this is a bad or overrated technique at all - just that it doesn't have to be used to win races. Of course, being the dedicated riders we are, always wanting to learn more about riding, the why is always what matters - because that is how we remember to do things. It's great to discuss the Center of Mass (CM) and Center of Gravity (CG), but what seems to be missing from most of the posters' train of thought is the "moment of torque" surrounding the application point relative to the CM on the bike - hence HotFoot's outstandingly simple barbell example. What is at play here is the delta between gravity operating on the Center of Mass, and the torque - or 'moment arm' - acting on the bike around the bike's CM due to pressure applied anywhere other than the CM. To calculate this moment arm, or torque, I present the formula t=rFsin(α) where r is the radius distance from the CM, F is the actual Force and α is the angle of r. So, if Keith weighs 180 pounds (full gear & the math is easier), and he is applying only 2/3 of his weight - I think I'm being conservative here - to the outside peg in a 45 degree angle turn, and the peg is 10" from bike centerline, that gives us t=10*120*.707 = 848.5 in-lbs (70 ft-lbs) of torque on that motorcycle frame. With 250cc bikes going around 350-400lbs wet, that torque is almost 20% of the weight (remember most of the rider doesn't count because he's causing the moment.) That is not insignificant. There's definitely SOMETHING happening there. When a rider is "hanging off" - are they actually hanging their weight? If so, on what part of the bike? One poster wrote that the pros shift their weight 20 times in a turn - while 'hanging off.' That's a lot of shifting. In TOTW2, Keith was using the outside peg as his "pivot point" - where his weight was focused. I'll bet money he was 'hanging off' as well, but keeping his weight pushed to his outside foot - no small physical task. And that he was on a 250cc bike tells me there wasn't a lot of relative bike mass for him to overcome - yes there were centripetal and centrifugal forces from the wheels, but when he applied his weight to the outside peg, it definitely mattered to the bike. The other significant point made in TOTW2 is that when pressing on that outside (or inside peg) the bike "feels" your body mass MUCH nearer its own CM and that makes the bike happy and stable, regardless of the angle. Adventure guys and Trials guys stand on their pegs - why? It lowers the perceived CM for the bike and is more stable. When we 'flick' our bikes over, we WANT instant instability, followed by complete stability while in the turn...make one good steering input, hold it there with your "criss-cross-torso-pressure-system," and you get to enjoy the turn. So, in summary... Yes the advantages outweigh the disadvantages, and it actually makes mathematical sense, so yes, Coach Cobie, it DOES matter. Thanks for reading. I'm looking forward to May at Baker Motorsports. Cheers, Steve
  32. 2 points
    Thinking takes a bit of time. While riding (or other high speed potentially lethal activities), that's too slow. A few different pieces of this, but the first one is I actually applaud the guys that take the time to come to this forum, and work through some of the pieces of riding. There is a technology to riding. But for one to be able to look at the technology of riding, has to be willing to think it over, work through the pieces, do some study. That is for sure the first step. I'd have to say that this is more a thinking man's forum than some others. Like I said, got a few parts that I want to cover on this, but are you all with me so far?
  33. 2 points
    The answer to the question is: from turn-in, off throttle, not trailing the brakes, the bike will slow at the rate of between 3mph to 8mph/sec. Lots of variables of course but that's the quick answer.
  34. 2 points
    You are correct, but only if such motorcycle is neutral steering-wise. As you know, many bikes have a natural tendency to either understeer or oversteer (if the rider releases the handlebar while the bike is leaned on a curve). Those tendencies depend mainly on geometry and profile of tires. The front contact patch of an understeering bike will "feel" less lateral force when coming out of a lean/corner as it had been forced to over-steer during the curve. In the steady conditions that you have described (while keeping zero angular input on the steering), the sliding force on each contact patch remains constant and it depends on the square value of the forward velocity of the bike and the inverse of the radius of the trajectory. As you properly have explained, any counter-steering input will instantaneously increase the value of that lateral or sliding force (especially for the front contact patch). The lean angle (and linked lateral forces) can remain constant along a curve, but real conditions of the road make it maximum only intermittently. Maximum grip or friction depends on the force that is normal or perpendicular to the surfaces in contact. The undulations of the road and the instantaneous accelerations that add to and subtract from the natural acceleration of gravity, induce a fluctuating amount of that normal force or available maximum friction or grip. Each tire has more available traction each time it rolls over a crest: that instantaneously increased normal force deforms the tire and partially compresses the springs, which push and accelerate the rider and the rest of the mass of the bike and fluids upwards. Exactly the opposite happens when the tire "falls" into a valley of the track's surface: less available traction for a fraction of a second. In other words, assuming a perfectly horizontal traverse surface of the curve (no sectional slant, slope or crown), which makes the value of the normal force that induces grip equal to the value of the weight supported by one tire, the undulating nature of that surface will make that tire and its suspension alternatively support more and less weight than normal (for a perfectly ideal flat surface). Hence, more that having a sharp value, the available grip of each tire constantly rises and falls / pulses / swings / oscillates around an average value. Similar effect (although at much higher frequencies) is produced by the vibrations coming from the rubber compound of the tire when supporting strong lateral forces (getting deformed, twisted, overheated, sheared) and when crabbing or sliding off the trajectory (while keeping grip). At microscopic level, things are changing at a very rapid rate and the surfaces are gripping each other and letting go in a very rapid sequence. Consider also that all the disturbances described above induce minimal steering inputs. Because of the trail of the front tire, while it is leaned, any close to vertical force has a perturbing effect (torque that is equivalent to a sideways force times trail distance) when the bike is in vertical position. A torque is induced into the steering, which can be over or under-steering, which significantly modifies the radius of the trajectory, which momentarily changes the magnitude of the lateral forces. Hotfoot's excellent post has perfectly explained the Physics of real life.
  35. 2 points
    I love this topic. I too am focusing on my turning ability, specifically Quick Turning. There’s an article where Keith says that learning to QT solves all of the SRs. I’m striving to become a disciple of that.
  36. 2 points
    Great questions. I was working hard at being a good copycat. I didn't brake at all, and I stuck to his fender and turned where he did. He was super-smooth and got the work done with speed and grace. I assume I was not as graceful, and I was probably off the throttle too soon, and not on again fast enough, because I was having some emotions at the time. As stated, I thought this was a mistake..but it was brilliant. Hard turning. I ski. To go down a steep face, you turn hard and often to keep your speed in check. Miss a few turns, and you have to slalom, fail to dig in, and you become a passenger. When I refer to 'hard turning' I am talking specifically about turning with the intent of using the conservation of angular momentum to convert velocity into a change in direction and reduction in speed. I wish I had talked more with my coach about the decades I spent racing offroad. One of the most common turns in the woods is jamming your bike into a berm or a ditch or a rootball, to shed speed and redirect yourself at a sharp angle to your incoming direction. Like a jump-turn in skiing. On the pavement of a racetrack, the best equivalent is getting all the physics right to lean in hard enough and fast enough that your suspension loads evenly and firmly, and you can feel the tires bite and rail you around a corner. And *thats* where I see the transition from 'oh I am in too deep/too fast' to 'wow, that was freaking awesome'. I would like to learn to do that a hell of a lot more, with a hell of a lot more intent.
  37. 2 points
    That's awesome, the pat on the back was great lol
  38. 2 points
    What would you say is the skill/thought process/etc. you get the biggest benefit from focusing on -- either for training/practice or in/around a race?
  39. 2 points
    I recognize that I’m almost exactly 3 years late to this party, but the past three weeks I’ve been using the forum search function and scrolling through pages of posts on a tire heat/traction research assignment from Cobie, and this thread is definitely the best I’ve come across yet. Cobie, you’ve done a great job of engaging and drawing participants out; there’s been a symbiotic contribution-response at almost every point along the way. The only thing I can add is an over-simplification of the topic, but based on the posts, I believe we all understand it: ’Train until you get it right, Practice until you can’t get it wrong” This encompasses the training of a new technique, and the refinement of that technique into a solid repeatable action (perhaps unthought).
  40. 2 points
    If you turn off the "off-track aid in the options, you well definitely fall on the grass lol, trust me lol
  41. 2 points
    I've ridden many different tire sizes on different bikes and really can't tell much of a difference once I get a few laps on them. I've ridden a 1000 with a 180 rear and it was fine... if you A/B compared you'd feel the difference I'm sure. Slicks last longer than street tires, at least the Dunlops do. Heat cycles are what our coach tires experience all day long every day they are ridden. It may make a 3% difference but nothing anyone could feel easily. 1) Don't sweat the size issue. 200's are fine. The AMA 600 class used to run 200 rear slicks... 2) Get slicks if you want durability (and grip). 3) Use warmers with the slicks to ensure you don't get a cold tire crash. 4) Worry more about tread depth than heat cycles.
  42. 2 points
    Jaybird, The skills build one on the other, with quite a thoroughly researched progression, and relationship. That being said, working on one skill at a time is the proven approach. Let's say a rider works on his Throttle Control, but has no clear idea of line. In the next class for Level 1, we discuss lines, and the components of them (one of which is good Throttle Control). So when we set out the Turn Points (to help create good lines) the rider often finds out he had a line that didn't allow for good Throttle Control. We do realize this is a lot to master, all the skills of each level. The coaches are trained in how to deal with this, and adjust the "drinking from a firehose". There is more to this, of course, but there's a mini-view. CF
  43. 2 points
    Being honest with oneself, a bit of a skill. Honest, yet not beat up on oneself, also a skill. Big part is just being able to observe. Keith is frickin' amazing at being able to observe.
  44. 2 points
    For sure this is difficult to judge, for anyone. Laptimes are a measurement, and being able to achieve very CONSISTENT laptimes is a good indicator that a rider is well in control of their lines and speed and that the error rate is low, all of which indicates good riding skills. Seeing one's own laptimes come down on a given day at a given track is a good indicator that the rider is figuring out the track and making improvements. Being able to stay relaxed and ride without errors and without exhaustion is a great improvement, and something the rider can observe relatively easily for themselves. However - trying to compare laptimes to other riders may not be very meaningful unless you are racing . At track days and especially at schools, riders ARE, by definition, working on making changes and sorting things out so their laptimes can vary considerably from actual go-for-it race pace times. At CSS riders are asked to ride at around 75% pace so that they have enough free attention to make observations and changes in their riding, plus there are formats and drills and sometimes different track configurations (compared to how other organizations run their day) so a school day laptime may not mean much when compared to a race laptime, or even open track day times. So if you are looking at a CSS laptime and trying to decide if you could race at that track, it may not really translate. Going out and doing a new racer's school at that track (unless you already have a race license?) would allow you to get a sense of whether you can be competitive, and most of them do a mock race at the end of the day, which is fun and instructive, and most schools will be able to tell you if your laptime is acceptable for you to race there. Racing creates a whole new set of challenges - the track pace is fast and that will immediately push you to find places where you can go faster, and likely make you push yourself enough to reveal next areas of improvement in your riding. I think most of all you will need to decide your personal priorities for improvement, THEN figure out how to measure. What are your goals as a rider? Are you interested in being calmer on the track? Safer? More accurate? More consistent? More comfortable? Do you want to be able to learn new tracks faster? Do you want quicker laptimes? Do you want to ride in A group at your local track? Do you want to start club racing? Once you have your own goals set, finding ways to measure that should be easier. Interesting question about whether it changes based on the track... I guess my answer would be that there are certain skills that identify a skilled rider. Consistent entry speeds, good control of the bike (accurate, effective steering with steering rate appropriate to the turn), secure, locked-on body position, relaxed upper body, and good visual skills come to mind. One can watch a skilled rider on a new track, and they may be riding slow and figuring out lines but you can see the skills are there and know that once they get the lines figured out they will be able to ride consistently and quickly. You can also go to an open track day and see someone getting good laptimes (by pushing really hard) but leaning the bike over too far on the gas, exiting corners at the ragged edge of the track, making steering corrections, stabbing the brake, hanging off too far and steering ineffectively, making rough downshifts, etc. and see that they may be going pretty fast but they are lacking some really important basics and although they know the track well, they are hitting some big barriers that will hold them back and/or cause them to crash if they try to go any quicker.
  45. 2 points
    There is good info on this in TOTWII, Chapter 25, Traction, there is a section about "traction riders" and if you read that whole chapter it gives a nice description of how different riders use and perceive traction, and the pros and cons of these different approaches, I think both you and Faffi will find it very interesting.
  46. 2 points
    Good point, and I made great use of that while racing this weekend. My bike was geared a little too high for a particular corners so my drive out of the corner was suffering, so I tried changing my line to stay leaned over a bit longer - somewhat counter intuitive for getting a good drive, but it worked. Before, I was riding a more squared off line and standing the bike up but then my RPM was too low; leaving it leaned over a bit longer put me about 500 rpm higher and the bike did not lug on the exit. (To be clear, I wasn't ADDING lean angle - I was just maintaining my lean angle longer instead of doing an earlier pick-up.) On my low horsepower bike it made a difference, and I was very happy I knew how to apply that information!
  47. 2 points
    It's a big subject at the schools these days, we see it a lot. One point that comes up as the cause is....too low turn entry speed. But...that has to be brought up gradually, or one gets into the minus is too much entry speed, a challenge to juggle. If it were easy, likely wouldn't be so much fun when you get it right :).
  48. 2 points
    On the street my absolute number one priority is safety. On the street I’m constantly trying to remain conscious of the variables outside of my control: most notably these include road conditions (loose gravel or a boulder in the middle of a blind turn), wildlife, oncoming traffic crossing over the double yellow, and the unimaginable/unexpected (like a Porsche making a 3-point U-turn in the middle of a blind corner on Mulholland, yes it happens). The most valuable tool I’ve learned from CSS for increased safety on the street is Wide Vision - without practicing wide vision it’s impossible to look through a corner and reserve attention/awareness for the unexpected. Wide vision and riding at 70-80% of my ability on the street has served me well. That way, hopefully, I become aware of the unexpected ASAP and I’ve got an extra $2-3 in savings to spend on it.
  49. 2 points
    Just bump into a few of the kids, push them out in the weeds. OK...I am kidding!
  50. 2 points
    Good points Hotfoot. Video can show some excellent things, but can also miss some things. There are also many different angles/camera placements. Interestingly enough, the one used at the school (arm over the shoulder) can be very instructive. Another is a follow camera, but then it helps to have a qualified rider being the cameraman. It actually can be very helpful for coach riding from behind to take the line he would normally, and show the difference between that and the student's line. Video is an excellent aid, but not the whole picture, and as Hotfoot mentions, if the rider isn't well educated on the subject being critiqued, it's going to miss the mark. Best, Cobie
×
×
  • Create New...