Jump to content

Dylan Code

Superbike School Riding Coach
  • Posts

    177
  • Joined

  • Last visited

  • Days Won

    21

Everything posted by Dylan Code

  1. Those are MX footpegs that are part of an experiment we are doing. More info to come in the coming months. That was video I took of myself on track last weekend at Vegas.
  2. Dropping the chin seems like a way to remind someone to stay hung off while picking up the bike at the exit. What you are describing is what I would identify with the Pick Up Drill at the end of Level 2. We don't couch it in those terms because that piece of advice could be misapplied and is better put in other words. This is my opinion based on training students on this technique.
  3. Here's a video showing CSS student trail braking at Laguna Seca.
  4. Here's a traction circle from 3 riders on a track. You can see spikes in braking which we would expect to see particularly when coming out of a tuck on a straight. We also see some cornering past 1g which I would say would be banked turns. The majority of the traces exist around or within the cofines of 1g.
  5. You're welcome. I'm very fortunate to have a few people to call on to help sort out things, or at least shed more light on them. The main one being Keith himself. We talk for 30-45 minutes almost every day.
  6. I asked Eric, my go-to physics guy, to comment on a few points. Here's his response which I find very helpful in painting a more complete picture. Dylan: Well, the tangent of 63° = 1.96, which should mean that a bike/rider assuming zero width tires, infinite traction, and rider center of mass in the plane of the bike should be able to corner at 1.96G with a lean angle of 63°. And tan(45°) = 1, so under the same assumptions a bike leaned over at 45° should yield 1G turns. That’s just pure mathematical physics, and there is zero controversy about the math or physics of it. There is only room for questioning the assumptions. You may recall my discussion of the effect of tire width on the effective lean angle. Tire width has a big impact here. I think I recall estimating that a 600cc bike with fairly high CG and ~5” wide tires would have an effective lean angle of ~41.5° at a measured bike lean angle of 45°. Doesn’t sound like much, but if the rider keeps his center of gravity in the plane of the bike, then an effective lean angle of 41.5° will only get you ~0.88G in a coordinated turn. With the same geometry assumptions, a bike leaned at 63° would experience a greater “lean angle penalty” than at 45° for two reasons: (1) The bike is riding on a fatter part of the tire profile at 63° measured lean angle than at a 45° measured lean angle, and (2) The bike is riding on a part of the tire that is at a smaller radius from the center of gravity. I haven’t run the numbers, but suspect that the lean angle penalty could be in the neighborhood of 10° or more at a measured lean angle of 63°, which would bring the effective lean angle down to ~53° or less, or ~1.33G or less in a coordinated turn. Since street tires can’t possibly deliver 1.33G cornering force, there’s not much point in providing the ground clearance for a 63° measured lean angle. With a wider tire and a lower bike/rider center of gravity, as you would expect in racing, the lean angle penalty would be even more pronounced. It wouldn’t greatly surprise me if the lean angle penalty got upwards of 15°, before accounting for the beneficial effect of rider hang-off. If that’s in the ballpark, then a 63° measured lean angle would only provide ~48° of effective lean angle (or 1.11G in a coordinated turn) if the rider stayed centered on the bike, maybe recoverable to ~53° of effective lean angle (or 1.33G in a coordinated turn) with good rider hang-off. I don’t know whether motorcycle race tire compounds can deliver 1.33G of turning force or not—that’s about as far as I can possibly stretch my head. But there are a couple of experiments you could try to see if my explanation is just bogus or maybe not so bogus. Experiment 1: Get two good riders, a 125CC racer, and an R1000SS out on a track. Station a camera on a tripod at the tangent to the apex of a turn. Use your radar gun to train both riders to go through the turn at exactly the same speed, such spped to require ~55° lean angle on the R1000SS. Also train the riders to ride exactly the same line and to not hang off the bike (i.e., stay on the bike’s centerline.) I’m betting you will find, if you compare photos of the bikes at the apex of the turn, that the 125 will require ~4° less lean angle than the R1000SS. Admittedly, that’s a pretty small angle to measure, given all the variability you’ll see from lap to lap, but if you average over 20 – 30 laps, I think the difference will be apparent. Experiment 2: Set up your camera and radar gun as before, but at the apex of a perfectly flat turn. (Use a carpenter’s level.) Paint or tape a constant radius arc through the apex, and measure its radius exactly. (Use a stake at the center of the turn and a piece of string to make sure the radius is constant. Train the rider to not hang off the bike at all, and to track as close to 12” outside the arc as possible. ((We don’t want the tire contact patch on the tape.) Using any bike of your choice, but with aggressive tires, send the rider around the track, and measure the rider’s speed at the exact instant you photograph the bike from exactly behind its rear wheel. Speed in the turn can vary a fair amount, but should require fairly aggressive lean angles (but, again, no hanging off!) Do this for 20-30 laps, making sure that you take photos and speed exactly when the camera is in the plane of the rear wheel. We can then measure the lean angle and estimate the effective lean angle from the photographs, and we can measure the exact G’s of the bike in every pass by comparing the bike’s speed with the turn radius. We will then be able to compare measured and effective lean angles against the actual Gs, and see if my explanation accounts for your concern. I’m betting it will. Finally, while I agree that braking or accelerating at much more than 1G is just not happening, I think that’s because the center of gravity of the bike/rider is so high that the G limit is imposed by wheelies or stoppies rather than tire traction. When stopping in a straight line, the G-limit is set by the ratio of the height of the combined bike/rider center of mass to the horizontal distance between the combined bike/rider center of mass and a vertical line drawn through the center of the front tire’s contact patch. If those distances were exactly equal, then the maximum braking Gs you could develop, even with infinite tire-pavement friction, would be 1G. (And, remember, you have to measure these distances when the front forks are compressed by the weight transfer!) In contrast, when in a turn, the combined bike/rider center of mass gets lower as the lean angle increases. So in a coordinated turn, you don’t high-side—and the G-limit is set by tire-pavement traction, not vaulting laterally over the tires. This is just a long-winded way of saying that you should not try to reason that cornering Gs on a bike would be no better than driving or stopping Gs. The G-limits of cornering are different from those of driving and stopping. Does this help? -Eric
  7. Very well put. I totally agree with your summation. Could not have said it better. What I would find interesting is listing out the various things that one would have to consider to try to figure out how fast a bike could corner. It would be a list but going through the exercise of naming all the physics/mechanics involved would be illuminating. Things like: Friction coefficient of tires. Actual lean angle/vs theoretical "zero width" tire. Combined CofG of bike/rider. Throttle application. Acceleration. Contact patch sizes. G forces created. Suspension. Tire spring rate. Tire temp. Road surface (bumps). Friction coefficient of road. Camber. Elasticity of rubber on tire. Tire width. Tire profile shapes in relation to each other. Slip angle, front and rear tires. Radius of turn. Radius of rider's line. Bar tension from rider. Weight distribution of rider's body. anyone want to add to the list?
  8. Here's some data to consider. Just a piece of the picture but it shows that the location of the contact patch changes the actual lean angle vs a zero width tire. This is also a clue to why Moto3 bikes don't lean as much as bigger bikes but corner very quickly.
  9. I'm going to check with my go-to physics expert and see about settling this matter of lean angle and g-force. A Ferrari F40 can't break 1G on the skidpad. The idea that a motorcycle leaned over at 63 degrees can just over double that does not make sense. I'll probably come back with a very long and detailed explanation from my expert, but it seems some of the readers of this thread would like that.
  10. Fact is I don't know what 63 degrees on a motorcycle is, however I do know that 54 degrees on a motorcycle has been measured right at 1g with instruments. The banking and g-force figures come from aviation. Different factors. For that matter cars do not lean 45 degrees at 1g either. Apples and oranges thing.
  11. With high-grip tires on a high-grip surface that is flat, smooth, with a fairly even radius, you are going to corner at a maximum of just under 1g of lateral acceleration. Past that you are putting more sideways force on the tire than gravity is pulling the bike down. If we were on a heavier planet with say, 2g's of gravity relative to earth, then you could corner much faster. Here on earth if you go through a corner that is banked, you will be able to corner even faster with more than 1g of lateral force. A bump, poor tires, poor application of throttle/lean/braking, poor surface, etc could foil your plans for a fast pass through a corner.
  12. When I say "pulls the contact patch in" I am referring to being leaned, arcing through a turn, then putting resistance at the front contact patch by means of applying the front brake. Now, aside from the forks compressing, the bars tend to turn further into the turn. That's the action I am referring to and is very slight, but this has an effect of steering the bike up out of the turn (from subtle to marked depending on attendant factors).
  13. I think any person would be biting off a big chunk of physics and mechanics to adequately confirm or disprove what you are saying. However what I know to be correct from what I have studied and tried in practice, your impression is at least partially wrong. Go through a longer corner with a constant throttle reach forward and gently apply the brake. In most instances, if not all, the bike will stand up. Ok we already agree on this. Applying the brake pulls the contact patch in more, pro-steering the bike up. "Pro-steer" means to rotate the bars further into the turn. When actively doing this, the bike stands up. Applying the brake when leaned seems to have this effect. There are without doubt other physics and mechanics that come into play but the simplest and largest influencing factor that I am aware of is stated above. This is one topic where empirical observations are the most important and then an explanation helps to complete the understanding. What I am happy about is that Keith mentions some aspects of trail braking that have not been broadly spoken about and sheds some light on the subject for everyone.
  14. This is an interview that Keith did with Misti Hurst who aside from coaching runs her own blog called "motomom" located here http://www.motomom.ca/ Keith Code- Interview on Trail braking There is a lot of misunderstanding about the technique of trail braking; specifically people seem to be either for using trail braking all the time, or against it. Most often your name comes up as someone that is against using trail braking and that you advise getting all your braking done before you begin to turn the motorcycle. Let’s start off first by defining trail braking. What exactly is trail braking? Keith: It’s the tapering-off of brake lever pressure for controlling the bike’s rate of deceleration. That’s the most basic definition. Commonly, the term is used to reference the action of tapering-off brake lever pressure while leaning into a corner. Probably the easiest way to illustrate this is to get the idea of keeping the forks compressed roughly the same amount from braking through to leaning the bike into the turn. You would have to coordinate the release of brake pressure with the increase of leaning. The deceleration load on the forks diminishes while the cornering centrifugal force of the turn increases as the bike is leaned. That’s how I originally described and photographed it back in 1983. Should new riders learn the technique of trail braking? Keith: Every brake release should have some trailing off of lever pressure. Barring something like running off the road, there is no on-road or track cornering circumstance where an abrupt release of brake pressure is optimum. Is trail braking a race and track only skill or should street riders use it as well? Keith: As just mentioned, it's the correct way to release the lever for any corner entry situation. An abrupt release makes it quite difficult to accurately judge your final entry speed--if we call "entry speed" the speed that is left over right after the brake is released. We also know that the bike will continue to slow until the gas is back on enough to accelerate it. That in itself is a very interesting subject which most people misunderstand. Most think that rolling the gas on 10 percent or so will maintain their speed but it won't, most bikes continue to slow. At race pace, the bike will be slowing an average of 8 mph per second between the brake release and throttle-on. Specifically, at Laguna Seca on a Supersport bike it requires from 12% to 43% throttle, depending on the corner, before the bike begins to slightly accelerate, up to then it is losing speed rapidly. Do you teach trail braking at the California Superbike School? Keith: It’s a key part of our RACE school drills. It also comes up on Level 3 during a drill called Attack Angles. It can be covered at any time during Level 4 classes for which we have specific drills. Otherwise it’s also covered on request at any other point. It's interesting that the very best riders who have trained with us don't ask about it, they've figured out where it applies. Recently, trail-braking has become a topic. On-board footage of top racers clearly shows this technique in use. Riders intently study this footage trying to pick up wisdom that will make their riding better. Trail braking as a technique seems to have developed its own fan club. From some of its fans one could mistakenly get the idea that it is the "silver bullet" that will cure all your riding problems. Thinking that any one technique in our sport is senior to the others is like saying all a painter needs to be able to paint a masterpiece is to make sure the color “red” is included. It's a multi-layered, multi-tasking, multi-sense oriented sport where there are no easy routes to achieving your riding goals. Are there any new braking drills? Keith: Recently, I've been researching all the aspects of braking, amongst other things. Right now my list contains 5 stages of braking control, each with its own on-track drills. There are half a dozen other important aspects to braking that we also use to train and coach our students. When you coach high-level motorcycle racers like AMA Supersport winner Joe Roberts, British Superbike Champion Leon Camier, etc. do you encourage or teach trail braking? Keith: It rarely comes up as a topic on its own. If a top level racer is having trouble with some aspect of his braking, often there is some underlying problem that when fixed, solves the whole thing. For that caliber of rider you are looking for the least time on the brakes and the earliest on with the gas. In all cases, they want to minimize the time on the brake and maximize the time on the throttle with no coasting. On the track there are cornering situations that demand some extended trailing of the brakes, mainly places where you can't get the bike turned quickly to your knee. For example, nearly all decreasing radius turns require a longer tapering off of the brake because the steering into them is more gradual. Some double apex turns we will see riders trailing the brakes well past the first apex. Where it applies it applies. Theoretically, you would be going the fastest if the tires were always just at the limit of traction, whether from acceleration, braking or cornering. In auto racing they commonly use circular graphic representation of G forces called the “traction circle”. It shows G forces in all directions while driving. The idea is to keep the meter as close to the edge of the circle (the theoretical limit of traction) as much as possible while going around a track. Trailing the brakes is required to accomplish this in most corners. However that style of riding/driving would not be recommended for a Sunday ride down your favorite road. In any case, you certainly wouldn't want to be thinking circles and numbers while riding at any sort of quick pace, you'd want to be feeling what the bike's tires were actually doing. So, the winning rider's you've coached and trained do or don't trail-brake? Keith: They do where it applies. You asked about Joe Roberts, who set the American racing community on its head last year by winning 5 out of 5 races he entered and who had never raced a 600 before; he doesn't like to trail-brake. His competition did like it and you could see the difference in their styles and the results. In the 8 years we've been training Joe I'd say we spoke of trail-braking 2 or 3 times. There are so many other important fundamentals to master which put the bike under the rider's control and, frankly, give him more options in how to ride corners. Just as the painter must learn to draw well and understand contrast and perspective and form and a dozen other things to make that masterpiece so the rider must have the underpinnings to be able to make decisions on his handling of corners and to make them his own. It's the ART OF CORNERING not just the techniques. Do all the top racers in AMA, World Superbike and Moto GP trail brake? Keith: For the corners where it applies, for sure. Keen observers of the sport will notice that the deep trailing of the brakes that was so popular a few years ago has evolved somewhat. In only some corners will you see the brake still on at the apex. When you see a rider’s hand back on the gas before the apex, which you see more and more, you also have to realize that it takes 1/2 second to transition from brake to gas. At 60mph that 1/2 second is equal to 44 feet (about 6 bike lengths) earlier where the brake was actually released. You can find all sorts of exceptions and variations to technique. A rare example is the Moto3 riders going into turn one at Phillip Island, you see them turning in with the throttle wide open, then going to the brakes after the bike was well-pointed into the turn. One of the reasons riders were deep-trailing the brakes is because they could. I mean that the newer race front tires allow very heavy, leaned over braking. One of our students who had won in Moto 3 and Moto 2 graduated to Moto GP and I'll never forget how enthusiastic he was about how amazing the Moto GP front tires were under braking. I suspect James Toseland fell under the spell of this when he went from WSBK to Moto GP, he even mentioned it in some interviews. It clouded the issue of how to ride those bikes well. Remember that was the time when MotoGP went down to 800cc and all the top riders were talking about keeping up mid-corner speed versus a point-and-shoot style. Even in slow corners he was giving up so much by deep-trailing. Rossi, Stoner, Pedrosa were off the brakes 15 to 30 feet earlier and back to gas at, for example, turn #11 at Laguna Seca while he was possibly thinking how great the front tires were sticking under braking to the apex. Seeing how deep-trailing has devolved reminds me of the era where nearly everyone was backing the bikes into corners. It was so much fun and so spectacular and the fans loved it. Where did it go? You see much less dramatic "backing in" compared to a few years ago. Now it’s more the chassis setup causing the bike to back in regardless of the rider’s intent, such as some of the Moto2 bikes. The riders did it because they could and then everyone realized it was huge fun but in most cases slower, especially for Superbikes and MotoGP bikes. Can you compare trail braking in cars vs. trail braking on a motorcycle? Keith: That's easy, you can't tuck the front wheel from over-braking while leaned over and you can’t fall off a car! But with cars you have a wide variation of how to use the brake and throttle depending on the car’s configuration: front-wheel drives require different technique than rear wheel drives, as do all-wheel drives; also if the car is front, rear or mid-engine. I’d say the application is more consistent regardless of the type of bike you ride. Of course trailing the brakes changes the bike’s geometry by compressing the forks, this changes fork rake, overall ride height, trail and wheelbase. Do those changes in geometry help or hinder the rider? Keith: It's a bit of a Devil's tradeoff; the steepened rake will make the bike turn easier as does the slightly shortened wheelbase help that, but, the increase in trail is what makes the bars feel heavy and somewhat unresponsive under brake trailing. Because the braking expands the contact patch area to the inside of the bike's center line, it counter-steers the bike upward, a little or a lot. You can do a simple experiment to feel a light version of this by getting the bike leaned over in the corner, go back to gas and then off the gas. When the weight transfers forward, off gas, the bike's first response is to stand up some. That same effect is amplified if brakes are used while leaned over. To counter that "stand up" action the rider must apply some bar pressure to hold his lean. Rider's learn to do this almost unconsciously. It's quite similar to the false perception that the bike stands up on corner exits from acceleration, which it does not. Riders unconsciously steer the bike up as they add gas. The big negative is that the fork's are restricted in their ability to rotate side to side that slight amount that you feel when cornering. That slight oscillation is necessary for the bike's stability, which I covered in A Twist of the Wrist, Vol II. These forces are in conflict with one another and the forks become less compliant, less able to follow the road's surface changes, under those conditions. The tire then begins to "dance" over the ripples and bumps. This, I'm convinced, contributes greatly in even the top riders losing the front and low-siding while trail-braking. How high a priority should trail braking be given to riders that are just getting involved in the sport? Keith: That depends on how you approach their training. You certainly wouldn't start a new rider off training him to trail brakes before he had some idea of how he should take a corner to begin with. You'd want to give him a solid grounding in several other basics like that before launching into that technique. Back to the controversy about trail braking, people believe that you either do it all the time in all corners or you don’t do it at all. What are your thoughts on this? Keith: It is irrelevant whether you are finishing off your braking straight up or leaned over, you always trail off the brakes. The logical approach is to train someone to do that straight up first. Later you could take up trailing them leaned over. Is there a hard fast rule that braking should be done BEFORE you tip the bike into the turn? Keith: There are 27 references to trailing brakes and why in my three books on riding. They were released in 1983, 1986 and 1993, way before there was any controversy on the subject. Interestingly, those books were the first time anyone had approached trail-braking in writing and photographed the advantages and uses of the technique for motorcycles. No one can argue with that, it is the first written history of trail-braking for motorcycles. These days, from how some riders talk about it you'd think that trail-braking was some new innovation, just invented. It’s probably due to me describing it as “braking while leaned” or “letting of the brakes while leaning in” instead of calling it “trail braking” which had previously been an exclusively car racing term. What is the difference between trail braking into the turn, and braking in the middle of a corner? Keith: Trailing in is for speed and line setting. Braking in the corner is an emergency situation, they are totally different. One is calculated the other is out of necessity and often panic. Would carrying some brake pressure into the corner help you if you had to brake suddenly in the middle of the turn because the brake pads are already touching the rotors? Keith: Keeping a finger or two resting on the lever helps reduce reaction time, but you don’t have to have the brakes slightly engaged whenever cornering “just in case”. You can apply the brake as fast as lightning provided you do so lightly. It's the pressure at the end of the brake pull that is critical not how fast you pull it in. A quick on-track braking action takes as little as 2/10ths of a second to get to full brake pressure for some turns. If you snapped the brakes on to a very light pressure you could get into the brakes even at a good lean. It wouldn't feel very stable but you can do it. Our Panic Brake Bike fitted with outriggers allows riders to practice rapidly going to the right amount of pressure without overstepping the boundaries. Five minutes on that bike is better than five hours of talking about braking.
  15. Well if you had an average of 1g acceleration for 3 seconds, that would be 66mph after 3 seconds. You'll also notice that most 0-60 times on modern sportbikes are right around 3 seconds. So if you went 0-60 in 0.5 seconds, that would be almost six times the acceleration. It would be about 5.4g's per my reckoning.
  16. In theory, you cannot go beyond 1g (if we ignore wind resistance). In reality, you can. Although never fully explained AFAIK, the soft rubber and textured road surface interact a bit like gears, allowing more than one G of force. Which is why motorcycles can corner beyond 45 degrees of lean and stop quicker than one G. And why dragsters can accelerate from 0-60mph in under half a second, which should be around 3g if I'm not too far off with my math. Formula 1 cars can stop and corner at up to 5g thanks to artificial downforce. 1g is going to be 22mph/sec and 0-60 in .5 sec= 120mph in a second. So how many G's does that come out in your math? However empirically we can see that this theoretical concept of 1G helps us understand braking and accelleration in a fashion that gives us real expectations when slowing down a motorcycle as well as the idea of introducing cornering force while braking. So how many G's does the fastest production car in the world pull when accelerating to 270mph from a stop? Here's your answer at 0:50 of the video *excuse tyops*
  17. So there you go, almost all very good 60-0 stops are going to be around 120ft. If you can get an 18 wheeler to develop 1g in braking force, it will stop in the same distance. Weight does not matter so much as good brakes and a good sticky contact with the road. I saw footage of an army tank that could stop very quickly. It had good brakes and sticky rubber treads. Why could someone get a better than 1g stop? As was previously mentioned: large surface area=wind resistance, or maybe a headwind, or maybe a slight uphill, or some aerodynamic feature that adds some downforce, which would be most noticeable at the beginning of the braking action at 60mph. If you can go straight to max braking pressure at 60mph, you are going to getting better than 1g because of the max braking plus wind resistance at the higher spped. Having ABS would possibly allow the rider to go to max pressure a little quicker. Even if it was a 1/10 of a second quicker, that would make a difference especially at higher speeds where the feet-per-second is so much higher. A 1/10th of a second at 60mph is 8.8 feet. If you find a particularly good or bad stop on a motorcycle it usually has its roots in what happened when the brake was initially engaged. C of G will have some bearing but it would be hard to do anything but speculate without hard facts (measurements) and someone well-trained in physics, which I am not. (answered quickly not checked for typos)
  18. does electronics count? eg: -CBS (combined braking system) -TC (traction control) -EBM (engine braking management) No, electronics will not change the maximum available stopping distances compatred to a skilled rider without these aids. Look at it like this: the earth is pulling you down with 1g, if you try to generate more than 1g in force laterally, you will start to endo or lock up. Unless of course there is additional downforce, lots of wind resistance from high speeds, etc.
  19. Scrmduc, You seem to have unanswered questions but with all this back and forth I'm a little lost. It seems like some questions are asking, but some also may be rhetorical. Why don't you bullet out a little list for me and I'll see about answering.
  20. Of course what you are saying is correct. The only thing I need to correct is where you say "CSS is not big on super hard late braking". Braking is braking and you can and should brake as hard as you want as long as you don't find yourself rushing to a corner in a fashion that makes your entry rough or on the edge of crashing. Motorcycles only have so much braking capability and they have not changed much for decades on the straight line 60mph to 0mph stops. Compare the 60-0 stopping distance of a 1983 Honda Interceptor and a 2014 Yamaha R1. They are the same or within a few feet. You can only get about 1.0g's maximum of braking unless you have added downforce (like a wing on a car), uphill, added wind resistance (parachute or very large surface area), or at very high speeds where the wind resistance is extreme.
  21. Exactly. I saw the video section that you referenced and it appears that you did a good job at keeping the forks evenly compressed during the transition from brake release to leaned over in the corner.
×
×
  • Create New...